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PostGIS 2.4.5 Manual

The PostGIS Development Group

Abstract

PostGIS is an extension to the PostgreSQL object-relational database system which allows GIS (Geographic Information Systems) objects to be stored in the database. PostGIS includes support for GiST-based R-Tree spatial indexes, and functions for analysis and processing of GIS objects.

This is the manual for version 2.4.5

This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License . Feel free to use this material any way you like, but we ask that you attribute credit to the PostGIS Project and wherever possible, a link back to http://postgis.net .


Table of Contents

1. Introduction
1.1. Project Steering Committee
1.2. Core Contributors Present
1.3. Core Contributors Past
1.4. Other Contributors
1.5. More Information
2. PostGIS Installation
2.1. Short Version
2.2. Install Requirements
2.3. Getting the Source
2.4. Compiling and Install from Source: Detailed
2.4.1. Configuration
2.4.2. Building
2.4.3. Building PostGIS Extensions and Deploying them
2.4.4. Testing
2.4.5. Installation
2.5. Creating a spatial database using EXTENSIONS
2.6. Create a spatially-enabled database without using extensions
2.7. Installing and Using the address standardizer
2.7.1. Installing Regex::Assemble
2.8. Installing, Upgrading Tiger Geocoder and loading data
2.8.1. Tiger Geocoder Enabling your PostGIS database: Using Extension
2.8.2. Tiger Geocoder Enabling your PostGIS database: Not Using Extensions
2.8.3. Using Address Standardizer Extension with Tiger geocoder
2.8.4. Loading Tiger Data
2.8.5. Upgrading your Tiger Geocoder Install
2.9. Create a spatially-enabled database from a template
2.10. Upgrading
2.10.1. Soft upgrade
2.10.2. Hard upgrade
2.11. Common Problems during installation
2.12. Loader/Dumper
3. PostGIS Frequently Asked Questions
4. Using PostGIS: Data Management and Queries
4.1. GIS Objects
4.1.1. OpenGIS WKB and WKT
4.1.2. PostGIS EWKB, EWKT and Canonical Forms
4.1.3. SQL-MM Part 3
4.2. PostGIS Geography Type
4.2.1. Geography Basics
4.2.2. When to use Geography Data type over Geometry data type
4.2.3. Geography Advanced FAQ
4.3. Using OpenGIS Standards
4.3.1. The SPATIAL_REF_SYS Table and Spatial Reference Systems
4.3.2. The GEOMETRY_COLUMNS VIEW
4.3.3. Creating a Spatial Table
4.3.4. Manually Registering Geometry Columns in geometry_columns
4.3.5. Ensuring OpenGIS compliancy of geometries
4.3.6. Dimensionally Extended 9 Intersection Model (DE-9IM)
4.4. Loading GIS (Vector) Data
4.4.1. Loading Data Using SQL
4.4.2. shp2pgsql: Using the ESRI Shapefile Loader
4.5. Retrieving GIS Data
4.5.1. Using SQL to Retrieve Data
4.5.2. Using the Dumper
4.6. Building Indexes
4.6.1. GiST Indexes
4.6.2. BRIN Indexes
4.6.3. Using Indexes
4.7. Complex Queries
4.7.1. Taking Advantage of Indexes
4.7.2. Examples of Spatial SQL
5. Raster Data Management, Queries, and Applications
5.1. Loading and Creating Rasters
5.1.1. Using raster2pgsql to load rasters
5.1.2. Creating rasters using PostGIS raster functions
5.2. Raster Catalogs
5.2.1. Raster Columns Catalog
5.2.2. Raster Overviews
5.3. Building Custom Applications with PostGIS Raster
5.3.1. PHP Example Outputting using ST_AsPNG in concert with other raster functions
5.3.2. ASP.NET C# Example Outputting using ST_AsPNG in concert with other raster functions
5.3.3. Java console app that outputs raster query as Image file
5.3.4. Use PLPython to dump out images via SQL
5.3.5. Outputting Rasters with PSQL
6. Using PostGIS Geometry: Building Applications
6.1. Using MapServer
6.1.1. Basic Usage
6.1.2. Frequently Asked Questions
6.1.3. Advanced Usage
6.1.4. Examples
6.2. Java Clients (JDBC)
6.3. C Clients (libpq)
6.3.1. Text Cursors
6.3.2. Binary Cursors
7. Performance tips
7.1. Small tables of large geometries
7.1.1. Problem description
7.1.2. Workarounds
7.2. CLUSTERing on geometry indices
7.3. Avoiding dimension conversion
7.4. Tuning your configuration
7.4.1. Startup
7.4.2. Runtime
8. PostGIS Reference
8.1. PostgreSQL PostGIS Geometry/Geography/Box Types
8.2. PostGIS Grand Unified Custom Variables (GUCs)
8.3. Management Functions
8.4. Geometry Constructors
8.5. Geometry Accessors
8.6. Geometry Editors
8.7. Geometry Outputs
8.8. Operators
8.9. Spatial Relationships and Measurements
8.10. SFCGAL Functions
8.11. Geometry Processing
8.12. Linear Referencing
8.13. Temporal Support
8.14. Long Transactions Support
8.15. Miscellaneous Functions
8.16. Exceptional Functions
9. Raster Reference
9.1. Raster Support Data types
9.2. Raster Management
9.3. Raster Constructors
9.4. Raster Accessors
9.5. Raster Band Accessors
9.6. Raster Pixel Accessors and Setters
9.7. Raster Editors
9.8. Raster Band Editors
9.9. Raster Band Statistics and Analytics
9.10. Raster Outputs
9.11. Raster Processing
9.11.1. Map Algebra
9.11.2. Built-in Map Algebra Callback Functions
9.11.3. DEM (Elevation)
9.11.4. Raster to Geometry
9.12. Raster Operators
9.13. Raster and Raster Band Spatial Relationships
10. PostGIS Raster Frequently Asked Questions
11. Topology
11.1. Topology Types
11.2. Topology Domains
11.3. Topology and TopoGeometry Management
11.4. Topology Constructors
11.5. Topology Editors
11.6. Topology Accessors
11.7. Topology Processing
11.8. TopoGeometry Constructors
11.9. TopoGeometry Editors
11.10. TopoGeometry Accessors
11.11. TopoGeometry Outputs
11.12. Topology Spatial Relationships
12. Address Standardizer
12.1. How the Parser Works
12.2. Address Standardizer Types
12.3. Address Standardizer Tables
12.4. Address Standardizer Functions
13. PostGIS Extras
13.1. Tiger Geocoder
14. PostGIS Special Functions Index
14.1. PostGIS Aggregate Functions
14.2. PostGIS Window Functions
14.3. PostGIS SQL-MM Compliant Functions
14.4. PostGIS Geography Support Functions
14.5. PostGIS Raster Support Functions
14.6. PostGIS Geometry / Geography / Raster Dump Functions
14.7. PostGIS Box Functions
14.8. PostGIS Functions that support 3D
14.9. PostGIS Curved Geometry Support Functions
14.10. PostGIS Polyhedral Surface Support Functions
14.11. PostGIS Function Support Matrix
14.12. New, Enhanced or changed PostGIS Functions
14.12.1. PostGIS Functions new or enhanced in 2.4
14.12.2. PostGIS Functions new or enhanced in 2.3
14.12.3. PostGIS Functions new or enhanced in 2.2
14.12.4. PostGIS functions breaking changes in 2.2
14.12.5. PostGIS Functions new or enhanced in 2.1
14.12.6. PostGIS functions breaking changes in 2.1
14.12.7. PostGIS Functions new, behavior changed, or enhanced in 2.0
14.12.8. PostGIS Functions changed behavior in 2.0
14.12.9. PostGIS Functions new, behavior changed, or enhanced in 1.5
14.12.10. PostGIS Functions new, behavior changed, or enhanced in 1.4
14.12.11. PostGIS Functions new in 1.3
15. Reporting Problems
15.1. Reporting Software Bugs
15.2. Reporting Documentation Issues
A. Appendix
A.1. Release 2.4.5
A.2. Release 2.4.4
A.3. Release 2.4.3
A.4. Release 2.4.2
A.5. Release 2.4.1
A.6. Release 2.4.0
A.7. Release 2.3.5
A.8. Release 2.3.4
A.9. Release 2.3.3
A.10. Release 2.3.2
A.11. Release 2.3.1
A.12. Release 2.3.0
A.13. Release 2.2.2
A.14. Release 2.2.1
A.15. Release 2.2.0
A.16. Release 2.1.8
A.17. Release 2.1.7
A.18. Release 2.1.6
A.19. Release 2.1.5
A.20. Release 2.1.4
A.21. Release 2.1.3
A.22. Release 2.1.2
A.23. Release 2.1.1
A.24. Release 2.1.0
A.25. Release 2.0.5
A.26. Release 2.0.4
A.27. Release 2.0.3
A.28. Release 2.0.2
A.29. Release 2.0.1
A.30. Release 2.0.0
A.31. Release 1.5.4
A.32. Release 1.5.3
A.33. Release 1.5.2
A.34. Release 1.5.1
A.35. Release 1.5.0
A.36. Release 1.4.0
A.37. Release 1.3.6
A.38. Release 1.3.5
A.39. Release 1.3.4
A.40. Release 1.3.3
A.41. Release 1.3.2
A.42. Release 1.3.1
A.43. Release 1.3.0
A.44. Release 1.2.1
A.45. Release 1.2.0
A.46. Release 1.1.6
A.47. Release 1.1.5
A.48. Release 1.1.4
A.49. Release 1.1.3
A.50. Release 1.1.2
A.51. Release 1.1.1
A.52. Release 1.1.0
A.53. Release 1.0.6
A.54. Release 1.0.5
A.55. Release 1.0.4
A.56. Release 1.0.3
A.57. Release 1.0.2
A.58. Release 1.0.1
A.59. Release 1.0.0
A.60. Release 1.0.0RC6
A.61. Release 1.0.0RC5
A.62. Release 1.0.0RC4
A.63. Release 1.0.0RC3
A.64. Release 1.0.0RC2
A.65. Release 1.0.0RC1

Chapter 1. Introduction

PostGIS was developed by Refractions Research Inc, as a spatial database technology research project. Refractions is a GIS and database consulting company in Victoria, British Columbia, Canada, specializing in data integration and custom software development. We plan on supporting and developing PostGIS to support a range of important GIS functionality, including full OpenGIS support, advanced topological constructs (coverages, surfaces, networks), desktop user interface tools for viewing and editing GIS data, and web-based access tools.

PostGIS is an incubation project of the OSGeo Foundation. PostGIS is being continually improved and funded by many FOSS4G Developers as well as corporations all over the world that gain great benefit from its functionality and versatility.

1.1. Project Steering Committee

The PostGIS Project Steering Committee (PSC) coordinates the general direction, release cycles, documentation, and outreach efforts for the PostGIS project. In addition the PSC provides general user support, accepts and approves patches from the general PostGIS community and votes on miscellaneous issues involving PostGIS such as developer commit access, new PSC members or significant API changes.

Mark Cave-Ayland

Coordinates bug fixing and maintenance effort, spatial index selectivity and binding, loader/dumper, and Shapefile GUI Loader, integration of new and new function enhancements.

Regina Obe

Buildbot Maintenance, windows production and experimental builds, Documentation, alignment of PostGIS with PostgreSQL releases, general user support on PostGIS newsgroup, X3D support, Tiger Geocoder Support, management functions, and smoke testing new functionality or major code changes.

Bborie Park

Raster development, integration with GDAL, raster loader, user support, general bug fixing, testing on various OS (Slackware, Mac, Windows, and more)

Paul Ramsey (Chair)

Co-founder of PostGIS project. General bug fixing, geography support, geography and geometry index support (2D, 3D, nD index and anything spatial index), underlying geometry internal structures, PointCloud (in development), GEOS functionality integration and alignment with GEOS releases, alignment of PostGIS with PostgreSQL releases, loader/dumper, and Shapefile GUI loader.

Sandro Santilli

Bug fixes and maintenance, git mirrors management, integration of new GEOS functionality and alignment with GEOS releases, Topology support, and Raster framework and low level api functions.

1.2. Core Contributors Present

Jorge Arévalo

Raster development, GDAL driver support, loader

Nicklas Avén

Distance function enhancements (including 3D distance and relationship functions) and additions, Tiny WKB output format (TWKB) (in development) and general user support

Dan Baston

Geometry clustering function additions, other geometry algorithm enhancements, GEOS enhancements and general user support

Olivier Courtin

Input output XML (KML,GML)/GeoJSON functions, 3D support and bug fixes.

Björn Harrtell

MapBox Vector Tile and GeoBuf functions. Gogs testing and GitLab experimentation.

Mateusz Loskot

CMake support for PostGIS, built original raster loader in python and low level raster api functions

Darafei Praliaskouski

Index improvements, bug fixing and geometry/geography function improvements, GitHub curator, and Travis bot maintenance.

Pierre Racine

Raster overall architecture, prototyping, programming support

1.3. Core Contributors Past

Chris Hodgson

Prior PSC Member. General development, site and buildbot maintenance, OSGeo incubation management

Kevin Neufeld

Prior PSC Member. Documentation and documentation support tools, buildbot maintenance, advanced user support on PostGIS newsgroup, and PostGIS maintenance function enhancements.

Dave Blasby

The original developer/Co-founder of PostGIS. Dave wrote the server side objects, index bindings, and many of the server side analytical functions.

Jeff Lounsbury

Original development of the Shape file loader/dumper. Current PostGIS Project Owner representative.

Mark Leslie

Ongoing maintenance and development of core functions. Enhanced curve support. Shapefile GUI loader.

David Zwarg

Raster development (mostly map algebra analytic functions)

1.4. Other Contributors

Individual Contributors

In alphabetical order: Alex Bodnaru, Alex Mayrhofer, Andrea Peri, Andreas Forø Tollefsen, Andreas Neumann, Anne Ghisla, Barbara Phillipot, Ben Jubb, Bernhard Reiter, Brian Hamlin, Bruce Rindahl, Bruno Wolff III, Bryce L. Nordgren, Carl Anderson, Charlie Savage, Dane Springmeyer, David Skea, David Techer, Eduin Carrillo, Even Rouault, Frank Warmerdam, George Silva, Gerald Fenoy, Gino Lucrezi, Guillaume Lelarge, IIDA Tetsushi, Ingvild Nystuen, Jason Smith, Jeff Adams, Jose Carlos Martinez Llari, Julien Rouhaud, Kashif Rasul, Klaus Foerster, Kris Jurka, Leo Hsu, Loic Dachary, Luca S. Percich, Maria Arias de Reyna, Mark Sondheim, Markus Schaber, Maxime Guillaud, Maxime van Noppen, Michael Fuhr, Mike Toews, Nathan Wagner, Nathaniel Clay, Nikita Shulga, Norman Vine, Rafal Magda, Ralph Mason, Rémi Cura, Richard Greenwood, Silvio Grosso, Steffen Macke, Stephen Frost, Tom van Tilburg, Vincent Mora, Vincent Picavet

Corporate Sponsors

These are corporate entities that have contributed developer time, hosting, or direct monetary funding to the PostGIS project

In alphabetical order: Arrival 3D, Associazione Italiana per l'Informazione Geografica Libera (GFOSS.it), AusVet, Avencia, Azavea, Cadcorp, CampToCamp, CartoDB, City of Boston (DND), Clever Elephant Solutions, Cooperativa Alveo, Deimos Space, Faunalia, Geographic Data BC, Hunter Systems Group, Lidwala Consulting Engineers, LisaSoft, Logical Tracking & Tracing International AG, Maponics, Michigan Tech Research Institute, Natural Resources Canada, Norwegian Forest and Landscape Institute, Boundless (former OpenGeo), OSGeo, Oslandia, Palantir Technologies, Paragon Corporation, R3 GIS, Refractions Research, Regione Toscana - SITA, Safe Software, Sirius Corporation plc, Stadt Uster, UC Davis Center for Vectorborne Diseases, University of Laval, U.S Department of State (HIU), Zonar Systems

Crowd Funding Campaigns

Crowd funding campaigns are campaigns we run to get badly wanted features funded that can service a large number of people. Each campaign is specifically focused on a particular feature or set of features. Each sponsor chips in a small fraction of the needed funding and with enough people/organizations contributing, we have the funds to pay for the work that will help many. If you have an idea for a feature you think many others would be willing to co-fund, please post to the PostGIS newsgroup your thoughts and together we can make it happen.

PostGIS 2.0.0 was the first release we tried this strategy. We used PledgeBank and we got two successful campaigns out of it.

postgistopology - 10 plus sponsors each contributed $250 USD to build toTopoGeometry function and beef up topology support in 2.0.0. It happened.

postgis64windows - 20 someodd sponsors each contributed $100 USD to pay for the work needed to work out PostGIS 64-bit issues on windows. It happened. We now have a 64-bit release for PostGIS 2.0.1 available on PostgreSQL stack builder.

Important Support Libraries

The GEOS geometry operations library, and the algorithmic work of Martin Davis in making it all work, ongoing maintenance and support of Mateusz Loskot, Sandro Santilli (strk), Paul Ramsey and others.

The GDAL Geospatial Data Abstraction Library, by Frank Warmerdam and others is used to power much of the raster functionality introduced in PostGIS 2.0.0. In kind, improvements needed in GDAL to support PostGIS are contributed back to the GDAL project.

The Proj4 cartographic projection library, and the work of Gerald Evenden and Frank Warmerdam in creating and maintaining it.

Last but not least, the PostgreSQL DBMS , The giant that PostGIS stands on. Much of the speed and flexibility of PostGIS would not be possible without the extensibility, great query planner, GIST index, and plethora of SQL features provided by PostgreSQL.

1.5. More Information

Chapter 2. PostGIS Installation

This chapter details the steps required to install PostGIS.

2.1. Short Version

To compile assuming you have all the dependencies in your search path:

tar xvfz postgis-2.4.5.tar.gz
cd postgis-2.4.5
./configure
make
make install

Once postgis is installed, it needs to be enabled in each individual database you want to use it in.

[Note]

The raster support is currently optional, but installed by default. For enabling using the PostgreSQL 9.1+ extensions model raster is required. Using the extension enable process is preferred and more user-friendly. To spatially enable your database:

psql -d yourdatabase -c "CREATE EXTENSION postgis;"
psql -d yourdatabase -c "CREATE EXTENSION postgis_topology;"
-- if you built with sfcgal support --
psql -d yourdatabase -c "CREATE EXTENSION postgis_sfcgal;"

-- if you want to install tiger geocoder --
psql -d yourdatabase -c "CREATE EXTENSION fuzzystrmatch"
psql -d yourdatabase -c "CREATE EXTENSION postgis_tiger_geocoder;"

-- if you installed with pcre
-- you should have address standardizer extension as well
psql -d yourdatabase -c "CREATE EXTENSION address_standardizer;"

Please refer to Section 2.4.3, “Building PostGIS Extensions and Deploying them” for more details about querying installed/available extensions and upgrading extensions, or switching from a non-extension install to an extension install.

For those running who decided for some reason not to compile with raster support, or just are old-fashioned, here are longer more painful instructions for you:

All the .sql files once installed will be installed in share/contrib/postgis-2.3 folder of your PostgreSQL install

createdb yourdatabase
createlang plpgsql yourdatabase
psql -d yourdatabase -f postgis.sql
psql -d yourdatabase -f postgis_comments.sql
psql -d yourdatabase -f spatial_ref_sys.sql
psql -d yourdatabase -f topology.sql
psql -d yourdatabase -f topology_comments.sql

-- only if you compiled with raster (GDAL)
psql -d yourdatabase -f rtpostgis.sql
psql -d yourdatabase -f raster_comments.sql

--if you built with sfcgal support --
psql -d yourdatabase -f sfcgal.sql
psql -d yourdatabase -f sfcgal_comments.sql

The rest of this chapter goes into detail each of the above installation steps.

As of PostGIS 2.1.3, out-of-db rasters and all raster drivers are disabled by default. In order to re-enable these, you need to set the following environment variables POSTGIS_GDAL_ENABLED_DRIVERS and POSTGIS_ENABLE_OUTDB_RASTERS in the server environment. For PostGIS 2.2, you can use the more cross-platform approach of setting the corresponding Section 8.2, “PostGIS Grand Unified Custom Variables (GUCs)” .

If you want to enable offline raster:

POSTGIS_ENABLE_OUTDB_RASTERS=1

Any other setting or no setting at all will disable out of db rasters.

In order to enable all GDAL drivers available in your GDAL install, set this environment variable as follows

POSTGIS_GDAL_ENABLED_DRIVERS=ENABLE_ALL

If you want to only enable specific drivers, set your environment variable as follows:

POSTGIS_GDAL_ENABLED_DRIVERS="GTiff PNG JPEG GIF XYZ"
[Note]

If you are on windows, do not quote the driver list

Setting environment variables varies depending on OS. For PostgreSQL installed on Ubuntu or Debian via apt-postgresql, the preferred way is to edit /etc/postgresql/ 9.3 / main /environment where 9.3 refers to version of PostgreSQL and main refers to the cluster.

On windows, if you are running as a service, you can set via System variables which for Windows 7 you can get to by right-clicking on Computer->Properties Advanced System Settings or in explorer navigating to Control Panel\All Control Panel Items\System . Then clicking Advanced System Settings ->Advanced->Environment Variables and adding new system variables.

After you set the environment variables, you'll need to restart your PostgreSQL service for the changes to take effect.

2.2. Install Requirements

PostGIS has the following requirements for building and usage:

Required

  • PostgreSQL 9.3 or higher. A complete installation of PostgreSQL (including server headers) is required. PostgreSQL is available from http://www.postgresql.org .

    For a full PostgreSQL / PostGIS support matrix and PostGIS/GEOS support matrix refer to http://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS

  • GNU C compiler ( gcc ). Some other ANSI C compilers can be used to compile PostGIS, but we find far fewer problems when compiling with gcc .

  • GNU Make ( gmake or make ). For many systems, GNU make is the default version of make. Check the version by invoking make -v . Other versions of make may not process the PostGIS Makefile properly.

  • Proj4 reprojection library, version 4.6.0 or greater. Proj4 4.9 or above is needed to take advantage of improved geodetic. The Proj4 library is used to provide coordinate reprojection support within PostGIS. Proj4 is available for download from http://trac.osgeo.org/proj/ .

  • GEOS geometry library, version 3.4 or greater, but GEOS 3.7+ is recommended to take full advantage of all the new functions and features. You should have at least GEOS 3.5, without which you will be missing some major enhancements such as ST_ClipByBox2D and ST_Subdivide . GEOS is available for download from http://trac.osgeo.org/geos/ and 3.5+ is backward-compatible with older versions so fairly safe to upgrade.

  • LibXML2, version 2.5.x or higher. LibXML2 is currently used in some imports functions (ST_GeomFromGML and ST_GeomFromKML). LibXML2 is available for download from http://xmlsoft.org/downloads.html .

  • JSON-C, version 0.9 or higher. JSON-C is currently used to import GeoJSON via the function ST_GeomFromGeoJson. JSON-C is available for download from https://github.com/json-c/json-c/releases/ .

  • GDAL, version 1.8 or higher (1.9 or higher is strongly recommended since some things will not work well or behavior differently with lower versions). This is required for raster support and to be able to install with CREATE EXTENSION postgis so highly recommended for those running 9.1+. http://trac.osgeo.org/gdal/wiki/DownloadSource .

Optional

  • GDAL (pseudo optional) only if you don't want raster and don't care about installing with CREATE EXTENSION postgis can you leave it out. Keep in mind other extensions may have a requires postgis extension which will prevent you from installing them unless you install postgis as an extension. So it is highly recommended you compile with GDAL support.

    Also make sure to enable the drivers you want to use as described in Section 2.1, “Short Version” .

  • GTK (requires GTK+2.0, 2.8+) to compile the shp2pgsql-gui shape file loader. http://www.gtk.org/ .

  • SFCGAL, version 1.1 (or higher) could be used to provide additional 2D and 3D advanced analysis functions to PostGIS cf Section 8.10, “SFCGAL Functions” . And also allow to use SFCGAL rather than GEOS for some 2D functions provided by both backends (like ST_Intersection or ST_Area, for instance). A PostgreSQL configuration variable postgis.backend allow end user to control which backend he want to use if SFCGAL is installed (GEOS by default). Nota: SFCGAL 1.2 require at least CGAL 4.3 and Boost 1.54 (cf: http://oslandia.github.io/SFCGAL/installation.html ) https://github.com/Oslandia/SFCGAL .

  • In order to build the Chapter 12, Address Standardizer you will also need PCRE http://www.pcre.org (which generally is already installed on nix systems). Regex::Assemble perl CPAN package is only needed if you want to rebuild the data encoded in parseaddress-stcities.h . Chapter 12, Address Standardizer will automatically be built if it detects a PCRE library, or you pass in a valid --with-pcre-dir=/path/to/pcre during configure.

  • To enable ST_AsMVT protobuf-c library (for usage) and the protoc-c compiler (for building) are required. Also, pkg-config is required to verify the correct minimum version of protobuf-c. See protobuf-c .

  • CUnit ( CUnit ). This is needed for regression testing. http://cunit.sourceforge.net/

  • DocBook ( xsltproc ) is required for building the documentation. Docbook is available from http://www.docbook.org/ .

  • DBLatex ( dblatex ) is required for building the documentation in PDF format. DBLatex is available from http://dblatex.sourceforge.net/ .

  • ImageMagick ( convert ) is required to generate the images used in the documentation. ImageMagick is available from http://www.imagemagick.org/ .

2.3. Getting the Source

Retrieve the PostGIS source archive from the downloads website http://download.osgeo.org/postgis/source/postgis-2.4.5.tar.gz

wget http://download.osgeo.org/postgis/source/postgis-2.4.5.tar.gz
tar -xvzf postgis-2.4.5.tar.gz

This will create a directory called postgis-2.4.5 in the current working directory.

Alternatively, checkout the source from the svn repository http://svn.osgeo.org/postgis/trunk/ .

svn checkout http://svn.osgeo.org/postgis/trunk/ postgis-2.4.5

Change into the newly created postgis-2.4.5 directory to continue the installation.

2.4. Compiling and Install from Source: Detailed

[Note]

Many OS systems now include pre-built packages for PostgreSQL/PostGIS. In many cases compilation is only necessary if you want the most bleeding edge versions or you are a package maintainer.

This section includes general compilation instructions, if you are compiling for Windows etc or another OS, you may find additional more detailed help at PostGIS User contributed compile guides and PostGIS Dev Wiki .

Pre-Built Packages for various OS are listed in PostGIS Pre-built Packages

If you are a windows user, you can get stable builds via Stackbuilder or PostGIS Windows download site We also have very bleeding-edge windows experimental builds that are built usually once or twice a week or whenever anything exciting happens. You can use these to experiment with the in progress releases of PostGIS

The PostGIS module is an extension to the PostgreSQL backend server. As such, PostGIS 2.4.5 requires full PostgreSQL server headers access in order to compile. It can be built against PostgreSQL versions 9.3 or higher. Earlier versions of PostgreSQL are not supported.

Refer to the PostgreSQL installation guides if you haven't already installed PostgreSQL. http://www.postgresql.org .

[Note]

For GEOS functionality, when you install PostgresSQL you may need to explicitly link PostgreSQL against the standard C++ library:

LDFLAGS=-lstdc++ ./configure [YOUR OPTIONS HERE]

This is a workaround for bogus C++ exceptions interaction with older development tools. If you experience weird problems (backend unexpectedly closed or similar things) try this trick. This will require recompiling your PostgreSQL from scratch, of course.

The following steps outline the configuration and compilation of the PostGIS source. They are written for Linux users and will not work on Windows or Mac.

2.4.1. Configuration

As with most linux installations, the first step is to generate the Makefile that will be used to build the source code. This is done by running the shell script

./configure

With no additional parameters, this command will attempt to automatically locate the required components and libraries needed to build the PostGIS source code on your system. Although this is the most common usage of ./configure , the script accepts several parameters for those who have the required libraries and programs in non-standard locations.

The following list shows only the most commonly used parameters. For a complete list, use the --help or --help=short parameters.

--prefix=PREFIX

This is the location the PostGIS libraries and SQL scripts will be installed to. By default, this location is the same as the detected PostgreSQL installation.

[Caution]

This parameter is currently broken, as the package will only install into the PostgreSQL installation directory. Visit http://trac.osgeo.org/postgis/ticket/635 to track this bug.

--with-pgconfig=FILE

PostgreSQL provides a utility called pg_config to enable extensions like PostGIS to locate the PostgreSQL installation directory. Use this parameter ( --with-pgconfig=/path/to/pg_config ) to manually specify a particular PostgreSQL installation that PostGIS will build against.

--with-gdalconfig=FILE

GDAL, a required library, provides functionality needed for raster support gdal-config to enable software installations to locate the GDAL installation directory. Use this parameter ( --with-gdalconfig=/path/to/gdal-config ) to manually specify a particular GDAL installation that PostGIS will build against.

--with-geosconfig=FILE

GEOS, a required geometry library, provides a utility called geos-config to enable software installations to locate the GEOS installation directory. Use this parameter ( --with-geosconfig=/path/to/geos-config ) to manually specify a particular GEOS installation that PostGIS will build against.

--with-xml2config=FILE

LibXML is the library required for doing GeomFromKML/GML processes. It normally is found if you have libxml installed, but if not or you want a specific version used, you'll need to point PostGIS at a specific xml2-config confi file to enable software installations to locate the LibXML installation directory. Use this parameter ( >--with-xml2config=/path/to/xml2-config ) to manually specify a particular LibXML installation that PostGIS will build against.

--with-projdir=DIR

Proj4 is a reprojection library required by PostGIS. Use this parameter ( --with-projdir=/path/to/projdir ) to manually specify a particular Proj4 installation directory that PostGIS will build against.

--with-libiconv=DIR

Directory where iconv is installed.

--with-jsondir=DIR

JSON-C is an MIT-licensed JSON library required by PostGIS ST_GeomFromJSON support. Use this parameter ( --with-jsondir=/path/to/jsondir ) to manually specify a particular JSON-C installation directory that PostGIS will build against.

--with-pcredir=DIR

PCRE is an BSD-licensed Perl Compatible Regular Expression library required by address_standardizer extension. Use this parameter ( --with-pcredir=/path/to/pcredir ) to manually specify a particular PCRE installation directory that PostGIS will build against.

--with-gui

Compile the data import GUI (requires GTK+2.0). This will create shp2pgsql-gui graphical interface to shp2pgsql.

--with-raster

Compile with raster support. This will build rtpostgis-2.4.5 library and rtpostgis.sql file. This may not be required in final release as plan is to build in raster support by default.

--without-topology

Disable topology support. There is no corresponding library as all logic needed for topology is in postgis-2.4.5 library.

--with-gettext=no

By default PostGIS will try to detect gettext support and compile with it, however if you run into incompatibility issues that cause breakage of loader, you can disable it entirely with this command. Refer to ticket http://trac.osgeo.org/postgis/ticket/748 for an example issue solved by configuring with this. NOTE: that you aren't missing much by turning this off. This is used for international help/label support for the GUI loader which is not yet documented and still experimental.

--with-sfcgal=PATH

By default PostGIS will not install with sfcgal support without this switch. PATH is an optional argument that allows to specify an alternate PATH to sfcgal-config.

[Note]

If you obtained PostGIS from the SVN repository , the first step is really to run the script

./autogen.sh

This script will generate the configure script that in turn is used to customize the installation of PostGIS.

If you instead obtained PostGIS as a tarball, running ./autogen.sh is not necessary as configure has already been generated.

2.4.2. Building

Once the Makefile has been generated, building PostGIS is as simple as running

make

The last line of the output should be " PostGIS was built successfully. Ready to install. "

As of PostGIS v1.4.0, all the functions have comments generated from the documentation. If you wish to install these comments into your spatial databases later, run the command which requires docbook. The postgis_comments.sql and other package comments files raster_comments.sql, topology_comments.sql are also packaged in the tar.gz distribution in the doc folder so no need to make comments if installing from the tar ball. Comments are also included as part of the CREATE EXTENSION install.

make comments

Introduced in PostGIS 2.0. This generates html cheat sheets suitable for quick reference or for student handouts. This requires xsltproc to build and will generate 4 files in doc folder topology_cheatsheet.html , tiger_geocoder_cheatsheet.html , raster_cheatsheet.html , postgis_cheatsheet.html

You can download some pre-built ones available in html and pdf from PostGIS / PostgreSQL Study Guides

make cheatsheets

2.4.3. Building PostGIS Extensions and Deploying them

The PostGIS extensions are built and installed automatically if you are using PostgreSQL 9.1+.

If you are building from source repository, you need to build the function descriptions first. These get built if you have docbook installed. You can also manually build with the statement:

make comments

Building the comments is not necessary if you are building from a release tar ball since these are packaged pre-built with the tar ball already.

If you are building against PostgreSQL 9.1, the extensions should automatically build as part of the make install process. You can if needed build from the extensions folders or copy files if you need them on a different server.

cd extensions
cd postgis
make clean
make
make install
cd ..
cd postgis_topology
make clean
make
make install
cd ..
cd postgis_sfcgal
make clean
make
make install

cd ..
cd address_standardizer
make clean
make
make install
make installcheck

cd ..
cd postgis_tiger_geocoder
make clean
make
make install
make installcheck
	  

The extension files will always be the same for the same version of PostGIS regardless of OS, so it is fine to copy over the extension files from one OS to another as long as you have the PostGIS binaries already installed on your servers.

If you want to install the extensions manually on a separate server different from your development, You need to copy the following files from the extensions folder into the PostgreSQL / share / extension folder of your PostgreSQL install as well as the needed binaries for regular PostGIS if you don't have them already on the server.

  • These are the control files that denote information such as the version of the extension to install if not specified. postgis.control, postgis_topology.control .

  • All the files in the /sql folder of each extension. Note that these need to be copied to the root of the PostgreSQL share/extension folder extensions/postgis/sql/*.sql , extensions/postgis_topology/sql/*.sql

Once you do that, you should see postgis , postgis_topology as available extensions in PgAdmin -> extensions.

If you are using psql, you can verify that the extensions are installed by running this query:

SELECT name, default_version,installed_version
FROM pg_available_extensions WHERE name LIKE 'postgis%' or name LIKE 'address%';

             name             | default_version | installed_version
------------------------------+-----------------+-------------------
 address_standardizer         | 2.4.5         | 2.4.5
 address_standardizer_data_us | 2.4.5         | 2.4.5
 postgis                      | 2.4.5         | 2.4.5
 postgis_sfcgal               | 2.4.5         |
 postgis_tiger_geocoder       | 2.4.5         | 2.4.5
 postgis_topology             | 2.4.5         |
(6 rows)

If you have the extension installed in the database you are querying, you'll see mention in the installed_version column. If you get no records back, it means you don't have postgis extensions installed on the server at all. PgAdmin III 1.14+ will also provide this information in the extensions section of the database browser tree and will even allow upgrade or uninstall by right-clicking.

If you have the extensions available, you can install postgis extension in your database of choice by either using pgAdmin extension interface or running these sql commands:

CREATE EXTENSION postgis;
CREATE EXTENSION postgis_sfcgal;
CREATE EXTENSION fuzzystrmatch; --needed for postgis_tiger_geocoder
--optional used by postgis_tiger_geocoder, or can be used standalone
CREATE EXTENSION address_standardizer;
CREATE EXTENSION address_standardizer_data_us;
CREATE EXTENSION postgis_tiger_geocoder;
CREATE EXTENSION postgis_topology;

In psql you can use to see what versions you have installed and also what schema they are installed.

\connect mygisdb
\x
\dx postgis*
List of installed extensions
-[ RECORD 1 ]-------------------------------------------------
-
Name        | postgis
Version     | 2.4.5
Schema      | public
Description | PostGIS geometry, geography, and raster spat..
-[ RECORD 2 ]-------------------------------------------------
-
Name        | postgis_tiger_geocoder
Version     | 2.4.5
Schema      | tiger
Description | PostGIS tiger geocoder and reverse geocoder
-[ RECORD 3 ]-------------------------------------------------
-
Name        | postgis_topology
Version     | 2.4.5
Schema      | topology
Description | PostGIS topology spatial types and functions
[Warning]

Extension tables spatial_ref_sys , layer , topology can not be explicitly backed up. They can only be backed up when the respective postgis or postgis_topology extension is backed up, which only seems to happen when you backup the whole database. As of PostGIS 2.0.1, only srid records not packaged with PostGIS are backed up when the database is backed up so don't go around changing srids we package and expect your changes to be there. Put in a ticket if you find an issue. The structures of extension tables are never backed up since they are created with CREATE EXTENSION and assumed to be the same for a given version of an extension. These behaviors are built into the current PostgreSQL extension model, so nothing we can do about it.

If you installed 2.4.5, without using our wonderful extension system, you can change it to be extension based by first upgrading to the latest micro version running the upgrade scripts: postgis_upgrade_22_minor.sql , raster_upgrade_22_minor.sql , topology_upgrade_22_minor.sql .

If you installed postgis without raster support, you'll need to install raster support first (using the full rtpostgis.sql

Then you can run the below commands to package the functions in their respective extension.

CREATE EXTENSION postgis FROM unpackaged;
CREATE EXTENSION postgis_topology FROM unpackaged;
CREATE EXTENSION postgis_tiger_geocoder FROM unpackaged;

2.4.4. Testing

If you wish to test the PostGIS build, run

make check

The above command will run through various checks and regression tests using the generated library against an actual PostgreSQL database.

[Note]

If you configured PostGIS using non-standard PostgreSQL, GEOS, or Proj4 locations, you may need to add their library locations to the LD_LIBRARY_PATH environment variable.

[Caution]

Currently, the make check relies on the PATH and PGPORT environment variables when performing the checks - it does not use the PostgreSQL version that may have been specified using the configuration parameter --with-pgconfig . So make sure to modify your PATH to match the detected PostgreSQL installation during configuration or be prepared to deal with the impending headaches.

If successful, the output of the test should be similar to the following:

    CUnit - A unit testing framework for C - Version 2.1-2
     http://cunit.sourceforge.net/


Suite: computational_geometry
  Test: test_lw_segment_side ...passed
  Test: test_lw_segment_intersects ...passed
  Test: test_lwline_crossing_short_lines ...passed
  Test: test_lwline_crossing_long_lines ...passed
  Test: test_lwline_crossing_bugs ...passed
  Test: test_lwpoint_set_ordinate ...passed
  Test: test_lwpoint_get_ordinate ...passed
  Test: test_point_interpolate ...passed
  Test: test_lwline_clip ...passed
  Test: test_lwline_clip_big ...passed
  Test: test_lwmline_clip ...passed
  Test: test_geohash_point ...passed
  Test: test_geohash_precision ...passed
  Test: test_geohash ...passed
  Test: test_geohash_point_as_int ...passed
  Test: test_isclosed ...passed
  Test: test_lwgeom_simplify ...passed
Suite: buildarea
  Test: buildarea1 ...passed
  Test: buildarea2 ...passed
  Test: buildarea3 ...passed
  Test: buildarea4 ...passed
  Test: buildarea4b ...passed
  Test: buildarea5 ...passed
  Test: buildarea6 ...passed
  Test: buildarea7 ...passed
Suite: geometry_clean
  Test: test_lwgeom_make_valid ...passed
Suite: clip_by_rectangle
  Test: test_lwgeom_clip_by_rect ...passed
Suite: force_sfs
  Test: test_sfs_11 ...passed
  Test: test_sfs_12 ...passed
  Test: test_sqlmm ...passed
Suite: geodetic
  Test: test_sphere_direction ...passed
  Test: test_sphere_project ...passed
  Test: test_lwgeom_area_sphere ...passed
  Test: test_signum ...passed
  Test: test_gbox_from_spherical_coordinates ...passed
  Test: test_gserialized_get_gbox_geocentric ...passed
  Test: test_clairaut ...passed
  Test: test_edge_intersection ...passed
  Test: test_edge_intersects ...passed
  Test: test_edge_distance_to_point ...passed
  Test: test_edge_distance_to_edge ...passed
  Test: test_lwgeom_distance_sphere ...passed
  Test: test_lwgeom_check_geodetic ...passed
  Test: test_gserialized_from_lwgeom ...passed
  Test: test_spheroid_distance ...passed
  Test: test_spheroid_area ...passed
  Test: test_lwpoly_covers_point2d ...passed
  Test: test_gbox_utils ...passed
  Test: test_vector_angle ...passed
  Test: test_vector_rotate ...passed
  Test: test_lwgeom_segmentize_sphere ...passed
  Test: test_ptarray_contains_point_sphere ...passed
  Test: test_ptarray_contains_point_sphere_iowa ...passed
Suite: GEOS
  Test: test_geos_noop ...passed
  Test: test_geos_subdivide ...passed
  Test: test_geos_linemerge ...passed
Suite: Clustering
  Test: basic_test ...passed
  Test: nonsequential_test ...passed
  Test: basic_distance_test ...passed
  Test: single_input_test ...passed
  Test: empty_inputs_test ...passed
Suite: Clustering Union-Find
  Test: test_unionfind_create ...passed
  Test: test_unionfind_union ...passed
  Test: test_unionfind_ordered_by_cluster ...passed
Suite: homogenize
  Test: test_coll_point ...passed
  Test: test_coll_line ...passed
  Test: test_coll_poly ...passed
  Test: test_coll_coll ...passed
  Test: test_geom ...passed
  Test: test_coll_curve ...passed
Suite: encoded_polyline_input
  Test: in_encoded_polyline_test_geoms ...passed
  Test: in_encoded_polyline_test_precision ...passed
Suite: geojson_input
  Test: in_geojson_test_srid ...passed
  Test: in_geojson_test_bbox ...passed
  Test: in_geojson_test_geoms ...passed
Suite: twkb_input
  Test: test_twkb_in_point ...passed
  Test: test_twkb_in_linestring ...passed
  Test: test_twkb_in_polygon ...passed
  Test: test_twkb_in_multipoint ...passed
  Test: test_twkb_in_multilinestring ...passed
  Test: test_twkb_in_multipolygon ...passed
  Test: test_twkb_in_collection ...passed
  Test: test_twkb_in_precision ...passed
Suite: serialization/deserialization
  Test: test_typmod_macros ...passed
  Test: test_flags_macros ...passed
  Test: test_serialized_srid ...passed
  Test: test_gserialized_from_lwgeom_size ...passed
  Test: test_gbox_serialized_size ...passed
  Test: test_lwgeom_from_gserialized ...passed
  Test: test_lwgeom_count_vertices ...passed
  Test: test_on_gser_lwgeom_count_vertices ...passed
  Test: test_geometry_type_from_string ...passed
  Test: test_lwcollection_extract ...passed
  Test: test_lwgeom_free ...passed
  Test: test_lwgeom_flip_coordinates ...passed
  Test: test_f2d ...passed
  Test: test_lwgeom_clone ...passed
  Test: test_lwgeom_force_clockwise ...passed
  Test: test_lwgeom_calculate_gbox ...passed
  Test: test_lwgeom_is_empty ...passed
  Test: test_lwgeom_same ...passed
  Test: test_lwline_from_lwmpoint ...passed
  Test: test_lwgeom_as_curve ...passed
  Test: test_lwgeom_scale ...passed
  Test: test_gserialized_is_empty ...passed
  Test: test_gbox_same_2d ...passed
Suite: measures
  Test: test_mindistance2d_tolerance ...passed
  Test: test_rect_tree_contains_point ...passed
  Test: test_rect_tree_intersects_tree ...passed
  Test: test_lwgeom_segmentize2d ...passed
  Test: test_lwgeom_locate_along ...passed
  Test: test_lw_dist2d_pt_arc ...passed
  Test: test_lw_dist2d_seg_arc ...passed
  Test: test_lw_dist2d_arc_arc ...passed
  Test: test_lw_arc_length ...passed
  Test: test_lw_dist2d_pt_ptarrayarc ...passed
  Test: test_lw_dist2d_ptarray_ptarrayarc ...passed
  Test: test_lwgeom_tcpa ...passed
  Test: test_lwgeom_is_trajectory ...passed
Suite: effectivearea
  Test: do_test_lwgeom_effectivearea_lines ...passed
  Test: do_test_lwgeom_effectivearea_polys ...passed
Suite: miscellaneous
  Test: test_misc_force_2d ...passed
  Test: test_misc_simplify ...passed
  Test: test_misc_count_vertices ...passed
  Test: test_misc_area ...passed
  Test: test_misc_wkb ...passed
  Test: test_grid ...passed
Suite: noding
  Test: test_lwgeom_node ...passed
Suite: encoded_polyline_output
  Test: out_encoded_polyline_test_geoms ...passed
  Test: out_encoded_polyline_test_srid ...passed
  Test: out_encoded_polyline_test_precision ...passed
Suite: geojson_output
  Test: out_geojson_test_precision ...passed
  Test: out_geojson_test_dims ...passed
  Test: out_geojson_test_srid ...passed
  Test: out_geojson_test_bbox ...passed
  Test: out_geojson_test_geoms ...passed
Suite: gml_output
  Test: out_gml_test_precision ...passed
  Test: out_gml_test_srid ...passed
  Test: out_gml_test_dims ...passed
  Test: out_gml_test_geodetic ...passed
  Test: out_gml_test_geoms ...passed
  Test: out_gml_test_geoms_prefix ...passed
  Test: out_gml_test_geoms_nodims ...passed
  Test: out_gml2_extent ...passed
  Test: out_gml3_extent ...passed
Suite: kml_output
  Test: out_kml_test_precision ...passed
  Test: out_kml_test_dims ...passed
  Test: out_kml_test_geoms ...passed
  Test: out_kml_test_prefix ...passed
Suite: svg_output
  Test: out_svg_test_precision ...passed
  Test: out_svg_test_dims ...passed
  Test: out_svg_test_relative ...passed
  Test: out_svg_test_geoms ...passed
  Test: out_svg_test_srid ...passed
Suite: x3d_output
  Test: out_x3d3_test_precision ...passed
  Test: out_x3d3_test_geoms ...passed
  Test: out_x3d3_test_option ...passed
Suite: ptarray
  Test: test_ptarray_append_point ...passed
  Test: test_ptarray_append_ptarray ...passed
  Test: test_ptarray_locate_point ...passed
  Test: test_ptarray_isccw ...passed
  Test: test_ptarray_signed_area ...passed
  Test: test_ptarray_unstroke ...passed
  Test: test_ptarray_insert_point ...passed
  Test: test_ptarray_contains_point ...passed
  Test: test_ptarrayarc_contains_point ...passed
  Test: test_ptarray_scale ...passed
Suite: printing
  Test: test_lwprint_default_format ...passed
  Test: test_lwprint_format_orders ...passed
  Test: test_lwprint_optional_format ...passed
  Test: test_lwprint_oddball_formats ...passed
  Test: test_lwprint_bad_formats ...passed
Suite: SFCGAL
  Test: test_sfcgal_noop ...passed
Suite: split
  Test: test_lwline_split_by_point_to ...passed
  Test: test_lwgeom_split ...passed
Suite: stringbuffer
  Test: test_stringbuffer_append ...passed
  Test: test_stringbuffer_aprintf ...passed
Suite: surface
  Test: triangle_parse ...passed
  Test: tin_parse ...passed
  Test: polyhedralsurface_parse ...passed
  Test: surface_dimension ...passed
Suite: Internal Spatial Trees
  Test: test_tree_circ_create ...passed
  Test: test_tree_circ_pip ...passed
  Test: test_tree_circ_pip2 ...passed
  Test: test_tree_circ_distance ...passed
  Test: test_tree_circ_distance_threshold ...passed
Suite: triangulate
  Test: test_lwgeom_delaunay_triangulation ...passed
Suite: twkb_output
  Test: test_twkb_out_point ...passed
  Test: test_twkb_out_linestring ...passed
  Test: test_twkb_out_polygon ...passed
  Test: test_twkb_out_multipoint ...passed
  Test: test_twkb_out_multilinestring ...passed
  Test: test_twkb_out_multipolygon ...passed
  Test: test_twkb_out_collection ...passed
  Test: test_twkb_out_idlist ...passed
Suite: varint
  Test: test_zigzag ...passed
  Test: test_varint ...passed
  Test: test_varint_roundtrip ...passed
Suite: wkb_input
  Test: test_wkb_in_point ...passed
  Test: test_wkb_in_linestring ...passed
  Test: test_wkb_in_polygon ...passed
  Test: test_wkb_in_multipoint ...passed
  Test: test_wkb_in_multilinestring ...passed
  Test: test_wkb_in_multipolygon ...passed
  Test: test_wkb_in_collection ...passed
  Test: test_wkb_in_circularstring ...passed
  Test: test_wkb_in_compoundcurve ...passed
  Test: test_wkb_in_curvpolygon ...passed
  Test: test_wkb_in_multicurve ...passed
  Test: test_wkb_in_multisurface ...passed
  Test: test_wkb_in_malformed ...passed
Suite: wkb_output
  Test: test_wkb_out_point ...passed
  Test: test_wkb_out_linestring ...passed
  Test: test_wkb_out_polygon ...passed
  Test: test_wkb_out_multipoint ...passed
  Test: test_wkb_out_multilinestring ...passed
  Test: test_wkb_out_multipolygon ...passed
  Test: test_wkb_out_collection ...passed
  Test: test_wkb_out_circularstring ...passed
  Test: test_wkb_out_compoundcurve ...passed
  Test: test_wkb_out_curvpolygon ...passed
  Test: test_wkb_out_multicurve ...passed
  Test: test_wkb_out_multisurface ...passed
  Test: test_wkb_out_polyhedralsurface ...passed
Suite: wkt_input
  Test: test_wkt_in_point ...passed
  Test: test_wkt_in_linestring ...passed
  Test: test_wkt_in_polygon ...passed
  Test: test_wkt_in_multipoint ...passed
  Test: test_wkt_in_multilinestring ...passed
  Test: test_wkt_in_multipolygon ...passed
  Test: test_wkt_in_collection ...passed
  Test: test_wkt_in_circularstring ...passed
  Test: test_wkt_in_compoundcurve ...passed
  Test: test_wkt_in_curvpolygon ...passed
  Test: test_wkt_in_multicurve ...passed
  Test: test_wkt_in_multisurface ...passed
  Test: test_wkt_in_tin ...passed
  Test: test_wkt_in_polyhedralsurface ...passed
  Test: test_wkt_in_errlocation ...passed
Suite: wkt_output
  Test: test_wkt_out_point ...passed
  Test: test_wkt_out_linestring ...passed
  Test: test_wkt_out_polygon ...passed
  Test: test_wkt_out_multipoint ...passed
  Test: test_wkt_out_multilinestring ...passed
  Test: test_wkt_out_multipolygon ...passed
  Test: test_wkt_out_collection ...passed
  Test: test_wkt_out_circularstring ...passed
  Test: test_wkt_out_compoundcurve ...passed
  Test: test_wkt_out_curvpolygon ...passed
  Test: test_wkt_out_multicurve ...passed
  Test: test_wkt_out_multisurface ...passed

Run Summary:    Type  Total    Ran Passed Failed Inactive
              suites     38     38    n/a      0        0
               tests    251    251    251      0        0
             asserts   2468   2468   2468      0      n/a

Elapsed time =    0.298 seconds

Creating database 'postgis_reg'
Loading PostGIS into 'postgis_reg'
  /projects/postgis/branches/2.2/regress/00-regress-install/share/contrib/postgis/postgis.sql
  /projects/postgis/branches/2.2/regress/00-regress-install/share/contrib/postgis/postgis_comments.sql
Loading SFCGAL into 'postgis_reg'
  /projects/postgis/branches/2.2/regress/00-regress-install/share/contrib/postgis/sfcgal.sql
  /projects/postgis/branches/2.2/regress/00-regress-install/share/contrib/postgis/sfcgal_comments.sql
PostgreSQL 9.4.4, compiled by Visual C++ build 1800, 32-bit
  Postgis 2.2.0dev - r13980 - 2015-08-23 06:13:07
  scripts 2.2.0dev r13980
  GEOS: 3.5.0-CAPI-1.9.0 r4088
  PROJ: Rel. 4.9.1, 04 March 2015
  SFCGAL: 1.1.0

Running tests

 loader/Point .............. ok
 loader/PointM .............. ok
 loader/PointZ .............. ok
 loader/MultiPoint .............. ok
 loader/MultiPointM .............. ok
 loader/MultiPointZ .............. ok
 loader/Arc .............. ok
 loader/ArcM .............. ok
 loader/ArcZ .............. ok
 loader/Polygon .............. ok
 loader/PolygonM .............. ok
 loader/PolygonZ .............. ok
 loader/TSTPolygon ......... ok
 loader/TSIPolygon ......... ok
 loader/TSTIPolygon ......... ok
 loader/PointWithSchema ..... ok
 loader/NoTransPoint ......... ok
 loader/NotReallyMultiPoint ......... ok
 loader/MultiToSinglePoint ......... ok
 loader/ReprojectPts ........ ok
 loader/ReprojectPtsGeog ........ ok
 loader/Latin1 .... ok
 loader/Latin1-implicit .... ok
 loader/mfile .... ok
 dumper/literalsrid ....... ok
 dumper/realtable ....... ok
 affine .. ok
 bestsrid .. ok
 binary .. ok
 boundary .. ok
 cluster .. ok
 concave_hull .. ok
 ctors .. ok
 dump .. ok
 dumppoints .. ok
 empty .. ok
 forcecurve .. ok
 geography .. ok
 in_geohash .. ok
 in_gml .. ok
 in_kml .. ok
 in_encodedpolyline .. ok
 iscollection .. ok
 legacy .. ok
 long_xact .. ok
 lwgeom_regress .. ok
 measures .. ok
 operators .. ok
 out_geometry .. ok
 out_geography .. ok
 polygonize .. ok
 polyhedralsurface .. ok
 postgis_type_name .. ok
 regress .. ok
 regress_bdpoly .. ok
 regress_index .. ok
 regress_index_nulls .. ok
 regress_management .. ok
 regress_selectivity .. ok
 regress_lrs .. ok
 regress_ogc .. ok
 regress_ogc_cover .. ok
 regress_ogc_prep .. ok
 regress_proj .. ok
 relate .. ok
 remove_repeated_points .. ok
 removepoint .. ok
 setpoint .. ok
 simplify .. ok
 simplifyvw .. ok
 size .. ok
 snaptogrid .. ok
 split .. ok
 sql-mm-serialize .. ok
 sql-mm-circularstring .. ok
 sql-mm-compoundcurve .. ok
 sql-mm-curvepoly .. ok
 sql-mm-general .. ok
 sql-mm-multicurve .. ok
 sql-mm-multisurface .. ok
 swapordinates .. ok
 summary .. ok
 temporal .. ok
 tickets .. ok
 twkb .. ok
 typmod .. ok
 wkb .. ok
 wkt .. ok
 wmsservers .. ok
 knn .. ok
 hausdorff .. ok
 regress_buffer_params .. ok
 offsetcurve .. ok
 relatematch .. ok
 isvaliddetail .. ok
 sharedpaths .. ok
 snap .. ok
 node .. ok
 unaryunion .. ok
 clean .. ok
 relate_bnr .. ok
 delaunaytriangles .. ok
 clipbybox2d .. ok
 subdivide .. ok
 in_geojson .. ok
 regress_sfcgal .. ok
 sfcgal/empty .. ok
 sfcgal/geography .. ok
 sfcgal/legacy .. ok
 sfcgal/measures .. ok
 sfcgal/regress_ogc_prep .. ok
 sfcgal/regress_ogc .. ok
 sfcgal/regress .. ok
 sfcgal/tickets .. ok
 sfcgal/concave_hull .. ok
 sfcgal/wmsservers .. ok
 sfcgal/approximatemedialaxis .. ok
 uninstall .  /projects/postgis/branches/2.2/regress/00-regress-install/share/contrib/postgis/uninstall_sfcgal.sql
  /projects/postgis/branches/2.2/regress/00-regress-install/share/contrib/postgis/uninstall_postgis.sql
. ok (4336)

Run tests: 118
Failed: 0

-- if you built --with-gui, you should see this too

     CUnit - A unit testing framework for C - Version 2.1-2
     http://cunit.sourceforge.net/


Suite: Shapefile Loader File shp2pgsql Test
  Test: test_ShpLoaderCreate() ...passed
  Test: test_ShpLoaderDestroy() ...passed
Suite: Shapefile Loader File pgsql2shp Test
  Test: test_ShpDumperCreate() ...passed
  Test: test_ShpDumperDestroy() ...passed

Run Summary:    Type  Total    Ran Passed Failed Inactive
              suites      2      2    n/a      0        0
               tests      4      4      4      0        0
             asserts      4      4      4      0      n/a

The postgis_tiger_geocoder and address_standardizer extensions, currenlty only support the standard PostgreSQL installcheck. To test these use the below. Note: the make install is not necessary if you already did make install at root of PostGIS code folder.

For address_standardizer:

cd extensions/address_standardizer
make install
make installcheck
	  

Output should look like:

============== dropping database "contrib_regression" ==============
DROP DATABASE
============== creating database "contrib_regression" ==============
CREATE DATABASE
ALTER DATABASE
============== running regression test queries        ==============
test test-init-extensions     ... ok
test test-parseaddress        ... ok
test test-standardize_address_1 ... ok
test test-standardize_address_2 ... ok

=====================
 All 4 tests passed.
=====================

For tiger geocoder, make sure you have postgis and fuzzystrmatch extensions available in your PostgreSQL instance. The address_standardizer tests will also kick in if you built postgis with address_standardizer support:

cd extensions/postgis_tiger_geocoder
make install
make installcheck
	  

output should look like:

============== dropping database "contrib_regression" ==============
DROP DATABASE
============== creating database "contrib_regression" ==============
CREATE DATABASE
ALTER DATABASE
============== installing fuzzystrmatch               ==============
CREATE EXTENSION
============== installing postgis                     ==============
CREATE EXTENSION
============== installing postgis_tiger_geocoder      ==============
CREATE EXTENSION
============== installing address_standardizer        ==============
CREATE EXTENSION
============== running regression test queries        ==============
test test-normalize_address   ... ok
test test-pagc_normalize_address ... ok

=====================
All 2 tests passed.
=====================

2.4.5. Installation

To install PostGIS, type

make install

This will copy the PostGIS installation files into their appropriate subdirectory specified by the --prefix configuration parameter. In particular:

  • The loader and dumper binaries are installed in [prefix]/bin .

  • The SQL files, such as postgis.sql , are installed in [prefix]/share/contrib .

  • The PostGIS libraries are installed in [prefix]/lib .

If you previously ran the make comments command to generate the postgis_comments.sql , raster_comments.sql file, install the sql file by running

make comments-install

[Note]

postgis_comments.sql , raster_comments.sql , topology_comments.sql was separated from the typical build and installation targets since with it comes the extra dependency of xsltproc .

2.5. Creating a spatial database using EXTENSIONS

If you are using PostgreSQL 9.1+ and have compiled and installed the extensions/ postgis modules, you can create a spatial database the new way.

createdb [yourdatabase]

The core postgis extension installs PostGIS geometry, geography, raster, spatial_ref_sys and all the functions and comments with a simple:

CREATE EXTENSION postgis;

command.

psql -d [yourdatabase] -c "CREATE EXTENSION postgis;"

Topology is packaged as a separate extension and installable with command:

psql -d [yourdatabase] -c "CREATE EXTENSION postgis_topology;"

If you plan to restore an old backup from prior versions in this new db, run:

psql -d [yourdatabase] -f legacy.sql

[Note]

If you need legacy functions, you'll need to reinstall the legacy.sql script whenever you upgrade the minor version of PostGIS. E.g. if you upgraded from 2.3.7 to 2.4.4, then you need to reinstall the legacy.sql packaged with 2.4.4. This is because some of the functions make reference to the library and the library is named with the minor in it.

You can later run uninstall_legacy.sql to get rid of the deprecated functions after you are done with restoring and cleanup.

2.6. Create a spatially-enabled database without using extensions

[Note]

This is generally only needed if you built-PostGIS without raster support. Since raster functions are part of the postgis extension, extension support is not enabled if PostGIS is built without raster.

The first step in creating a PostGIS database is to create a simple PostgreSQL database.

createdb [yourdatabase]

Many of the PostGIS functions are written in the PL/pgSQL procedural language. As such, the next step to create a PostGIS database is to enable the PL/pgSQL language in your new database. This is accomplish by the command below command. For PostgreSQL 8.4+, this is generally already installed

createlang plpgsql [yourdatabase]

Now load the PostGIS object and function definitions into your database by loading the postgis.sql definitions file (located in [prefix]/share/contrib as specified during the configuration step).

psql -d [yourdatabase] -f postgis.sql

For a complete set of EPSG coordinate system definition identifiers, you can also load the spatial_ref_sys.sql definitions file and populate the spatial_ref_sys table. This will permit you to perform ST_Transform() operations on geometries.

psql -d [yourdatabase] -f spatial_ref_sys.sql

If you wish to add comments to the PostGIS functions, the final step is to load the postgis_comments.sql into your spatial database. The comments can be viewed by simply typing \dd [function_name] from a psql terminal window.

psql -d [yourdatabase] -f postgis_comments.sql

Install raster support

psql -d [yourdatabase] -f rtpostgis.sql

Install raster support comments. This will provide quick help info for each raster function using psql or PgAdmin or any other PostgreSQL tool that can show function comments

psql -d [yourdatabase] -f raster_comments.sql

Install topology support

psql -d [yourdatabase] -f topology/topology.sql

Install topology support comments. This will provide quick help info for each topology function / type using psql or PgAdmin or any other PostgreSQL tool that can show function comments

psql -d [yourdatabase] -f topology/topology_comments.sql

If you plan to restore an old backup from prior versions in this new db, run:

psql -d [yourdatabase] -f legacy.sql

[Note]

There is an alternative legacy_minimal.sql you can run instead which will install barebones needed to recover tables and work with apps like MapServer and GeoServer. If you have views that use things like distance / length etc, you'll need the full blown legacy.sql

You can later run uninstall_legacy.sql to get rid of the deprecated functions after you are done with restoring and cleanup.

2.7. Installing and Using the address standardizer

The address_standardizer extension used to be a separate package that required separate download. From PostGIS 2.2 on, it is now bundled in. For more information about the address_standardize, what it does, and how to configure it for your needs, refer to Chapter 12, Address Standardizer .

This standardizer can be used in conjunction with the PostGIS packaged tiger geocoder extension as a replacement for the Normalize_Address discussed. To use as replacement refer to Section 2.8.3, “Using Address Standardizer Extension with Tiger geocoder” . You can also use it as a building block for your own geocoder or use it to standardize your addresses for easier compare of addresses.

The address standardizer relies on PCRE which is usually already installed on many Nix systems, but you can download the latest at: http://www.pcre.org . If during Section 2.4.1, “Configuration” , PCRE is found, then the address standardizer extension will automatically be built. If you have a custom pcre install you want to use instead, pass to configure --with-pcredir=/path/to/pcre where /path/to/pcre is the root folder for your pcre include and lib directories.

For Windows users, the PostGIS 2.1+ bundle is packaged with the address_standardizer already so no need to compile and can move straight to CREATE EXTENSION step.

Once you have installed, you can connect to your database and run the SQL:

CREATE EXTENSION address_standardizer;

The following test requires no rules, gaz, or lex tables

SELECT num, street, city, state, zip
 FROM parse_address('1 Devonshire Place PH301, Boston, MA 02109');

Output should be

 num |         street         |  city  | state |  zip
-----+------------------------+--------+-------+-------
 1   | Devonshire Place PH301 | Boston | MA    | 02109

2.7.1. Installing Regex::Assemble

Perl Regex:Assemble is no longer needed for compiling address_standardizer extension since the files it generates are part of the source tree. However if you need to edit the usps-st-city-orig.txt or usps-st-city-orig.txt usps-st-city-adds.tx , you need to rebuild parseaddress-stcities.h which does require Regex:Assemble.

cpan Regexp::Assemble

or if you are on Ubuntu / Debian you might need to do

sudo perl -MCPAN -e "install Regexp::Assemble"

2.8. Installing, Upgrading Tiger Geocoder and loading data

Extras like Tiger geocoder may not be packaged in your PostGIS distribution. If you are missing the tiger geocoder extension or want a newer version than what your install comes with, then use the share/extension/postgis_tiger_geocoder.* files from the packages in Windows Unreleased Versions section for your version of PostgreSQL. Although these packages are for windows, the postgis_tiger_geocoder extension files will work on any OS since the extension is an SQL/plpgsql only extension.

2.8.1. Tiger Geocoder Enabling your PostGIS database: Using Extension

If you are using PostgreSQL 9.1+ and PostGIS 2.1+, you can take advantage of the new extension model for installing tiger geocoder. To do so:

  1. First get binaries for PostGIS 2.1+ or compile and install as usual. This should install the necessary extension files as well for tiger geocoder.

  2. Connect to your database via psql or pgAdmin or some other tool and run the following SQL commands. Note that if you are installing in a database that already has postgis, you don't need to do the first step. If you have fuzzystrmatch extension already installed, you don't need to do the second step either.

    CREATE EXTENSION postgis;
    CREATE EXTENSION fuzzystrmatch;
    CREATE EXTENSION postgis_tiger_geocoder;
    --this one is optional if you want to use the rules based standardizer (pagc_normalize_address)
    CREATE EXTENSION address_standardizer;

    If you already have postgis_tiger_geocoder extension installed, and just want to update to the latest run:

    ALTER EXTENSION postgis UPDATE;
    ALTER EXTENSION postgis_tiger_geocoder UPDATE;

    If you made custom entries or changes to tiger.loader_platform and tiger.loader_variables you may need to update these.

  3. To confirm your install is working correctly, run this sql in your database:

    SELECT na.address, na.streetname,na.streettypeabbrev, na.zip
    	FROM normalize_address('1 Devonshire Place, Boston, MA 02109') AS na;

    Which should output

     address | streetname | streettypeabbrev |  zip
    ---------+------------+------------------+-------
    	   1 | Devonshire | Pl               | 02109
  4. Create a new record in tiger.loader_platform table with the paths of your executables and server.

    So for example to create a profile called debbie that follows sh convention. You would do:

    INSERT INTO tiger.loader_platform(os, declare_sect, pgbin, wget, unzip_command, psql, path_sep,
    		   loader, environ_set_command, county_process_command)
    SELECT 'debbie', declare_sect, pgbin, wget, unzip_command, psql, path_sep,
    	   loader, environ_set_command, county_process_command
      FROM tiger.loader_platform
      WHERE os = 'sh';

    And then edit the paths in the declare_sect column to those that fit Debbie's pg, unzip,shp2pgsql, psql, etc path locations.

    If you don't edit this loader_platform table, it will just contain common case locations of items and you'll have to edit the generated script after the script is generated.

  5. As of PostGIS 2.4.1 the Zip code-5 digit tabulation area zcta5 load step was revised to load current zcta5 data and is part of the Loader_Generate_Nation_Script when enabled. It is turned off by default because it takes quite a bit of time to load (20 to 60 minutes), takes up quite a bit of disk space, and is not used that often.

    To enable it, do the following:

    UPDATE tiger.loader_lookuptables SET load = true WHERE table_name = 'zcta510';

    If present the Geocode function can use it if a boundary filter is added to limit to just zips in that boundary. The Reverse_Geocode function uses it if the returned address is missing a zip, which often happens with highway reverse geocoding.

  6. Create a folder called gisdata on root of server or your local pc if you have a fast network connection to the server. This folder is where the tiger files will be downloaded to and processed. If you are not happy with having the folder on the root of the server, or simply want to change to a different folder for staging, then edit the field staging_fold in the tiger.loader_variables table.

  7. Create a folder called temp in the gisdata folder or whereever you designated the staging_fold to be. This will be the folder where the loader extracts the downloaded tiger data.

  8. Then run the Loader_Generate_Nation_Script SQL function make sure to use the name of your custom profile and copy the script to a .sh or .bat file. So for example to build the nation load:

    psql -c "SELECT Loader_Generate_Nation_Script('debbie')" -d geocoder -tA > /gisdata/nation_script_load.sh
  9. Run the generated nation load commandline scripts.

    cd /gisdata
    sh nation_script_load.sh
  10. After you are done running the nation script, you should have three tables in your tiger_data schema and they should be filled with data. Confirm you do by doing the following queries from psql or pgAdmin

    SELECT count(*) FROM tiger_data.county_all;
     count
    -------
      3233
    (1 row)
    SELECT count(*) FROM tiger_data.state_all;
     count
    -------
        56
    (1 row)
    
  11. By default the tables corresponding to bg , tract , tabblock are not loaded. These tables are not used by the geocoder but are used by folks for population statistics. If you wish to load them as part of your state loads, run the following statement to enable them.

    UPDATE tiger.loader_lookuptables SET load = true WHERE load = false AND lookup_name IN('tract', 'bg', 'tabblock');

    Alternatively you can load just these tables after loading state data using the Loader_Generate_Census_Script

  12. For each state you want to load data for, generate a state script Loader_Generate_Script .

    [Warning]

    DO NOT Generate the state script until you have already loaded the nation data, because the state script utilizes county list loaded by nation script.

  13. psql -c "SELECT Loader_Generate_Script(ARRAY['MA'], 'debbie')" -d geocoder -tA > /gisdata/ma_load.sh
  14. Run the generated commandline scripts.

    cd /gisdata
    sh ma_load.sh
  15. After you are done loading all data or at a stopping point, it's a good idea to analyze all the tiger tables to update the stats (include inherited stats)

    SELECT install_missing_indexes();
    vacuum analyze verbose tiger.addr;
    vacuum analyze verbose tiger.edges;
    vacuum analyze verbose tiger.faces;
    vacuum analyze verbose tiger.featnames;
    vacuum analyze verbose tiger.place;
    vacuum analyze verbose tiger.cousub;
    vacuum analyze verbose tiger.county;
    vacuum analyze verbose tiger.state;
    vacuum analyze verbose tiger.zip_lookup_base;
    vacuum analyze verbose tiger.zip_state;
    vacuum analyze verbose tiger.zip_state_loc;

2.8.1.1. Converting a Tiger Geocoder Regular Install to Extension Model

If you installed the tiger geocoder without using the extension model, you can convert to the extension model as follows:

  1. Follow instructions in Section 2.8.5, “Upgrading your Tiger Geocoder Install” for the non-extension model upgrade.

  2. Connect to your database with psql or pgAdmin and run the following command:

    CREATE EXTENSION postgis_tiger_geocoder FROM unpackaged;

2.8.2. Tiger Geocoder Enabling your PostGIS database: Not Using Extensions

First install PostGIS using the prior instructions.

If you don't have an extras folder, download http://download.osgeo.org/postgis/source/postgis-2.4.5.tar.gz

tar xvfz postgis-2.4.5.tar.gz

cd postgis-2.4.5/extras/tiger_geocoder

Edit the tiger_loader_2015.sql (or latest loader file you find, unless you want to load different year) to the paths of your executables server etc or alternatively you can update the loader_platform table once installed. If you don't edit this file or the loader_platform table, it will just contain common case locations of items and you'll have to edit the generated script after the fact when you run the Loader_Generate_Nation_Script and Loader_Generate_Script SQL functions.

If you are installing Tiger geocoder for the first time edit either the create_geocode.bat script If you are on windows or the create_geocode.sh if you are on Linux/Unix/Mac OSX with your PostgreSQL specific settings and run the corresponding script from the commandline.

Verify that you now have a tiger schema in your database and that it is part of your database search_path. If it is not, add it with a command something along the line of:

ALTER DATABASE geocoder SET search_path=public, tiger;

The normalizing address functionality works more or less without any data except for tricky addresses. Run this test and verify things look like this:

SELECT pprint_addy(normalize_address('202 East Fremont Street, Las Vegas, Nevada 89101')) As pretty_address;
pretty_address
---------------------------------------
202 E Fremont St, Las Vegas, NV 89101
			

2.8.3. Using Address Standardizer Extension with Tiger geocoder

One of the many complaints of folks is the address normalizer function Normalize_Address function that normalizes an address for prepping before geocoding. The normalizer is far from perfect and trying to patch its imperfectness takes a vast amount of resources. As such we have integrated with another project that has a much better address standardizer engine. To use this new address_standardizer, you compile the extension as described in Section 2.7, “Installing and Using the address standardizer” and install as an extension in your database.

Once you install this extension in the same database as you have installed postgis_tiger_geocoder , then the Pagc_Normalize_Address can be used instead of Normalize_Address . This extension is tiger agnostic, so can be used with other data sources such as international addresses. The tiger geocoder extension does come packaged with its own custom versions of rules table ( tiger.pagc_rules ) , gaz table ( tiger.pagc_gaz ), and lex table ( tiger.pagc_lex ). These you can add and update to improve your standardizing experience for your own needs.

2.8.4. Loading Tiger Data

The instructions for loading data are available in a more detailed form in the extras/tiger_geocoder/tiger_2011/README . This just includes the general steps.

The load process downloads data from the census website for the respective nation files, states requested, extracts the files, and then loads each state into its own separate set of state tables. Each state table inherits from the tables defined in tiger schema so that its sufficient to just query those tables to access all the data and drop a set of state tables at any time using the Drop_State_Tables_Generate_Script if you need to reload a state or just don't need a state anymore.

In order to be able to load data you'll need the following tools:

  • A tool to unzip the zip files from census website.

    For Unix like systems: unzip executable which is usually already installed on most Unix like platforms.

    For Windows, 7-zip which is a free compress/uncompress tool you can download from http://www.7-zip.org/

  • shp2pgsql commandline which is installed by default when you install PostGIS.

  • wget which is a web grabber tool usually installed on most Unix/Linux systems.

    If you are on windows, you can get pre-compiled binaries from http://gnuwin32.sourceforge.net/packages/wget.htm

If you are upgrading from tiger_2010, you'll need to first generate and run Drop_Nation_Tables_Generate_Script . Before you load any state data, you need to load the nation wide data which you do with Loader_Generate_Nation_Script . Which will generate a loader script for you. Loader_Generate_Nation_Script is a one-time step that should be done for upgrading (from 2010) and for new installs.

To load state data refer to Loader_Generate_Script to generate a data load script for your platform for the states you desire. Note that you can install these piecemeal. You don't have to load all the states you want all at once. You can load them as you need them.

After the states you desire have been loaded, make sure to run the:

SELECT install_missing_indexes();

as described in Install_Missing_Indexes .

To test that things are working as they should, try to run a geocode on an address in your state using Geocode

2.8.5. Upgrading your Tiger Geocoder Install

If you have Tiger Geocoder packaged with 2.0+ already installed, you can upgrade the functions at any time even from an interim tar ball if there are fixes you badly need. This will only work for Tiger geocoder not installed with extensions.

If you don't have an extras folder, download http://download.osgeo.org/postgis/source/postgis-2.4.5.tar.gz

tar xvfz postgis-2.4.5.tar.gz

cd postgis-2.4.5/extras/tiger_geocoder/tiger_2011

Locate the upgrade_geocoder.bat script If you are on windows or the upgrade_geocoder.sh if you are on Linux/Unix/Mac OSX. Edit the file to have your postgis database credentials.

If you are upgrading from 2010 or 2011, make sure to unremark out the loader script line so you get the latest script for loading 2012 data.

Then run th corresponding script from the commandline.

Next drop all nation tables and load up the new ones. Generate a drop script with this SQL statement as detailed in Drop_Nation_Tables_Generate_Script

SELECT drop_nation_tables_generate_script();

Run the generated drop SQL statements.

Generate a nation load script with this SELECT statement as detailed in Loader_Generate_Nation_Script

For windows

SELECT loader_generate_nation_script('windows'); 

For unix/linux

SELECT loader_generate_nation_script('sh');

Refer to Section 2.8.4, “Loading Tiger Data” for instructions on how to run the generate script. This only needs to be done once.

[Note]

You can have a mix of 2010/2011 state tables and can upgrade each state separately. Before you upgrade a state to 2011, you first need to drop the 2010 tables for that state using Drop_State_Tables_Generate_Script .

2.9. Create a spatially-enabled database from a template

Some packaged distributions of PostGIS (in particular the Win32 installers for PostGIS >= 1.1.5) load the PostGIS functions into a template database called template_postgis . If the template_postgis database exists in your PostgreSQL installation then it is possible for users and/or applications to create spatially-enabled databases using a single command. Note that in both cases, the database user must have been granted the privilege to create new databases.

From the shell:

# createdb -T template_postgis my_spatial_db

From SQL:

postgres=# CREATE DATABASE my_spatial_db TEMPLATE=template_postgis

2.10. Upgrading

Upgrading existing spatial databases can be tricky as it requires replacement or introduction of new PostGIS object definitions.

Unfortunately not all definitions can be easily replaced in a live database, so sometimes your best bet is a dump/reload process.

PostGIS provides a SOFT UPGRADE procedure for minor or bugfix releases, and a HARD UPGRADE procedure for major releases.

Before attempting to upgrade PostGIS, it is always worth to backup your data. If you use the -Fc flag to pg_dump you will always be able to restore the dump with a HARD UPGRADE.

2.10.1. Soft upgrade

If you installed your database using extensions, you'll need to upgrade using the extension model as well. If you installed using the old sql script way, then you should upgrade using the sql script way. Please refer to the appropriate.

2.10.1.1. Soft Upgrade Pre 9.1+ or without extensions

This section applies only to those who installed PostGIS not using extensions. If you have extensions and try to upgrade with this approach you'll get messages like:

can't drop ... because postgis extension depends on it

After compiling and installing (make install) you should find a postgis_upgrade.sql and rtpostgis_upgrade.sql in the installation folders. For example /usr/share/postgresql/9.3/contrib/postgis_upgrade.sql . Install the postgis_upgrade.sql . If you have raster functionality installed, you will also need to install the /usr/share/postgresql/9.3/contrib/postgis_upgrade.sql . If you are moving from PostGIS 1.* to PostGIS 2.* or from PostGIS 2.* prior to r7409, you need to do a HARD UPGRADE.

psql -f postgis_upgrade.sql -d your_spatial_database

The same procedure applies to raster and topology extensions, with upgrade files named rtpostgis_upgrade*.sql and topology_upgrade*.sql respectively. If you need them:

psql -f rtpostgis_upgrade.sql -d your_spatial_database
psql -f topology_upgrade.sql -d your_spatial_database
[Note]

If you can't find the postgis_upgrade*.sql specific for upgrading your version you are using a version too early for a soft upgrade and need to do a HARD UPGRADE.

The PostGIS_Full_Version function should inform you about the need to run this kind of upgrade using a "procs need upgrade" message.

2.10.1.2. Soft Upgrade 9.1+ using extensions

If you originally installed PostGIS with extensions, then you need to upgrade using extensions as well. Doing a minor upgrade with extensions, is fairly painless.

ALTER EXTENSION postgis UPDATE TO "2.4.5";
ALTER EXTENSION postgis_topology UPDATE TO "2.4.5";

If you get an error notice something like:

No migration path defined for ... to 2.4.5

Then you'll need to backup your database, create a fresh one as described in Section 2.5, “Creating a spatial database using EXTENSIONS” and then restore your backup ontop of this new database.

If you get a notice message like:

Version "2.4.5" of extension "postgis" is already installed

Then everything is already up to date and you can safely ignore it. UNLESS you're attempting to upgrade from an SVN version to the next (which doesn't get a new version number); in that case you can append "next" to the version string, and next time you'll need to drop the "next" suffix again:

ALTER EXTENSION postgis UPDATE TO "2.4.5next";
ALTER EXTENSION postgis_topology UPDATE TO "2.4.5next";
[Note]

If you installed PostGIS originally without a version specified, you can often skip the reinstallation of postgis extension before restoring since the backup just has CREATE EXTENSION postgis and thus picks up the newest latest version during restore.

2.10.2. Hard upgrade

By HARD UPGRADE we mean full dump/reload of postgis-enabled databases. You need a HARD UPGRADE when PostGIS objects' internal storage changes or when SOFT UPGRADE is not possible. The Release Notes appendix reports for each version whether you need a dump/reload (HARD UPGRADE) to upgrade.

The dump/reload process is assisted by the postgis_restore.pl script which takes care of skipping from the dump all definitions which belong to PostGIS (including old ones), allowing you to restore your schemas and data into a database with PostGIS installed without getting duplicate symbol errors or bringing forward deprecated objects.

Supplementary instructions for windows users are available at Windows Hard upgrade .

The Procedure is as follows:

  1. Create a "custom-format" dump of the database you want to upgrade (let's call it olddb ) include binary blobs (-b) and verbose (-v) output. The user can be the owner of the db, need not be postgres super account.

    pg_dump -h localhost -p 5432 -U postgres -Fc -b -v -f "/somepath/olddb.backup" olddb
  2. Do a fresh install of PostGIS in a new database -- we'll refer to this database as newdb . Please refer to Section 2.6, “Create a spatially-enabled database without using extensions” and Section 2.5, “Creating a spatial database using EXTENSIONS” for instructions on how to do this.

    The spatial_ref_sys entries found in your dump will be restored, but they will not override existing ones in spatial_ref_sys. This is to ensure that fixes in the official set will be properly propagated to restored databases. If for any reason you really want your own overrides of standard entries just don't load the spatial_ref_sys.sql file when creating the new db.

    If your database is really old or you know you've been using long deprecated functions in your views and functions, you might need to load legacy.sql for all your functions and views etc. to properly come back. Only do this if _really_ needed. Consider upgrading your views and functions before dumping instead, if possible. The deprecated functions can be later removed by loading uninstall_legacy.sql .

  3. Restore your backup into your fresh newdb database using postgis_restore.pl. Unexpected errors, if any, will be printed to the standard error stream by psql. Keep a log of those.

    perl utils/postgis_restore.pl "/somepath/olddb.backup" | psql -h localhost -p 5432 -U postgres newdb 2> errors.txt

Errors may arise in the following cases:

  1. Some of your views or functions make use of deprecated PostGIS objects. In order to fix this you may try loading legacy.sql script prior to restore or you'll have to restore to a version of PostGIS which still contains those objects and try a migration again after porting your code. If the legacy.sql way works for you, don't forget to fix your code to stop using deprecated functions and drop them loading uninstall_legacy.sql .

  2. Some custom records of spatial_ref_sys in dump file have an invalid SRID value. Valid SRID values are bigger than 0 and smaller than 999000. Values in the 999000.999999 range are reserved for internal use while values > 999999 can't be used at all. All your custom records with invalid SRIDs will be retained, with those > 999999 moved into the reserved range, but the spatial_ref_sys table would lose a check constraint guarding for that invariant to hold and possibly also its primary key ( when multiple invalid SRIDS get converted to the same reserved SRID value ).

    In order to fix this you should copy your custom SRS to a SRID with a valid value (maybe in the 910000..910999 range), convert all your tables to the new srid (see UpdateGeometrySRID ), delete the invalid entry from spatial_ref_sys and re-construct the check(s) with:

    ALTER TABLE spatial_ref_sys ADD CONSTRAINT spatial_ref_sys_srid_check check (srid > 0 AND srid < 999000 );

    ALTER TABLE spatial_ref_sys ADD PRIMARY KEY(srid));

2.11. Common Problems during installation

There are several things to check when your installation or upgrade doesn't go as you expected.

  1. Check that you have installed PostgreSQL 9.3 or newer, and that you are compiling against the same version of the PostgreSQL source as the version of PostgreSQL that is running. Mix-ups can occur when your (Linux) distribution has already installed PostgreSQL, or you have otherwise installed PostgreSQL before and forgotten about it. PostGIS will only work with PostgreSQL 9.3 or newer, and strange, unexpected error messages will result if you use an older version. To check the version of PostgreSQL which is running, connect to the database using psql and run this query:

    SELECT version();

    If you are running an RPM based distribution, you can check for the existence of pre-installed packages using the rpm command as follows: rpm -qa | grep postgresql

  2. If your upgrade fails, make sure you are restoring into a database that already has PostGIS installed.

    SELECT postgis_full_version();

Also check that configure has correctly detected the location and version of PostgreSQL, the Proj4 library and the GEOS library.

  1. The output from configure is used to generate the postgis_config.h file. Check that the POSTGIS_PGSQL_VERSION , POSTGIS_PROJ_VERSION and POSTGIS_GEOS_VERSION variables have been set correctly.

2.12. Loader/Dumper

The data loader and dumper are built and installed automatically as part of the PostGIS build. To build and install them manually:

# cd postgis-2.4.5/loader
# make
# make install

The loader is called shp2pgsql and converts ESRI Shape files into SQL suitable for loading in PostGIS/PostgreSQL. The dumper is called pgsql2shp and converts PostGIS tables (or queries) into ESRI Shape files. For more verbose documentation, see the online help, and the manual pages.

Chapter 3. PostGIS Frequently Asked Questions

3.1. Where can I find tutorials, guides and workshops on working with PostGIS
3.2. My applications and desktop tools worked with PostGIS 1.5,but they don't work with PostGIS 2.0. How do I fix this?
3.3. When I load OpenStreetMap data with osm2pgsql, I'm getting an error failed: ERROR: operator class "gist_geometry_ops" does not exist for access method "gist" Error occurred. This worked fine in PostGIS 1.5.
3.4. I'm running PostgreSQL 9.0 and I can no longer read/view geometries in OpenJump, Safe FME, and some other tools?
3.5. I tried to use PgAdmin to view my geometry column and it is blank, what gives?
3.6. What kind of geometric objects can I store?
3.7. I'm all confused. Which data store should I use geometry or geography?
3.8. I have more intense questions about geography, such as how big of a geographic region can I stuff in a geography column and still get reasonable answers. Are there limitations such as poles, everything in the field must fit in a hemisphere (like SQL Server 2008 has), speed etc?
3.9. How do I insert a GIS object into the database?
3.10. How do I construct a spatial query?
3.11. How do I speed up spatial queries on large tables?
3.12. Why aren't PostgreSQL R-Tree indexes supported?
3.13. Why should I use the AddGeometryColumn() function and all the other OpenGIS stuff?
3.14. What is the best way to find all objects within a radius of another object?
3.15. How do I perform a coordinate reprojection as part of a query?
3.16. I did an ST_AsEWKT and ST_AsText on my rather large geometry and it returned blank field. What gives?
3.17. When I do an ST_Intersects, it says my two geometries don't intersect when I KNOW THEY DO. What gives?
3.18. I am releasing software that uses PostGIS, does that mean my software has to be licensed using the GPL like PostGIS? Will I have to publish all my code if I use PostGIS?

3.1.

Where can I find tutorials, guides and workshops on working with PostGIS

OpenGeo has a step by step tutorial guide workshop Introduction to PostGIS . It includes packaged data as well as intro to working with OpenGeo Suite. It is probably the best tutorial on PostGIS.

BostonGIS also has a PostGIS almost idiot's guide on getting started . That one is more focused on the windows user.

3.2.

My applications and desktop tools worked with PostGIS 1.5,but they don't work with PostGIS 2.0. How do I fix this?

A lot of deprecated functions were removed from the PostGIS code base in PostGIS 2.0. This has affected applications in addition to third-party tools such as Geoserver, MapServer, QuantumGIS, and OpenJump to name a few. There are a couple of ways to resolve this. For the third-party apps, you can try to upgrade to the latest versions of these which have many of these issues fixed. For your own code, you can change your code to not use the functions removed. Most of these functions are non ST_ aliases of ST_Union, ST_Length etc. and as a last resort, install the whole of legacy.sql or just the portions of legacy.sql you need.

The legacy.sql file is located in the same folder as postgis.sql. You can install this file after you have installed postgis.sql and spatial_ref_sys.sql to get back all the 200 some-odd old functions we removed.

3.3.

When I load OpenStreetMap data with osm2pgsql, I'm getting an error failed: ERROR: operator class "gist_geometry_ops" does not exist for access method "gist" Error occurred. This worked fine in PostGIS 1.5.

In PostGIS 2, the default geometry operator class gist_geometry_ops was changed to gist_geometry_ops_2d and the gist_geometry_ops was completely removed. This was done because PostGIS 2 also introduced Nd spatial indexes for 3D support and the old name was deemed confusing and a misnomer.

Some older applications that as part of the process create tables and indexes, explicitly referenced the operator class name. This was unnecessary if you want the default 2D index. So if you manage said good, change index creation from:

BAD:

CREATE INDEX idx_my_table_geom ON my_table USING gist(geom gist_geometry_ops);

To GOOD:

CREATE INDEX idx_my_table_geom ON my_table USING gist(geom);

The only case where you WILL need to specify the operator class is if you want a 3D spatial index as follows:

CREATE INDEX idx_my_super3d_geom ON my_super3d USING gist(geom gist_geometry_ops_nd);

If you are unfortunate to be stuck with compiled code you can't change that has the old gist_geometry_ops hard-coded, then you can create the old class using the legacy_gist.sql packaged in PostGIS 2.0.2+. However if you use this fix, you are advised to at a later point drop the index and recreate it without the operator class. This will save you grief in the future when you need to upgrade again.

3.4.

I'm running PostgreSQL 9.0 and I can no longer read/view geometries in OpenJump, Safe FME, and some other tools?

In PostgreSQL 9.0+, the default encoding for bytea data has been changed to hex and older JDBC drivers still assume escape format. This has affected some applications such as Java applications using older JDBC drivers or .NET applications that use the older npgsql driver that expect the old behavior of ST_AsBinary. There are two approaches to getting this to work again.

You can upgrade your JDBC driver to the latest PostgreSQL 9.0 version which you can get from http://jdbc.postgresql.org/download.html

If you are running a .NET app, you can use Npgsql 2.0.11 or higher which you can download from http://pgfoundry.org/frs/?group_id=1000140 and as described on Francisco Figueiredo's NpgSQL 2.0.11 released blog entry

If upgrading your PostgreSQL driver is not an option, then you can set the default back to the old behavior with the following change:

ALTER DATABASE mypostgisdb SET bytea_output='escape';

3.5.

I tried to use PgAdmin to view my geometry column and it is blank, what gives?

PgAdmin doesn't show anything for large geometries. The best ways to verify you do have data in your geometry columns are?

-- this should return no records if all your geom fields are filled in
SELECT somefield FROM mytable WHERE geom IS NULL;
-- To tell just how large your geometry is do a query of the form
--which will tell you the most number of points you have in any of your geometry columns
SELECT MAX(ST_NPoints(geom)) FROM sometable;

3.6.

What kind of geometric objects can I store?

You can store Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection geometries. In PostGIS 2.0 and above you can also store TINS and Polyhedral Surfaces in the basic geometry type. These are specified in the Open GIS Well Known Text Format (with Z, M, and ZM extensions). There are three data types currently supported. The standard OGC geometry data type which uses a planar coordinate system for measurement, the geography data type which uses a geodetic coordinate system, with calculations on either a sphere or spheroid. The newest family member of the PostGIS spatial type family is raster for storing and analyzing raster data. Raster has its very own FAQ. Refer to Chapter 10, PostGIS Raster Frequently Asked Questions and Chapter 9, Raster Reference for more details.

3.7.

I'm all confused. Which data store should I use geometry or geography?

Short Answer: geography is a newer data type that supports long range distances measurements, but most computations on it are slower than they are on geometry. If you use geography, you don't need to learn much about planar coordinate systems. Geography is generally best if all you care about is measuring distances and lengths and you have data from all over the world. Geometry data type is an older data type that has many more functions supporting it, enjoys greater support from third party tools, and operations on it are generally faster -- sometimes as much as 10 fold faster for larger geometries. Geometry is best if you are pretty comfortable with spatial reference systems or you are dealing with localized data where all your data fits in a single spatial reference system (SRID) , or you need to do a lot of spatial processing. Note: It is fairly easy to do one-off conversions between the two types to gain the benefits of each. Refer to Section 14.11, “PostGIS Function Support Matrix” to see what is currently supported and what is not.

Long Answer: Refer to our more lengthy discussion in the Section 4.2.2, “When to use Geography Data type over Geometry data type” and function type matrix .

3.8.

I have more intense questions about geography, such as how big of a geographic region can I stuff in a geography column and still get reasonable answers. Are there limitations such as poles, everything in the field must fit in a hemisphere (like SQL Server 2008 has), speed etc?

Your questions are too deep and complex to be adequately answered in this section. Please refer to our Section 4.2.3, “Geography Advanced FAQ” .

3.9.

How do I insert a GIS object into the database?

First, you need to create a table with a column of type "geometry" or "geography" to hold your GIS data. Storing geography type data is a little different than storing geometry. Refer to Section 4.2.1, “Geography Basics” for details on storing geography.

For geometry: Connect to your database with psql and try the following SQL:

CREATE TABLE gtest ( gid serial primary key, name varchar(20)
        , geom geometry(LINESTRING) );

If the geometry column definition fails, you probably have not loaded the PostGIS functions and objects into this database or are using a pre-2.0 version of PostGIS. See the Section 2.4, “Compiling and Install from Source: Detailed” .

Then, you can insert a geometry into the table using a SQL insert statement. The GIS object itself is formatted using the OpenGIS Consortium "well-known text" format:

INSERT INTO gtest (ID, NAME, GEOM)
VALUES (
  1,
  'First Geometry',
  ST_GeomFromText('LINESTRING(2 3,4 5,6 5,7 8)')
);

For more information about other GIS objects, see the object reference .

To view your GIS data in the table:

SELECT id, name, ST_AsText(geom) AS geom FROM gtest;

The return value should look something like this:

 id | name           | geom
----+----------------+-----------------------------
  1 | First Geometry | LINESTRING(2 3,4 5,6 5,7 8)
(1 row)

3.10.

How do I construct a spatial query?

The same way you construct any other database query, as an SQL combination of return values, functions, and boolean tests.

For spatial queries, there are two issues that are important to keep in mind while constructing your query: is there a spatial index you can make use of; and, are you doing expensive calculations on a large number of geometries.

In general, you will want to use the "intersects operator" (&&) which tests whether the bounding boxes of features intersect. The reason the && operator is useful is because if a spatial index is available to speed up the test, the && operator will make use of this. This can make queries much much faster.

You will also make use of spatial functions, such as Distance(), ST_Intersects(), ST_Contains() and ST_Within(), among others, to narrow down the results of your search. Most spatial queries include both an indexed test and a spatial function test. The index test serves to limit the number of return tuples to only tuples that might meet the condition of interest. The spatial functions are then use to test the condition exactly.

SELECT id, the_geom
FROM thetable
WHERE
  ST_Contains(the_geom,'POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))');

3.11.

How do I speed up spatial queries on large tables?

Fast queries on large tables is the raison d'etre of spatial databases (along with transaction support) so having a good index is important.

To build a spatial index on a table with a geometry column, use the "CREATE INDEX" function as follows:

CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );

The "USING GIST" option tells the server to use a GiST (Generalized Search Tree) index.

[Note]

GiST indexes are assumed to be lossy. Lossy indexes uses a proxy object (in the spatial case, a bounding box) for building the index.

You should also ensure that the PostgreSQL query planner has enough information about your index to make rational decisions about when to use it. To do this, you have to "gather statistics" on your geometry tables.

For PostgreSQL 8.0.x and greater, just run the VACUUM ANALYZE command.

For PostgreSQL 7.4.x and below, run the SELECT UPDATE_GEOMETRY_STATS() command.

3.12.

Why aren't PostgreSQL R-Tree indexes supported?

Early versions of PostGIS used the PostgreSQL R-Tree indexes. However, PostgreSQL R-Trees have been completely discarded since version 0.6, and spatial indexing is provided with an R-Tree-over-GiST scheme.

Our tests have shown search speed for native R-Tree and GiST to be comparable. Native PostgreSQL R-Trees have two limitations which make them undesirable for use with GIS features (note that these limitations are due to the current PostgreSQL native R-Tree implementation, not the R-Tree concept in general):

  • R-Tree indexes in PostgreSQL cannot handle features which are larger than 8K in size. GiST indexes can, using the "lossy" trick of substituting the bounding box for the feature itself.

  • R-Tree indexes in PostgreSQL are not "null safe", so building an index on a geometry column which contains null geometries will fail.

3.13.

Why should I use the AddGeometryColumn() function and all the other OpenGIS stuff?

If you do not want to use the OpenGIS support functions, you do not have to. Simply create tables as in older versions, defining your geometry columns in the CREATE statement. All your geometries will have SRIDs of -1, and the OpenGIS meta-data tables will not be filled in properly. However, this will cause most applications based on PostGIS to fail, and it is generally suggested that you do use AddGeometryColumn() to create geometry tables.

MapServer is one application which makes use of the geometry_columns meta-data. Specifically, MapServer can use the SRID of the geometry column to do on-the-fly reprojection of features into the correct map projection.

3.14.

What is the best way to find all objects within a radius of another object?

To use the database most efficiently, it is best to do radius queries which combine the radius test with a bounding box test: the bounding box test uses the spatial index, giving fast access to a subset of data which the radius test is then applied to.

The ST_DWithin(geometry, geometry, distance) function is a handy way of performing an indexed distance search. It works by creating a search rectangle large enough to enclose the distance radius, then performing an exact distance search on the indexed subset of results.

For example, to find all objects with 100 meters of POINT(1000 1000) the following query would work well:

SELECT * FROM geotable
WHERE ST_DWithin(geocolumn, 'POINT(1000 1000)', 100.0);

3.15.

How do I perform a coordinate reprojection as part of a query?

To perform a reprojection, both the source and destination coordinate systems must be defined in the SPATIAL_REF_SYS table, and the geometries being reprojected must already have an SRID set on them. Once that is done, a reprojection is as simple as referring to the desired destination SRID. The below projects a geometry to NAD 83 long lat. The below will only work if the srid of the_geom is not -1 (not undefined spatial ref)

SELECT ST_Transform(the_geom,4269) FROM geotable;

3.16.

I did an ST_AsEWKT and ST_AsText on my rather large geometry and it returned blank field. What gives?

You are probably using PgAdmin or some other tool that doesn't output large text. If your geometry is big enough, it will appear blank in these tools. Use PSQL if you really need to see it or output it in WKT.

				--To check number of geometries are really blank
				SELECT count(gid) FROM geotable WHERE the_geom IS NULL;

3.17.

When I do an ST_Intersects, it says my two geometries don't intersect when I KNOW THEY DO. What gives?

This generally happens in two common cases. Your geometry is invalid -- check ST_IsValid or you are assuming they intersect because ST_AsText truncates the numbers and you have lots of decimals after it is not showing you.

3.18.

I am releasing software that uses PostGIS, does that mean my software has to be licensed using the GPL like PostGIS? Will I have to publish all my code if I use PostGIS?

Almost certainly not. As an example, consider Oracle database running on Linux. Linux is GPL, Oracle is not: does Oracle running on Linux have to be distributed using the GPL? No. Similarly your software can use a PostgreSQL/PostGIS database as much as it wants and be under any license you like.

The only exception would be if you made changes to the PostGIS source code, and distributed your changed version of PostGIS. In that case you would have to share the code of your changed PostGIS (but not the code of applications running on top of it). Even in this limited case, you would still only have to distribute source code to people you distributed binaries to. The GPL does not require that you publish your source code, only that you share it with people you give binaries to.

The above remains true even if you use PostGIS in conjunction with the optional CGAL-enabled functions. Portions of CGAL are GPL, but so is all of PostGIS already: using CGAL does not make PostGIS any more GPL than it was to start with.

Chapter 4. Using PostGIS: Data Management and Queries

4.1. GIS Objects

The GIS objects supported by PostGIS are a superset of the "Simple Features" defined by the OpenGIS Consortium (OGC). As of version 0.9, PostGIS supports all the objects and functions specified in the OGC "Simple Features for SQL" specification.

PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates.

4.1.1. OpenGIS WKB and WKT

The OpenGIS specification defines two standard ways of expressing spatial objects: the Well-Known Text (WKT) form and the Well-Known Binary (WKB) form. Both WKT and WKB include information about the type of the object and the coordinates which form the object.

Examples of the text representations (WKT) of the spatial objects of the features are as follows:

  • POINT(0 0)

  • LINESTRING(0 0,1 1,1 2)

  • POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))

  • MULTIPOINT((0 0),(1 2))

  • MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4))

  • MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

  • GEOMETRYCOLLECTION(POINT(2 3),LINESTRING(2 3,3 4))

The OpenGIS specification also requires that the internal storage format of spatial objects include a spatial referencing system identifier (SRID). The SRID is required when creating spatial objects for insertion into the database.

Input/Output of these formats are available using the following interfaces:

bytea WKB = ST_AsBinary(geometry);
text WKT = ST_AsText(geometry);
geometry = ST_GeomFromWKB(bytea WKB, SRID);
geometry = ST_GeometryFromText(text WKT, SRID);

For example, a valid insert statement to create and insert an OGC spatial object would be:

INSERT INTO geotable ( the_geom, the_name )
  VALUES ( ST_GeomFromText('POINT(-126.4 45.32)', 312), 'A Place');

4.1.2. PostGIS EWKB, EWKT and Canonical Forms

OGC formats only support 2d geometries, and the associated SRID is *never* embedded in the input/output representations.

PostGIS extended formats are currently superset of OGC one (every valid WKB/WKT is a valid EWKB/EWKT) but this might vary in the future, specifically if OGC comes out with a new format conflicting with our extensions. Thus you SHOULD NOT rely on this feature!

PostGIS EWKB/EWKT add 3dm,3dz,4d coordinates support and embedded SRID information.

Examples of the text representations (EWKT) of the extended spatial objects of the features are as follows.

  • POINT(0 0 0) -- XYZ

  • SRID=32632;POINT(0 0) -- XY with SRID

  • POINTM(0 0 0) -- XYM

  • POINT(0 0 0 0) -- XYZM

  • SRID=4326;MULTIPOINTM(0 0 0,1 2 1) -- XYM with SRID

  • MULTILINESTRING((0 0 0,1 1 0,1 2 1),(2 3 1,3 2 1,5 4 1))

  • POLYGON((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

  • MULTIPOLYGON(((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)),((-1 -1 0,-1 -2 0,-2 -2 0,-2 -1 0,-1 -1 0)))

  • GEOMETRYCOLLECTIONM( POINTM(2 3 9), LINESTRINGM(2 3 4, 3 4 5) )

  • MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4) )

  • POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

  • TRIANGLE ((0 0, 0 9, 9 0, 0 0))

  • TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

Input/Output of these formats are available using the following interfaces:

bytea EWKB = ST_AsEWKB(geometry);
text EWKT = ST_AsEWKT(geometry);
geometry = ST_GeomFromEWKB(bytea EWKB);
geometry = ST_GeomFromEWKT(text EWKT);

For example, a valid insert statement to create and insert a PostGIS spatial object would be:

INSERT INTO geotable ( the_geom, the_name )
  VALUES ( ST_GeomFromEWKT('SRID=312;POINTM(-126.4 45.32 15)'), 'A Place' )

The "canonical forms" of a PostgreSQL type are the representations you get with a simple query (without any function call) and the one which is guaranteed to be accepted with a simple insert, update or copy. For the postgis 'geometry' type these are:

- Output
  - binary: EWKB
	ascii: HEXEWKB (EWKB in hex form)
- Input
  - binary: EWKB
	ascii: HEXEWKB|EWKT 

For example this statement reads EWKT and returns HEXEWKB in the process of canonical ascii input/output:

=# SELECT 'SRID=4;POINT(0 0)'::geometry;

geometry
----------------------------------------------------
01010000200400000000000000000000000000000000000000
(1 row)

4.1.3. SQL-MM Part 3

The SQL Multimedia Applications Spatial specification extends the simple features for SQL spec by defining a number of circularly interpolated curves.

The SQL-MM definitions include 3dm, 3dz and 4d coordinates, but do not allow the embedding of SRID information.

The well-known text extensions are not yet fully supported. Examples of some simple curved geometries are shown below:

  • CIRCULARSTRING(0 0, 1 1, 1 0)

    CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0)

    The CIRCULARSTRING is the basic curve type, similar to a LINESTRING in the linear world. A single segment required three points, the start and end points (first and third) and any other point on the arc. The exception to this is for a closed circle, where the start and end points are the same. In this case the second point MUST be the center of the arc, ie the opposite side of the circle. To chain arcs together, the last point of the previous arc becomes the first point of the next arc, just like in LINESTRING. This means that a valid circular string must have an odd number of points greater than 1.

  • COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))

    A compound curve is a single, continuous curve that has both curved (circular) segments and linear segments. That means that in addition to having well-formed components, the end point of every component (except the last) must be coincident with the start point of the following component.

  • CURVEPOLYGON(CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),(1 1, 3 3, 3 1, 1 1))

    Example compound curve in a curve polygon: CURVEPOLYGON(COMPOUNDCURVE(CIRCULARSTRING(0 0,2 0, 2 1, 2 3, 4 3),(4 3, 4 5, 1 4, 0 0)), CIRCULARSTRING(1.7 1, 1.4 0.4, 1.6 0.4, 1.6 0.5, 1.7 1) )

    A CURVEPOLYGON is just like a polygon, with an outer ring and zero or more inner rings. The difference is that a ring can take the form of a circular string, linear string or compound string.

    As of PostGIS 1.4 PostGIS supports compound curves in a curve polygon.

  • MULTICURVE((0 0, 5 5),CIRCULARSTRING(4 0, 4 4, 8 4))

    The MULTICURVE is a collection of curves, which can include linear strings, circular strings or compound strings.

  • MULTISURFACE(CURVEPOLYGON(CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),(1 1, 3 3, 3 1, 1 1)),((10 10, 14 12, 11 10, 10 10),(11 11, 11.5 11, 11 11.5, 11 11)))

    This is a collection of surfaces, which can be (linear) polygons or curve polygons.

[Note]

PostGIS prior to 1.4 does not support compound curves in a curve polygon, but PostGIS 1.4 and above do support the use of Compound Curves in a Curve Polygon.

[Note]

All floating point comparisons within the SQL-MM implementation are performed to a specified tolerance, currently 1E-8.

4.2. PostGIS Geography Type

The geography type provides native support for spatial features represented on "geographic" coordinates (sometimes called "geodetic" coordinates, or "lat/lon", or "lon/lat"). Geographic coordinates are spherical coordinates expressed in angular units (degrees).

The basis for the PostGIS geometry type is a plane. The shortest path between two points on the plane is a straight line. That means calculations on geometries (areas, distances, lengths, intersections, etc) can be calculated using cartesian mathematics and straight line vectors.

The basis for the PostGIS geographic type is a sphere. The shortest path between two points on the sphere is a great circle arc. That means that calculations on geographies (areas, distances, lengths, intersections, etc) must be calculated on the sphere, using more complicated mathematics. For more accurate measurements, the calculations must take the actual spheroidal shape of the world into account, and the mathematics becomes very complicated indeed.

Because the underlying mathematics is much more complicated, there are fewer functions defined for the geography type than for the geometry type. Over time, as new algorithms are added, the capabilities of the geography type will expand.

It uses a data type called geography . None of the GEOS functions support the geography type. As a workaround one can convert back and forth between geometry and geography types.

Prior to PostGIS 2.2, the geography type only supported WGS 84 long lat (SRID:4326). For PostGIS 2.2 and above, any long/lat based spatial reference system defined in the spatial_ref_sys table can be used. You can even add your own custom spheroidal spatial refence system as described in geography type is not limited to earth .

Regardless which spatial reference system you use, the units returned by the measurement ( ST_Distance , ST_Length , ST_Perimeter , ST_Area ) and for input of ST_DWithin are in meters.

The geography type uses the PostgreSQL 8.3+ typmod definition format so that a table with a geography field can be added in a single step. All the standard OGC formats except for curves are supported.

4.2.1. Geography Basics

The geography type does not support curves, TINS, or POLYHEDRALSURFACEs, but other geometry types are supported. Standard geometry type data will autocast to geography if it is of SRID 4326. You can also use the EWKT and EWKB conventions to insert data.

  • POINT: Creating a table with 2d point geography when srid is not specified defaults to 4326 WGS 84 long lat:

    CREATE TABLE ptgeogwgs(gid serial PRIMARY KEY, geog geography(POINT) );

    POINT: Creating a table with 2d point geography in NAD83 longlat:

    CREATE TABLE ptgeognad83(gid serial PRIMARY KEY, geog geography(POINT,4269) );

    Creating a table with z coordinate point and explicitly specifying srid

    CREATE TABLE ptzgeogwgs84(gid serial PRIMARY KEY, geog geography(POINTZ,4326) );
  • LINESTRING

    CREATE TABLE lgeog(gid serial PRIMARY KEY, geog geography(LINESTRING) );
  • POLYGON

    --polygon NAD 1927 long lat
    CREATE TABLE lgeognad27(gid serial PRIMARY KEY, geog geography(POLYGON,4267) );
  • MULTIPOINT

  • MULTILINESTRING

  • MULTIPOLYGON

  • GEOMETRYCOLLECTION

The geography fields don't get registered in the geometry_columns . They get registered in a view called geography_columns which is a view against the system catalogs so is always automatically kept up to date without need for an AddGeom... like function.

Now, check the "geography_columns" view and see that your table is listed.

You can create a new table with a GEOGRAPHY column using the CREATE TABLE syntax.

CREATE TABLE global_points (
    id SERIAL PRIMARY KEY,
    name VARCHAR(64),
    location GEOGRAPHY(POINT,4326)
  );

Note that the location column has type GEOGRAPHY and that geography type supports two optional modifier: a type modifier that restricts the kind of shapes and dimensions allowed in the column; an SRID modifier that restricts the coordinate reference identifier to a particular number.

Allowable values for the type modifier are: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON. The modifier also supports dimensionality restrictions through suffixes: Z, M and ZM. So, for example a modifier of 'LINESTRINGM' would only allow line strings with three dimensions in, and would treat the third dimension as a measure. Similarly, 'POINTZM' would expect four dimensional data.

If you do not specify an SRID, the SRID will default to 4326 WGS 84 long/lat will be used, and all calculations will proceed using WGS84.

Once you have created your table, you can see it in the GEOGRAPHY_COLUMNS table:

-- See the contents of the metadata view
SELECT * FROM geography_columns;

You can insert data into the table the same as you would if it was using a GEOMETRY column:

-- Add some data into the test table
INSERT INTO global_points (name, location) VALUES ('Town', ST_GeogFromText('SRID=4326;POINT(-110 30)') );
INSERT INTO global_points (name, location) VALUES ('Forest', ST_GeogFromText('SRID=4326;POINT(-109 29)') );
INSERT INTO global_points (name, location) VALUES ('London', ST_GeogFromText('SRID=4326;POINT(0 49)') );

Creating an index works the same as GEOMETRY. PostGIS will note that the column type is GEOGRAPHY and create an appropriate sphere-based index instead of the usual planar index used for GEOMETRY.

-- Index the test table with a spherical index
  CREATE INDEX global_points_gix ON global_points USING GIST ( location );

Query and measurement functions use units of meters. So distance parameters should be expressed in meters, and return values should be expected in meters (or square meters for areas).

-- Show a distance query and note, London is outside the 1000km tolerance
  SELECT name FROM global_points WHERE ST_DWithin(location, ST_GeogFromText('SRID=4326;POINT(-110 29)'), 1000000);

You can see the power of GEOGRAPHY in action by calculating how close a plane flying from Seattle to London (LINESTRING(-122.33 47.606, 0.0 51.5)) comes to Reykjavik (POINT(-21.96 64.15)).

-- Distance calculation using GEOGRAPHY (122.2km)
  SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geography, 'POINT(-21.96 64.15)':: geography);

-- Distance calculation using GEOMETRY (13.3 "degrees")
  SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geometry, 'POINT(-21.96 64.15)':: geometry);

Testing different lon/lat projects, requires PostGIS 2.2+. Any long lat spatial reference system listed in spatial_ref_sys table is allowed.

-- NAD 83 lon/lat
SELECT 'SRID=4269;POINT(-123 34)'::geography;
                    geography
----------------------------------------------------
 0101000020AD1000000000000000C05EC00000000000004140
(1 row)

-- NAD27 lon/lat
SELECT 'SRID=4267;POINT(-123 34)'::geography;

                    geography
----------------------------------------------------
 0101000020AB1000000000000000C05EC00000000000004140
(1 row)

-- NAD83 UTM zone meters, yields error since its a meter based projection
SELECT 'SRID=26910;POINT(-123 34)'::geography;

ERROR:  Only lon/lat coordinate systems are supported in geography.
LINE 1: SELECT 'SRID=26910;POINT(-123 34)'::geography;

The GEOGRAPHY type calculates the true shortest distance over the sphere between Reykjavik and the great circle flight path between Seattle and London.

Great Circle mapper The GEOMETRY type calculates a meaningless cartesian distance between Reykjavik and the straight line path from Seattle to London plotted on a flat map of the world. The nominal units of the result might be called "degrees", but the result doesn't correspond to any true angular difference between the points, so even calling them "degrees" is inaccurate.

4.2.2. When to use Geography Data type over Geometry data type

The geography type allows you to store data in longitude/latitude coordinates, but at a cost: there are fewer functions defined on GEOGRAPHY than there are on GEOMETRY; those functions that are defined take more CPU time to execute.

The type you choose should be conditioned on the expected working area of the application you are building. Will your data span the globe or a large continental area, or is it local to a state, county or municipality?

  • If your data is contained in a small area, you might find that choosing an appropriate projection and using GEOMETRY is the best solution, in terms of performance and functionality available.

  • If your data is global or covers a continental region, you may find that GEOGRAPHY allows you to build a system without having to worry about projection details. You store your data in longitude/latitude, and use the functions that have been defined on GEOGRAPHY.

  • If you don't understand projections, and you don't want to learn about them, and you're prepared to accept the limitations in functionality available in GEOGRAPHY, then it might be easier for you to use GEOGRAPHY than GEOMETRY. Simply load your data up as longitude/latitude and go from there.

Refer to Section 14.11, “PostGIS Function Support Matrix” for compare between what is supported for Geography vs. Geometry. For a brief listing and description of Geography functions, refer to Section 14.4, “PostGIS Geography Support Functions”

4.2.3. Geography Advanced FAQ

4.2.3.1. Do you calculate on the sphere or the spheroid?
4.2.3.2. What about the date-line and the poles?
4.2.3.3. What is the longest arc you can process?
4.2.3.4. Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

4.2.3.1.

Do you calculate on the sphere or the spheroid?

By default, all distance and area calculations are done on the spheroid. You should find that the results of calculations in local areas match up will with local planar results in good local projections. Over larger areas, the spheroidal calculations will be more accurate than any calculation done on a projected plane.

All the geography functions have the option of using a sphere calculation, by setting a final boolean parameter to 'FALSE'. This will somewhat speed up calculations, particularly for cases where the geometries are very simple.

4.2.3.2.

What about the date-line and the poles?

All the calculations have no conception of date-line or poles, the coordinates are spherical (longitude/latitude) so a shape that crosses the dateline is, from a calculation point of view, no different from any other shape.

4.2.3.3.

What is the longest arc you can process?

We use great circle arcs as the "interpolation line" between two points. That means any two points are actually joined up two ways, depending on which direction you travel along the great circle. All our code assumes that the points are joined by the *shorter* of the two paths along the great circle. As a consequence, shapes that have arcs of more than 180 degrees will not be correctly modelled.

4.2.3.4.

Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

Because the polygon is so darned huge! Big areas are bad for two reasons: their bounds are huge, so the index tends to pull the feature no matter what query you run; the number of vertices is huge, and tests (distance, containment) have to traverse the vertex list at least once and sometimes N times (with N being the number of vertices in the other candidate feature).

As with GEOMETRY, we recommend that when you have very large polygons, but are doing queries in small areas, you "denormalize" your geometric data into smaller chunks so that the index can effectively subquery parts of the object and so queries don't have to pull out the whole object every time. Just because you *can* store all of Europe in one polygon doesn't mean you *should*.

4.3. Using OpenGIS Standards

The OpenGIS "Simple Features Specification for SQL" defines standard GIS object types, the functions required to manipulate them, and a set of meta-data tables. In order to ensure that meta-data remain consistent, operations such as creating and removing a spatial column are carried out through special procedures defined by OpenGIS.

There are two OpenGIS meta-data tables: SPATIAL_REF_SYS and GEOMETRY_COLUMNS . The SPATIAL_REF_SYS table holds the numeric IDs and textual descriptions of coordinate systems used in the spatial database.

4.3.1. The SPATIAL_REF_SYS Table and Spatial Reference Systems

The spatial_ref_sys table is a PostGIS included and OGC compliant database table that lists over 3000 known spatial reference systems and details needed to transform/reproject between them.

Although the PostGIS spatial_ref_sys table contains over 3000 of the more commonly used spatial reference system definitions that can be handled by the proj library, it does not contain all known to man and you can even define your own custom projection if you are familiar with proj4 constructs. Keep in mind that most spatial reference systems are regional and have no meaning when used outside of the bounds they were intended for.

An excellent resource for finding spatial reference systems not defined in the core set is http://spatialreference.org/

Some of the more commonly used spatial reference systems are: 4326 - WGS 84 Long Lat , 4269 - NAD 83 Long Lat , 3395 - WGS 84 World Mercator , 2163 - US National Atlas Equal Area , Spatial reference systems for each NAD 83, WGS 84 UTM zone - UTM zones are one of the most ideal for measurement, but only cover 6-degree regions.

Various US state plane spatial reference systems (meter or feet based) - usually one or 2 exists per US state. Most of the meter ones are in the core set, but many of the feet based ones or ESRI created ones you will need to pull from spatialreference.org .

For details on determining which UTM zone to use for your area of interest, check out the utmzone PostGIS plpgsql helper function .

The SPATIAL_REF_SYS table definition is as follows:

CREATE TABLE spatial_ref_sys (
  srid       INTEGER NOT NULL PRIMARY KEY,
  auth_name  VARCHAR(256),
  auth_srid  INTEGER,
  srtext     VARCHAR(2048),
  proj4text  VARCHAR(2048)
)

The SPATIAL_REF_SYS columns are as follows:

SRID

An integer value that uniquely identifies the Spatial Referencing System (SRS) within the database.

AUTH_NAME

The name of the standard or standards body that is being cited for this reference system. For example, "EPSG" would be a valid AUTH_NAME .

AUTH_SRID

The ID of the Spatial Reference System as defined by the Authority cited in the AUTH_NAME . In the case of EPSG, this is where the EPSG projection code would go.

SRTEXT

The Well-Known Text representation of the Spatial Reference System. An example of a WKT SRS representation is:

PROJCS["NAD83 / UTM Zone 10N",
  GEOGCS["NAD83",
	DATUM["North_American_Datum_1983",
	  SPHEROID["GRS 1980",6378137,298.257222101]
	],
	PRIMEM["Greenwich",0],
	UNIT["degree",0.0174532925199433]
  ],
  PROJECTION["Transverse_Mercator"],
  PARAMETER["latitude_of_origin",0],
  PARAMETER["central_meridian",-123],
  PARAMETER["scale_factor",0.9996],
  PARAMETER["false_easting",500000],
  PARAMETER["false_northing",0],
  UNIT["metre",1]
]

For a listing of EPSG projection codes and their corresponding WKT representations, see http://www.opengeospatial.org/ . For a discussion of WKT in general, see the OpenGIS "Coordinate Transformation Services Implementation Specification" at http://www.opengeospatial.org/standards . For information on the European Petroleum Survey Group (EPSG) and their database of spatial reference systems, see http://www.epsg.org .

PROJ4TEXT

PostGIS uses the Proj4 library to provide coordinate transformation capabilities. The PROJ4TEXT column contains the Proj4 coordinate definition string for a particular SRID. For example:

+proj=utm +zone=10 +ellps=clrk66 +datum=NAD27 +units=m

For more information about, see the Proj4 web site at http://trac.osgeo.org/proj/ . The spatial_ref_sys.sql file contains both SRTEXT and PROJ4TEXT definitions for all EPSG projections.

4.3.2. The GEOMETRY_COLUMNS VIEW

In versions of PostGIS prior to 2.0.0, geometry_columns was a table that could be directly edited, and sometimes got out of synch with the actual definition of the geometry columns. In PostGIS 2.0.0, GEOMETRY_COLUMNS became a view with the same front-facing structure as prior versions, but reading from database system catalogs Its structure is as follows:

\d geometry_columns
             View "public.geometry_columns"
      Column       |          Type          | Modifiers
-------------------+------------------------+-----------
 f_table_catalog   | character varying(256) |
 f_table_schema    | character varying(256) |
 f_table_name      | character varying(256) |
 f_geometry_column | character varying(256) |
 coord_dimension   | integer                |
 srid              | integer                |
 type              | character varying(30)  |

The column meanings have not changed from prior versions and are:

F_TABLE_CATALOG, F_TABLE_SCHEMA, F_TABLE_NAME

The fully qualified name of the feature table containing the geometry column. Note that the terms "catalog" and "schema" are Oracle-ish. There is not PostgreSQL analogue of "catalog" so that column is left blank -- for "schema" the PostgreSQL schema name is used ( public is the default).

F_GEOMETRY_COLUMN

The name of the geometry column in the feature table.

COORD_DIMENSION

The spatial dimension (2, 3 or 4 dimensional) of the column.

SRID

The ID of the spatial reference system used for the coordinate geometry in this table. It is a foreign key reference to the SPATIAL_REF_SYS .

TYPE

The type of the spatial object. To restrict the spatial column to a single type, use one of: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION or corresponding XYM versions POINTM, LINESTRINGM, POLYGONM, MULTIPOINTM, MULTILINESTRINGM, MULTIPOLYGONM, GEOMETRYCOLLECTIONM. For heterogeneous (mixed-type) collections, you can use "GEOMETRY" as the type.

[Note]

This attribute is (probably) not part of the OpenGIS specification, but is required for ensuring type homogeneity.

4.3.3. Creating a Spatial Table

Creating a table with spatial data, can be done in one step. As shown in the following example which creates a roads table with a 2D linestring geometry column in WGS84 long lat

CREATE TABLE ROADS ( ID int4
		, ROAD_NAME varchar(25), geom geometry(LINESTRING,4326) );

We can add additional columns using standard ALTER TABLE command as we do in this next example where we add a 3-D linestring.

ALTER TABLE roads ADD COLUMN geom2 geometry(LINESTRINGZ,4326);

For backwards compability, you can still create a spatial table in two stages using the management functions.

  • Create a normal non-spatial table.

    For example: CREATE TABLE ROADS ( ID int4, ROAD_NAME varchar(25) )

  • Add a spatial column to the table using the OpenGIS "AddGeometryColumn" function. Refer to AddGeometryColumn for more details.

    The syntax is:

    AddGeometryColumn(
      <schema_name>,
      <table_name>,
      <column_name>,
      <srid>,
      <type>,
      <dimension>
    )

    Or, using current schema:

    AddGeometryColumn(
      <table_name>,
      <column_name>,
      <srid>,
      <type>,
      <dimension>
    )

    Example1: SELECT AddGeometryColumn('public', 'roads', 'geom', 423, 'LINESTRING', 2)

    Example2: SELECT AddGeometryColumn( 'roads', 'geom', 423, 'LINESTRING', 2)

Here is an example of SQL used to create a table and add a spatial column (assuming that an SRID of 128 exists already):

CREATE TABLE parks (
  park_id    INTEGER,
  park_name  VARCHAR,
  park_date  DATE,
  park_type  VARCHAR
);
SELECT AddGeometryColumn('parks', 'park_geom', 128, 'MULTIPOLYGON', 2 );

Here is another example, using the generic "geometry" type and the undefined SRID value of 0:

CREATE TABLE roads (
  road_id INTEGER,
  road_name VARCHAR
);
SELECT AddGeometryColumn( 'roads', 'roads_geom', 0, 'GEOMETRY', 3 );

4.3.4. Manually Registering Geometry Columns in geometry_columns

The AddGeometryColumn() approach creates a geometry column of specified type. This type and dimension are queryable from the geometry_columns view. Starting with PostGIS 2.0, geometry_columns is no longer editable and all geometry columns are autoregistered.

If your geometry columns were created as generic in a table or view and no constraints applied, they will not have a dimension, type or srid in geometry_columns views, but will still be listed.

Two of the cases where this may happen, but you can't use AddGeometryColumn, is in the case of SQL Views and bulk inserts. For bulk insert case, you can correct the registration in the geometry_columns table by constraining the column or doing an alter table. For views, you could expose using a CAST operation. Note in PostGIS 2.0+ if your column is typmod based, the creation process would register it correctly, so no need to do anything. Also views that have no spatial function applied to the geometry will register the same as the underlying table geometry column.

--Lets say you have a view created like this
CREATE VIEW  public.vwmytablemercator AS
	SELECT gid, ST_Transform(geom,3395) As geom, f_name
	FROM public.mytable;

-- For it to register correctly in PostGIS 2.0+
-- You need to cast the geometry
--
DROP VIEW public.vwmytablemercator;
CREATE VIEW  public.vwmytablemercator AS
	SELECT gid, ST_Transform(geom,3395)::geometry(Geometry, 3395) As geom, f_name
	FROM public.mytable;

-- If you know the geometry type for sure is a 2D POLYGON then you could do
DROP VIEW public.vwmytablemercator;
CREATE VIEW  public.vwmytablemercator AS
	SELECT gid, ST_Transform(geom,3395)::geometry(Polygon, 3395) As geom, f_name
	FROM public.mytable;
--Lets say you created a derivative table by doing a bulk insert
SELECT poi.gid, poi.geom, citybounds.city_name
INTO myschema.my_special_pois
FROM poi INNER JOIN citybounds ON ST_Intersects(citybounds.geom, poi.geom);

--Create 2d index on new table
CREATE INDEX idx_myschema_myspecialpois_geom_gist
  ON myschema.my_special_pois USING gist(geom);

-- If your points are 3D points or 3M points,
-- then you might want to create an nd index instead of a 2d index
-- like so
CREATE INDEX my_special_pois_geom_gist_nd
	ON my_special_pois USING gist(geom gist_geometry_ops_nd);

--To manually register this new table's geometry column in geometry_columns
-- Note that this approach will work for both PostGIS 2.0+ and PostGIS 1.4+
-- For PostGIS 2.0 it will also change the underlying structure of the table to
-- to make the column typmod based.
-- For PostGIS prior to 2.0, this technique can also be used to register views
SELECT populate_geometry_columns('myschema.my_special_pois'::regclass);

--If you are using PostGIS 2.0 and for whatever reason, you
-- you need the old constraint based definition behavior
-- (such as case of inherited tables where all children do not have the same type and srid)
-- set new optional  use_typmod argument to false
SELECT populate_geometry_columns('myschema.my_special_pois'::regclass, false); 

Although the old-constraint based method is still supported, a constraint-based geometry column used directly in a view, will not register correctly in geometry_columns, as will a typmod one. In this example we define a column using typmod and another using constraints.

CREATE TABLE pois_ny(gid SERIAL PRIMARY KEY
   , poi_name text, cat varchar(20)
   , geom geometry(POINT,4326) );
SELECT AddGeometryColumn('pois_ny', 'geom_2160', 2160, 'POINT', 2, false);

If we run in psql

\d pois_ny;

We observe they are defined differently -- one is typmod, one is constraint

                                  Table "public.pois_ny"
  Column   |         Type          |                       Modifiers

-----------+-----------------------+------------------------------------------------------
 gid       | integer               | not null default nextval('pois_ny_gid_seq'::regclass)
 poi_name  | text                  |
 cat       | character varying(20) |
 geom      | geometry(Point,4326)  |
 geom_2160 | geometry              |
Indexes:
    "pois_ny_pkey" PRIMARY KEY, btree (gid)
Check constraints:
    "enforce_dims_geom_2160" CHECK (st_ndims(geom_2160) = 2)
    "enforce_geotype_geom_2160" CHECK (geometrytype(geom_2160) = 'POINT'::text
        OR geom_2160 IS NULL)
    "enforce_srid_geom_2160" CHECK (st_srid(geom_2160) = 2160)

In geometry_columns, they both register correctly

SELECT f_table_name, f_geometry_column, srid, type
	FROM geometry_columns
	WHERE f_table_name = 'pois_ny';
f_table_name | f_geometry_column | srid | type
-------------+-------------------+------+-------
pois_ny      | geom              | 4326 | POINT
pois_ny      | geom_2160         | 2160 | POINT

However -- if we were to create a view like this

CREATE VIEW vw_pois_ny_parks AS
SELECT *
  FROM pois_ny
  WHERE cat='park';

SELECT f_table_name, f_geometry_column, srid, type
	FROM geometry_columns
	WHERE f_table_name = 'vw_pois_ny_parks';

The typmod based geom view column registers correctly, but the constraint based one does not.

   f_table_name   | f_geometry_column | srid |   type
------------------+-------------------+------+----------
 vw_pois_ny_parks | geom              | 4326 | POINT
 vw_pois_ny_parks | geom_2160         |    0 | GEOMETRY

This may change in future versions of PostGIS, but for now To force the constraint based view column to register correctly, we need to do this:

DROP VIEW vw_pois_ny_parks;
CREATE VIEW vw_pois_ny_parks AS
SELECT gid, poi_name, cat
  , geom
  , geom_2160::geometry(POINT,2160) As geom_2160
  FROM pois_ny
  WHERE cat='park';
SELECT f_table_name, f_geometry_column, srid, type
	FROM geometry_columns
	WHERE f_table_name = 'vw_pois_ny_parks';
   f_table_name   | f_geometry_column | srid | type
------------------+-------------------+------+-------
 vw_pois_ny_parks | geom              | 4326 | POINT
 vw_pois_ny_parks | geom_2160         | 2160 | POINT

4.3.5. Ensuring OpenGIS compliancy of geometries

PostGIS is compliant with the Open Geospatial Consortium’s (OGC) OpenGIS Specifications. As such, many PostGIS methods require, or more accurately, assume that geometries that are operated on are both simple and valid. For example, it does not make sense to calculate the area of a polygon that has a hole defined outside of the polygon, or to construct a polygon from a non-simple boundary line.

According to the OGC Specifications, a simple geometry is one that has no anomalous geometric points, such as self intersection or self tangency and primarily refers to 0 or 1-dimensional geometries (i.e. [MULTI]POINT, [MULTI]LINESTRING ). Geometry validity, on the other hand, primarily refers to 2-dimensional geometries (i.e. [MULTI]POLYGON) and defines the set of assertions that characterizes a valid polygon. The description of each geometric class includes specific conditions that further detail geometric simplicity and validity.

A POINT is inheritably simple as a 0-dimensional geometry object.

MULTIPOINT s are simple if no two coordinates ( POINT s) are equal (have identical coordinate values).

A LINESTRING is simple if it does not pass through the same POINT twice (except for the endpoints, in which case it is referred to as a linear ring and additionally considered closed).

(a)

(b)

(c)

(d)

(a) and (c) are simple LINESTRING s, (b) and (d) are not.

A MULTILINESTRING is simple only if all of its elements are simple and the only intersection between any two elements occurs at POINT s that are on the boundaries of both elements.

(e)

(f)

(g)

(e) and (f) are simple MULTILINESTRING s, (g) is not.

By definition, a POLYGON is always simple . It is valid if no two rings in the boundary (made up of an exterior ring and interior rings) cross. The boundary of a POLYGON may intersect at a POINT but only as a tangent (i.e. not on a line). A POLYGON may not have cut lines or spikes and the interior rings must be contained entirely within the exterior ring.

(h)

(i)

(j)

(k)

(l)

(m)

(h) and (i) are valid POLYGON s, (j-m) cannot be represented as single POLYGON s, but (j) and (m) could be represented as a valid MULTIPOLYGON .

A MULTIPOLYGON is valid if and only if all of its elements are valid and the interiors of no two elements intersect. The boundaries of any two elements may touch, but only at a finite number of POINT s.

(n)

(o)

(p)

(n) and (o) are not valid MULTIPOLYGON s. (p) , however, is valid.

Most of the functions implemented by the GEOS library rely on the assumption that your geometries are valid as specified by the OpenGIS Simple Feature Specification. To check simplicity or validity of geometries you can use the ST_IsSimple() and ST_IsValid()

-- Typically, it doesn't make sense to check
-- for validity on linear features since it will always return TRUE.
-- But in this example, PostGIS extends the definition of the OGC IsValid
-- by returning false if a LineString has less than 2 *distinct* vertices.
gisdb=# SELECT
   ST_IsValid('LINESTRING(0 0, 1 1)'),
   ST_IsValid('LINESTRING(0 0, 0 0, 0 0)');

 st_isvalid | st_isvalid
------------+-----------
      t     |     f

By default, PostGIS does not apply this validity check on geometry input, because testing for validity needs lots of CPU time for complex geometries, especially polygons. If you do not trust your data sources, you can manually enforce such a check to your tables by adding a check constraint:

ALTER TABLE mytable
  ADD CONSTRAINT geometry_valid_check
	CHECK (ST_IsValid(the_geom));

If you encounter any strange error messages such as "GEOS Intersection() threw an error!" or "JTS Intersection() threw an error!" when calling PostGIS functions with valid input geometries, you likely found an error in either PostGIS or one of the libraries it uses, and you should contact the PostGIS developers. The same is true if a PostGIS function returns an invalid geometry for valid input.

[Note]

Strictly compliant OGC geometries cannot have Z or M values. The ST_IsValid() function won't consider higher dimensioned geometries invalid! Invocations of AddGeometryColumn() will add a constraint checking geometry dimensions, so it is enough to specify 2 there.

4.3.6. Dimensionally Extended 9 Intersection Model (DE-9IM)

It is sometimes the case that the typical spatial predicates ( ST_Contains , ST_Crosses , ST_Intersects , ST_Touches , ...) are insufficient in and of themselves to adequately provide that desired spatial filter.

For example, consider a linear dataset representing a road network. It may be the task of a GIS analyst to identify all road segments that cross each other, not at a point, but on a line, perhaps invalidating some business rule. In this case, ST_Crosses does not adequately provide the necessary spatial filter since, for linear features, it returns true only where they cross at a point.

One two-step solution might be to first perform the actual intersection ( ST_Intersection ) of pairs of road segments that spatially intersect ( ST_Intersects ), and then compare the intersection's ST_GeometryType with ' LINESTRING ' (properly dealing with cases that return GEOMETRYCOLLECTION s of [MULTI]POINT s, [MULTI]LINESTRING s, etc.).

A more elegant / faster solution may indeed be desirable.

A second [theoretical] example may be that of a GIS analyst trying to locate all wharfs or docks that intersect a lake's boundary on a line and where only one end of the wharf is up on shore. In other words, where a wharf is within, but not completely within a lake, intersecting the boundary of a lake on a line, and where the wharf's endpoints are both completely within and on the boundary of the lake. The analyst may need to use a combination of spatial predicates to isolate the sought after features:

So enters the Dimensionally Extended 9 Intersection Model, or DE-9IM for short.

4.3.6.1. Theory

According to the OpenGIS Simple Features Implementation Specification for SQL , "the basic approach to comparing two geometries is to make pair-wise tests of the intersections between the Interiors, Boundaries and Exteriors of the two geometries and to classify the relationship between the two geometries based on the entries in the resulting 'intersection' matrix."

Boundary

The boundary of a geometry is the set of geometries of the next lower dimension. For POINT s, which have a dimension of 0, the boundary is the empty set. The boundary of a LINESTRING are the two endpoints. For POLYGON s, the boundary is the linework that make up the exterior and interior rings.

Interior

The interior of a geometry are those points of a geometry that are left when the boundary is removed. For POINT s, the interior is the POINT itself. The interior of a LINESTRING are the set of real points between the endpoints. For POLYGON s, the interior is the areal surface inside the polygon.

Exterior

The exterior of a geometry is the universe, an areal surface, not on the interior or boundary of the geometry.

Given geometry a , where the I(a) , B(a) , and E(a) are the Interior , Boundary , and Exterior of a, the mathematical representation of the matrix is:

  Interior Boundary Exterior
Interior dim( I(a) ∩ I(b) ) dim( I(a) ∩ B(b) ) dim( I(a) ∩ E(b) )
Boundary dim( B(a) ∩ I(b) ) dim( B(a) ∩ B(b) ) dim( B(a) ∩ E(b) )
Exterior dim( E(a) ∩ I(b) ) dim( E(a) ∩ B(b) ) dim( E(a) ∩ E(b) )

Where dim(a) is the dimension of a as specified by ST_Dimension but has the domain of {0,1,2,T,F,*}

  • 0 => point

  • 1 => line

  • 2 => area

  • T => {0,1,2}

  • F => empty set

  • * => don't care

Visually, for two overlapping polygonal geometries, this looks like:

 

  Interior Boundary Exterior
Interior

dim(...) = 2

dim(...) = 1

dim(...) = 2

Boundary

dim(...) = 1

dim(...) = 0

dim(...) = 1

Exterior

dim(...) = 2

dim(...) = 1

dim(...) = 2

Read from left to right and from top to bottom, the dimensional matrix is represented, ' 212101212 '.

A relate matrix that would therefore represent our first example of two lines that intersect on a line would be: ' 1*1***1** '

-- Identify road segments that cross on a line
SELECT a.id
FROM roads a, roads b
WHERE a.id != b.id
AND a.geom && b.geom
AND ST_Relate(a.geom, b.geom, '1*1***1**');

A relate matrix that represents the second example of wharfs partly on the lake's shoreline would be ' 102101FF2 '

-- Identify wharfs partly on a lake's shoreline
SELECT a.lake_id, b.wharf_id
FROM lakes a, wharfs b
WHERE a.geom && b.geom
AND ST_Relate(a.geom, b.geom, '102101FF2');

For more information or reading, see:

4.4. Loading GIS (Vector) Data

Once you have created a spatial table, you are ready to upload GIS data to the database. Currently, there are two ways to get data into a PostGIS/PostgreSQL database: using formatted SQL statements or using the Shape file loader/dumper.

4.4.1. Loading Data Using SQL

If you can convert your data to a text representation, then using formatted SQL might be the easiest way to get your data into PostGIS. As with Oracle and other SQL databases, data can be bulk loaded by piping a large text file full of SQL "INSERT" statements into the SQL terminal monitor.

A data upload file ( roads.sql for example) might look like this:

BEGIN;
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (1,ST_GeomFromText('LINESTRING(191232 243118,191108 243242)',-1),'Jeff Rd');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (2,ST_GeomFromText('LINESTRING(189141 244158,189265 244817)',-1),'Geordie Rd');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (3,ST_GeomFromText('LINESTRING(192783 228138,192612 229814)',-1),'Paul St');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (4,ST_GeomFromText('LINESTRING(189412 252431,189631 259122)',-1),'Graeme Ave');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (5,ST_GeomFromText('LINESTRING(190131 224148,190871 228134)',-1),'Phil Tce');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (6,ST_GeomFromText('LINESTRING(198231 263418,198213 268322)',-1),'Dave Cres');
COMMIT;

The data file can be piped into PostgreSQL very easily using the "psql" SQL terminal monitor:

psql -d [database] -f roads.sql

4.4.2. shp2pgsql: Using the ESRI Shapefile Loader

The shp2pgsql data loader converts ESRI Shape files into SQL suitable for insertion into a PostGIS/PostgreSQL database either in geometry or geography format. The loader has several operating modes distinguished by command line flags:

In addition to the shp2pgsql command-line loader, there is an shp2pgsql-gui graphical interface with most of the options as the command-line loader, but may be easier to use for one-off non-scripted loading or if you are new to PostGIS. It can also be configured as a plugin to PgAdminIII.

(c|a|d|p) These are mutually exclusive options:

-c

Creates a new table and populates it from the shapefile. This is the default mode.

-a

Appends data from the Shape file into the database table. Note that to use this option to load multiple files, the files must have the same attributes and same data types.

-d

Drops the database table before creating a new table with the data in the Shape file.

-p

Only produces the table creation SQL code, without adding any actual data. This can be used if you need to completely separate the table creation and data loading steps.

-?

Display help screen.

-D

Use the PostgreSQL "dump" format for the output data. This can be combined with -a, -c and -d. It is much faster to load than the default "insert" SQL format. Use this for very large data sets.

-s [<FROM_SRID%gt;:]<SRID>

Creates and populates the geometry tables with the specified SRID. Optionally specifies that the input shapefile uses the given FROM_SRID, in which case the geometries will be reprojected to the target SRID. FROM_SRID cannot be specified with -D.

-k

Keep identifiers' case (column, schema and attributes). Note that attributes in Shapefile are all UPPERCASE.

-i

Coerce all integers to standard 32-bit integers, do not create 64-bit bigints, even if the DBF header signature appears to warrant it.

-I

Create a GiST index on the geometry column.

-m

-m a_file_name Specify a file containing a set of mappings of (long) column names to 10 character DBF column names. The content of the file is one or more lines of two names separated by white space and no trailing or leading space. For example:

COLUMNNAME DBFFIELD1
AVERYLONGCOLUMNNAME DBFFIELD2

-S

Generate simple geometries instead of MULTI geometries. Will only succeed if all the geometries are actually single (I.E. a MULTIPOLYGON with a single shell, or or a MULTIPOINT with a single vertex).

-t <dimensionality>

Force the output geometry to have the specified dimensionality. Use the following strings to indicate the dimensionality: 2D, 3DZ, 3DM, 4D.

If the input has fewer dimensions that specified, the output will have those dimensions filled in with zeroes. If the input has more dimensions that specified, the unwanted dimensions will be stripped.

-w

Output WKT format, instead of WKB. Note that this can introduce coordinate drifts due to loss of precision.

-e

Execute each statement on its own, without using a transaction. This allows loading of the majority of good data when there are some bad geometries that generate errors. Note that this cannot be used with the -D flag as the "dump" format always uses a transaction.

-W <encoding>

Specify encoding of the input data (dbf file). When used, all attributes of the dbf are converted from the specified encoding to UTF8. The resulting SQL output will contain a SET CLIENT_ENCODING to UTF8 command, so that the backend will be able to reconvert from UTF8 to whatever encoding the database is configured to use internally.

-N <policy>

NULL geometries handling policy (insert*,skip,abort)

-n

-n Only import DBF file. If your data has no corresponding shapefile, it will automatically switch to this mode and load just the dbf. So setting this flag is only needed if you have a full shapefile set, and you only want the attribute data and no geometry.

-G

Use geography type instead of geometry (requires lon/lat data) in WGS84 long lat (SRID=4326)

-T <tablespace>

Specify the tablespace for the new table. Indexes will still use the default tablespace unless the -X parameter is also used. The PostgreSQL documentation has a good description on when to use custom tablespaces.

-X <tablespace>

Specify the tablespace for the new table's indexes. This applies to the primary key index, and the GIST spatial index if -I is also used.

An example session using the loader to create an input file and uploading it might look like this:

# shp2pgsql -c -D -s 4269 -i -I shaperoads.shp myschema.roadstable > roads.sql
# psql -d roadsdb -f roads.sql

A conversion and upload can be done all in one step using UNIX pipes:

# shp2pgsql shaperoads.shp myschema.roadstable | psql -d roadsdb

4.5. Retrieving GIS Data

Data can be extracted from the database using either SQL or the Shape file loader/dumper. In the section on SQL we will discuss some of the operators available to do comparisons and queries on spatial tables.

4.5.1. Using SQL to Retrieve Data

The most straightforward means of pulling data out of the database is to use a SQL select query to reduce the number of RECORDS and COLUMNS returned and dump the resulting columns into a parsable text file:

db=# SELECT road_id, ST_AsText(road_geom) AS geom, road_name FROM roads;

road_id | geom                                    | road_name
--------+-----------------------------------------+-----------
	  1 | LINESTRING(191232 243118,191108 243242) | Jeff Rd
	  2 | LINESTRING(189141 244158,189265 244817) | Geordie Rd
	  3 | LINESTRING(192783 228138,192612 229814) | Paul St
	  4 | LINESTRING(189412 252431,189631 259122) | Graeme Ave
	  5 | LINESTRING(190131 224148,190871 228134) | Phil Tce
	  6 | LINESTRING(198231 263418,198213 268322) | Dave Cres
	  7 | LINESTRING(218421 284121,224123 241231) | Chris Way
(6 rows)

However, there will be times when some kind of restriction is necessary to cut down the number of fields returned. In the case of attribute-based restrictions, just use the same SQL syntax as normal with a non-spatial table. In the case of spatial restrictions, the following operators are available/useful:

&&

This operator tells whether the bounding box of one geometry intersects the bounding box of another.

ST_OrderingEquals

This tests whether two geometries are geometrically identical. For example, if 'POLYGON((0 0,1 1,1 0,0 0))' is the same as 'POLYGON((0 0,1 1,1 0,0 0))' (it is).

=

This operator is a little more naive, it only tests whether the bounding boxes of two geometries are the same.

Next, you can use these operators in queries. Note that when specifying geometries and boxes on the SQL command line, you must explicitly turn the string representations into geometries by using the "ST_GeomFromText()" function. The 312 is a fictitious spatial reference system that matches our data. So, for example:

SELECT road_id, road_name
  FROM roads
  WHERE ST_OrderingEquals(roads_geom , ST_GeomFromText('LINESTRING(191232 243118,191108 243242)',312) ) ;

The above query would return the single record from the "ROADS_GEOM" table in which the geometry was equal to that value.

When using the "&&" operator, you can specify either a BOX3D as the comparison feature or a GEOMETRY. When you specify a GEOMETRY, however, its bounding box will be used for the comparison.

SELECT road_id, road_name
FROM roads
WHERE roads_geom && ST_GeomFromText('POLYGON((...))',312);

The above query will use the bounding box of the polygon for comparison purposes.

The most common spatial query will probably be a "frame-based" query, used by client software, like data browsers and web mappers, to grab a "map frame" worth of data for display. Using a "BOX3D" object for the frame, such a query looks like this:

SELECT ST_AsText(roads_geom) AS geom
FROM roads
WHERE
  roads_geom && ST_MakeEnvelope(191232, 243117,191232, 243119,312);

Note the use of the SRID 312, to specify the projection of the envelope.

4.5.2. Using the Dumper

The pgsql2shp table dumper connects directly to the database and converts a table (possibly defined by a query) into a shape file. The basic syntax is:

pgsql2shp [<options>] <database> [<schema>.]<table>
pgsql2shp [<options>] <database> <query>

The commandline options are:

-f <filename>

Write the output to a particular filename.

-h <host>

The database host to connect to.

-p <port>

The port to connect to on the database host.

-P <password>

The password to use when connecting to the database.

-u <user>

The username to use when connecting to the database.

-g <geometry column>

In the case of tables with multiple geometry columns, the geometry column to use when writing the shape file.

-b

Use a binary cursor. This will make the operation faster, but will not work if any NON-geometry attribute in the table lacks a cast to text.

-r

Raw mode. Do not drop the gid field, or escape column names.

-d

For backward compatibility: write a 3-dimensional shape file when dumping from old (pre-1.0.0) postgis databases (the default is to write a 2-dimensional shape file in that case). Starting from postgis-1.0.0+, dimensions are fully encoded.

-m filename

Remap identifiers to ten character names. The content of the file is lines of two symbols separated by a single white space and no trailing or leading space: VERYLONGSYMBOL SHORTONE ANOTHERVERYLONGSYMBOL SHORTER etc.

4.6. Building Indexes

Indexes are what make using a spatial database for large data sets possible. Without indexing, any search for a feature would require a "sequential scan" of every record in the database. Indexing speeds up searching by organizing the data into a search tree which can be quickly traversed to find a particular record. PostgreSQL supports three kinds of indexes by default: B-Tree indexes, R-Tree indexes, and GiST indexes.

  • B-Trees are used for data which can be sorted along one axis; for example, numbers, letters, dates. GIS data cannot be rationally sorted along one axis (which is greater, (0,0) or (0,1) or (1,0)?) so B-Tree indexing is of no use for us.

  • R-Trees break up data into rectangles, and sub-rectangles, and sub-sub rectangles, etc. R-Trees are used by some spatial databases to index GIS data, but the PostgreSQL R-Tree implementation is not as robust as the GiST implementation.

  • GiST (Generalized Search Trees) indexes break up data into "things to one side", "things which overlap", "things which are inside" and can be used on a wide range of data-types, including GIS data. PostGIS uses an R-Tree index implemented on top of GiST to index GIS data.

4.6.1. GiST Indexes

GiST stands for "Generalized Search Tree" and is a generic form of indexing. In addition to GIS indexing, GiST is used to speed up searches on all kinds of irregular data structures (integer arrays, spectral data, etc) which are not amenable to normal B-Tree indexing.

Once a GIS data table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data (unless all your searches are based on attributes, in which case you'll want to build a normal index on the attribute fields).

The syntax for building a GiST index on a "geometry" column is as follows:

CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometryfield] ); 

The above syntax will always build a 2D-index. To get the an n-dimensional index supported in PostGIS 2.0+ for the geometry type, you can create one using this syntax

CREATE INDEX [indexname] ON [tablename] USING GIST ([geometryfield] gist_geometry_ops_nd);

Building a spatial index is a computationally intensive exercise: on tables of around 1 million rows, on a 300MHz Solaris machine, we have found building a GiST index takes about 1 hour. After building an index, it is important to force PostgreSQL to collect table statistics, which are used to optimize query plans:

VACUUM ANALYZE [table_name] [(column_name)];
-- This is only needed for PostgreSQL 7.4 installations and below
SELECT UPDATE_GEOMETRY_STATS([table_name], [column_name]);

GiST indexes have two advantages over R-Tree indexes in PostgreSQL. Firstly, GiST indexes are "null safe", meaning they can index columns which include null values. Secondly, GiST indexes support the concept of "lossiness" which is important when dealing with GIS objects larger than the PostgreSQL 8K page size. Lossiness allows PostgreSQL to store only the "important" part of an object in an index -- in the case of GIS objects, just the bounding box. GIS objects larger than 8K will cause R-Tree indexes to fail in the process of being built.

4.6.2. BRIN Indexes

BRIN stands for "Block Range Index" and is a generic form of indexing that has been introduced in PostgreSQL 9.5. BRIN is a lossy kind of index, and its main usage is to provide a compromise for both read and write performance. Its primary goal is to handle very large tables for which some of the columns have some natural correlation with their physical location within the table. In addition to GIS indexing, BRIN is used to speed up searches on various kinds of regular or irregular data structures (integer, arrays etc).

Once a GIS data table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data (unless all your searches are based on attributes, in which case you'll want to build a normal index on the attribute fields). GiST indexes are really performant as long as their size doesn't exceed the amount of RAM available for the database, and as long as you can afford the storage size, and the penalty in write workload. Otherwise, BRIN index can be considered as an alternative.

The idea of a BRIN index is to store only the bouding box englobing all the geometries contained in all the rows in a set of table blocks, called a range. Obviously, this indexing method will only be efficient if the data is physically ordered in a way where the resulting bouding boxes for block ranges will be mutually exclusive. The resulting index will be really small, but will be less efficient than a GiST index in many cases.

Building a BRIN index is way less intensive than building a GiST index. It's quite common to build a BRIN index in more than ten time less than a GiST index would have required. As a BRIN index only store one bouding box for one to many table blocks, it's pretty common to consume up to a thousand time less disk space for this kind of indexes.

You can choose the number of blocks to summarize in a range. If you decrease this number, the index will be bigger but will probably help to get better performance.

The syntax for building a BRIN index on a "geometry" column is as follows:

CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geometryfield] ); 

The above syntax will always build a 2D-index. To get a 3d-dimensional index, you can create one using this syntax

CREATE INDEX [indexname] ON [tablename] USING BRIN ([geometryfield] brin_geometry_inclusion_ops_3d);

You can also get a 4d-dimensional index using the 4d operator class

CREATE INDEX [indexname] ON [tablename] USING BRIN ([geometryfield] brin_geometry_inclusion_ops_4d);

These above syntaxes will use the default number or block in a range, which is 128. To specify the number of blocks you want to summarise in a range, you can create one using this syntax

CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geometryfield] ) WITH (pages_per_range = [number]); 

Also, keep in mind that a BRIN index will only store one index value for a large number of rows. If your table stores geometries with a mixed number of dimensions, it's likely that the resulting index will have poor performance. You can avoid this drop of performance by choosing the operator class whith the least number of dimensions of the stored geometries

Also the "geography" datatype is supported for BRIN indexing. The syntax for building a BRIN index on a "geography" column is as follows:

CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geographyfield] ); 

The above syntax will always build a 2D-index for geospatial objects on the spheroid.

Currently, just the "inclusion support" is considered here, meaning that just && , ~ and @ operators can be used for the 2D cases (both for "geometry" and for "geography"), and just the &&& operator can be used for the 3D geometries. There is no support for kNN searches at the moment.

VACUUM ANALYZE [table_name] [(column_name)];
-- This is only needed for PostgreSQL 7.4 installations and below
SELECT UPDATE_GEOMETRY_STATS([table_name], [column_name]);

4.6.3. Using Indexes

Ordinarily, indexes invisibly speed up data access: once the index is built, the query planner transparently decides when to use index information to speed up a query plan. Unfortunately, the PostgreSQL query planner does not optimize the use of GiST indexes well, so sometimes searches which should use a spatial index instead default to a sequence scan of the whole table.

If you find your spatial indexes are not being used (or your attribute indexes, for that matter) there are a couple things you can do:

  • Firstly, make sure statistics are gathered about the number and distributions of values in a table, to provide the query planner with better information to make decisions around index usage. For PostgreSQL 7.4 installations and below this is done by running update_geometry_stats([table_name, column_name]) (compute distribution) and VACUUM ANALYZE [table_name] [column_name] (compute number of values). Starting with PostgreSQL 8.0 running VACUUM ANALYZE will do both operations. You should regularly vacuum your databases anyways -- many PostgreSQL DBAs have VACUUM run as an off-peak cron job on a regular basis.

  • If vacuuming does not work, you can force the planner to use the index information by using the SET ENABLE_SEQSCAN=OFF command. You should only use this command sparingly, and only on spatially indexed queries: generally speaking, the planner knows better than you do about when to use normal B-Tree indexes. Once you have run your query, you should consider setting ENABLE_SEQSCAN back on, so that other queries will utilize the planner as normal.

    [Note]

    As of version 0.6, it should not be necessary to force the planner to use the index with ENABLE_SEQSCAN .

  • If you find the planner wrong about the cost of sequential vs index scans try reducing the value of random_page_cost in postgresql.conf or using SET random_page_cost=#. Default value for the parameter is 4, try setting it to 1 or 2. Decrementing the value makes the planner more inclined of using Index scans.

4.7. Complex Queries

The raison d'etre of spatial database functionality is performing queries inside the database which would ordinarily require desktop GIS functionality. Using PostGIS effectively requires knowing what spatial functions are available, and ensuring that appropriate indexes are in place to provide good performance. The SRID of 312 used in these examples is purely for demonstration. You should be using a REAL SRID listed in the the spatial_ref_sys table and one that matches the projection of your data. If your data has no spatial reference system specified, you should be THINKING very thoughtfully why it doesn't and maybe it should.

If your reason is because you are modeling something that doesn't have a geographic spatial reference system defined such as the internals of a molecule or the floorplan of a not yet built amusement park then that's fine. If the location of the amusement park has been planned however, then it would make sense to use a suitable planar coordinate system for that location if nothing more than to ensure the amusement part is not trespassing on already existing structures.

Even in the case where you are planning a Mars expedition to transport the human race in the event of a nuclear holocaust and you want to map out the Mars planet for rehabitation, you can use a non-earthly coordinate system such as Mars 2000 make one up and insert it in the spatial_ref_sys table. Though this Mars coordinate system is a non-planar one (it's in degrees spheroidal), you can use it with the geography type to have your length and proximity measurements in meters instead of degrees.

4.7.1. Taking Advantage of Indexes

When constructing a query it is important to remember that only the bounding-box-based operators such as && can take advantage of the GiST spatial index. Functions such as ST_Distance() cannot use the index to optimize their operation. For example, the following query would be quite slow on a large table:

SELECT the_geom
FROM geom_table
WHERE ST_Distance(the_geom, ST_GeomFromText('POINT(100000 200000)', 312)) < 100

This query is selecting all the geometries in geom_table which are within 100 units of the point (100000, 200000). It will be slow because it is calculating the distance between each point in the table and our specified point, ie. one ST_Distance() calculation for each row in the table. We can avoid this by using the && operator to reduce the number of distance calculations required:

SELECT the_geom
FROM geom_table
WHERE ST_DWithin(the_geom,  ST_MakeEnvelope(90900, 190900, 100100, 200100,312), 100)

This query selects the same geometries, but it does it in a more efficient way. Assuming there is a GiST index on the_geom, the query planner will recognize that it can use the index to reduce the number of rows before calculating the result of the ST_distance() function. Notice that the ST_MakeEnvelope geometry which is used in the && operation is a 200 unit square box centered on the original point - this is our "query box". The && operator uses the index to quickly reduce the result set down to only those geometries which have bounding boxes that overlap the "query box". Assuming that our query box is much smaller than the extents of the entire geometry table, this will drastically reduce the number of distance calculations that need to be done.

[Note] Change in Behavior

As of PostGIS 1.3.0, most of the Geometry Relationship Functions, with the notable exceptions of ST_Disjoint and ST_Relate, include implicit bounding box overlap operators.

4.7.2. Examples of Spatial SQL

The examples in this section will make use of two tables, a table of linear roads, and a table of polygonal municipality boundaries. The table definitions for the bc_roads table is:

Column      | Type              | Description
------------+-------------------+-------------------
gid         | integer           | Unique ID
name        | character varying | Road Name
the_geom    | geometry          | Location Geometry (Linestring)

The table definition for the bc_municipality table is:

Column     | Type              | Description
-----------+-------------------+-------------------
gid        | integer           | Unique ID
code       | integer           | Unique ID
name       | character varying | City / Town Name
the_geom   | geometry          | Location Geometry (Polygon)
4.7.2.1. What is the total length of all roads, expressed in kilometers?
4.7.2.2. How large is the city of Prince George, in hectares?
4.7.2.3. What is the largest municipality in the province, by area?
4.7.2.4. What is the length of roads fully contained within each municipality?
4.7.2.5. Create a new table with all the roads within the city of Prince George.
4.7.2.6. What is the length in kilometers of "Douglas St" in Victoria?
4.7.2.7. What is the largest municipality polygon that has a hole?

4.7.2.1.

What is the total length of all roads, expressed in kilometers?

You can answer this question with a very simple piece of SQL:

SELECT sum(ST_Length(the_geom))/1000 AS km_roads FROM bc_roads;

km_roads
------------------
70842.1243039643
(1 row)

4.7.2.2.

How large is the city of Prince George, in hectares?

This query combines an attribute condition (on the municipality name) with a spatial calculation (of the area):

SELECT
  ST_Area(the_geom)/10000 AS hectares
FROM bc_municipality
WHERE name = 'PRINCE GEORGE';

hectares
------------------
32657.9103824927
(1 row)

4.7.2.3.

What is the largest municipality in the province, by area?

This query brings a spatial measurement into the query condition. There are several ways of approaching this problem, but the most efficient is below:

SELECT
  name,
  ST_Area(the_geom)/10000 AS hectares
FROM
  bc_municipality
ORDER BY hectares DESC
LIMIT 1;

name           | hectares
---------------+-----------------
TUMBLER RIDGE  | 155020.02556131
(1 row)

Note that in order to answer this query we have to calculate the area of every polygon. If we were doing this a lot it would make sense to add an area column to the table that we could separately index for performance. By ordering the results in a descending direction, and them using the PostgreSQL "LIMIT" command we can easily pick off the largest value without using an aggregate function like max().

4.7.2.4.

What is the length of roads fully contained within each municipality?

This is an example of a "spatial join", because we are bringing together data from two tables (doing a join) but using a spatial interaction condition ("contained") as the join condition rather than the usual relational approach of joining on a common key:

SELECT
  m.name,
  sum(ST_Length(r.the_geom))/1000 as roads_km
FROM
  bc_roads AS r,
  bc_municipality AS m
WHERE
  ST_Contains(m.the_geom,r.the_geom)
GROUP BY m.name
ORDER BY roads_km;

name                        | roads_km
----------------------------+------------------
SURREY                      | 1539.47553551242
VANCOUVER                   | 1450.33093486576
LANGLEY DISTRICT            | 833.793392535662
BURNABY                     | 773.769091404338
PRINCE GEORGE               | 694.37554369147
...

This query takes a while, because every road in the table is summarized into the final result (about 250K roads for our particular example table). For smaller overlays (several thousand records on several hundred) the response can be very fast.

4.7.2.5.

Create a new table with all the roads within the city of Prince George.

This is an example of an "overlay", which takes in two tables and outputs a new table that consists of spatially clipped or cut resultants. Unlike the "spatial join" demonstrated above, this query actually creates new geometries. An overlay is like a turbo-charged spatial join, and is useful for more exact analysis work:

CREATE TABLE pg_roads as
SELECT
  ST_Intersection(r.the_geom, m.the_geom) AS intersection_geom,
  ST_Length(r.the_geom) AS rd_orig_length,
  r.*
FROM
  bc_roads AS r,
  bc_municipality AS m
WHERE  m.name = 'PRINCE GEORGE' AND ST_Intersects(r.the_geom, m.the_geom);

4.7.2.6.

What is the length in kilometers of "Douglas St" in Victoria?

SELECT
  sum(ST_Length(r.the_geom))/1000 AS kilometers
FROM
  bc_roads r,
  bc_municipality m
WHERE  r.name = 'Douglas St' AND m.name = 'VICTORIA'
	AND ST_Contains(m.the_geom, r.the_geom) ;

kilometers
------------------
4.89151904172838
(1 row)

4.7.2.7.

What is the largest municipality polygon that has a hole?

SELECT gid, name, ST_Area(the_geom) AS area
FROM bc_municipality
WHERE ST_NRings(the_geom) > 1
ORDER BY area DESC LIMIT 1;

gid  | name         | area
-----+--------------+------------------
12   | SPALLUMCHEEN | 257374619.430216
(1 row)

Chapter 5. Raster Data Management, Queries, and Applications

5.1. Loading and Creating Rasters

For most use cases, you will create PostGIS rasters by loading existing raster files using the packaged raster2pgsql raster loader.

5.1.1. Using raster2pgsql to load rasters

The raster2pgsql is a raster loader executable that loads GDAL supported raster formats into sql suitable for loading into a PostGIS raster table. It is capable of loading folders of raster files as well as creating overviews of rasters.

Since the raster2pgsql is compiled as part of PostGIS most often (unless you compile your own GDAL library), the raster types supported by the executable will be the same as those compiled in the GDAL dependency library. To get a list of raster types your particular raster2pgsql supports use the -G switch. These should be the same as those provided by your PostGIS install documented here ST_GDALDrivers if you are using the same gdal library for both.

[Note]

The older version of this tool was a python script. The executable has replaced the python script. If you still find the need for the Python script Examples of the python one can be found at GDAL PostGIS Raster Driver Usage . Please note that the raster2pgsql python script may not work with future versions of PostGIS raster and is no longer supported.

[Note]

When creating overviews of a specific factor from a set of rasters that are aligned, it is possible for the overviews to not align. Visit http://trac.osgeo.org/postgis/ticket/1764 for an example where the overviews do not align.

EXAMPLE USAGE:

raster2pgsql raster_options_go_here raster_file someschema.sometable > out.sql

-?

Display help screen. Help will also display if you don't pass in any arguments.

-G

Print the supported raster formats.

(c|a|d|p) These are mutually exclusive options:

-c

Create new table and populate it with raster(s), this is the default mode

-a

Append raster(s) to an existing table.

-d

Drop table, create new one and populate it with raster(s)

-p

Prepare mode, only create the table.

Raster processing: Applying constraints for proper registering in raster catalogs

-C

Apply raster constraints -- srid, pixelsize etc. to ensure raster is properly registered in raster_columns view.

-x

Disable setting the max extent constraint. Only applied if -C flag is also used.

-r

Set the constraints (spatially unique and coverage tile) for regular blocking. Only applied if -C flag is also used.

Raster processing: Optional parameters used to manipulate input raster dataset

-s <SRID>

Assign output raster with specified SRID. If not provided or is zero, raster's metadata will be checked to determine an appropriate SRID.

-b BAND

Index (1-based) of band to extract from raster. For more than one band index, separate with comma (,). If unspecified, all bands of raster will be extracted.

-t TILE_SIZE

Cut raster into tiles to be inserted one per table row. TILE_SIZE is expressed as WIDTHxHEIGHT or set to the value "auto" to allow the loader to compute an appropriate tile size using the first raster and applied to all rasters.

-P

Pad right-most and bottom-most tiles to guarantee that all tiles have the same width and height.

-R, --register

Register the raster as a filesystem (out-db) raster.

Only the metadata of the raster and path location to the raster is stored in the database (not the pixels).

-l OVERVIEW_FACTOR

Create overview of the raster. For more than one factor, separate with comma(,). Overview table name follows the pattern o_ overview factor _ table , where overview factor is a placeholder for numerical overview factor and table is replaced with the base table name. Created overview is stored in the database and is not affected by -R. Note that your generated sql file will contain both the main table and overview tables.

-N NODATA

NODATA value to use on bands without a NODATA value.

Optional parameters used to manipulate database objects

-q

Wrap PostgreSQL identifiers in quotes

-f COLUMN

Specify name of destination raster column, default is 'rast'

-F

Add a column with the name of the file

-n COLUMN

Specify the name of the filename column. Implies -F.

-q

Wrap PostgreSQL identifiers in quotes.

-I

Create a GiST index on the raster column.

-M

Vacuum analyze the raster table.

-k

Skip NODATA value checks for each raster band.

-T tablespace

Specify the tablespace for the new table. Note that indices (including the primary key) will still use the default tablespace unless the -X flag is also used.

-X tablespace

Specify the tablespace for the table's new index. This applies to the primary key and the spatial index if the -I flag is used.

-Y

Use copy statements instead of insert statements.

-e

Execute each statement individually, do not use a transaction.

-E ENDIAN

Control endianness of generated binary output of raster; specify 0 for XDR and 1 for NDR (default); only NDR output is supported now

-V version

Specify version of output format. Default is 0. Only 0 is supported at this time.

An example session using the loader to create an input file and uploading it chunked in 100x100 tiles might look like this:

[Note]

You can leave the schema name out e.g demelevation instead of public.demelevation and the raster table will be created in the default schema of the database or user

raster2pgsql -s 4326 -I -C -M *.tif -F -t 100x100 public.demelevation > elev.sql
psql -d gisdb -f elev.sql

A conversion and upload can be done all in one step using UNIX pipes:

raster2pgsql -s 4326 -I -C -M *.tif -F -t 100x100 public.demelevation | psql -d gisdb

Load rasters Massachusetts state plane meters aerial tiles into a schema called aerial and create a full view, 2 and 4 level overview tables, use copy mode for inserting (no intermediary file just straight to db), and -e don't force everything in a transaction (good if you want to see data in tables right away without waiting). Break up the rasters into 128x128 pixel tiles and apply raster constraints. Use copy mode instead of table insert. (-F) Include a field called filename to hold the name of the file the tiles were cut from.

raster2pgsql -I -C -e -Y -F -s 26986 -t 128x128  -l 2,4 bostonaerials2008/*.jpg aerials.boston | psql -U postgres -d gisdb -h localhost -p 5432
--get a list of raster types supported:
raster2pgsql -G

The -G commands outputs a list something like

Available GDAL raster formats:
  Virtual Raster
  GeoTIFF
  National Imagery Transmission Format
  Raster Product Format TOC format
  ECRG TOC format
  Erdas Imagine Images (.img)
  CEOS SAR Image
  CEOS Image
  JAXA PALSAR Product Reader (Level 1.1/1.5)
  Ground-based SAR Applications Testbed File Format (.gff)
  ELAS
  Arc/Info Binary Grid
  Arc/Info ASCII Grid
  GRASS ASCII Grid
  SDTS Raster
  DTED Elevation Raster
  Portable Network Graphics
  JPEG JFIF
  In Memory Raster
  Japanese DEM (.mem)
  Graphics Interchange Format (.gif)
  Graphics Interchange Format (.gif)
  Envisat Image Format
  Maptech BSB Nautical Charts
  X11 PixMap Format
  MS Windows Device Independent Bitmap
  SPOT DIMAP
  AirSAR Polarimetric Image
  RadarSat 2 XML Product
  PCIDSK Database File
  PCRaster Raster File
  ILWIS Raster Map
  SGI Image File Format 1.0
  SRTMHGT File Format
  Leveller heightfield
  Terragen heightfield
  USGS Astrogeology ISIS cube (Version 3)
  USGS Astrogeology ISIS cube (Version 2)
  NASA Planetary Data System
  EarthWatch .TIL
  ERMapper .ers Labelled
  NOAA Polar Orbiter Level 1b Data Set
  FIT Image
  GRIdded Binary (.grb)
  Raster Matrix Format
  EUMETSAT Archive native (.nat)
  Idrisi Raster A.1
  Intergraph Raster
  Golden Software ASCII Grid (.grd)
  Golden Software Binary Grid (.grd)
  Golden Software 7 Binary Grid (.grd)
  COSAR Annotated Binary Matrix (TerraSAR-X)
  TerraSAR-X Product
  DRDC COASP SAR Processor Raster
  R Object Data Store
  Portable Pixmap Format (netpbm)
  USGS DOQ (Old Style)
  USGS DOQ (New Style)
  ENVI .hdr Labelled
  ESRI .hdr Labelled
  Generic Binary (.hdr Labelled)
  PCI .aux Labelled
  Vexcel MFF Raster
  Vexcel MFF2 (HKV) Raster
  Fuji BAS Scanner Image
  GSC Geogrid
  EOSAT FAST Format
  VTP .bt (Binary Terrain) 1.3 Format
  Erdas .LAN/.GIS
  Convair PolGASP
  Image Data and Analysis
  NLAPS Data Format
  Erdas Imagine Raw
  DIPEx
  FARSITE v.4 Landscape File (.lcp)
  NOAA Vertical Datum .GTX
  NADCON .los/.las Datum Grid Shift
  NTv2 Datum Grid Shift
  ACE2
  Snow Data Assimilation System
  Swedish Grid RIK (.rik)
  USGS Optional ASCII DEM (and CDED)
  GeoSoft Grid Exchange Format
  Northwood Numeric Grid Format .grd/.tab
  Northwood Classified Grid Format .grc/.tab
  ARC Digitized Raster Graphics
  Standard Raster Product (ASRP/USRP)
  Magellan topo (.blx)
  SAGA GIS Binary Grid (.sdat)
  Kml Super Overlay
  ASCII Gridded XYZ
  HF2/HFZ heightfield raster
  OziExplorer Image File
  USGS LULC Composite Theme Grid
  Arc/Info Export E00 GRID
  ZMap Plus Grid
  NOAA NGS Geoid Height Grids

5.1.2. Creating rasters using PostGIS raster functions

On many occasions, you'll want to create rasters and raster tables right in the database. There are a plethora of functions to do that. The general steps to follow.

  1. Create a table with a raster column to hold the new raster records which can be accomplished with:

    CREATE TABLE myrasters(rid serial primary key, rast raster);
  2. There are many functions to help with that goal. If you are creating rasters not as a derivative of other rasters, you will want to start with: ST_MakeEmptyRaster , followed by ST_AddBand

    You can also create rasters from geometries. To achieve that you'll want to use ST_AsRaster perhaps accompanied with other functions such as ST_Union or ST_MapAlgebraFct or any of the family of other map algebra functions.

    There are even many more options for creating new raster tables from existing tables. For example you can create a raster table in a different projection from an existing one using ST_Transform

  3. Once you are done populating your table initially, you'll want to create a spatial index on the raster column with something like:

    CREATE INDEX myrasters_rast_st_convexhull_idx ON myrasters USING gist( ST_ConvexHull(rast) );

    Note the use of ST_ConvexHull since most raster operators are based on the convex hull of the rasters.

    [Note]

    Pre-2.0 versions of PostGIS raster were based on the envelop rather than the convex hull. For the spatial indexes to work properly you'll need to drop those and replace with convex hull based index.

  4. Apply raster constraints using AddRasterConstraints

5.2. Raster Catalogs

There are two raster catalog views that come packaged with PostGIS. Both views utilize information embedded in the constraints of the raster tables. As a result the catalog views are always consistent with the raster data in the tables since the constraints are enforced.

  1. raster_columns this view catalogs all the raster table columns in your database.

  2. raster_overviews this view catalogs all the raster table columns in your database that serve as overviews for a finer grained table. Tables of this type are generated when you use the -l switch during load.

5.2.1. Raster Columns Catalog

The raster_columns is a catalog of all raster table columns in your database that are of type raster. It is a view utilizing the constraints on the tables so the information is always consistent even if you restore one raster table from a backup of another database. The following columns exist in the raster_columns catalog.

If you created your tables not with the loader or forgot to specify the -C flag during load, you can enforce the constraints after the fact using AddRasterConstraints so that the raster_columns catalog registers the common information about your raster tiles.

  • r_table_catalog The database the table is in. This will always read the current database.

  • r_table_schema The database schema the raster table belongs to.

  • r_table_name raster table

  • r_raster_column the column in the r_table_name table that is of type raster. There is nothing in PostGIS preventing you from having multiple raster columns per table so its possible to have a raster table listed multiple times with a different raster column for each.

  • srid The spatial reference identifier of the raster. Should be an entry in the Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems” .

  • scale_x The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same scale_x and this constraint is applied. Refer to ST_ScaleX for more details.

  • scale_y The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same scale_y and the scale_y constraint is applied. Refer to ST_ScaleY for more details.

  • blocksize_x The width (number of pixels across) of each raster tile . Refer to ST_Width for more details.

  • blocksize_y The width (number of pixels down) of each raster tile . Refer to ST_Height for more details.

  • same_alignment A boolean that is true if all the raster tiles have the same alignment . Refer to ST_SameAlignment for more details.

  • regular_blocking If the raster column has the spatially unique and coverage tile constraints, the value with be TRUE. Otherwise, it will be FALSE.

  • num_bands The number of bands in each tile of your raster set. This is the same information as what is provided by ST_NumBands

  • pixel_types An array defining the pixel type for each band. You will have the same number of elements in this array as you have number of bands. The pixel_types are one of the following defined in ST_BandPixelType .

  • nodata_values An array of double precision numbers denoting the nodata_value for each band. You will have the same number of elements in this array as you have number of bands. These numbers define the pixel value for each band that should be ignored for most operations. This is similar information provided by ST_BandNoDataValue .

  • out_db An array of boolean flags indicating if the raster bands data is maintained outside the database. You will have the same number of elements in this array as you have number of bands.

  • extent This is the extent of all the raster rows in your raster set. If you plan to load more data that will change the extent of the set, you'll want to run the DropRasterConstraints function before load and then reapply constraints with AddRasterConstraints after load.

  • spatial_index A boolean that is true if raster column has a spatial index.

5.2.2. Raster Overviews

raster_overviews catalogs information about raster table columns used for overviews and additional information about them that is useful to know when utilizing overviews. Overview tables are cataloged in both raster_columns and raster_overviews because they are rasters in their own right but also serve an additional special purpose of being a lower resolution caricature of a higher resolution table. These are generated along-side the main raster table when you use the -l switch in raster loading or can be generated manually using AddOverviewConstraints .

Overview tables contain the same constraints as other raster tables as well as additional informational only constraints specific to overviews.

[Note]

The information in raster_overviews does not duplicate the information in raster_columns . If you need the information about an overview table present in raster_columns you can join the raster_overviews and raster_columns together to get the full set of information you need.

Two main reasons for overviews are:

  1. Low resolution representation of the core tables commonly used for fast mapping zoom-out.

  2. Computations are generally faster to do on them than their higher resolution parents because there are fewer records and each pixel covers more territory. Though the computations are not as accurate as the high-res tables they support, they can be sufficient in many rule-of-thumb computations.

The raster_overviews catalog contains the following columns of information.

  • o_table_catalog The database the overview table is in. This will always read the current database.

  • o_table_schema The database schema the overview raster table belongs to.

  • o_table_name raster overview table name

  • o_raster_column the raster column in the overview table.

  • r_table_catalog The database the raster table that this overview services is in. This will always read the current database.

  • r_table_schema The database schema the raster table that this overview services belongs to.

  • r_table_name raster table that this overview services.

  • r_raster_column the raster column that this overview column services.

  • overview_factor - this is the pyramid level of the overview table. The higher the number the lower the resolution of the table. raster2pgsql if given a folder of images, will compute overview of each image file and load separately. Level 1 is assumed and always the original file. Level 2 is will have each tile represent 4 of the original. So for example if you have a folder of 5000x5000 pixel image files that you chose to chunk 125x125, for each image file your base table will have (5000*5000)/(125*125) records = 1600, your (l=2) o_2 table will have ceiling(1600/Power(2,2)) = 400 rows, your (l=3) o_3 will have ceiling(1600/Power(2,3) ) = 200 rows. If your pixels aren't divisible by the size of your tiles, you'll get some scrap tiles (tiles not completely filled). Note that each overview tile generated by raster2pgsql has the same number of pixels as its parent, but is of a lower resolution where each pixel of it represents (Power(2,overview_factor) pixels of the original).

5.3. Building Custom Applications with PostGIS Raster

The fact that PostGIS raster provides you with SQL functions to render rasters in known image formats gives you a lot of optoins for rendering them. For example you can use OpenOffice / LibreOffice for rendering as demonstrated in Rendering PostGIS Raster graphics with LibreOffice Base Reports . In addition you can use a wide variety of languages as demonstrated in this section.

5.3.1. PHP Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we'll demonstrate how to use the PHP PostgreSQL driver and the ST_AsGDALRaster family of functions to output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect a particular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms to user specified projection using ST_Transform , and then outputs the results as a png using ST_AsPNG .

You would call the below using

http://mywebserver/test_raster.php?srid=2249

to get the raster image in Massachusetts state plane feet.

<?php
/** contents of test_raster.php **/
$conn_str ='dbname=mydb host=localhost port=5432 user=myuser password=mypwd';
$dbconn = pg_connect($conn_str);
header('Content-Type: image/png');
/**If a particular projection was requested use it otherwise use mass state plane meters **/
if (!empty( $_REQUEST['srid'] ) && is_numeric( $_REQUEST['srid']) ){
		$input_srid = intval($_REQUEST['srid']);
}
else { $input_srid = 26986; }
/** The set bytea_output may be needed for PostgreSQL 9.0+, but not for 8.4 **/
$sql = "set bytea_output='escape';
SELECT ST_AsPNG(ST_Transform(
			ST_AddBand(ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)])
				,$input_srid) ) As new_rast
 FROM aerials.boston
	WHERE
	 ST_Intersects(rast, ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, 42.218,4326),26986) )";
$result = pg_query($sql);
$row = pg_fetch_row($result);
pg_free_result($result);
if ($row === false) return;
echo pg_unescape_bytea($row[0]);
?>

5.3.2. ASP.NET C# Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we'll demonstrate how to use Npgsql PostgreSQL .NET driver and the ST_AsGDALRaster family of functions to output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

You will need the npgsql .NET PostgreSQL driver for this exercise which you can get the latest of from http://npgsql.projects.postgresql.org/ . Just download the latest and drop into your ASP.NET bin folder and you'll be good to go.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect a particular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms to user specified projection using ST_Transform , and then outputs the results as a png using ST_AsPNG .

This is same example as Section 5.3.1, “PHP Example Outputting using ST_AsPNG in concert with other raster functions” except implemented in C#.

You would call the below using

http://mywebserver/TestRaster.ashx?srid=2249

to get the raster image in Massachusetts state plane feet.

 -- web.config connection string section --
<connectionStrings>
    <add name="DSN"
        connectionString="server=localhost;database=mydb;Port=5432;User Id=myuser;password=mypwd"/>
</connectionStrings>
// Code for TestRaster.ashx
<%@ WebHandler Language="C#" Class="TestRaster" %>
using System;
using System.Data;
using System.Web;
using Npgsql;

public class TestRaster : IHttpHandler
{
	public void ProcessRequest(HttpContext context)
	{

		context.Response.ContentType = "image/png";
		context.Response.BinaryWrite(GetResults(context));

	}

	public bool IsReusable {
		get { return false; }
	}

	public byte[] GetResults(HttpContext context)
	{
		byte[] result = null;
		NpgsqlCommand command;
		string sql = null;
		int input_srid = 26986;
        try {
		    using (NpgsqlConnection conn = new NpgsqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DSN"].ConnectionString)) {
			    conn.Open();

                if (context.Request["srid"] != null)
                {
                    input_srid = Convert.ToInt32(context.Request["srid"]);
                }
                sql = @"SELECT ST_AsPNG(
                            ST_Transform(
			                ST_AddBand(
                                ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)])
				                    ,:input_srid) ) As new_rast
                        FROM aerials.boston
	                        WHERE
	                            ST_Intersects(rast,
                                    ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, 42.218,4326),26986) )";
			    command = new NpgsqlCommand(sql, conn);
                command.Parameters.Add(new NpgsqlParameter("input_srid", input_srid));


			    result = (byte[]) command.ExecuteScalar();
                conn.Close();
			}

		}
        catch (Exception ex)
        {
            result = null;
            context.Response.Write(ex.Message.Trim());
        }
		return result;
	}
}

5.3.3. Java console app that outputs raster query as Image file

This is a simple java console app that takes a query that returns one image and outputs to specified file.

You can download the latest PostgreSQL JDBC drivers from http://jdbc.postgresql.org/download.html

You can compile the following code using a command something like:

set env CLASSPATH .:..\postgresql-9.0-801.jdbc4.jar
javac SaveQueryImage.java
jar cfm SaveQueryImage.jar Manifest.txt *.class

And call it from the command-line with something like

java -jar SaveQueryImage.jar "SELECT ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),10, 'quad_segs=2'),150, 150, '8BUI',100));" "test.png" 
 -- Manifest.txt --
Class-Path: postgresql-9.0-801.jdbc4.jar
Main-Class: SaveQueryImage
// Code for SaveQueryImage.java
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.io.*;

public class SaveQueryImage {
  public static void main(String[] argv) {
      System.out.println("Checking if Driver is registered with DriverManager.");

      try {
        //java.sql.DriverManager.registerDriver (new org.postgresql.Driver());
        Class.forName("org.postgresql.Driver");
      }
      catch (ClassNotFoundException cnfe) {
        System.out.println("Couldn't find the driver!");
        cnfe.printStackTrace();
        System.exit(1);
      }

      Connection conn = null;

      try {
        conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/mydb","myuser", "mypwd");
        conn.setAutoCommit(false);

        PreparedStatement sGetImg = conn.prepareStatement(argv[0]);

        ResultSet rs = sGetImg.executeQuery();

		FileOutputStream fout;
		try
		{
			rs.next();
			/** Output to file name requested by user **/
			fout = new FileOutputStream(new File(argv[1]) );
			fout.write(rs.getBytes(1));
			fout.close();
		}
		catch(Exception e)
		{
			System.out.println("Can't create file");
			e.printStackTrace();
		}

        rs.close();
		sGetImg.close();
        conn.close();
      }
      catch (SQLException se) {
        System.out.println("Couldn't connect: print out a stack trace and exit.");
        se.printStackTrace();
        System.exit(1);
      }
  }
}

5.3.4. Use PLPython to dump out images via SQL

This is a plpython stored function that creates a file in the server directory for each record. Requires you have plpython installed. Should work fine with both plpythonu and plpython3u.

CREATE OR REPLACE FUNCTION write_file (param_bytes bytea, param_filepath text)
RETURNS text
AS $$
f = open(param_filepath, 'wb+')
f.write(param_bytes)
return param_filepath
$$ LANGUAGE plpythonu;
--write out 5 images to the PostgreSQL server in varying sizes
-- note the postgresql daemon account needs to have write access to folder
-- this echos back the file names created;
 SELECT write_file(ST_AsPNG(
	ST_AsRaster(ST_Buffer(ST_Point(1,5),j*5, 'quad_segs=2'),150*j, 150*j, '8BUI',100)),
	 'C:/temp/slices'|| j || '.png')
	 FROM generate_series(1,5) As j;

     write_file
---------------------
 C:/temp/slices1.png
 C:/temp/slices2.png
 C:/temp/slices3.png
 C:/temp/slices4.png
 C:/temp/slices5.png

5.3.5. Outputting Rasters with PSQL

Sadly PSQL doesn't have easy to use built-in functionality for outputting binaries. This is a bit of a hack that piggy backs on PostgreSQL somewhat legacy large object support. To use first launch your psql commandline connected to your database.

Unlike the python approach, this approach creates the file on your local computer.

SELECT oid, lowrite(lo_open(oid, 131072), png) As num_bytes
 FROM
 ( VALUES (lo_create(0),
   ST_AsPNG( (SELECT rast FROM aerials.boston WHERE rid=1) )
  ) ) As v(oid,png);
-- you'll get an output something like --
   oid   | num_bytes
---------+-----------
 2630819 |     74860

-- next note the oid and do this replacing the c:/test.png to file path location
-- on your local computer
 \lo_export 2630819 'C:/temp/aerial_samp.png'

-- this deletes the file from large object storage on db
SELECT lo_unlink(2630819);
			

Chapter 6. Using PostGIS Geometry: Building Applications

6.1. Using MapServer

The Minnesota MapServer is an internet web-mapping server which conforms to the OpenGIS Web Mapping Server specification.

6.1.1. Basic Usage

To use PostGIS with MapServer, you will need to know about how to configure MapServer, which is beyond the scope of this documentation. This section will cover specific PostGIS issues and configuration details.

To use PostGIS with MapServer, you will need:

  • Version 0.6 or newer of PostGIS.

  • Version 3.5 or newer of MapServer.

MapServer accesses PostGIS/PostgreSQL data like any other PostgreSQL client -- using the libpq interface. This means that MapServer can be installed on any machine with network access to the PostGIS server, and use PostGIS as a source of data. The faster the connection between the systems, the better.

  1. Compile and install MapServer, with whatever options you desire, including the "--with-postgis" configuration option.

  2. In your MapServer map file, add a PostGIS layer. For example:

    LAYER
      CONNECTIONTYPE postgis
      NAME "widehighways"
      # Connect to a remote spatial database
      CONNECTION "user=dbuser dbname=gisdatabase host=bigserver"
      PROCESSING "CLOSE_CONNECTION=DEFER"
      # Get the lines from the 'geom' column of the 'roads' table
      DATA "geom from roads using srid=4326 using unique gid"
      STATUS ON
      TYPE LINE
      # Of the lines in the extents, only render the wide highways
      FILTER "type = 'highway' and numlanes >= 4"
      CLASS
        # Make the superhighways brighter and 2 pixels wide
        EXPRESSION ([numlanes] >= 6)
        STYLE
          COLOR 255 22 22
          WIDTH 2
        END
      END
      CLASS
        # All the rest are darker and only 1 pixel wide
        EXPRESSION ([numlanes] < 6)
        STYLE
          COLOR 205 92 82
        END
      END
    END

    In the example above, the PostGIS-specific directives are as follows:

    CONNECTIONTYPE

    For PostGIS layers, this is always "postgis".

    CONNECTION

    The database connection is governed by the a 'connection string' which is a standard set of keys and values like this (with the default values in <>):

    user=<username> password=<password> dbname=<username> hostname=<server> port=<5432>

    An empty connection string is still valid, and any of the key/value pairs can be omitted. At a minimum you will generally supply the database name and username to connect with.

    DATA

    The form of this parameter is "<geocolumn> from <tablename> using srid=<srid> using unique <primary key>" where the column is the spatial column to be rendered to the map, the SRID is SRID used by the column and the primary key is the table primary key (or any other uniquely-valued column with an index).

    You can omit the "using srid" and "using unique" clauses and MapServer will automatically determine the correct values if possible, but at the cost of running a few extra queries on the server for each map draw.

    PROCESSING

    Putting in a CLOSE_CONNECTION=DEFER if you have multiple layers reuses existing connections instead of closing them. This improves speed. Refer to for MapServer PostGIS Performance Tips for a more detailed explanation.

    FILTER

    The filter must be a valid SQL string corresponding to the logic normally following the "WHERE" keyword in a SQL query. So, for example, to render only roads with 6 or more lanes, use a filter of "num_lanes >= 6".

  3. In your spatial database, ensure you have spatial (GiST) indexes built for any the layers you will be drawing.

    CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );
  4. If you will be querying your layers using MapServer you will also need to use the "using unique" clause in your DATA statement.

    MapServer requires unique identifiers for each spatial record when doing queries, and the PostGIS module of MapServer uses the unique value you specify in order to provide these unique identifiers. Using the table primary key is the best practice.

6.1.2. Frequently Asked Questions

6.1.2.1. When I use an EXPRESSION in my map file, the condition never returns as true, even though I know the values exist in my table.
6.1.2.2. The FILTER I use for my Shape files is not working for my PostGIS table of the same data.
6.1.2.3. My PostGIS layer draws much slower than my Shape file layer, is this normal?
6.1.2.4. My PostGIS layer draws fine, but queries are really slow. What is wrong?
6.1.2.5. Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?

6.1.2.1.

When I use an EXPRESSION in my map file, the condition never returns as true, even though I know the values exist in my table.

Unlike shape files, PostGIS field names have to be referenced in EXPRESSIONS using lower case .

EXPRESSION ([numlanes] >= 6)

6.1.2.2.

The FILTER I use for my Shape files is not working for my PostGIS table of the same data.

Unlike shape files, filters for PostGIS layers use SQL syntax (they are appended to the SQL statement the PostGIS connector generates for drawing layers in MapServer).

FILTER "type = 'highway' and numlanes >= 4"

6.1.2.3.

My PostGIS layer draws much slower than my Shape file layer, is this normal?

In general, the more features you are drawing into a given map, the more likely it is that PostGIS will be slower than Shape files. For maps with relatively few features (100s), PostGIS will often be faster. For maps with high feature density (1000s), PostGIS will always be slower.

If you are finding substantial draw performance problems, it is possible that you have not built a spatial index on your table.

postgis# CREATE INDEX geotable_gix ON geotable USING GIST ( geocolumn );
postgis# VACUUM ANALYZE;

6.1.2.4.

My PostGIS layer draws fine, but queries are really slow. What is wrong?

For queries to be fast, you must have a unique key for your spatial table and you must have an index on that unique key.

You can specify what unique key for mapserver to use with the USING UNIQUE clause in your DATA line:

DATA "geom FROM geotable USING UNIQUE gid"

6.1.2.5.

Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?

Yes! MapServer understands geography columns as being the same as geometry columns, but always using an SRID of 4326. Just make sure to include a "using srid=4326" clause in your DATA statement. Everything else works exactly the same as with geometry.

DATA "geog FROM geogtable USING SRID=4326 USING UNIQUE gid"

6.1.3. Advanced Usage

The USING pseudo-SQL clause is used to add some information to help mapserver understand the results of more complex queries. More specifically, when either a view or a subselect is used as the source table (the thing to the right of "FROM" in a DATA definition) it is more difficult for mapserver to automatically determine a unique identifier for each row and also the SRID for the table. The USING clause can provide mapserver with these two pieces of information as follows:

DATA "geom FROM (
  SELECT
    table1.geom AS geom,
    table1.gid AS gid,
    table2.data AS data
  FROM table1
  LEFT JOIN table2
  ON table1.id = table2.id
) AS new_table USING UNIQUE gid USING SRID=4326"
USING UNIQUE <uniqueid>

MapServer requires a unique id for each row in order to identify the row when doing map queries. Normally it identifies the primary key from the system tables. However, views and subselects don't automatically have an known unique column. If you want to use MapServer's query functionality, you need to ensure your view or subselect includes a uniquely valued column, and declare it with USING UNIQUE . For example, you could explicitly select nee of the table's primary key values for this purpose, or any other column which is guaranteed to be unique for the result set.

[Note]

"Querying a Map" is the action of clicking on a map to ask for information about the map features in that location. Don't confuse "map queries" with the SQL query in a DATA definition.

USING SRID=<srid>

PostGIS needs to know which spatial referencing system is being used by the geometries in order to return the correct data back to MapServer. Normally it is possible to find this information in the "geometry_columns" table in the PostGIS database, however, this is not possible for tables which are created on the fly such as subselects and views. So the USING SRID= option allows the correct SRID to be specified in the DATA definition.

6.1.4. Examples

Lets start with a simple example and work our way up. Consider the following MapServer layer definition:

LAYER
  CONNECTIONTYPE postgis
  NAME "roads"
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  DATA "geom from roads"
  STATUS ON
  TYPE LINE
  CLASS
    STYLE
      COLOR 0 0 0
    END
  END
END

This layer will display all the road geometries in the roads table as black lines.

Now lets say we want to show only the highways until we get zoomed in to at least a 1:100000 scale - the next two layers will achieve this effect:

LAYER
  CONNECTIONTYPE postgis
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  PROCESSING "CLOSE_CONNECTION=DEFER"
  DATA "geom from roads"
  MINSCALE 100000
  STATUS ON
  TYPE LINE
  FILTER "road_type = 'highway'"
  CLASS
    COLOR 0 0 0
  END
END
LAYER
  CONNECTIONTYPE postgis
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  PROCESSING "CLOSE_CONNECTION=DEFER"
  DATA "geom from roads"
  MAXSCALE 100000
  STATUS ON
  TYPE LINE
  CLASSITEM road_type
  CLASS
    EXPRESSION "highway"
    STYLE
      WIDTH 2
      COLOR 255 0 0
    END
  END
  CLASS
    STYLE
      COLOR 0 0 0
    END
  END
END

The first layer is used when the scale is greater than 1:100000, and displays only the roads of type "highway" as black lines. The FILTER option causes only roads of type "highway" to be displayed.

The second layer is used when the scale is less than 1:100000, and will display highways as double-thick red lines, and other roads as regular black lines.

So, we have done a couple of interesting things using only MapServer functionality, but our DATA SQL statement has remained simple. Suppose that the name of the road is stored in another table (for whatever reason) and we need to do a join to get it and label our roads.

LAYER
  CONNECTIONTYPE postgis
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  DATA "geom FROM (SELECT roads.gid AS gid, roads.geom AS geom,
        road_names.name as name FROM roads LEFT JOIN road_names ON
        roads.road_name_id = road_names.road_name_id)
        AS named_roads USING UNIQUE gid USING SRID=4326"
  MAXSCALE 20000
  STATUS ON
  TYPE ANNOTATION
  LABELITEM name
  CLASS
    LABEL
      ANGLE auto
      SIZE 8
      COLOR 0 192 0
      TYPE truetype
      FONT arial
    END
  END
END

This annotation layer adds green labels to all the roads when the scale gets down to 1:20000 or less. It also demonstrates how to use an SQL join in a DATA definition.

6.2. Java Clients (JDBC)

Java clients can access PostGIS "geometry" objects in the PostgreSQL database either directly as text representations or using the JDBC extension objects bundled with PostGIS. In order to use the extension objects, the "postgis.jar" file must be in your CLASSPATH along with the "postgresql.jar" JDBC driver package.

import java.sql.*;
import java.util.*;
import java.lang.*;
import org.postgis.*;

public class JavaGIS {

public static void main(String[] args) {

  java.sql.Connection conn;

  try {
    /*
    * Load the JDBC driver and establish a connection.
    */
    Class.forName("org.postgresql.Driver");
    String url = "jdbc:postgresql://localhost:5432/database";
    conn = DriverManager.getConnection(url, "postgres", "");
    /*
    * Add the geometry types to the connection. Note that you
    * must cast the connection to the pgsql-specific connection
    * implementation before calling the addDataType() method.
    */
    ((org.postgresql.PGConnection)conn).addDataType("geometry",Class.forName("org.postgis.PGgeometry"));
    ((org.postgresql.PGConnection)conn).addDataType("box3d",Class.forName("org.postgis.PGbox3d"));
    /*
    * Create a statement and execute a select query.
    */
    Statement s = conn.createStatement();
    ResultSet r = s.executeQuery("select geom,id from geomtable");
    while( r.next() ) {
      /*
      * Retrieve the geometry as an object then cast it to the geometry type.
      * Print things out.
      */
      PGgeometry geom = (PGgeometry)r.getObject(1);
      int id = r.getInt(2);
      System.out.println("Row " + id + ":");
      System.out.println(geom.toString());
    }
    s.close();
    conn.close();
  }
catch( Exception e ) {
  e.printStackTrace();
  }
}
}

The "PGgeometry" object is a wrapper object which contains a specific topological geometry object (subclasses of the abstract class "Geometry") depending on the type: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon.

PGgeometry geom = (PGgeometry)r.getObject(1);
if( geom.getType() == Geometry.POLYGON ) {
  Polygon pl = (Polygon)geom.getGeometry();
  for( int r = 0; r < pl.numRings(); r++) {
    LinearRing rng = pl.getRing(r);
    System.out.println("Ring: " + r);
    for( int p = 0; p < rng.numPoints(); p++ ) {
      Point pt = rng.getPoint(p);
      System.out.println("Point: " + p);
      System.out.println(pt.toString());
    }
  }
}

The JavaDoc for the extension objects provides a reference for the various data accessor functions in the geometric objects.

6.3. C Clients (libpq)

...

6.3.1. Text Cursors

...

6.3.2. Binary Cursors

...

Chapter 7. Performance tips

7.1. Small tables of large geometries

7.1.1. Problem description

Current PostgreSQL versions (including 9.6) suffer from a query optimizer weakness regarding TOAST tables. TOAST tables are a kind of "extension room" used to store large (in the sense of data size) values that do not fit into normal data pages (like long texts, images or complex geometries with lots of vertices), see the PostgreSQL Documentation for TOAST for more information).

The problem appears if you happen to have a table with rather large geometries, but not too manyrows of them (like a table containing the boundaries of all European countries in high resolution). Then the table itself is small, but it uses lots of TOAST space. In our example case, the table itself had about 80 rows and used only 3 data pages, but the TOAST table used 8225 pages.

Now issue a query where you use the geometry operator && to search for a bounding box that matches only very few of those rows. Now the query optimizer sees that the table has only 3 pages and 80 rows. It estimates that a sequential scan on such a small table is much faster than using an index. And so it decides to ignore the GIST index. Usually, this estimation is correct. But in our case, the && operator has to fetch every geometry from disk to compare the bounding boxes, thus reading all TOAST pages, too.

To see whether your suffer from this issue, use the "EXPLAIN ANALYZE" postgresql command. For more information and the technical details, you can read the thread on the postgres performance mailing list: http://archives.postgresql.org/pgsql-performance/2005-02/msg00030.php

and newer thread on PostGIS https://lists.osgeo.org/pipermail/postgis-devel/2017-June/026209.html

7.1.2. Workarounds

The PostgreSQL people are trying to solve this issue by making the query estimation TOAST-aware. For now, here are two workarounds:

The first workaround is to force the query planner to use the index. Send "SET enable_seqscan TO off;" to the server before issuing the query. This basically forces the query planner to avoid sequential scans whenever possible. So it uses the GIST index as usual. But this flag has to be set on every connection, and it causes the query planner to make misestimations in other cases, so you should "SET enable_seqscan TO on;" after the query.

The second workaround is to make the sequential scan as fast as the query planner thinks. This can be achieved by creating an additional column that "caches" the bbox, and matching against this. In our example, the commands are like:

SELECT AddGeometryColumn('myschema','mytable','bbox','4326','GEOMETRY','2');
UPDATE mytable SET bbox = ST_Envelope(ST_Force2D(the_geom));

Now change your query to use the && operator against bbox instead of geom_column, like:

SELECT geom_column
FROM mytable
WHERE bbox && ST_SetSRID('BOX3D(0 0,1 1)'::box3d,4326);

Of course, if you change or add rows to mytable, you have to keep the bbox "in sync". The most transparent way to do this would be triggers, but you also can modify your application to keep the bbox column current or run the UPDATE query above after every modification.

7.2. CLUSTERing on geometry indices

For tables that are mostly read-only, and where a single index is used for the majority of queries, PostgreSQL offers the CLUSTER command. This command physically reorders all the data rows in the same order as the index criteria, yielding two performance advantages: First, for index range scans, the number of seeks on the data table is drastically reduced. Second, if your working set concentrates to some small intervals on the indices, you have a more efficient caching because the data rows are spread along fewer data pages. (Feel invited to read the CLUSTER command documentation from the PostgreSQL manual at this point.)

However, currently PostgreSQL does not allow clustering on PostGIS GIST indices because GIST indices simply ignores NULL values, you get an error message like:

lwgeom=# CLUSTER my_geom_index ON my_table;
ERROR: cannot cluster when index access method does not handle null values
HINT: You may be able to work around this by marking column "the_geom" NOT NULL.

As the HINT message tells you, one can work around this deficiency by adding a "not null" constraint to the table:

lwgeom=# ALTER TABLE my_table ALTER COLUMN the_geom SET not null;
ALTER TABLE

Of course, this will not work if you in fact need NULL values in your geometry column. Additionally, you must use the above method to add the constraint, using a CHECK constraint like "ALTER TABLE blubb ADD CHECK (geometry is not null);" will not work.

7.3. Avoiding dimension conversion

Sometimes, you happen to have 3D or 4D data in your table, but always access it using OpenGIS compliant ST_AsText() or ST_AsBinary() functions that only output 2D geometries. They do this by internally calling the ST_Force2D() function, which introduces a significant overhead for large geometries. To avoid this overhead, it may be feasible to pre-drop those additional dimensions once and forever:

UPDATE mytable SET the_geom = ST_Force2D(the_geom);
VACUUM FULL ANALYZE mytable;

Note that if you added your geometry column using AddGeometryColumn() there'll be a constraint on geometry dimension. To bypass it you will need to drop the constraint. Remember to update the entry in the geometry_columns table and recreate the constraint afterwards.

In case of large tables, it may be wise to divide this UPDATE into smaller portions by constraining the UPDATE to a part of the table via a WHERE clause and your primary key or another feasible criteria, and running a simple "VACUUM;" between your UPDATEs. This drastically reduces the need for temporary disk space. Additionally, if you have mixed dimension geometries, restricting the UPDATE by "WHERE dimension(the_geom)>2" skips re-writing of geometries that already are in 2D.

7.4. Tuning your configuration

Tuning for PostGIS is much like tuning for any PostgreSQL workload. The only additional note to keep in mind is that geometries and rasters are heavy so memory related optimizations generally have more of an impact on PostGIS than other types of PostgreSQL queries.

For general details about optimizing PostgreSQL, refer to Tuning your PostgreSQL Server .

For PostgreSQL 9.4+ all these can be set at the server level without touching postgresql.conf or postgresql.auto.conf by using the ALTER SYSTEM.. command.

ALTER SYSTEM SET work_mem = '256MB';
-- this will force, non-startup configs to take effect for new connections
SELECT pg_reload_conf();
-- show current setting value
-- use SHOW ALL to see all settings
SHOW work_mem;

In addition to these settings, PostGIS also has some custom settings which you can find listed in Section 8.2, “PostGIS Grand Unified Custom Variables (GUCs)” .

7.4.1. Startup

These settings are configured in postgresql.conf:

constraint_exclusion

  • Default: partition

  • This is generally used for table partitioning. The default for this is set to "partition" which is ideal for PostgreSQL 8.4 and above since it will force the planner to only analyze tables for constraint consideration if they are in an inherited hierarchy and not pay the planner penalty otherwise.

shared_buffers

  • Default: ~128MB in PostgreSQL 9.6

  • Set to about 25% to 40% of available RAM. On windows you may not be able to set as high.

max_worker_processes This setting is only available for PostgreSQL 9.4+. For PostgreSQL 9.6+ this setting has additional importance in that it controls the max number of processes you can have for parallel queries.

  • Default: 8

  • Sets the maximum number of background processes that the system can support. This parameter can only be set at server start.

7.4.2. Runtime

work_mem (the memory used for sort operations and complex queries)

  • Default: 1-4MB

  • Adjust up for large dbs, complex queries, lots of RAM

  • Adjust down for many concurrent users or low RAM.

  • If you have lots of RAM and few developers:

                        SET work_mem TO '256MB';
                    

maintenance_work_mem (used for VACUUM, CREATE INDEX, etc.)

  • Default: 16-64MB

  • Generally too low - ties up I/O, locks objects while swapping memory

  • Recommend 32MB to 1GB on production servers w/lots of RAM, but depends on the # of concurrent users. If you have lots of RAM and few developers:

                       SET maintenance_work_mem TO '1GB';
                    

max_parallel_workers_per_gather This setting is only available for PostgreSQL 9.6+ and will only affect PostGIS 2.3+, since only PostGIS 2.3+ supports parallel queries. If set to higher than 0, then some queries such as those involving relation functions like ST_Intersects can use multiple processes and can run more than twice as fast when doing so. If you have a lot of processors to spare, you should change the value of this to as many processors as you have. Also make sure to bump up max_worker_processes to at least as high as this number.

  • Default: 0

  • Sets the maximum number of workers that can be started by a single Gather node. Parallel workers are taken from the pool of processes established by max_worker_processes . Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may be inefficient. Setting this value to 0, which is the default, disables parallel query execution.

Chapter 8. PostGIS Reference

The functions given below are the ones which a user of PostGIS is likely to need. There are other functions which are required support functions to the PostGIS objects which are not of use to a general user.

[Note]

PostGIS has begun a transition from the existing naming convention to an SQL-MM-centric convention. As a result, most of the functions that you know and love have been renamed using the standard spatial type (ST) prefix. Previous functions are still available, though are not listed in this document where updated functions are equivalent. The non ST_ functions not listed in this documentation are deprecated and will be removed in a future release so STOP USING THEM.

8.1. PostgreSQL PostGIS Geometry/Geography/Box Types

Abstract

This section lists the PostgreSQL data types installed by PostGIS. Note we describe the casting behavior of these which is very important especially when designing your own functions.

A Cast is when one type is coerced into another type. PostgreSQL is unique from most databases in that it allows you to define casting behavior for custom types and the functions used for casting. A cast can be specified as automatic in which case, you do not have to do a CAST(myfoo As otherfootype) or myfoo::otherfootype if you are feeding it to a function that only works with otherfootype and there is an automatic cast in place for it.

The danger of relying on automatic cast behavior is when you have an overloaded function say one that takes a box2d and one that takes a box3d but no geometry. What happens is that both functions are equally good to use with geometry since geometry has an autocast for both -- so you end up with an ambiguous function error. To force PostgreSQL to choose, you do a CAST(mygeom As box3d) or mygeom::box3d.

At least as of PostgreSQL 8.3 - Everything can be CAST to text (presumably because of the magical unknown type), so no defined CASTS for that need to be present for you to CAST an object to text.

box2d — A box composed of x min, ymin, xmax, ymax. Often used to return the 2d enclosing box of a geometry.
box3d — A box composed of x min, ymin, zmin, xmax, ymax, zmax. Often used to return the 3d extent of a geometry or collection of geometries.
geometry — Planar spatial data type.
geometry_dump — A spatial datatype with two fields - geom (holding a geometry object) and path[] (a 1-d array holding the position of the geometry within the dumped object.)
geography — Ellipsoidal spatial data type.

Name

box2d — A box composed of x min, ymin, xmax, ymax. Often used to return the 2d enclosing box of a geometry.

Description

box2d is a spatial data type used to represent the enclosing box of a geometry or set of geometries. ST_Extent in earlier versions prior to PostGIS 1.4 would return a box2d.


Name

box3d — A box composed of x min, ymin, zmin, xmax, ymax, zmax. Often used to return the 3d extent of a geometry or collection of geometries.

Description

box3d is a postgis spatial data type used to represent the enclosing box of a geometry or set of geometries. ST_3DExtent returns a box3d object.

Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To Behavior
box automatic
box2d automatic
geometry automatic

Name

geometry — Planar spatial data type.

Description

geometry is a fundamental postgis spatial data type used to represent a feature in the Euclidean coordinate system.

Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To Behavior
box automatic
box2d automatic
box3d automatic
bytea automatic
geography automatic
text automatic

Name

geometry_dump — A spatial datatype with two fields - geom (holding a geometry object) and path[] (a 1-d array holding the position of the geometry within the dumped object.)

Description

geometry_dump is a compound data type consisting of a geometry object referenced by the .geom field and path[] a 1-dimensional integer array (starting at 1 e.g. path[1] to get first element) array that defines the navigation path within the dumped geometry to find this element. It is used by the ST_Dump* family of functions as an output type to explode a more complex geometry into its constituent parts and location of parts.


Name

geography — Ellipsoidal spatial data type.

Description

geography is a spatial data type used to represent a feature in the round-earth coordinate system.

Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To Behavior
geometry explicit

8.2. PostGIS Grand Unified Custom Variables (GUCs)

Abstract

This section lists custom PostGIS Grand Unified Custom Variables(GUC). These can be set globally, by database, by session or by transaction. Best set at global or database level.

postgis.backend — The backend to service a function where GEOS and SFCGAL overlap. Options: geos or sfcgal. Defaults to geos.
postgis.gdal_datapath — A configuration option to assign the value of GDAL's GDAL_DATA option. If not set, the environmentally set GDAL_DATA variable is used.
postgis.gdal_enabled_drivers — A configuration option to set the enabled GDAL drivers in the PostGIS environment. Affects the GDAL configuration variable GDAL_SKIP.
postgis.enable_outdb_rasters — A boolean configuration option to enable access to out-db raster bands.

Name

postgis.backend — The backend to service a function where GEOS and SFCGAL overlap. Options: geos or sfcgal. Defaults to geos.

Description

This GUC is only relevant if you compiled PostGIS with sfcgal support. By default geos backend is used for functions where both GEOS and SFCGAL have the same named function. This variable allows you to override and make sfcgal the backend to service the request.

Availability: 2.1.0

Examples

Sets backend just for life of connection

set postgis.backend = sfcgal;

Sets backend for new connections to database

ALTER DATABASE mygisdb SET postgis.backend = sfcgal;

Name

postgis.gdal_datapath — A configuration option to assign the value of GDAL's GDAL_DATA option. If not set, the environmentally set GDAL_DATA variable is used.

Description

A PostgreSQL GUC variable for setting the value of GDAL's GDAL_DATA option. The postgis.gdal_datapath value should be the complete physical path to GDAL's data files.

This configuration option is of most use for Windows platforms where GDAL's data files path is not hard-coded. This option should also be set when GDAL's data files are not located in GDAL's expected path.

[Note]

This option can be set in PostgreSQL's configuration file postgresql.conf. It can also be set by connection or transaction.

Availability: 2.2.0

[Note]

Additional information about GDAL_DATA is available at GDAL's Configuration Options .

Examples

Set and reset postgis.gdal_datapath

SET postgis.gdal_datapath TO '/usr/local/share/gdal.hidden';
SET postgis.gdal_datapath TO default;
				

Setting on windows for a particular database

ALTER DATABASE gisdb
SET postgis.gdal_datapath = 'C:/Program Files/PostgreSQL/9.3/gdal-data';

Name

postgis.gdal_enabled_drivers — A configuration option to set the enabled GDAL drivers in the PostGIS environment. Affects the GDAL configuration variable GDAL_SKIP.

Description

A configuration option to set the enabled GDAL drivers in the PostGIS environment. Affects the GDAL configuration variable GDAL_SKIP. This option can be set in PostgreSQL's configuration file: postgresql.conf. It can also be set by connection or transaction.

The initial value of postgis.gdal_enabled_drivers may also be set by passing the environment variable POSTGIS_GDAL_ENABLED_DRIVERS with the list of enabled drivers to the process starting PostgreSQL.

Enabled GDAL specified drivers can be specified by the driver's short-name or code. Driver short-names or codes can be found at GDAL Raster Formats . Multiple drivers can be specified by putting a space between each driver.

[Note]

There are three special codes available for postgis.gdal_enabled_drivers . The codes are case-sensitive.

  • DISABLE_ALL disables all GDAL drivers. If present, DISABLE_ALL overrides all other values in postgis.gdal_enabled_drivers .

  • ENABLE_ALL enables all GDAL drivers.

  • VSICURL enables GDAL's /vsicurl/ virtual file system.

When postgis.gdal_enabled_drivers is set to DISABLE_ALL, attempts to use out-db rasters, ST_FromGDALRaster(), ST_AsGDALRaster(), ST_AsTIFF(), ST_AsJPEG() and ST_AsPNG() will result in error messages.

[Note]

In the standard PostGIS installation, postgis.gdal_enabled_drivers is set to DISABLE_ALL.

[Note]

Additional information about GDAL_SKIP is available at GDAL's Configuration Options .

Availability: 2.2.0

Examples

Set and reset postgis.gdal_enabled_drivers

Sets backend for all new connections to database

ALTER DATABASE mygisdb SET postgis.gdal_enabled_drivers TO 'GTiff PNG JPEG';

Sets default enabled drivers for all new connections to server. Requires super user access and PostgreSQL 9.4+. Also not that database, session, and user settings override this.

ALTER SYSTEM SET postgis.gdal_enabled_drivers TO 'GTiff PNG JPEG';
SELECT pg_reload_conf();
				
SET postgis.gdal_enabled_drivers TO 'GTiff PNG JPEG';
SET postgis.gdal_enabled_drivers = default;
				

Enable all GDAL Drivers

SET postgis.gdal_enabled_drivers = 'ENABLE_ALL';
				

Disable all GDAL Drivers

SET postgis.gdal_enabled_drivers = 'DISABLE_ALL';
				

Name

postgis.enable_outdb_rasters — A boolean configuration option to enable access to out-db raster bands.

Description

A boolean configuration option to enable access to out-db raster bands. This option can be set in PostgreSQL's configuration file: postgresql.conf. It can also be set by connection or transaction.

The initial value of postgis.enable_outdb_rasters may also be set by passing the environment variable POSTGIS_ENABLE_OUTDB_RASTERS with a non-zero value to the process starting PostgreSQL.

[Note]

Even if postgis.enable_outdb_rasters is True, the GUC postgis.enable_outdb_rasters determines the accessible raster formats.

[Note]

In the standard PostGIS installation, postgis.enable_outdb_rasters is set to False.

Availability: 2.2.0

Examples

Set and reset postgis.enable_outdb_rasters

SET postgis.enable_outdb_rasters TO True;
SET postgis.enable_outdb_rasters = default;
SET postgis.enable_outdb_rasters = True;
SET postgis.enable_outdb_rasters = False;
				

8.3. Management Functions

AddGeometryColumn — Adds a geometry column to an existing table of attributes. By default uses type modifier to define rather than constraints. Pass in false for use_typmod to get old check constraint based behavior
DropGeometryColumn — Removes a geometry column from a spatial table.
DropGeometryTable — Drops a table and all its references in geometry_columns.
PostGIS_Full_Version — Reports full postgis version and build configuration infos.
PostGIS_GEOS_Version — Returns the version number of the GEOS library.
PostGIS_Liblwgeom_Version — Returns the version number of the liblwgeom library. This should match the version of PostGIS.
PostGIS_LibXML_Version — Returns the version number of the libxml2 library.
PostGIS_Lib_Build_Date — Returns build date of the PostGIS library.
PostGIS_Lib_Version — Returns the version number of the PostGIS library.
PostGIS_PROJ_Version — Returns the version number of the PROJ4 library.
PostGIS_Scripts_Build_Date — Returns build date of the PostGIS scripts.
PostGIS_Scripts_Installed — Returns version of the postgis scripts installed in this database.
PostGIS_Scripts_Released — Returns the version number of the postgis.sql script released with the installed postgis lib.
PostGIS_Version — Returns PostGIS version number and compile-time options.
Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints This ensures they will be registered correctly in geometry_columns view. By default will convert all geometry columns with no type modifier to ones with type modifiers. To get old behavior set use_typmod=false
UpdateGeometrySRID — Updates the SRID of all features in a geometry column, geometry_columns metadata and srid. If it was enforced with constraints, the constraints will be updated with new srid constraint. If the old was enforced by type definition, the type definition will be changed.

Name

AddGeometryColumn — Adds a geometry column to an existing table of attributes. By default uses type modifier to define rather than constraints. Pass in false for use_typmod to get old check constraint based behavior

Synopsis

text AddGeometryColumn ( varchar table_name , varchar column_name , integer srid , varchar type , integer dimension , boolean use_typmod=true ) ;

text AddGeometryColumn ( varchar schema_name , varchar table_name , varchar column_name , integer srid , varchar type , integer dimension , boolean use_typmod=true ) ;

text AddGeometryColumn ( varchar catalog_name , varchar schema_name , varchar table_name , varchar column_name , integer srid , varchar type , integer dimension , boolean use_typmod=true ) ;

Description

Adds a geometry column to an existing table of attributes. The schema_name is the name of the table schema. The srid must be an integer value reference to an entry in the SPATIAL_REF_SYS table. The type must be a string corresponding to the geometry type, eg, 'POLYGON' or 'MULTILINESTRING' . An error is thrown if the schemaname doesn't exist (or not visible in the current search_path) or the specified SRID, geometry type, or dimension is invalid.

[Note]

Changed: 2.0.0 This function no longer updates geometry_columns since geometry_columns is a view that reads from system catalogs. It by default also does not create constraints, but instead uses the built in type modifier behavior of PostgreSQL. So for example building a wgs84 POINT column with this function is now equivalent to: ALTER TABLE some_table ADD COLUMN geom geometry(Point,4326);

Changed: 2.0.0 If you require the old behavior of constraints use the default use_typmod , but set it to false.

[Note]

Changed: 2.0.0 Views can no longer be manually registered in geometry_columns, however views built against geometry typmod tables geometries and used without wrapper functions will register themselves correctly because they inherit the typmod behavior of their parent table column. Views that use geometry functions that output other geometries will need to be cast to typmod geometries for these view geometry columns to be registered correctly in geometry_columns. Refer to Section 4.3.4, “Manually Registering Geometry Columns in geometry_columns” .

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Enhanced: 2.0.0 use_typmod argument introduced. Defaults to creating typmod geometry column instead of constraint-based.

Examples

-- Create schema to hold data
CREATE SCHEMA my_schema;
-- Create a new simple PostgreSQL table
CREATE TABLE my_schema.my_spatial_table (id serial);

-- Describing the table shows a simple table with a single "id" column.
postgis=# \d my_schema.my_spatial_table
							 Table "my_schema.my_spatial_table"
 Column |  Type   |                                Modifiers
--------+---------+-------------------------------------------------------------------------
 id     | integer | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)

-- Add a spatial column to the table
SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom',4326,'POINT',2);

-- Add a point using the old constraint based behavior
SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom_c',4326,'POINT',2, false);

--Add a curvepolygon using old constraint behavior
SELECT AddGeometryColumn ('my_schema','my_spatial_table','geomcp_c',4326,'CURVEPOLYGON',2, false);

-- Describe the table again reveals the addition of a new geometry columns.
\d my_schema.my_spatial_table
                            addgeometrycolumn
-------------------------------------------------------------------------
 my_schema.my_spatial_table.geomcp_c SRID:4326 TYPE:CURVEPOLYGON DIMS:2
(1 row)

                                    Table "my_schema.my_spatial_table"
  Column  |         Type         |                                Modifiers
----------+----------------------+-------------------------------------------------------------------------
 id       | integer              | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)
 geom     | geometry(Point,4326) |
 geom_c   | geometry             |
 geomcp_c | geometry             |
Check constraints:
    "enforce_dims_geom_c" CHECK (st_ndims(geom_c) = 2)
    "enforce_dims_geomcp_c" CHECK (st_ndims(geomcp_c) = 2)
    "enforce_geotype_geom_c" CHECK (geometrytype(geom_c) = 'POINT'::text OR geom_c IS NULL)
    "enforce_geotype_geomcp_c" CHECK (geometrytype(geomcp_c) = 'CURVEPOLYGON'::text OR geomcp_c IS NULL)
    "enforce_srid_geom_c" CHECK (st_srid(geom_c) = 4326)
    "enforce_srid_geomcp_c" CHECK (st_srid(geomcp_c) = 4326)

-- geometry_columns view also registers the new columns --
SELECT f_geometry_column As col_name, type, srid, coord_dimension As ndims
    FROM geometry_columns
    WHERE f_table_name = 'my_spatial_table' AND f_table_schema = 'my_schema';

 col_name |     type     | srid | ndims
----------+--------------+------+-------
 geom     | Point        | 4326 |     2
 geom_c   | Point        | 4326 |     2
 geomcp_c | CurvePolygon | 4326 |     2

Name

DropGeometryColumn — Removes a geometry column from a spatial table.

Synopsis

text DropGeometryColumn ( varchar table_name , varchar column_name ) ;

text DropGeometryColumn ( varchar schema_name , varchar table_name , varchar column_name ) ;

text DropGeometryColumn ( varchar catalog_name , varchar schema_name , varchar table_name , varchar column_name ) ;

Description

Removes a geometry column from a spatial table. Note that schema_name will need to match the f_table_schema field of the table's row in the geometry_columns table.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a geometry column like any other table column using ALTER TABLE

Examples

			SELECT DropGeometryColumn ('my_schema','my_spatial_table','geom');
			----RESULT output ---
			                  dropgeometrycolumn
------------------------------------------------------
 my_schema.my_spatial_table.geom effectively removed.

-- In PostGIS 2.0+ the above is also equivalent to the standard
-- the standard alter table.  Both will deregister from geometry_columns
ALTER TABLE my_schema.my_spatial_table DROP column geom;
		

Name

DropGeometryTable — Drops a table and all its references in geometry_columns.

Synopsis

boolean DropGeometryTable ( varchar table_name ) ;

boolean DropGeometryTable ( varchar schema_name , varchar table_name ) ;

boolean DropGeometryTable ( varchar catalog_name , varchar schema_name , varchar table_name ) ;

Description

Drops a table and all its references in geometry_columns. Note: uses current_schema() on schema-aware pgsql installations if schema is not provided.

[Note]

Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a table with geometry columns like any other table using DROP TABLE

Examples

SELECT DropGeometryTable ('my_schema','my_spatial_table');
----RESULT output ---
my_schema.my_spatial_table dropped.

-- The above is now equivalent to --
DROP TABLE my_schema.my_spatial_table;
		

Name

PostGIS_Full_Version — Reports full postgis version and build configuration infos.

Synopsis

text PostGIS_Full_Version ( ) ;

Description

Reports full postgis version and build configuration infos. Also informs about synchronization between libraries and scripts suggesting upgrades as needed.

Examples

SELECT PostGIS_Full_Version();
							   postgis_full_version
----------------------------------------------------------------------------------
POSTGIS="2.2.0dev r12699" GEOS="3.5.0dev-CAPI-1.9.0 r3989" SFCGAL="1.0.4" PROJ="Rel. 4.8.0, 6 March 2012"
GDAL="GDAL 1.11.0, released 2014/04/16" LIBXML="2.7.8" LIBJSON="0.12" RASTER
(1 row)

Name

PostGIS_GEOS_Version — Returns the version number of the GEOS library.

Synopsis

text PostGIS_GEOS_Version ( ) ;

Description

Returns the version number of the GEOS library, or NULL if GEOS support is not enabled.

Examples

SELECT PostGIS_GEOS_Version();
 postgis_geos_version
----------------------
 3.1.0-CAPI-1.5.0
(1 row)

Name

PostGIS_Liblwgeom_Version — Returns the version number of the liblwgeom library. This should match the version of PostGIS.

Synopsis

text PostGIS_Liblwgeom_Version ( ) ;

Description

Returns the version number of the liblwgeom library/

Examples

SELECT PostGIS_Liblwgeom_Version();
postgis_liblwgeom_version
--------------------------
2.3.3 r15473
(1 row)

Name

PostGIS_LibXML_Version — Returns the version number of the libxml2 library.

Synopsis

text PostGIS_LibXML_Version ( ) ;

Description

Returns the version number of the LibXML2 library.

Availability: 1.5

Examples

SELECT PostGIS_LibXML_Version();
 postgis_libxml_version
----------------------
 2.7.6
(1 row)

Name

PostGIS_Lib_Build_Date — Returns build date of the PostGIS library.

Synopsis

text PostGIS_Lib_Build_Date ( ) ;

Description

Returns build date of the PostGIS library.

Examples

SELECT PostGIS_Lib_Build_Date();
 postgis_lib_build_date
------------------------
 2008-06-21 17:53:21
(1 row)

Name

PostGIS_Lib_Version — Returns the version number of the PostGIS library.

Synopsis

text PostGIS_Lib_Version ( ) ;

Description

Returns the version number of the PostGIS library.

Examples

SELECT PostGIS_Lib_Version();
 postgis_lib_version
---------------------
 1.3.3
(1 row)

Name

PostGIS_PROJ_Version — Returns the version number of the PROJ4 library.

Synopsis

text PostGIS_PROJ_Version ( ) ;

Description

Returns the version number of the PROJ4 library, or NULL if PROJ4 support is not enabled.

Examples

SELECT PostGIS_PROJ_Version();
  postgis_proj_version
-------------------------
 Rel. 4.4.9, 29 Oct 2004
(1 row)

Name

PostGIS_Scripts_Build_Date — Returns build date of the PostGIS scripts.

Synopsis

text PostGIS_Scripts_Build_Date ( ) ;

Description

Returns build date of the PostGIS scripts.

Availability: 1.0.0RC1

Examples

SELECT PostGIS_Scripts_Build_Date();
  postgis_scripts_build_date
-------------------------
 2007-08-18 09:09:26
(1 row)

Name

PostGIS_Scripts_Installed — Returns version of the postgis scripts installed in this database.

Synopsis

text PostGIS_Scripts_Installed ( ) ;

Description

Returns version of the postgis scripts installed in this database.

[Note]

If the output of this function doesn't match the output of PostGIS_Scripts_Released you probably missed to properly upgrade an existing database. See the Upgrading section for more info.

Availability: 0.9.0

Examples

SELECT PostGIS_Scripts_Installed();
  postgis_scripts_installed
-------------------------
 1.5.0SVN
(1 row)

Name

PostGIS_Scripts_Released — Returns the version number of the postgis.sql script released with the installed postgis lib.

Synopsis

text PostGIS_Scripts_Released ( ) ;

Description

Returns the version number of the postgis.sql script released with the installed postgis lib.

[Note]

Starting with version 1.1.0 this function returns the same value of PostGIS_Lib_Version . Kept for backward compatibility.

Availability: 0.9.0

Examples

SELECT PostGIS_Scripts_Released();
  postgis_scripts_released
-------------------------
 1.3.4SVN
(1 row)

Name

PostGIS_Version — Returns PostGIS version number and compile-time options.

Synopsis

text PostGIS_Version ( ) ;

Description

Returns PostGIS version number and compile-time options.

Examples

SELECT PostGIS_Version();
			postgis_version
---------------------------------------
 1.3 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
(1 row)

Name

Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints This ensures they will be registered correctly in geometry_columns view. By default will convert all geometry columns with no type modifier to ones with type modifiers. To get old behavior set use_typmod=false

Synopsis

text Populate_Geometry_Columns ( boolean use_typmod=true ) ;

int Populate_Geometry_Columns ( oid relation_oid , boolean use_typmod=true ) ;

Description

Ensures geometry columns have appropriate type modifiers or spatial constraints to ensure they are registered correctly in geometry_columns table.

For backwards compatibility and for spatial needs such as table inheritance where each child table may have different geometry type, the old check constraint behavior is still supported. If you need the old behavior, you need to pass in the new optional argument as false use_typmod=false . When this is done geometry columns will be created with no type modifiers but will have 3 constraints defined. In particular, this means that every geometry column belonging to a table has at least three constraints:

  • enforce_dims_the_geom - ensures every geometry has the same dimension (see ST_NDims )

  • enforce_geotype_the_geom - ensures every geometry is of the same type (see GeometryType )

  • enforce_srid_the_geom - ensures every geometry is in the same projection (see ST_SRID )

If a table oid is provided, this function tries to determine the srid, dimension, and geometry type of all geometry columns in the table, adding constraints as necessary. If successful, an appropriate row is inserted into the geometry_columns table, otherwise, the exception is caught and an error notice is raised describing the problem.

If the oid of a view is provided, as with a table oid, this function tries to determine the srid, dimension, and type of all the geometries in the view, inserting appropriate entries into the geometry_columns table, but nothing is done to enforce constraints.

The parameterless variant is a simple wrapper for the parameterized variant that first truncates and repopulates the geometry_columns table for every spatial table and view in the database, adding spatial constraints to tables where appropriate. It returns a summary of the number of geometry columns detected in the database and the number that were inserted into the geometry_columns table. The parameterized version simply returns the number of rows inserted into the geometry_columns table.

Availability: 1.4.0

Changed: 2.0.0 By default, now uses type modifiers instead of check constraints to constrain geometry types. You can still use check constraint behavior instead by using the new use_typmod and setting it to false.

Enhanced: 2.0.0 use_typmod optional argument was introduced that allows controlling if columns are created with typmodifiers or with check constraints.

Examples

CREATE TABLE public.myspatial_table(gid serial, geom geometry);
INSERT INTO myspatial_table(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
-- This will now use typ modifiers.  For this to work, there must exist data
SELECT Populate_Geometry_Columns('public.myspatial_table'::regclass);

populate_geometry_columns
--------------------------
                        1


\d myspatial_table

                                   Table "public.myspatial_table"
 Column |           Type            |                           Modifiers
--------+---------------------------+---------------------------------------------------------------
 gid    | integer                   | not null default nextval('myspatial_table_gid_seq'::regclass)
 geom   | geometry(LineString,4326) |
-- This will change the geometry columns to use constraints if they are not typmod or have constraints already.
--For this to work, there must exist data
CREATE TABLE public.myspatial_table_cs(gid serial, geom geometry);
INSERT INTO myspatial_table_cs(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
SELECT Populate_Geometry_Columns('public.myspatial_table_cs'::regclass, false);
populate_geometry_columns
--------------------------
                        1
\d myspatial_table_cs

                          Table "public.myspatial_table_cs"
 Column |   Type   |                            Modifiers
--------+----------+------------------------------------------------------------------
 gid    | integer  | not null default nextval('myspatial_table_cs_gid_seq'::regclass)
 geom   | geometry |
Check constraints:
    "enforce_dims_geom" CHECK (st_ndims(geom) = 2)
    "enforce_geotype_geom" CHECK (geometrytype(geom) = 'LINESTRING'::text OR geom IS NULL)
    "enforce_srid_geom" CHECK (st_srid(geom) = 4326)

Name

UpdateGeometrySRID — Updates the SRID of all features in a geometry column, geometry_columns metadata and srid. If it was enforced with constraints, the constraints will be updated with new srid constraint. If the old was enforced by type definition, the type definition will be changed.

Synopsis

text UpdateGeometrySRID ( varchar table_name , varchar column_name , integer srid ) ;

text UpdateGeometrySRID ( varchar schema_name , varchar table_name , varchar column_name , integer srid ) ;

text UpdateGeometrySRID ( varchar catalog_name , varchar schema_name , varchar table_name , varchar column_name , integer srid ) ;

Description

Updates the SRID of all features in a geometry column, updating constraints and reference in geometry_columns. Note: uses current_schema() on schema-aware pgsql installations if schema is not provided.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

This will change the srid of the roads table to 4326 from whatever it was before

SELECT UpdateGeometrySRID('roads','geom',4326);

The prior example is equivalent to this DDL statement

ALTER TABLE roads
  ALTER COLUMN geom TYPE geometry(MULTILINESTRING, 4326)
    USING ST_SetSRID(geom,4326);

If you got the projection wrong (or brought it in as unknown) in load and you wanted to transform to web mercator all in one shot You can do this with DDL but there is no equivalent PostGIS management function to do so in one go.

ALTER TABLE roads
 ALTER COLUMN geom TYPE geometry(MULTILINESTRING, 3857) USING ST_Transform(ST_SetSRID(geom,4326),3857) ;

8.4. Geometry Constructors

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.
ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString text representation Well-Known text representation.
ST_Box2dFromGeoHash — Return a BOX2D from a GeoHash string.
ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).
ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).
ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).
ST_GeomFromTWKB Creates a geometry instance from a TWKB ("Tiny Well-Known Binary") geometry representation.
ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText
ST_GeomFromGeoHash — Return a geometry from a GeoHash string.
ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object
ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object
ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).
ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.
ST_LineFromEncodedPolyline — Creates a LineString from an Encoded Polyline.
ST_LineFromMultiPoint — Creates a LineString from a MultiPoint geometry.
ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to 0.
ST_LineFromWKB — Makes a LINESTRING from WKB with the given SRID
ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.
ST_MakeBox2D — Creates a BOX2D defined by the given point geometries.
ST_3DMakeBox — Creates a BOX3D defined by the given 3d point geometries.
ST_MakeLine — Creates a Linestring from point, multipoint, or line geometries.
ST_MakeEnvelope — Creates a rectangular Polygon formed from the given minimums and maximums. Input values must be in SRS specified by the SRID.
ST_MakePolygon — Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS.
ST_MakePoint — Creates a 2D,3DZ or 4D point geometry.
ST_MakePointM — Creates a point geometry with an x y and m coordinate.
ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.
ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_Point — Returns an ST_Point with the given coordinate values. OGC alias for ST_MakePoint.
ST_PointFromGeoHash — Return a point from a GeoHash string.
ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.
ST_PointFromWKB — Makes a geometry from WKB with the given SRID
ST_Polygon — Returns a polygon built from the specified linestring and SRID.
ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid
ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

Name

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

Synopsis

geometry ST_BdPolyFromText ( text WKT , integer srid ) ;

Description

Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

[Note]

Throws an error if WKT is not a MULTILINESTRING. Throws an error if output is a MULTIPOLYGON; use ST_BdMPolyFromText in that case, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Availability: 1.1.0 - requires GEOS >= 2.1.0.

Examples

Forthcoming

Name

ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString text representation Well-Known text representation.

Synopsis

geometry ST_BdMPolyFromText ( text WKT , integer srid ) ;

Description

Construct a Polygon given an arbitrary collection of closed linestrings, polygons, MultiLineStrings as Well-Known text representation.

[Note]

Throws an error if WKT is not a MULTILINESTRING. Forces MULTIPOLYGON output even when result is really only composed by a single POLYGON; use ST_BdPolyFromText if you're sure a single POLYGON will result from operation, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Availability: 1.1.0 - requires GEOS >= 2.1.0.

Examples

Forthcoming

Name

ST_Box2dFromGeoHash — Return a BOX2D from a GeoHash string.

Synopsis

box2d ST_Box2dFromGeoHash ( text geohash , integer precision=full_precision_of_geohash ) ;

Description

Return a BOX2D from a GeoHash string.

If no precision is specficified ST_Box2dFromGeoHash returns a BOX2D based on full precision of the input GeoHash string.

If precision is specified ST_Box2dFromGeoHash will use that many characters from the GeoHash to create the BOX2D. Lower precision values results in larger BOX2Ds and larger values increase the precision.

Availability: 2.1.0

Examples

SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0');

                st_geomfromgeohash
--------------------------------------------------
 BOX(-115.172816 36.114646,-115.172816 36.114646)

SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 0);

 st_box2dfromgeohash
----------------------
 BOX(-180 -90,180 90)

 SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10);
                            st_box2dfromgeohash
---------------------------------------------------------------------------
 BOX(-115.17282128334 36.1146408319473,-115.172810554504 36.1146461963654)
		
		

Name

ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

Synopsis

geography ST_GeogFromText ( text EWKT ) ;

Description

Returns a geography object from the well-known text or extended well-known representation. SRID 4326 is assumed if unspecified. This is an alias for ST_GeographyFromText. Points are always expressed in long lat form.

Examples

--- converting lon lat coords to geography
ALTER TABLE sometable ADD COLUMN geog geography(POINT,4326);
UPDATE sometable SET geog = ST_GeogFromText('SRID=4326;POINT(' || lon || ' ' || lat || ')');

--- specify a geography point using EPSG:4267, NAD27
SELECT ST_AsEWKT(ST_GeogFromText('SRID=4267;POINT(-77.0092 38.889588)'));
			

Name

ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

Synopsis

geography ST_GeographyFromText ( text EWKT ) ;

Description

Returns a geography object from the well-known text representation. SRID 4326 is assumed if unspecified.


Name

ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).

Synopsis

geography ST_GeogFromWKB ( bytea wkb ) ;

Description

The ST_GeogFromWKB function, takes a well-known binary representation (WKB) of a geometry or PostGIS Extended WKB and creates an instance of the appropriate geography type. This function plays the role of the Geometry Factory in SQL.

If SRID is not specified, it defaults to 4326 (WGS 84 long lat).

This method supports Circular Strings and Curves

Examples

--Although bytea rep contains single \, these need to be escaped when inserting into a table
SELECT ST_AsText(
ST_GeogFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@')
);
					  st_astext
------------------------------------------------------
 LINESTRING(-113.98 39.198,-113.981 39.195)
(1 row)


Name

ST_GeomFromTWKB — Creates a geometry instance from a TWKB (" Tiny Well-Known Binary ") geometry representation.

Synopsis

geometry ST_GeomFromTWKB ( bytea twkb ) ;

Description

The ST_GeomFromTWKB function, takes a a TWKB (" Tiny Well-Known Binary ") geometry representation (WKB) and creates an instance of the appropriate geometry type.

Examples

SELECT ST_AsText(ST_GeomFromTWKB(ST_AsTWKB('LINESTRING(126 34, 127 35)'::geometry)));

         st_astext
-----------------------------
 LINESTRING(126 34, 127 35)
(1 row)


SELECT ST_AsEWKT(
  ST_GeomFromTWKB(E'\\x620002f7f40dbce4040105')
);
					  st_asewkt
------------------------------------------------------
LINESTRING(-113.98 39.198,-113.981 39.195)
(1 row)

See Also

ST_AsTWKB


Name

ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_GeomCollFromText ( text WKT , integer srid ) ;

geometry ST_GeomCollFromText ( text WKT ) ;

Description

Makes a collection Geometry from the Well-Known-Text (WKT) representation with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a GEOMETRYCOLLECTION

[Note]

If you are absolutely sure all your WKT geometries are collections, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.

Examples

SELECT ST_GeomCollFromText('GEOMETRYCOLLECTION(POINT(1 2),LINESTRING(1 2, 3 4))');

Name

ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).

Synopsis

geometry ST_GeomFromEWKB ( bytea EWKB ) ;

Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known binary (EWKT) representation.

[Note]

The EWKB format is not an OGC standard, but a PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

line string binary rep 0f LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932) in NAD 83 long lat (4269).

[Note]

NOTE: Even though byte arrays are delimited with \ and may have ', we need to escape both out with \ and '' if standard_conforming_strings is off. So it does not look exactly like its AsEWKB representation.

SELECT ST_GeomFromEWKB(E'\\001\\002\\000\\000 \\255\\020\\000\\000\\003\\000\\000\\000\\344J=
\\013B\\312Q\\300n\\303(\\010\\036!E@''\\277E''K
\\312Q\\300\\366{b\\235*!E@\\225|\\354.P\\312Q
\\300p\\231\\323e1!E@');
[Note]

In PostgreSQL 9.1+ - standard_conforming_strings is set to on by default, where as in past versions it was set to off. You can change defaults as needed for a single query or at the database or server level. Below is how you would do it with standard_conforming_strings = on. In this case we escape the ' with standard ansi ', but slashes are not escaped

	    set standard_conforming_strings = on;
SELECT ST_GeomFromEWKB('\001\002\000\000 \255\020\000\000\003\000\000\000\344J=\012\013B
    \312Q\300n\303(\010\036!E@''\277E''K\012\312Q\300\366{b\235*!E@\225|\354.P\312Q\012\300p\231\323e1')

Name

ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).

Synopsis

geometry ST_GeomFromEWKT ( text EWKT ) ;

Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known text (EWKT) representation.

[Note]

The EWKT format is not an OGC standard, but an PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

SELECT ST_GeomFromEWKT('SRID=4269;LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
SELECT ST_GeomFromEWKT('SRID=4269;MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

SELECT ST_GeomFromEWKT('SRID=4269;POINT(-71.064544 42.28787)');

SELECT ST_GeomFromEWKT('SRID=4269;POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

SELECT ST_GeomFromEWKT('SRID=4269;MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
-71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
-71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
-71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
-71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
-71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
-71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
-71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
-71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
-71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
-71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
-71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
-71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
-71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
-71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
-71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
-71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
-71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
-71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
-71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
-71.1031880899493 42.3152774590236)),
((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
-71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))');
--3d circular string
SELECT ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)');
--Polyhedral Surface example
SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
	((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
	((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
	((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
	((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
	((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
	((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
)');

Name

ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

Synopsis

geometry ST_GeometryFromText ( text WKT ) ;

geometry ST_GeometryFromText ( text WKT , integer srid ) ;

Description

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40


Name

ST_GeomFromGeoHash — Return a geometry from a GeoHash string.

Synopsis

geometry ST_GeomFromGeoHash ( text geohash , integer precision=full_precision_of_geohash ) ;

Description

Return a geometry from a GeoHash string. The geometry will be a polygon representing the GeoHash bounds.

If no precision is specified ST_GeomFromGeoHash returns a polygon based on full precision of the input GeoHash string.

If precision is specified ST_GeomFromGeoHash will use that many characters from the GeoHash to create the polygon.

Availability: 2.1.0

Examples

SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0'));
                                                        st_astext
--------------------------------------------------------------------------------------------------------------------------
 POLYGON((-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646))

SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 4));
                                                          st_astext
------------------------------------------------------------------------------------------------------------------------------
 POLYGON((-115.3125 36.03515625,-115.3125 36.2109375,-114.9609375 36.2109375,-114.9609375 36.03515625,-115.3125 36.03515625))

SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10));
                                                                                       st_astext
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 POLYGON((-115.17282128334 36.1146408319473,-115.17282128334 36.1146461963654,-115.172810554504 36.1146461963654,-115.172810554504 36.1146408319473,-115.17282128334 36.1146408319473))
		
		

Name

ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromGML ( text geomgml ) ;

geometry ST_GeomFromGML ( text geomgml , integer srid ) ;

Description

Constructs a PostGIS ST_Geometry object from the OGC GML representation.

ST_GeomFromGML works only for GML Geometry fragments. It throws an error if you try to use it on a whole GML document.

OGC GML versions supported:

  • GML 3.2.1 Namespace

  • GML 3.1.1 Simple Features profile SF-2 (with GML 3.1.0 and 3.0.0 backward compatibility)

  • GML 2.1.2

OGC GML standards, cf: http://www.opengeospatial.org/standards/gml :

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

GML allow mixed dimensions (2D and 3D inside the same MultiGeometry for instance). As PostGIS geometries don't, ST_GeomFromGML convert the whole geometry to 2D if a missing Z dimension is found once.

GML support mixed SRS inside the same MultiGeometry. As PostGIS geometries don't, ST_GeomFromGML, in this case, reproject all subgeometries to the SRS root node. If no srsName attribute available for the GML root node, the function throw an error.

ST_GeomFromGML function is not pedantic about an explicit GML namespace. You could avoid to mention it explicitly for common usages. But you need it if you want to use XLink feature inside GML.

[Note]

ST_GeomFromGML function not support SQL/MM curves geometries.

Examples - A single geometry with srsName

SELECT ST_GeomFromGML('
		<gml:LineString srsName="EPSG:4269">
			<gml:coordinates>
				-71.16028,42.258729 -71.160837,42.259112 -71.161143,42.25932
			</gml:coordinates>
		</gml:LineString>');
		

Examples - XLink usage

SELECT ST_GeomFromGML('
		<gml:LineString xmlns:gml="http://www.opengis.net/gml"
				xmlns:xlink="http://www.w3.org/1999/xlink"
				srsName="urn:ogc:def:crs:EPSG::4269">
			<gml:pointProperty>
				<gml:Point gml:id="p1"><gml:pos>42.258729 -71.16028</gml:pos></gml:Point>
			</gml:pointProperty>
			<gml:pos>42.259112 -71.160837</gml:pos>
			<gml:pointProperty>
				<gml:Point xlink:type="simple" xlink:href="#p1"/>
			</gml:pointProperty>
		</gml:LineString>'););
		

Examples - Polyhedral Surface

SELECT ST_AsEWKT(ST_GeomFromGML('
<gml:PolyhedralSurface>
<gml:polygonPatches>
  <gml:PolygonPatch>
    <gml:exterior>
      <gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
	<gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
	<gml:LinearRing><gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
	<gml:LinearRing><gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
	<gml:LinearRing><gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
	<gml:LinearRing><gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
</gml:polygonPatches>
</gml:PolyhedralSurface>'));

-- result --
 POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
 ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
 ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
 ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
 ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
 ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))
		

Name

ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromGeoJSON ( text geomjson ) ;

Description

Constructs a PostGIS geometry object from the GeoJSON representation.

ST_GeomFromGeoJSON works only for JSON Geometry fragments. It throws an error if you try to use it on a whole JSON document.

Availability: 2.0.0 requires - JSON-C >= 0.9

[Note]

If you do not have JSON-C enabled, support you will get an error notice instead of seeing an output. To enable JSON-C, run configure --with-jsondir=/path/to/json-c. See Section 2.4.1, “Configuration” for details.

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"Point","coordinates":[-48.23456,20.12345]}')) As wkt;
wkt
------
POINT(-48.23456 20.12345)
-- a 3D linestring
SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"LineString","coordinates":[[1,2,3],[4,5,6],[7,8,9]]}')) As wkt;

wkt
-------------------
LINESTRING(1 2,4 5,7 8)

Name

ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromKML ( text geomkml ) ;

Description

Constructs a PostGIS ST_Geometry object from the OGC KML representation.

ST_GeomFromKML works only for KML Geometry fragments. It throws an error if you try to use it on a whole KML document.

OGC KML versions supported:

  • KML 2.2.0 Namespace

OGC KML standards, cf: http://www.opengeospatial.org/standards/kml :

Availability: 1.5,libxml2 2.6+

This function supports 3d and will not drop the z-index.

[Note]

ST_GeomFromKML function not support SQL/MM curves geometries.

Examples - A single geometry with srsName

SELECT ST_GeomFromKML('
		<LineString>
			<coordinates>-71.1663,42.2614
				-71.1667,42.2616</coordinates>
		</LineString>');
		

Name

ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML

Synopsis

geometry ST_GMLToSQL ( text geomgml ) ;

geometry ST_GMLToSQL ( text geomgml , integer srid ) ;

Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.50 (except for curves support).

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.


Name

ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).

Synopsis

geometry ST_GeomFromText ( text WKT ) ;

geometry ST_GeomFromText ( text WKT , integer srid ) ;

Description

Constructs a PostGIS ST_Geometry object from the OGC Well-Known text representation.

[Note]

There are two variants of ST_GeomFromText function. The first takes no SRID and returns a geometry with no defined spatial reference system (SRID=0). The second takes a SRID as the second argument and returns a geometry that includes this SRID as part of its metadata.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

This method supports Circular Strings and Curves

[Warning]

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written as ST_GeomFromText('GEOMETRYCOLLECTION EMPTY')

Examples

SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)',4269);

SELECT ST_GeomFromText('MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

SELECT ST_GeomFromText('POINT(-71.064544 42.28787)');

SELECT ST_GeomFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

SELECT ST_GeomFromText('MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
-71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
-71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
-71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
-71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
-71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
-71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
-71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
-71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
-71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
-71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
-71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
-71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
-71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
-71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
-71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
-71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
-71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
-71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
-71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
-71.1031880899493 42.3152774590236)),
((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
-71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))',4326);

SELECT ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)');
	

Name

ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.

Synopsis

geometry ST_GeomFromWKB ( bytea geom ) ;

geometry ST_GeomFromWKB ( bytea geom , integer srid ) ;

Description

The ST_GeomFromWKB function, takes a well-known binary representation of a geometry and a Spatial Reference System ID ( SRID ) and creates an instance of the appropriate geometry type. This function plays the role of the Geometry Factory in SQL. This is an alternate name for ST_WKBToSQL.

If SRID is not specified, it defaults to 0 (Unknown).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.7.2 - the optional SRID is from the conformance suite

This method implements the SQL/MM specification. SQL-MM 3: 5.1.41

This method supports Circular Strings and Curves

Examples

--Although bytea rep contains single \, these need to be escaped when inserting into a table
		-- unless standard_conforming_strings is set to on.
SELECT ST_AsEWKT(
ST_GeomFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@',4326)
);
					  st_asewkt
------------------------------------------------------
 SRID=4326;LINESTRING(-113.98 39.198,-113.981 39.195)
(1 row)

SELECT
  ST_AsText(
	ST_GeomFromWKB(
	  ST_AsEWKB('POINT(2 5)'::geometry)
	)
  );
 st_astext
------------
 POINT(2 5)
(1 row)

Name

ST_LineFromEncodedPolyline — Creates a LineString from an Encoded Polyline.

Synopsis

geometry ST_LineFromEncodedPolyline ( text polyline , integer precision=5 ) ;

Description

Creates a LineString from an Encoded Polyline string.

See http://developers.google.com/maps/documentation/utilities/polylinealgorithm

Availability: 2.2.0

Examples

--Create a line string from a polyline
SELECT ST_AsEWKT(ST_LineFromEncodedPolyline('_p~iF~ps|U_ulLnnqC_mqNvxq`@'));
--result--
LINESTRING(-120.2 38.5,-120.95 40.7,-126.453 43.252)
    

Name

ST_LineFromMultiPoint — Creates a LineString from a MultiPoint geometry.

Synopsis

geometry ST_LineFromMultiPoint ( geometry aMultiPoint ) ;

Description

Creates a LineString from a MultiPoint geometry.

This function supports 3d and will not drop the z-index.

Examples

--Create a 3d line string from a 3d multipoint
SELECT ST_AsEWKT(ST_LineFromMultiPoint(ST_GeomFromEWKT('MULTIPOINT(1 2 3, 4 5 6, 7 8 9)')));
--result--
LINESTRING(1 2 3,4 5 6,7 8 9)
		

Name

ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_LineFromText ( text WKT ) ;

geometry ST_LineFromText ( text WKT , integer srid ) ;

Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0. If WKT passed in is not a LINESTRING, then null is returned.

[Note]

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

[Note]

If you know all your geometries are LINESTRINGS, its more efficient to just use ST_GeomFromText. This just calls ST_GeomFromText and adds additional validation that it returns a linestring.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.8

Examples

SELECT ST_LineFromText('LINESTRING(1 2, 3 4)') AS aline, ST_LineFromText('POINT(1 2)') AS null_return;
aline                            | null_return
------------------------------------------------
010200000002000000000000000000F ... | t
		

Name

ST_LineFromWKB — Makes a LINESTRING from WKB with the given SRID

Synopsis

geometry ST_LineFromWKB ( bytea WKB ) ;

geometry ST_LineFromWKB ( bytea WKB , integer srid ) ;

Description

The ST_LineFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID ( SRID ) and creates an instance of the appropriate geometry type - in this case, a LINESTRING geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. NULL is returned if the input bytea does not represent a LINESTRING .

[Note]

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

[Note]

If you know all your geometries are LINESTRING s, its more efficient to just use ST_GeomFromWKB . This function just calls ST_GeomFromWKB and adds additional validation that it returns a linestring.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

Examples

SELECT ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))) AS aline,
		ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('POINT(1 2)'))) IS NULL AS null_return;
aline                            | null_return
------------------------------------------------
010200000002000000000000000000F ... | t
		

Name

ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.

Synopsis

geometry ST_LinestringFromWKB ( bytea WKB ) ;

geometry ST_LinestringFromWKB ( bytea WKB , integer srid ) ;

Description

The ST_LinestringFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID ( SRID ) and creates an instance of the appropriate geometry type - in this case, a LINESTRING geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. NULL is returned if the input bytea does not represent a LINESTRING geometry. This an alias for ST_LineFromWKB .

[Note]

OGC SPEC 3.2.6.2 - optional SRID is from the conformance suite.

[Note]

If you know all your geometries are LINESTRING s, it's more efficient to just use ST_GeomFromWKB . This function just calls ST_GeomFromWKB and adds additional validation that it returns a LINESTRING .

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

Examples

SELECT
  ST_LineStringFromWKB(
	ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))
  ) AS aline,
  ST_LinestringFromWKB(
	ST_AsBinary(ST_GeomFromText('POINT(1 2)'))
  ) IS NULL AS null_return;
   aline                            | null_return
------------------------------------------------
010200000002000000000000000000F ... | t

Name

ST_MakeBox2D — Creates a BOX2D defined by the given point geometries.

Synopsis

box2d ST_MakeBox2D ( geometry pointLowLeft , geometry pointUpRight ) ;

Description

Creates a BOX2D defined by the given point geometries. This is useful for doing range queries

Examples

--Return all features that fall reside or partly reside in a US national atlas coordinate bounding box
--It is assumed here that the geometries are stored with SRID = 2163 (US National atlas equal area)
SELECT feature_id, feature_name, the_geom
FROM features
WHERE the_geom && ST_SetSRID(ST_MakeBox2D(ST_Point(-989502.1875, 528439.5625),
	ST_Point(-987121.375 ,529933.1875)),2163)

Name

ST_3DMakeBox — Creates a BOX3D defined by the given 3d point geometries.

Synopsis

box3d ST_3DMakeBox ( geometry point3DLowLeftBottom , geometry point3DUpRightTop ) ;

Description

Creates a BOX3D defined by the given 2 3D point geometries.

This function supports 3d and will not drop the z-index.

Changed: 2.0.0 In prior versions this used to be called ST_MakeBox3D

Examples

SELECT ST_3DMakeBox(ST_MakePoint(-989502.1875, 528439.5625, 10),
	ST_MakePoint(-987121.375 ,529933.1875, 10)) As abb3d

--bb3d--
--------
BOX3D(-989502.1875 528439.5625 10,-987121.375 529933.1875 10)
	

Name

ST_MakeLine — Creates a Linestring from point, multipoint, or line geometries.

Synopsis

geometry ST_MakeLine ( geometry set geoms ) ;

geometry ST_MakeLine ( geometry geom1 , geometry geom2 ) ;

geometry ST_MakeLine ( geometry[] geoms_array ) ;

Description

ST_MakeLine comes in 3 forms: a spatial aggregate that takes rows of point, multipoint, or line geometries and returns a line string, a function that takes an array of point, multipoint, or line, and a regular function that takes two point, multipoint, or line geometries. You might want to use a subselect to order points before feeding them to the aggregate version of this function.

Inputs other than point, multipoint, or lines are ignored.

When adding line components common nodes at the beginning of lines are removed from the output. Common nodes in point and multipoint inputs are not removed.

This function supports 3d and will not drop the z-index.

Availability: 2.3.0 - Support for multipoint input elements was introduced

Availability: 2.0.0 - Support for linestring input elements was introduced

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

Examples: Spatial Aggregate version

This example takes a sequence of GPS points and creates one record for each gps travel where the geometry field is a line string composed of the gps points in the order of the travel.

-- For pre-PostgreSQL 9.0 - this usually works,
-- but the planner may on occasion choose not to respect the order of the subquery
SELECT gps.gps_track, ST_MakeLine(gps.the_geom) As newgeom
	FROM (SELECT gps_track,gps_time, the_geom
			FROM gps_points ORDER BY gps_track, gps_time) As gps
	GROUP BY gps.gps_track;
-- If you are using PostgreSQL 9.0+
-- (you can use the new ORDER BY support for aggregates)
-- this is a guaranteed way to get a correctly ordered linestring
-- Your order by part can order by more than one column if needed
SELECT gps.gps_track, ST_MakeLine(gps.the_geom ORDER BY gps_time) As newgeom
	FROM gps_points As gps
	GROUP BY gps.gps_track;

Examples: Non-Spatial Aggregate version

First example is a simple one off line string composed of 2 points. The second formulates line strings from 2 points a user draws. The third is a one-off that joins 2 3d points to create a line in 3d space.

SELECT ST_AsText(ST_MakeLine(ST_MakePoint(1,2), ST_MakePoint(3,4)));
	  st_astext
---------------------
 LINESTRING(1 2,3 4)

SELECT userpoints.id, ST_MakeLine(startpoint, endpoint) As drawn_line
	FROM userpoints ;

SELECT ST_AsEWKT(ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5)));
		st_asewkt
-------------------------
 LINESTRING(1 2 3,3 4 5)
			

Examples: Using Array version

SELECT ST_MakeLine(ARRAY(SELECT ST_Centroid(the_geom) FROM visit_locations ORDER BY visit_time));

--Making a 3d line with 3 3-d points
SELECT ST_AsEWKT(ST_MakeLine(ARRAY[ST_MakePoint(1,2,3),
				ST_MakePoint(3,4,5), ST_MakePoint(6,6,6)]));
		st_asewkt
-------------------------
LINESTRING(1 2 3,3 4 5,6 6 6)
			

Name

ST_MakeEnvelope — Creates a rectangular Polygon formed from the given minimums and maximums. Input values must be in SRS specified by the SRID.

Synopsis

geometry ST_MakeEnvelope ( double precision xmin , double precision ymin , double precision xmax , double precision ymax , integer srid=unknown ) ;

Description

Creates a rectangular Polygon formed from the minima and maxima. by the given shell. Input values must be in SRS specified by the SRID. If no SRID is specified the unknown spatial reference system is assumed

Availability: 1.5

Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.

Example: Building a bounding box polygon

SELECT ST_AsText(ST_MakeEnvelope(10, 10, 11, 11, 4326));

st_asewkt
-----------
POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))
			  

Name

ST_MakePolygon — Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS.

Synopsis

geometry ST_MakePolygon ( geometry linestring ) ;

geometry ST_MakePolygon ( geometry outerlinestring , geometry[] interiorlinestrings ) ;

Description

Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS. Comes in 2 variants.

Variant 1: Takes one closed linestring.

Variant 2: Creates a Polygon formed by the given shell and array of holes. You can construct a geometry array using ST_Accum or the PostgreSQL ARRAY[] and ARRAY() constructs. Input geometries must be closed LINESTRINGS.

[Note]

This function will not accept a MULTILINESTRING. Use ST_LineMerge or ST_Dump to generate line strings.

This function supports 3d and will not drop the z-index.

Examples: Single closed LINESTRING

--2d line
SELECT ST_MakePolygon(ST_GeomFromText('LINESTRING(75.15 29.53,77 29,77.6 29.5, 75.15 29.53)'));
--If linestring is not closed
--you can add the start point to close it
SELECT ST_MakePolygon(ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)))
FROM (
SELECT ST_GeomFromText('LINESTRING(75.15 29.53,77 29,77.6 29.5)') As open_line) As foo;

--3d closed line
SELECT ST_MakePolygon(ST_GeomFromText('LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'));

st_asewkt
-----------
POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

--measured line --
SELECT ST_MakePolygon(ST_GeomFromText('LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)'));

st_asewkt
----------
POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))
			  

Examples: Outer shell with inner shells

Build a donut with an ant hole

SELECT ST_MakePolygon(
		ST_ExteriorRing(ST_Buffer(foo.line,10)),
	ARRAY[ST_Translate(foo.line,1,1),
		ST_ExteriorRing(ST_Buffer(ST_MakePoint(20,20),1)) ]
	)
FROM
	(SELECT ST_ExteriorRing(ST_Buffer(ST_MakePoint(10,10),10,10))
		As line )
		As foo;
		

Build province boundaries with holes representing lakes in the province from a set of province polygons/multipolygons and water linestrings. This is an example of using PostGIS ST_Accum.

[Note]

The CASE construct is used because feeding a null array into ST_MakePolygon results in NULL.

[Note]

A left join is used to guarantee we get all provinces back even if they have no lakes.

	SELECT p.gid, p.province_name,
		CASE WHEN
			ST_Accum(w.the_geom) IS NULL THEN p.the_geom
		ELSE  ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)), ST_Accum(w.the_geom)) END
	FROM
		provinces p LEFT JOIN waterlines w
			ON (ST_Within(w.the_geom, p.the_geom) AND ST_IsClosed(w.the_geom))
	GROUP BY p.gid, p.province_name, p.the_geom;

	--Same example above but utilizing a correlated subquery
	--and PostgreSQL built-in ARRAY() function that converts a row set to an array

	SELECT p.gid,  p.province_name, CASE WHEN
		EXISTS(SELECT w.the_geom
			FROM waterlines w
			WHERE ST_Within(w.the_geom, p.the_geom)
			AND ST_IsClosed(w.the_geom))
		THEN
		ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)),
			ARRAY(SELECT w.the_geom
				FROM waterlines w
				WHERE ST_Within(w.the_geom, p.the_geom)
				AND ST_IsClosed(w.the_geom)))
		ELSE p.the_geom END As the_geom
	FROM
		provinces p;
			  

Name

ST_MakePoint — Creates a 2D,3DZ or 4D point geometry.

Synopsis

geometry ST_MakePoint ( double precision x , double precision y ) ;

geometry ST_MakePoint ( double precision x , double precision y , double precision z ) ;

geometry ST_MakePoint ( double precision x , double precision y , double precision z , double precision m ) ;

Description

Creates a 2D,3DZ or 4D point geometry (geometry with measure). ST_MakePoint while not being OGC compliant is generally faster and more precise than ST_GeomFromText and ST_PointFromText . It is also easier to use if you have raw coordinates rather than WKT.

[Note]

Note x is longitude and y is latitude

[Note]

Use ST_MakePointM if you need to make a point with x,y,m.

This function supports 3d and will not drop the z-index.

Examples

--Return point with unknown SRID
SELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

--Return point marked as WGS 84 long lat
SELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

--Return a 3D point (e.g. has altitude)
SELECT ST_MakePoint(1, 2,1.5);

--Get z of point
SELECT ST_Z(ST_MakePoint(1, 2,1.5));
result
-------
1.5

Name

ST_MakePointM — Creates a point geometry with an x y and m coordinate.

Synopsis

geometry ST_MakePointM ( float x , float y , float m ) ;

Description

Creates a point with x, y and measure coordinates.

[Note]

Note x is longitude and y is latitude.

Examples

We use ST_AsEWKT in these examples to show the text representation instead of ST_AsText because ST_AsText does not support returning M.

--Return EWKT representation of point with unknown SRID
SELECT ST_AsEWKT(ST_MakePointM(-71.1043443253471, 42.3150676015829, 10));

--result
				   st_asewkt
-----------------------------------------------
 POINTM(-71.1043443253471 42.3150676015829 10)

--Return EWKT representation of point with measure marked as WGS 84 long lat
SELECT ST_AsEWKT(ST_SetSRID(ST_MakePointM(-71.1043443253471, 42.3150676015829,10),4326));

						st_asewkt
---------------------------------------------------------
SRID=4326;POINTM(-71.1043443253471 42.3150676015829 10)

--Return a 3d point (e.g. has altitude)
SELECT ST_MakePoint(1, 2,1.5);

--Get m of point
SELECT ST_M(ST_MakePointM(-71.1043443253471, 42.3150676015829,10));
result
-------
10
			  

Name

ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.

Synopsis

geometry ST_MLineFromText ( text WKT , integer srid ) ;

geometry ST_MLineFromText ( text WKT ) ;

Description

Makes a Geometry from Well-Known-Text (WKT) with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTILINESTRING

[Note]

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.SQL-MM 3: 9.4.4

Examples

SELECT ST_MLineFromText('MULTILINESTRING((1 2, 3 4), (4 5, 6 7))');

Name

ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_MPointFromText ( text WKT , integer srid ) ;

geometry ST_MPointFromText ( text WKT ) ;

Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTIPOINT

[Note]

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.2.4

Examples

SELECT ST_MPointFromText('MULTIPOINT(1 2, 3 4)');
SELECT ST_MPointFromText('MULTIPOINT(-70.9590 42.1180, -70.9611 42.1223)', 4326);

Name

ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_MPolyFromText ( text WKT , integer srid ) ;

geometry ST_MPolyFromText ( text WKT ) ;

Description

Makes a MultiPolygon from WKT with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Throws an error if the WKT is not a MULTIPOLYGON

[Note]

If you are absolutely sure all your WKT geometries are multipolygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.6.4

Examples

SELECT ST_MPolyFromText('MULTIPOLYGON(((0 0 1,20 0 1,20 20 1,0 20 1,0 0 1),(5 5 3,5 7 3,7 7 3,7 5 3,5 5 3)))');
SELECt ST_MPolyFromText('MULTIPOLYGON(((-70.916 42.1002,-70.9468 42.0946,-70.9765 42.0872,-70.9754 42.0875,-70.9749 42.0879,-70.9752 42.0881,-70.9754 42.0891,-70.9758 42.0894,-70.9759 42.0897,-70.9759 42.0899,-70.9754 42.0902,-70.9756 42.0906,-70.9753 42.0907,-70.9753 42.0917,-70.9757 42.0924,-70.9755 42.0928,-70.9755 42.0942,-70.9751 42.0948,-70.9755 42.0953,-70.9751 42.0958,-70.9751 42.0962,-70.9759 42.0983,-70.9767 42.0987,-70.9768 42.0991,-70.9771 42.0997,-70.9771 42.1003,-70.9768 42.1005,-70.977 42.1011,-70.9766 42.1019,-70.9768 42.1026,-70.9769 42.1033,-70.9775 42.1042,-70.9773 42.1043,-70.9776 42.1043,-70.9778 42.1048,-70.9773 42.1058,-70.9774 42.1061,-70.9779 42.1065,-70.9782 42.1078,-70.9788 42.1085,-70.9798 42.1087,-70.9806 42.109,-70.9807 42.1093,-70.9806 42.1099,-70.9809 42.1109,-70.9808 42.1112,-70.9798 42.1116,-70.9792 42.1127,-70.979 42.1129,-70.9787 42.1134,-70.979 42.1139,-70.9791 42.1141,-70.9987 42.1116,-71.0022 42.1273,
	-70.9408 42.1513,-70.9315 42.1165,-70.916 42.1002)))',4326);

Name

ST_Point — Returns an ST_Point with the given coordinate values. OGC alias for ST_MakePoint.

Synopsis

geometry ST_Point ( float x_lon , float y_lat ) ;

Description

Returns an ST_Point with the given coordinate values. MM compliant alias for ST_MakePoint that takes just an x and y.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.2

Examples: Geometry

SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)

Examples: Geography

SELECT CAST(ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326) As geography);
-- the :: is PostgreSQL short-hand for casting.
SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)::geography;
--If your point coordinates are in a different spatial reference from WGS-84 long lat, then you need to transform before casting
-- This example we convert a point in Pennsylvania State Plane feet to WGS 84 and then geography
SELECT ST_Transform(ST_SetSRID(ST_Point(3637510, 3014852),2273),4326)::geography;

Name

ST_PointFromGeoHash — Return a point from a GeoHash string.

Synopsis

point ST_PointFromGeoHash ( text geohash , integer precision=full_precision_of_geohash ) ;

Description

Return a point from a GeoHash string. The point represents the center point of the GeoHash.

If no precision is specified ST_PointFromGeoHash returns a point based on full precision of the input GeoHash string.

If precision is specified ST_PointFromGeoHash will use that many characters from the GeoHash to create the point.

Availability: 2.1.0

Examples

SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0'));
          st_astext
------------------------------
 POINT(-115.172816 36.114646)

SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 4));
             st_astext
-----------------------------------
 POINT(-115.13671875 36.123046875)

SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10));
                 st_astext
-------------------------------------------
 POINT(-115.172815918922 36.1146435141563)
		
		

Name

ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.

Synopsis

geometry ST_PointFromText ( text WKT ) ;

geometry ST_PointFromText ( text WKT , integer srid ) ;

Description

Constructs a PostGIS ST_Geometry point object from the OGC Well-Known text representation. If SRID is not given, it defaults to unknown (currently 0). If geometry is not a WKT point representation, returns null. If completely invalid WKT, then throws an error.

[Note]

There are 2 variants of ST_PointFromText function, the first takes no SRID and returns a geometry with no defined spatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometry that includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

[Note]

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step. If you are building points from long lat coordinates and care more about performance and accuracy than OGC compliance, use ST_MakePoint or OGC compliant alias ST_Point .

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.8

Examples

SELECT ST_PointFromText('POINT(-71.064544 42.28787)');
SELECT ST_PointFromText('POINT(-71.064544 42.28787)', 4326);
	

Name

ST_PointFromWKB — Makes a geometry from WKB with the given SRID

Synopsis

geometry ST_GeomFromWKB ( bytea geom ) ;

geometry ST_GeomFromWKB ( bytea geom , integer srid ) ;

Description

The ST_PointFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID ( SRID ) and creates an instance of the appropriate geometry type - in this case, a POINT geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. NULL is returned if the input bytea does not represent a POINT geometry.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.7.2

This method implements the SQL/MM specification. SQL-MM 3: 6.1.9

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT
  ST_AsText(
	ST_PointFromWKB(
	  ST_AsEWKB('POINT(2 5)'::geometry)
	)
  );
 st_astext
------------
 POINT(2 5)
(1 row)

SELECT
  ST_AsText(
	ST_PointFromWKB(
	  ST_AsEWKB('LINESTRING(2 5, 2 6)'::geometry)
	)
  );
 st_astext
-----------

(1 row)

Name

ST_Polygon — Returns a polygon built from the specified linestring and SRID.

Synopsis

geometry ST_Polygon ( geometry aLineString , integer srid ) ;

Description

Returns a polygon built from the specified linestring and SRID.

[Note]

ST_Polygon is similar to first version of ST_MakePolygon except it also sets the spatial ref sys (SRID) of the polygon. Will not work with MULTILINESTRINGS so use LineMerge to merge multilines. Also does not create polygons with holes. Use ST_MakePolygon for that.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.3.2

This function supports 3d and will not drop the z-index.

Examples

--a 2d polygon
SELECT ST_Polygon(ST_GeomFromText('LINESTRING(75.15 29.53,77 29,77.6 29.5, 75.15 29.53)'), 4326);

--result--
POLYGON((75.15 29.53,77 29,77.6 29.5,75.15 29.53))
--a 3d polygon
SELECT ST_AsEWKT(ST_Polygon(ST_GeomFromEWKT('LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'), 4326));

result
------
SRID=4326;POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))
			

Name

ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_PolygonFromText ( text WKT ) ;

geometry ST_PolygonFromText ( text WKT , integer srid ) ;

Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0. Returns null if WKT is not a polygon.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

[Note]

If you are absolutely sure all your WKT geometries are polygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 8.3.6

Examples

SELECT ST_PolygonFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');
st_polygonfromtext
------------------
010300000001000000050000006...


SELECT ST_PolygonFromText('POINT(1 2)') IS NULL as point_is_notpoly;

point_is_not_poly
----------
t

Name

ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid

Synopsis

geometry ST_WKBToSQL ( bytea WKB ) ;

Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.36


Name

ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

Synopsis

geometry ST_WKTToSQL ( text WKT ) ;

Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.34

8.5. Geometry Accessors

GeometryType — Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.
ST_Boundary — Returns the closure of the combinatorial boundary of this Geometry.
ST_CoordDim — Return the coordinate dimension of the ST_Geometry value.
ST_Dimension — The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension.
ST_EndPoint — Returns the last point of a LINESTRING or CIRCULARLINESTRING geometry as a POINT .
ST_Envelope — Returns a geometry representing the double precision (float8) bounding box of the supplied geometry.
ST_BoundingDiagonal — Returns the diagonal of the supplied geometry's bounding box.
ST_ExteriorRing — Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon. Will not work with MULTIPOLYGON
ST_GeometryN — Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.
ST_GeometryType — Return the geometry type of the ST_Geometry value.
ST_InteriorRingN — Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range.
ST_IsPolygonCCW — Returns true if all exterior rings are oriented counter-clockwise and all interior rings are oriented clockwise.
ST_IsPolygonCW — Returns true if all exterior rings are oriented clockwise and all interior rings are oriented counter-clockwise.
ST_IsClosed — Returns TRUE if the LINESTRING 's start and end points are coincident. For Polyhedral surface is closed (volumetric).
ST_IsCollection — Returns TRUE if the argument is a collection ( MULTI* , GEOMETRYCOLLECTION , ...)
ST_IsEmpty — Returns true if this Geometry is an empty geometrycollection, polygon, point etc.
ST_IsRing — Returns TRUE if this LINESTRING is both closed and simple.
ST_IsSimple — Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency.
ST_IsValid — Returns true if the ST_Geometry is well formed.
ST_IsValidReason — Returns text stating if a geometry is valid or not and if not valid, a reason why.
ST_IsValidDetail — Returns a valid_detail (valid,reason,location) row stating if a geometry is valid or not and if not valid, a reason why and a location where.
ST_M — Return the M coordinate of the point, or NULL if not available. Input must be a point.
ST_NDims — Returns coordinate dimension of the geometry as a small int. Values are: 2,3 or 4.
ST_NPoints — Return the number of points (vertexes) in a geometry.
ST_NRings — If the geometry is a polygon or multi-polygon returns the number of rings.
ST_NumGeometries — If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.
ST_NumInteriorRings — Return the number of interior rings of a polygon geometry.
ST_NumInteriorRing — Return the number of interior rings of a polygon in the geometry. Synonym for ST_NumInteriorRings.
ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
ST_NumPoints — Return the number of points in an ST_LineString or ST_CircularString value.
ST_PatchN — Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL.
ST_PointN — Return the Nth point in the first LineString or circular LineString in the geometry. Negative values are counted backwards from the end of the LineString. Returns NULL if there is no linestring in the geometry.
ST_Points — Returns a MultiPoint containing all of the coordinates of a geometry.
ST_SRID — Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.
ST_StartPoint — Returns the first point of a LINESTRING geometry as a POINT .
ST_Summary — Returns a text summary of the contents of the geometry.
ST_X — Return the X coordinate of the point, or NULL if not available. Input must be a point.
ST_XMax — Returns X maxima of a bounding box 2d or 3d or a geometry.
ST_XMin — Returns X minima of a bounding box 2d or 3d or a geometry.
ST_Y — Return the Y coordinate of the point, or NULL if not available. Input must be a point.
ST_YMax — Returns Y maxima of a bounding box 2d or 3d or a geometry.
ST_YMin — Returns Y minima of a bounding box 2d or 3d or a geometry.
ST_Z — Return the Z coordinate of the point, or NULL if not available. Input must be a point.
ST_ZMax — Returns Z minima of a bounding box 2d or 3d or a geometry.
ST_Zmflag — Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.
ST_ZMin — Returns Z minima of a bounding box 2d or 3d or a geometry.

Name

GeometryType — Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.

Synopsis

text GeometryType ( geometry geomA ) ;

Description

Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.

OGC SPEC s2.1.1.1 - Returns the name of the instantiable subtype of Geometry of which this Geometry instance is a member. The name of the instantiable subtype of Geometry is returned as a string.

[Note]

This function also indicates if the geometry is measured, by returning a string of the form 'POINTM'.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

SELECT GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
 geometrytype
--------------
 LINESTRING
SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
			--result
			POLYHEDRALSURFACE
			
SELECT GeometryType(geom) as result
  FROM
    (SELECT
       ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )')  AS geom
    ) AS g;
 result
--------
 TIN    

Name

ST_Boundary — Returns the closure of the combinatorial boundary of this Geometry.

Synopsis

geometry ST_Boundary ( geometry geomA ) ;

Description

Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described in section 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resulting boundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.

Performed by the GEOS module

[Note]

Prior to 2.0.0, this function throws an exception if used with GEOMETRYCOLLECTION . From 2.0.0 up it will return NULL instead (unsupported input).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. OGC SPEC s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.14

This function supports 3d and will not drop the z-index.

Enhanced: 2.1.0 support for Triangle was introduced

Examples

Linestring with boundary points overlaid

SELECT ST_Boundary(geom)
FROM (SELECT 'LINESTRING(100 150,50 60, 70 80, 160 170)'::geometry As geom) As f;
				

-- ST_AsText output
MULTIPOINT(100 150,160 170)

polygon holes with boundary multilinestring

SELECT ST_Boundary(geom)
FROM (SELECT
'POLYGON (( 10 130, 50 190, 110 190, 140 150, 150 80, 100 10, 20 40, 10 130 ),
	( 70 40, 100 50, 120 80, 80 110, 50 90, 70 40 ))'::geometry As geom) As f;
				

-- ST_AsText output
MULTILINESTRING((10 130,50 190,110 190,140 150,150 80,100 10,20 40,10 130),
	(70 40,100 50,120 80,80 110,50 90,70 40))

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(1 1,0 0, -1 1)')));
st_astext
-----------
MULTIPOINT(1 1,-1 1)

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))')));
st_astext
----------
LINESTRING(1 1,0 0,-1 1,1 1)

--Using a 3d polygon
SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))')));

st_asewkt
-----------------------------------
LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)

--Using a 3d multilinestring
SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )')));

st_asewkt
----------
MULTIPOINT(-1 1 1,1 1 0.75)

Name

ST_CoordDim — Return the coordinate dimension of the ST_Geometry value.

Synopsis

integer ST_CoordDim ( geometry geomA ) ;

Description

Return the coordinate dimension of the ST_Geometry value.

This is the MM compliant alias name for ST_NDims

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.3

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

SELECT ST_CoordDim('CIRCULARSTRING(1 2 3, 1 3 4, 5 6 7, 8 9 10, 11 12 13)');
			---result--
				3

				SELECT ST_CoordDim(ST_Point(1,2));
			--result--
				2

		

See Also

ST_NDims


Name

ST_Dimension — The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension.

Synopsis

integer ST_Dimension ( geometry g ) ;

Description

The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension. OGC SPEC s2.1.1.1 - returns 0 for POINT , 1 for LINESTRING , 2 for POLYGON , and the largest dimension of the components of a GEOMETRYCOLLECTION . If the dimension is unknown (empty GEOMETRYCOLLECTION ) 0 is returned.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.2

Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given empty geometry.

[Note]

Prior to 2.0.0, this function throws an exception if used with empty geometry.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

SELECT ST_Dimension('GEOMETRYCOLLECTION(LINESTRING(1 1,0 0),POINT(0 0))');
ST_Dimension
-----------
1

See Also

ST_NDims


Name

ST_EndPoint — Returns the last point of a LINESTRING or CIRCULARLINESTRING geometry as a POINT .

Synopsis

boolean ST_EndPoint ( geometry g ) ;

Description

Returns the last point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING .

This method implements the SQL/MM specification. SQL-MM 3: 7.1.4

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.

Examples

postgis=# SELECT ST_AsText(ST_EndPoint('LINESTRING(1 1, 2 2, 3 3)'::geometry));
 st_astext
------------
 POINT(3 3)
(1 row)

postgis=# SELECT ST_EndPoint('POINT(1 1)'::geometry) IS NULL AS is_null;
  is_null
----------
 t
(1 row)

--3d endpoint
SELECT ST_AsEWKT(ST_EndPoint('LINESTRING(1 1 2, 1 2 3, 0 0 5)'));
  st_asewkt
--------------
 POINT(0 0 5)
(1 row)

Name

ST_Envelope — Returns a geometry representing the double precision (float8) bounding box of the supplied geometry.

Synopsis

geometry ST_Envelope ( geometry g1 ) ;

Description

Returns the float8 minimum bounding box for the supplied geometry, as a geometry. The polygon is defined by the corner points of the bounding box (( MINX , MINY ), ( MINX , MAXY ), ( MAXX , MAXY ), ( MAXX , MINY ), ( MINX , MINY )). (PostGIS will add a ZMIN / ZMAX coordinate as well).

Degenerate cases (vertical lines, points) will return a geometry of lower dimension than POLYGON , ie. POINT or LINESTRING .

Availability: 1.5.0 behavior changed to output double precision instead of float4

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.15

Examples

SELECT ST_AsText(ST_Envelope('POINT(1 3)'::geometry));
 st_astext
------------
 POINT(1 3)
(1 row)


SELECT ST_AsText(ST_Envelope('LINESTRING(0 0, 1 3)'::geometry));
		   st_astext
--------------------------------
 POLYGON((0 0,0 3,1 3,1 0,0 0))
(1 row)


SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))'::geometry));
						  st_astext
--------------------------------------------------------------
 POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
(1 row)
SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))'::geometry));
						  st_astext
--------------------------------------------------------------
 POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
(1 row)

SELECT Box3D(geom), Box2D(geom), ST_AsText(ST_Envelope(geom)) As envelopewkt
	FROM (SELECT 'POLYGON((0 0, 0 1000012333334.34545678, 1.0000001 1, 1.0000001 0, 0 0))'::geometry As geom) As foo;


	

Name

ST_BoundingDiagonal — Returns the diagonal of the supplied geometry's bounding box.

Synopsis

geometry ST_BoundingDiagonal ( geometry geom , boolean fits=false ) ;

Description

Returns the diagonal of the supplied geometry's bounding box as linestring. If the input geometry is empty, the diagonal line is also empty, otherwise it is a 2-points linestring with minimum values of each dimension in its start point and maximum values in its end point.

The returned linestring geometry always retains SRID and dimensionality (Z and M presence) of the input geometry.

The fits parameter specifies if the best fit is needed. If false, the diagonal of a somewhat larger bounding box can be accepted (is faster to obtain for geometries with a lot of vertices). In any case the bounding box of the returned diagonal line always covers the input geometry.

[Note]

In degenerate cases (a single vertex in input) the returned linestring will be topologically invalid (no interior). This does not make the return semantically invalid.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

Examples

-- Get the minimum X in a buffer around a point
SELECT ST_X(ST_StartPoint(ST_BoundingDiagonal(
  ST_Buffer(ST_MakePoint(0,0),10)
)));
 st_x
------
  -10
		

Name

ST_ExteriorRing — Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon. Will not work with MULTIPOLYGON

Synopsis

geometry ST_ExteriorRing ( geometry a_polygon ) ;

Description

Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon.

[Note]

Only works with POLYGON geometry types

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 8.2.3, 8.3.3

This function supports 3d and will not drop the z-index.

Examples

--If you have a table of polygons
SELECT gid, ST_ExteriorRing(the_geom) AS ering
FROM sometable;

--If you have a table of MULTIPOLYGONs
--and want to return a MULTILINESTRING composed of the exterior rings of each polygon
SELECT gid, ST_Collect(ST_ExteriorRing(the_geom)) AS erings
	FROM (SELECT gid, (ST_Dump(the_geom)).geom As the_geom
			FROM sometable) As foo
GROUP BY gid;

--3d Example
SELECT ST_AsEWKT(
	ST_ExteriorRing(
	ST_GeomFromEWKT('POLYGON((0 0 1, 1 1 1, 1 2 1, 1 1 1, 0 0 1))')
	)
);

st_asewkt
---------
LINESTRING(0 0 1,1 1 1,1 2 1,1 1 1,0 0 1)

Name

ST_GeometryN — Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.

Synopsis

geometry ST_GeometryN ( geometry geomA , integer n ) ;

Description

Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL

[Note]

Index is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead.

[Note]

If you want to extract all geometries, of a geometry, ST_Dump is more efficient and will also work for singular geoms.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Standard Examples

--Extracting a subset of points from a 3d multipoint
SELECT n, ST_AsEWKT(ST_GeometryN(the_geom, n)) As geomewkt
FROM (
VALUES (ST_GeomFromEWKT('MULTIPOINT(1 2 7, 3 4 7, 5 6 7, 8 9 10)') ),
( ST_GeomFromEWKT('MULTICURVE(CIRCULARSTRING(2.5 2.5,4.5 2.5, 3.5 3.5), (10 11, 12 11))') )
	)As foo(the_geom)
	CROSS JOIN generate_series(1,100) n
WHERE n <= ST_NumGeometries(the_geom);

 n |               geomewkt
---+-----------------------------------------
 1 | POINT(1 2 7)
 2 | POINT(3 4 7)
 3 | POINT(5 6 7)
 4 | POINT(8 9 10)
 1 | CIRCULARSTRING(2.5 2.5,4.5 2.5,3.5 3.5)
 2 | LINESTRING(10 11,12 11)


--Extracting all geometries (useful when you want to assign an id)
SELECT gid, n, ST_GeometryN(the_geom, n)
FROM sometable CROSS JOIN generate_series(1,100) n
WHERE n <= ST_NumGeometries(the_geom);

Polyhedral Surfaces, TIN and Triangle Examples

-- Polyhedral surface example
-- Break a Polyhedral surface into its faces
SELECT ST_AsEWKT(ST_GeometryN(p_geom,3)) As geom_ewkt
  FROM (SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
)')  AS p_geom )  AS a;

                geom_ewkt
------------------------------------------
 POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))
-- TIN --
SELECT ST_AsEWKT(ST_GeometryN(geom,2)) as wkt
  FROM
    (SELECT
       ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )')  AS geom
    ) AS g;
-- result --
                 wkt
-------------------------------------
 TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

Name

ST_GeometryType — Return the geometry type of the ST_Geometry value.

Synopsis

text ST_GeometryType ( geometry g1 ) ;

Description

Returns the type of the geometry as a string. EG: 'ST_Linestring', 'ST_Polygon','ST_MultiPolygon' etc. This function differs from GeometryType(geometry) in the case of the string and ST in front that is returned, as well as the fact that it will not indicate whether the geometry is measured.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Examples

SELECT ST_GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
			--result
			ST_LineString
SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
			--result
			ST_PolyhedralSurface
SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
			--result
			ST_PolyhedralSurface
SELECT ST_GeometryType(geom) as result
  FROM
    (SELECT
       ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )')  AS geom
    ) AS g;
 result
--------
 ST_Tin    

Name

ST_InteriorRingN — Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range.

Synopsis

geometry ST_InteriorRingN ( geometry a_polygon , integer n ) ;

Description

Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range. index starts at 1.

[Note]

This will not work for MULTIPOLYGONs. Use in conjunction with ST_Dump for MULTIPOLYGONS

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_AsText(ST_InteriorRingN(the_geom, 1)) As the_geom
FROM (SELECT ST_BuildArea(
		ST_Collect(ST_Buffer(ST_Point(1,2), 20,3),
			ST_Buffer(ST_Point(1, 2), 10,3))) As the_geom
		)  as foo
		

Name

ST_IsPolygonCCW — Returns true if all exterior rings are oriented counter-clockwise and all interior rings are oriented clockwise.

Synopsis

boolean ST_IsPolygonCCW ( geometry geom ) ;

Description

Returns true if all polygonal components of the input geometry use a counter-clockwise orientation for their exterior ring, and a clockwise direction for all interior rings.

Returns true if the geometry has no polygonal components.

[Note]

Closed linestrings are not considered polygonal components, so you would still get a true return by passing a single closed linestring no matter its orientation.

[Note]

If a polygonal geometry does not use reversed orientation for interior rings (i.e., if one or more interior rings are oriented in the same direction as an exterior ring) then both ST_IsPolygonCW and ST_IsPolygonCCW will return false.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_IsPolygonCW — Returns true if all exterior rings are oriented clockwise and all interior rings are oriented counter-clockwise.

Synopsis

boolean ST_IsPolygonCW ( geometry geom ) ;

Description

Returns true if all polygonal components of the input geometry use a clockwise orientation for their exterior ring, and a counter-clockwise direction for all interior rings.

Returns true if the geometry has no polygonal components.

[Note]

Closed linestrings are not considered polygonal components, so you would still get a true return by passing a single closed linestring no matter its orientation.

[Note]

If a polygonal geometry does not use reversed orientation for interior rings (i.e., if one or more interior rings are oriented in the same direction as an exterior ring) then both ST_IsPolygonCW and ST_IsPolygonCCW will return false.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_IsClosed — Returns TRUE if the LINESTRING 's start and end points are coincident. For Polyhedral surface is closed (volumetric).

Synopsis

boolean ST_IsClosed ( geometry g ) ;

Description

Returns TRUE if the LINESTRING 's start and end points are coincident. For Polyhedral Surfaces, it tells you if the surface is areal (open) or volumetric (closed).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.5, 9.3.3

[Note]

SQL-MM defines the result of ST_IsClosed( NULL ) to be 0, while PostGIS returns NULL .

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports Polyhedral surfaces.

Line String and Point Examples

postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 1 1)'::geometry);
 st_isclosed
-------------
 f
(1 row)

postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 0 1, 1 1, 0 0)'::geometry);
 st_isclosed
-------------
 t
(1 row)

postgis=# SELECT ST_IsClosed('MULTILINESTRING((0 0, 0 1, 1 1, 0 0),(0 0, 1 1))'::geometry);
 st_isclosed
-------------
 f
(1 row)

postgis=# SELECT ST_IsClosed('POINT(0 0)'::geometry);
 st_isclosed
-------------
 t
(1 row)

postgis=# SELECT ST_IsClosed('MULTIPOINT((0 0), (1 1))'::geometry);
 st_isclosed
-------------
 t
(1 row)

Polyhedral Surface Examples

		-- A cube --
		SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));

 st_isclosed
-------------
 t


 -- Same as cube but missing a side --
 SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)) )'));

 st_isclosed
-------------
 f

See Also

ST_IsRing


Name

ST_IsCollection — Returns TRUE if the argument is a collection ( MULTI* , GEOMETRYCOLLECTION , ...)

Synopsis

boolean ST_IsCollection ( geometry g ) ;

Description

Returns TRUE if the geometry type of the argument is either:

  • GEOMETRYCOLLECTION

  • MULTI{POINT,POLYGON,LINESTRING,CURVE,SURFACE}

  • COMPOUNDCURVE

[Note]

This function analyzes the type of the geometry. This means that it will return TRUE on collections that are empty or that contain a single element.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

postgis=# SELECT ST_IsCollection('LINESTRING(0 0, 1 1)'::geometry);
 st_iscollection
-------------
 f
(1 row)

postgis=# SELECT ST_IsCollection('MULTIPOINT EMPTY'::geometry);
 st_iscollection
-------------
 t
(1 row)

postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0))'::geometry);
 st_iscollection
-------------
 t
(1 row)

postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'::geometry);
 st_iscollection
-------------
 t
(1 row)

postgis=# SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'::geometry);
 st_iscollection
-------------
 t
(1 row)

Name

ST_IsEmpty — Returns true if this Geometry is an empty geometrycollection, polygon, point etc.

Synopsis

boolean ST_IsEmpty ( geometry geomA ) ;

Description

Returns true if this Geometry is an empty geometry. If true, then this Geometry represents an empty geometry collection, polygon, point etc.

[Note]

SQL-MM defines the result of ST_IsEmpty(NULL) to be 0, while PostGIS returns NULL.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.7

This method supports Circular Strings and Curves

[Warning]

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards

Examples

SELECT ST_IsEmpty(ST_GeomFromText('GEOMETRYCOLLECTION EMPTY'));
 st_isempty
------------
 t
(1 row)

 SELECT ST_IsEmpty(ST_GeomFromText('POLYGON EMPTY'));
 st_isempty
------------
 t
(1 row)

SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));

 st_isempty
------------
 f
(1 row)

 SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')) = false;
 ?column?
----------
 t
(1 row)

 SELECT ST_IsEmpty(ST_GeomFromText('CIRCULARSTRING EMPTY'));
  st_isempty
------------
 t
(1 row)


		

Name

ST_IsRing — Returns TRUE if this LINESTRING is both closed and simple.

Synopsis

boolean ST_IsRing ( geometry g ) ;

Description

Returns TRUE if this LINESTRING is both ST_IsClosed ( ST_StartPoint( g ) ~= ST_Endpoint( g ) ) and ST_IsSimple (does not self intersect).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.6

[Note]

SQL-MM defines the result of ST_IsRing( NULL ) to be 0, while PostGIS returns NULL .

Examples

SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)
FROM (SELECT 'LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'::geometry AS the_geom) AS foo;
 st_isring | st_isclosed | st_issimple
-----------+-------------+-------------
 t         | t           | t
(1 row)

SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)
FROM (SELECT 'LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)'::geometry AS the_geom) AS foo;
 st_isring | st_isclosed | st_issimple
-----------+-------------+-------------
 f         | t           | f
(1 row)

Name

ST_IsSimple — Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency.

Synopsis

boolean ST_IsSimple ( geometry geomA ) ;

Description

Returns true if this Geometry has no anomalous geometric points, such as self intersection or self tangency. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"

[Note]

SQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.8

This function supports 3d and will not drop the z-index.

Examples

 SELECT ST_IsSimple(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));
 st_issimple
-------------
 t
(1 row)

 SELECT ST_IsSimple(ST_GeomFromText('LINESTRING(1 1,2 2,2 3.5,1 3,1 2,2 1)'));
 st_issimple
-------------
 f
(1 row)

Name

ST_IsValid — Returns true if the ST_Geometry is well formed.

Synopsis

boolean ST_IsValid ( geometry g ) ;

boolean ST_IsValid ( geometry g , integer flags ) ;

Description

Test if an ST_Geometry value is well formed. For geometries that are invalid, the PostgreSQL NOTICE will provide details of why it is not valid. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"

[Note]

SQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL.

The version accepting flags is available starting with 2.0.0 and requires GEOS >= 3.3.0. Such version does not print a NOTICE explaining the invalidity. Allowed flags are documented in ST_IsValidDetail .

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.9

[Note]

Neither OGC-SFS nor SQL-MM specifications include a flag argument for ST_IsValid. The flag is a PostGIS extension.

Examples

SELECT ST_IsValid(ST_GeomFromText('LINESTRING(0 0, 1 1)')) As good_line,
	ST_IsValid(ST_GeomFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) As bad_poly
--results
NOTICE:  Self-intersection at or near point 0 0
 good_line | bad_poly
-----------+----------
 t         | f

Name

ST_IsValidReason — Returns text stating if a geometry is valid or not and if not valid, a reason why.

Synopsis

text ST_IsValidReason ( geometry geomA ) ;

text ST_IsValidReason ( geometry geomA , integer flags ) ;

Description

Returns text stating if a geometry is valid or not an if not valid, a reason why.

Useful in combination with ST_IsValid to generate a detailed report of invalid geometries and reasons.

Allowed flags are documented in ST_IsValidDetail .

Availability: 1.4 - requires GEOS >= 3.1.0.

Availability: 2.0 - requires GEOS >= 3.3.0 for the version taking flags.

Examples

--First 3 Rejects from a successful quintuplet experiment
SELECT gid, ST_IsValidReason(the_geom) as validity_info
FROM
(SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gid
FROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
	FROM generate_series(-4,6) x1
	CROSS JOIN generate_series(2,5) y1
	CROSS JOIN generate_series(1,8) z1
	WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
	INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1*1, z1*2) As line
	FROM generate_series(-3,6) x1
	CROSS JOIN generate_series(2,5) y1
	CROSS JOIN generate_series(1,10) z1
	WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
GROUP BY gid, e.buff) As quintuplet_experiment
WHERE ST_IsValid(the_geom) = false
ORDER BY gid
LIMIT 3;

 gid  |      validity_info
------+--------------------------
 5330 | Self-intersection [32 5]
 5340 | Self-intersection [42 5]
 5350 | Self-intersection [52 5]

 --simple example
SELECT ST_IsValidReason('LINESTRING(220227 150406,2220227 150407,222020 150410)');

 st_isvalidreason
------------------
 Valid Geometry

		

Name

ST_IsValidDetail — Returns a valid_detail (valid,reason,location) row stating if a geometry is valid or not and if not valid, a reason why and a location where.

Synopsis

valid_detail ST_IsValidDetail ( geometry geom ) ;

valid_detail ST_IsValidDetail ( geometry geom , integer flags ) ;

Description

Returns a valid_detail row, formed by a boolean (valid) stating if a geometry is valid, a varchar (reason) stating a reason why it is invalid and a geometry (location) pointing out where it is invalid.

Useful to substitute and improve the combination of ST_IsValid and ST_IsValidReason to generate a detailed report of invalid geometries.

The 'flags' argument is a bitfield. It can have the following values:

  • 1: Consider self-intersecting rings forming holes as valid. This is also know as "the ESRI flag". Note that this is against the OGC model.

Availability: 2.0.0 - requires GEOS >= 3.3.0.

Examples

--First 3 Rejects from a successful quintuplet experiment
SELECT gid, reason(ST_IsValidDetail(the_geom)), ST_AsText(location(ST_IsValidDetail(the_geom))) as location
FROM
(SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gid
FROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
	FROM generate_series(-4,6) x1
	CROSS JOIN generate_series(2,5) y1
	CROSS JOIN generate_series(1,8) z1
	WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
	INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1*1, z1*2) As line
	FROM generate_series(-3,6) x1
	CROSS JOIN generate_series(2,5) y1
	CROSS JOIN generate_series(1,10) z1
	WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
GROUP BY gid, e.buff) As quintuplet_experiment
WHERE ST_IsValid(the_geom) = false
ORDER BY gid
LIMIT 3;

 gid  |      reason       |  location
------+-------------------+-------------
 5330 | Self-intersection | POINT(32 5)
 5340 | Self-intersection | POINT(42 5)
 5350 | Self-intersection | POINT(52 5)

 --simple example
SELECT * FROM ST_IsValidDetail('LINESTRING(220227 150406,2220227 150407,222020 150410)');

 valid | reason | location
-------+--------+----------
 t     |        |

		

Name

ST_M — Return the M coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_M ( geometry a_point ) ;

Description

Return the M coordinate of the point, or NULL if not available. Input must be a point.

[Note]

This is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_M(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_m
------
	4
(1 row)

		

Name

ST_NDims — Returns coordinate dimension of the geometry as a small int. Values are: 2,3 or 4.

Synopsis

integer ST_NDims ( geometry g1 ) ;

Description

Returns the coordinate dimension of the geometry. PostGIS supports 2 - (x,y) , 3 - (x,y,z) or 2D with measure - x,y,m, and 4 - 3D with measure space x,y,z,m

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_NDims(ST_GeomFromText('POINT(1 1)')) As d2point,
	ST_NDims(ST_GeomFromEWKT('POINT(1 1 2)')) As d3point,
	ST_NDims(ST_GeomFromEWKT('POINTM(1 1 0.5)')) As d2pointm;

	 d2point | d3point | d2pointm
---------+---------+----------
	   2 |       3 |        3
			

Name

ST_NPoints — Return the number of points (vertexes) in a geometry.

Synopsis

integer ST_NPoints ( geometry g1 ) ;

Description

Return the number of points in a geometry. Works for all geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Examples

SELECT ST_NPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
--result
4

--Polygon in 3D space
SELECT ST_NPoints(ST_GeomFromEWKT('LINESTRING(77.29 29.07 1,77.42 29.26 0,77.27 29.31 -1,77.29 29.07 3)'))
--result
4

Name

ST_NRings — If the geometry is a polygon or multi-polygon returns the number of rings.

Synopsis

integer ST_NRings ( geometry geomA ) ;

Description

If the geometry is a polygon or multi-polygon returns the number of rings. Unlike NumInteriorRings, it counts the outer rings as well.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_NRings(the_geom) As Nrings, ST_NumInteriorRings(the_geom) As ninterrings
					FROM (SELECT ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))') As the_geom) As foo;
	 nrings | ninterrings
--------+-------------
	  1 |           0
(1 row)

Name

ST_NumGeometries — If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.

Synopsis

integer ST_NumGeometries ( geometry geom ) ;

Description

Returns the number of Geometries. If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

--Prior versions would have returned NULL for this -- in 2.0.0 this returns 1
SELECT ST_NumGeometries(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
--result
1

--Geometry Collection Example - multis count as one geom in a collection
SELECT ST_NumGeometries(ST_GeomFromEWKT('GEOMETRYCOLLECTION(MULTIPOINT(-2 3 , -2 2),
LINESTRING(5 5 ,10 10),
POLYGON((-7 4.2,-7.1 5,-7.1 4.3,-7 4.2)))'));
--result
3

Name

ST_NumInteriorRings — Return the number of interior rings of a polygon geometry.

Synopsis

integer ST_NumInteriorRings ( geometry a_polygon ) ;

Description

Return the number of interior rings of a polygon geometry. Return NULL if the geometry is not a polygon.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.5

Changed: 2.0.0 - in prior versions it would allow passing a MULTIPOLYGON, returning the number of interior rings of first POLYGON.

Examples

--If you have a regular polygon
SELECT gid, field1, field2, ST_NumInteriorRings(the_geom) AS numholes
FROM sometable;

--If you have multipolygons
--And you want to know the total number of interior rings in the MULTIPOLYGON
SELECT gid, field1, field2, SUM(ST_NumInteriorRings(the_geom)) AS numholes
FROM (SELECT gid, field1, field2, (ST_Dump(the_geom)).geom As the_geom
	FROM sometable) As foo
GROUP BY gid, field1,field2;
			

Name

ST_NumInteriorRing — Return the number of interior rings of a polygon in the geometry. Synonym for ST_NumInteriorRings.

Synopsis

integer ST_NumInteriorRing ( geometry a_polygon ) ;


Name

ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.

Synopsis

integer ST_NumPatches ( geometry g1 ) ;

Description

Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This is an alias for ST_NumGeometries to support MM naming. Faster to use ST_NumGeometries if you don't care about MM convention.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: ?

This function supports Polyhedral surfaces.

Examples

SELECT ST_NumPatches(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
		--result
		6
		

Name

ST_NumPoints — Return the number of points in an ST_LineString or ST_CircularString value.

Synopsis

integer ST_NumPoints ( geometry g1 ) ;

Description

Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with Linestrings as the specs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertexes for not just line strings. Consider using ST_NPoints instead which is multi-purpose and works with many geometry types.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.4

Examples

SELECT ST_NumPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
		--result
		4
		

Name

ST_PatchN — Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL.

Synopsis

geometry ST_PatchN ( geometry geomA , integer n ) ;

Description

>Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL. This returns the same answer as ST_GeometryN for Polyhedral Surfaces. Using ST_GemoetryN is faster.

[Note]

Index is 1-based.

[Note]

If you want to extract all geometries, of a geometry, ST_Dump is more efficient.

Availability: 2.0.0

This method implements the SQL/MM specification. SQL-MM 3: ?

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Examples

--Extract the 2nd face of the polyhedral surface
SELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewkt
FROM (
VALUES (ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
	((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
	((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
	((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ) As foo(geom);

              geomewkt
---+-----------------------------------------
 POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

Name

ST_PointN — Return the Nth point in the first LineString or circular LineString in the geometry. Negative values are counted backwards from the end of the LineString. Returns NULL if there is no linestring in the geometry.

Synopsis

geometry ST_PointN ( geometry a_linestring , integer n ) ;

Description

Return the Nth point in a single linestring or circular linestring in the geometry. Negative values are counted backwards from the end of the LineString, so that -1 is the last point. Returns NULL if there is no linestring in the geometry.

[Note]

Index is 1-based as for OGC specs since version 0.8.0. Backward indexing (negative index) is not in OGC Previous versions implemented this as 0-based instead.

[Note]

If you want to get the nth point of each line string in a multilinestring, use in conjunction with ST_Dump

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.5, 7.3.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring.

Changed: 2.3.0 : negative indexing available (-1 is last point)

Examples

-- Extract all POINTs from a LINESTRING
SELECT ST_AsText(
   ST_PointN(
	  column1,
	  generate_series(1, ST_NPoints(column1))
   ))
FROM ( VALUES ('LINESTRING(0 0, 1 1, 2 2)'::geometry) ) AS foo;

 st_astext
------------
 POINT(0 0)
 POINT(1 1)
 POINT(2 2)
(3 rows)

--Example circular string
SELECT ST_AsText(ST_PointN(ST_GeomFromText('CIRCULARSTRING(1 2, 3 2, 1 2)'),2));

st_astext
----------
POINT(3 2)

SELECT st_astext(f)
FROM ST_GeometryFromtext('LINESTRING(0 0 0, 1 1 1, 2 2 2)') as g
	,ST_PointN(g, -2) AS f -- 1 based index

st_astext
----------
"POINT Z (1 1 1)"


Name

ST_Points — Returns a MultiPoint containing all of the coordinates of a geometry.

Synopsis

geometry ST_Points ( geometry geom ) ;

Description

Returns a MultiPoint containing all of the coordinates of a geometry. Does not remove points that are duplicated in the input geometry, including start and end points of ring geometries. (If this behavior is undesired, duplicates may be removed using ST_RemoveRepeatedPoints ).

M and Z ordinates will be preserved if present.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

Availability: 2.3.0

Examples

SELECT ST_AsText(ST_Points('POLYGON Z ((30 10 4,10 30 5,40 40 6, 30 10))'));

--result
MULTIPOINT Z (30 10 4,10 30 5,40 40 6, 30 10 4)
			

Name

ST_SRID — Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.

Synopsis

integer ST_SRID ( geometry g1 ) ;

Description

Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. Section 4.3.1, “The SPATIAL_REF_SYS Table and Spatial Reference Systems”

[Note]

spatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformations from one spatial reference system to another. So verifying you have the right spatial reference system identifier is important if you plan to ever transform your geometries.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.5

This method supports Circular Strings and Curves

Examples

SELECT ST_SRID(ST_GeomFromText('POINT(-71.1043 42.315)',4326));
		--result
		4326
		

Name

ST_StartPoint — Returns the first point of a LINESTRING geometry as a POINT .

Synopsis

geometry ST_StartPoint ( geometry geomA ) ;

Description

Returns the first point of a LINESTRING or CIRCULARLINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING or CIRCULARLINESTRING .

This method implements the SQL/MM specification. SQL-MM 3: 7.1.3

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.

Examples

SELECT ST_AsText(ST_StartPoint('LINESTRING(0 1, 0 2)'::geometry));
 st_astext
------------
 POINT(0 1)
(1 row)

SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null;
  is_null
----------
 t
(1 row)

--3d line
SELECT ST_AsEWKT(ST_StartPoint('LINESTRING(0 1 1, 0 2 2)'::geometry));
 st_asewkt
------------
 POINT(0 1 1)
(1 row)

-- circular linestring --
SELECT ST_AsText(ST_StartPoint('CIRCULARSTRING(5 2,-3 1.999999, -2 1, -4 2, 5 2)'::geometry));
 st_astext
------------
 POINT(5 2)

Name

ST_Summary — Returns a text summary of the contents of the geometry.

Synopsis

text ST_Summary ( geometry g ) ;

text ST_Summary ( geography g ) ;

Description

Returns a text summary of the contents of the geometry.

Flags shown square brackets after the geometry type have the following meaning:

  • M: has M ordinate

  • Z: has Z ordinate

  • B: has a cached bounding box

  • G: is geodetic (geography)

  • S: has spatial reference system

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Availability: 1.2.2

Enhanced: 2.0.0 added support for geography

Enhanced: 2.1.0 S flag to denote if has a known spatial reference system

Enhanced: 2.2.0 Added support for TIN and Curves

Examples

=# SELECT ST_Summary(ST_GeomFromText('LINESTRING(0 0, 1 1)')) as geom,
        ST_Summary(ST_GeogFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) geog;
            geom             |          geog
-----------------------------+--------------------------
 LineString[B] with 2 points | Polygon[BGS] with 1 rings
                             | ring 0 has 5 points
                             :
(1 row)


=# SELECT ST_Summary(ST_GeogFromText('LINESTRING(0 0 1, 1 1 1)')) As geog_line,
        ST_Summary(ST_GeomFromText('SRID=4326;POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))')) As geom_poly;
;
           geog_line             |        geom_poly
-------------------------------- +--------------------------
 LineString[ZBGS] with 2 points | Polygon[ZBS] with 1 rings
                                :    ring 0 has 5 points
                                :
(1 row)


Name

ST_X — Return the X coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_X ( geometry a_point ) ;

Description

Return the X coordinate of the point, or NULL if not available. Input must be a point.

[Note]

If you want to get the max min x values of any geometry look at ST_XMin, ST_XMax functions.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.3

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_X(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_x
------
	1
(1 row)

SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
 st_y
------
  1.5
(1 row)

		

Name

ST_XMax — Returns X maxima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_XMax ( box3d aGeomorBox2DorBox3D ) ;

Description

Returns X maxima of a bounding box 2d or 3d or a geometry.

[Note]

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_XMax('BOX3D(1 2 3, 4 5 6)');
st_xmax
-------
4

SELECT ST_XMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
st_xmax
-------
5

SELECT ST_XMax(CAST('BOX(-3 2, 3 4)' As box2d));
st_xmax
-------
3
--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
SELECT ST_XMax('LINESTRING(1 3, 5 6)');

--ERROR:  BOX3D parser - doesn't start with BOX3D(

SELECT ST_XMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
st_xmax
--------
220288.248780547
		

Name

ST_XMin — Returns X minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_XMin ( box3d aGeomorBox2DorBox3D ) ;

Description

Returns X minima of a bounding box 2d or 3d or a geometry.

[Note]

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_XMin('BOX3D(1 2 3, 4 5 6)');
st_xmin
-------
1

SELECT ST_XMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
st_xmin
-------
1

SELECT ST_XMin(CAST('BOX(-3 2, 3 4)' As box2d));
st_xmin
-------
-3
--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
SELECT ST_XMin('LINESTRING(1 3, 5 6)');

--ERROR:  BOX3D parser - doesn't start with BOX3D(

SELECT ST_XMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
st_xmin
--------
220186.995121892
		

Name

ST_Y — Return the Y coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_Y ( geometry a_point ) ;

Description

Return the Y coordinate of the point, or NULL if not available. Input must be a point.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.4

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_Y(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_y
------
	2
(1 row)

SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
 st_y
------
  1.5
(1 row)


		

Name

ST_YMax — Returns Y maxima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_YMax ( box3d aGeomorBox2DorBox3D ) ;

Description

Returns Y maxima of a bounding box 2d or 3d or a geometry.

[Note]

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_YMax('BOX3D(1 2 3, 4 5 6)');
st_ymax
-------
5

SELECT ST_YMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
st_ymax
-------
6

SELECT ST_YMax(CAST('BOX(-3 2, 3 4)' As box2d));
st_ymax
-------
4
--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
SELECT ST_YMax('LINESTRING(1 3, 5 6)');

--ERROR:  BOX3D parser - doesn't start with BOX3D(

SELECT ST_YMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
st_ymax
--------
150506.126829327
		

Name

ST_YMin — Returns Y minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_YMin ( box3d aGeomorBox2DorBox3D ) ;

Description

Returns Y minima of a bounding box 2d or 3d or a geometry.

[Note]

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_YMin('BOX3D(1 2 3, 4 5 6)');
st_ymin
-------
2

SELECT ST_YMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
st_ymin
-------
3

SELECT ST_YMin(CAST('BOX(-3 2, 3 4)' As box2d));
st_ymin
-------
2
--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
SELECT ST_YMin('LINESTRING(1 3, 5 6)');

--ERROR:  BOX3D parser - doesn't start with BOX3D(

SELECT ST_YMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
st_ymin
--------
150406
		

Name

ST_Z — Return the Z coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_Z ( geometry a_point ) ;

Description

Return the Z coordinate of the point, or NULL if not available. Input must be a point.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_Z(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_z
------
	3
(1 row)

		

Name

ST_ZMax — Returns Z minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_ZMax ( box3d aGeomorBox2DorBox3D ) ;

Description

Returns Z maxima of a bounding box 2d or 3d or a geometry.

[Note]

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_ZMax('BOX3D(1 2 3, 4 5 6)');
st_zmax
-------
6

SELECT ST_ZMax(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)'));
st_zmax
-------
7

SELECT ST_ZMax('BOX3D(-3 2 1, 3 4 1)' );
st_zmax
-------
1
--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
SELECT ST_ZMax('LINESTRING(1 3 4, 5 6 7)');

--ERROR:  BOX3D parser - doesn't start with BOX3D(

SELECT ST_ZMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
st_zmax
--------
3
		

Name

ST_Zmflag — Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.

Synopsis

smallint ST_Zmflag ( geometry geomA ) ;

Description

Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRING(1 2, 3 4)'));
 st_zmflag
-----------
		 0

SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRINGM(1 2 3, 3 4 3)'));
 st_zmflag
-----------
		 1

SELECT ST_Zmflag(ST_GeomFromEWKT('CIRCULARSTRING(1 2 3, 3 4 3, 5 6 3)'));
 st_zmflag
-----------
		 2
SELECT ST_Zmflag(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_zmflag
-----------
		 3

Name

ST_ZMin — Returns Z minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_ZMin ( box3d aGeomorBox2DorBox3D ) ;

Description

Returns Z minima of a bounding box 2d or 3d or a geometry.

[Note]

Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_ZMin('BOX3D(1 2 3, 4 5 6)');
st_zmin
-------
3

SELECT ST_ZMin(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)'));
st_zmin
-------
4

SELECT ST_ZMin('BOX3D(-3 2 1, 3 4 1)' );
st_zmin
-------
1
--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D
SELECT ST_ZMin('LINESTRING(1 3 4, 5 6 7)');

--ERROR:  BOX3D parser - doesn't start with BOX3D(

SELECT ST_ZMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
st_zmin
--------
1
		

8.6. Geometry Editors

ST_AddPoint — Add a point to a LineString.
ST_Affine — Apply a 3d affine transformation to a geometry.
ST_Force2D — Force the geometries into a "2-dimensional mode".
ST_Force3D — Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
ST_Force3DZ — Force the geometries into XYZ mode.
ST_Force3DM — Force the geometries into XYM mode.
ST_Force4D — Force the geometries into XYZM mode.
ST_ForcePolygonCCW — Orients all exterior rings counter-clockwise and all interior rings clockwise.
ST_ForceCollection — Convert the geometry into a GEOMETRYCOLLECTION.
ST_ForcePolygonCW — Orients all exterior rings clockwise and all interior rings counter-clockwise.
ST_ForceSFS — Force the geometries to use SFS 1.1 geometry types only.
ST_ForceRHR — Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
ST_ForceCurve — Upcast a geometry into its curved type, if applicable.
ST_LineMerge — Return a (set of) LineString(s) formed by sewing together a MULTILINESTRING.
ST_CollectionExtract — Given a (multi)geometry, return a (multi)geometry consisting only of elements of the specified type.
ST_CollectionHomogenize — Given a geometry collection, return the "simplest" representation of the contents.
ST_Multi — Return the geometry as a MULTI* geometry.
ST_Normalize — Return the geometry in its canonical form.
ST_RemovePoint — Remove point from a linestring.
ST_Reverse — Return the geometry with vertex order reversed.
ST_Rotate — Rotate a geometry rotRadians counter-clockwise about an origin.
ST_RotateX — Rotate a geometry rotRadians about the X axis.
ST_RotateY — Rotate a geometry rotRadians about the Y axis.
ST_RotateZ — Rotate a geometry rotRadians about the Z axis.
ST_Scale — Scale a geometry by given factors.
ST_Segmentize — Return a modified geometry/geography having no segment longer than the given distance.
ST_SetPoint — Replace point of a linestring with a given point.
ST_SetSRID — Set the SRID on a geometry to a particular integer value.
ST_SnapToGrid — Snap all points of the input geometry to a regular grid.
ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.
ST_Transform — Return a new geometry with its coordinates transformed to a different spatial reference.
ST_Translate — Translate a geometry by given offsets.
ST_TransScale — Translate a geometry by given factors and offsets.

Name

ST_AddPoint — Add a point to a LineString.

Synopsis

geometry ST_AddPoint ( geometry linestring , geometry point ) ;

geometry ST_AddPoint ( geometry linestring , geometry point , integer position ) ;

Description

Adds a point to a LineString before point <position> (0-based index). Third parameter can be omitted or set to -1 for appending.

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

Examples

		--guarantee all linestrings in a table are closed
		--by adding the start point of each linestring to the end of the line string
		--only for those that are not closed
		UPDATE sometable
		SET the_geom = ST_AddPoint(the_geom, ST_StartPoint(the_geom))
		FROM sometable
		WHERE ST_IsClosed(the_geom) = false;

		--Adding point to a 3-d line
		SELECT ST_AsEWKT(ST_AddPoint(ST_GeomFromEWKT('LINESTRING(0 0 1, 1 1 1)'), ST_MakePoint(1, 2, 3)));

		--result
		st_asewkt
		----------
		LINESTRING(0 0 1,1 1 1,1 2 3)
			

Name

ST_Affine — Apply a 3d affine transformation to a geometry.

Synopsis

geometry ST_Affine ( geometry geomA , float a , float b , float c , float d , float e , float f , float g , float h , float i , float xoff , float yoff , float zoff ) ;

geometry ST_Affine ( geometry geomA , float a , float b , float d , float e , float xoff , float yoff ) ;

Description

Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.

Version 1: The call

ST_Affine(geom, a, b, c, d, e, f, g, h, i, xoff, yoff, zoff) 

represents the transformation matrix

/ a  b  c  xoff \
| d  e  f  yoff |
| g  h  i  zoff |
\ 0  0  0     1 /

and the vertices are transformed as follows:

x' = a*x + b*y + c*z + xoff
y' = d*x + e*y + f*z + yoff
z' = g*x + h*y + i*z + zoff

All of the translate / scale functions below are expressed via such an affine transformation.

Version 2: Applies a 2d affine transformation to the geometry. The call

ST_Affine(geom, a, b, d, e, xoff, yoff)

represents the transformation matrix

/  a  b  0  xoff  \       /  a  b  xoff  \
|  d  e  0  yoff  | rsp.  |  d  e  yoff  |
|  0  0  1     0  |       \  0  0     1  /
\  0  0  0     1  /

and the vertices are transformed as follows:

x' = a*x + b*y + xoff
y' = d*x + e*y + yoff
z' = z 

This method is a subcase of the 3D method above.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from Affine to ST_Affine in 1.2.2

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

--Rotate a 3d line 180 degrees about the z axis.  Note this is long-hand for doing ST_Rotate();
 SELECT ST_AsEWKT(ST_Affine(the_geom,  cos(pi()), -sin(pi()), 0,  sin(pi()), cos(pi()), 0,  0, 0, 1,  0, 0, 0)) As using_affine,
	 ST_AsEWKT(ST_Rotate(the_geom, pi())) As using_rotate
	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As the_geom) As foo;
        using_affine         |        using_rotate
-----------------------------+-----------------------------
 LINESTRING(-1 -2 3,-1 -4 3) | LINESTRING(-1 -2 3,-1 -4 3)
(1 row)

--Rotate a 3d line 180 degrees in both the x and z axis
SELECT ST_AsEWKT(ST_Affine(the_geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0))
	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As the_geom) As foo;
           st_asewkt
-------------------------------
 LINESTRING(-1 -2 -3,-1 -4 -3)
(1 row)
		

Name

ST_Force2D — Force the geometries into a "2-dimensional mode".

Synopsis

geometry ST_Force2D ( geometry geomA ) ;

Description

Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates. This is useful for force OGC-compliant output (since OGC only specifies 2-D geometries).

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_2D.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_AsEWKT(ST_Force2D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
		st_asewkt
-------------------------------------
CIRCULARSTRING(1 1,2 3,4 5,6 7,5 6)

SELECT  ST_AsEWKT(ST_Force2D('POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))'));

				  st_asewkt
----------------------------------------------
 POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))

		

Name

ST_Force3D — Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.

Synopsis

geometry ST_Force3D ( geometry geomA ) ;

Description

Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ. If a geometry has no Z component, then a 0 Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3D.

This function supports Polyhedral surfaces.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

Examples

		--Nothing happens to an already 3D geometry
		SELECT ST_AsEWKT(ST_Force3D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
				   st_asewkt
-----------------------------------------------
 CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)


SELECT  ST_AsEWKT(ST_Force3D('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

						 st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))
		

Name

ST_Force3DZ — Force the geometries into XYZ mode.

Synopsis

geometry ST_Force3DZ ( geometry geomA ) ;

Description

Forces the geometries into XYZ mode. This is a synonym for ST_Force3DZ. If a geometry has no Z component, then a 0 Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DZ.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

--Nothing happens to an already 3D geometry
SELECT ST_AsEWKT(ST_Force3DZ(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
				   st_asewkt
-----------------------------------------------
 CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)


SELECT  ST_AsEWKT(ST_Force3DZ('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

						 st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))
		

Name

ST_Force3DM — Force the geometries into XYM mode.

Synopsis

geometry ST_Force3DM ( geometry geomA ) ;

Description

Forces the geometries into XYM mode. If a geometry has no M component, then a 0 M coordinate is tacked on. If it has a Z component, then Z is removed

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DM.

This method supports Circular Strings and Curves

Examples

--Nothing happens to an already 3D geometry
SELECT ST_AsEWKT(ST_Force3DM(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
				   st_asewkt
------------------------------------------------
 CIRCULARSTRINGM(1 1 0,2 3 0,4 5 0,6 7 0,5 6 0)


SELECT  ST_AsEWKT(ST_Force3DM('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

						  st_asewkt
---------------------------------------------------------------
 POLYGONM((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

		

Name

ST_Force4D — Force the geometries into XYZM mode.

Synopsis

geometry ST_Force4D ( geometry geomA ) ;

Description

Forces the geometries into XYZM mode. 0 is tacked on for missing Z and M dimensions.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_4D.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

--Nothing happens to an already 3D geometry
SELECT ST_AsEWKT(ST_Force4D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
						st_asewkt
---------------------------------------------------------
 CIRCULARSTRING(1 1 2 0,2 3 2 0,4 5 2 0,6 7 2 0,5 6 2 0)



SELECT  ST_AsEWKT(ST_Force4D('MULTILINESTRINGM((0 0 1,0 5 2,5 0 3,0 0 4),(1 1 1,3 1 1,1 3 1,1 1 1))'));

									  st_asewkt
--------------------------------------------------------------------------------------
 MULTILINESTRING((0 0 0 1,0 5 0 2,5 0 0 3,0 0 0 4),(1 1 0 1,3 1 0 1,1 3 0 1,1 1 0 1))

		

Name

ST_ForcePolygonCCW — Orients all exterior rings counter-clockwise and all interior rings clockwise.

Synopsis

geometry ST_ForcePolygonCCW ( geometry geom ) ;

Description

Forces (Multi)Polygons to use a counter-clockwise orientation for their exterior ring, and a clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_ForceCollection — Convert the geometry into a GEOMETRYCOLLECTION.

Synopsis

geometry ST_ForceCollection ( geometry geomA ) ;

Description

Converts the geometry into a GEOMETRYCOLLECTION. This is useful for simplifying the WKB representation.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.2.2, prior to 1.3.4 this function will crash with Curves. This is fixed in 1.3.4+

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_Collection.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples


SELECT  ST_AsEWKT(ST_ForceCollection('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

								   st_asewkt
----------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1)))


  SELECT ST_AsText(ST_ForceCollection('CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));
								   st_astext
--------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))
(1 row)

		
-- POLYHEDRAL example --
SELECT ST_AsEWKT(ST_ForceCollection('POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
 ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
 ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
 ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
 ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
 ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))'))

								   st_asewkt
----------------------------------------------------------------------------------
GEOMETRYCOLLECTION(
  POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
  POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
  POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
  POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
  POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
  POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))
)
		

Name

ST_ForcePolygonCW — Orients all exterior rings clockwise and all interior rings counter-clockwise.

Synopsis

geometry ST_ForcePolygonCW ( geometry geom ) ;

Description

Forces (Multi)Polygons to use a clockwise orientation for their exterior ring, and a counter-clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_ForceSFS — Force the geometries to use SFS 1.1 geometry types only.

Synopsis

geometry ST_ForceSFS ( geometry geomA ) ;

geometry ST_ForceSFS ( geometry geomA , text version ) ;

Description

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.


Name

ST_ForceRHR — Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.

Synopsis

geometry ST_ForceRHR ( geometry g ) ;

Description

Forces the orientation of the vertices in a polygon to follow a Right-Hand-Rule, in which the area that is bounded by the polygon is to the right of the boundary. In particular, the exterior ring is orientated in a clockwise direction and the interior rings in a counter-clockwise direction. This function is a synonym for ST_ForcePolygonCW

[Note]

The above definition of the Right-Hand-Rule conflicts with definitions used in other contexts. To avoid confusion, it is recommended to use ST_ForcePolygonCW.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Examples

SELECT ST_AsEWKT(
  ST_ForceRHR(
	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'
  )
);
						  st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))
(1 row)

Name

ST_ForceCurve — Upcast a geometry into its curved type, if applicable.

Synopsis

geometry ST_ForceCurve ( geometry g ) ;

Description

Turns a geometry into its curved representation, if applicable: lines become compoundcurves, multilines become multicurves polygons become curvepolygons multipolygons become multisurfaces. If the geometry input is already a curved representation returns back same as input.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_AsText(
  ST_ForceCurve(
	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'::geometry
  )
);
                              st_astext
----------------------------------------------------------------------
 CURVEPOLYGON Z ((0 0 2,5 0 2,0 5 2,0 0 2),(1 1 2,1 3 2,3 1 2,1 1 2))
(1 row)

Name

ST_LineMerge — Return a (set of) LineString(s) formed by sewing together a MULTILINESTRING.

Synopsis

geometry ST_LineMerge ( geometry amultilinestring ) ;

Description

Returns a (set of) LineString(s) formed by sewing together the constituent line work of a MULTILINESTRING.

[Note]

Only use with MULTILINESTRING/LINESTRINGs. If you feed a polygon or geometry collection into this function, it will return an empty GEOMETRYCOLLECTION

Availability: 1.1.0

[Note]

requires GEOS >= 2.1.0

Examples

SELECT ST_AsText(ST_LineMerge(
ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
		)
);
st_astext
--------------------------------------------------------------------------------------------------
LINESTRING(-29 -27,-30 -29.7,-36 -31,-45 -33,-46 -32)
(1 row)

--If can't be merged - original MULTILINESTRING is returned
SELECT ST_AsText(ST_LineMerge(
ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45.2 -33.2,-46 -32))')
)
);
st_astext
----------------
MULTILINESTRING((-45.2 -33.2,-46 -32),(-29 -27,-30 -29.7,-36 -31,-45 -33))
			

Name

ST_CollectionExtract — Given a (multi)geometry, return a (multi)geometry consisting only of elements of the specified type.

Synopsis

geometry ST_CollectionExtract ( geometry collection , integer type ) ;

Description

Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type. Sub-geometries that are not the specified type are ignored. If there are no sub-geometries of the right type, an EMPTY geometry will be returned. Only points, lines and polygons are supported. Type numbers are 1 == POINT, 2 == LINESTRING, 3 == POLYGON.

Availability: 1.5.0

[Note]

Prior to 1.5.3 this function returned non-collection inputs untouched, no matter type. In 1.5.3 non-matching single geometries result in a NULL return. In of 2.0.0 every case of missing match results in a typed EMPTY return.

[Warning]

When specifying 3 == POLYGON a multipolygon is returned even when the edges are shared. This results in an invalid multipolygon for many cases such as applying this function on an ST_Split result.

Examples

-- Constants: 1 == POINT, 2 == LINESTRING, 3 == POLYGON
SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText('GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(POINT(0 0)))'),1));
st_astext
---------------
MULTIPOINT(0 0)
(1 row)

SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText('GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(LINESTRING(0 0, 1 1)),LINESTRING(2 2, 3 3))'),2));
st_astext
---------------
MULTILINESTRING((0 0, 1 1), (2 2, 3 3))
(1 row)
			

Name

ST_CollectionHomogenize — Given a geometry collection, return the "simplest" representation of the contents.

Synopsis

geometry ST_CollectionHomogenize ( geometry collection ) ;

Description

Given a geometry collection, returns the "simplest" representation of the contents. Singletons will be returned as singletons. Collections that are homogeneous will be returned as the appropriate multi-type.

[Warning]

When specifying 3 == POLYGON a multipolygon is returned even when the edges are shared. This results in an invalid multipolygon for many cases such as applying this function on an ST_Split result.

Availability: 2.0.0

Examples

  SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0))'));

	st_astext
	------------
	 POINT(0 0)
	(1 row)

  SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0),POINT(1 1))'));

	st_astext
	---------------------
	 MULTIPOINT(0 0,1 1)
	(1 row)

				

Name

ST_Multi — Return the geometry as a MULTI* geometry.

Synopsis

geometry ST_Multi ( geometry g1 ) ;

Description

Returns the geometry as a MULTI* geometry. If the geometry is already a MULTI*, it is returned unchanged.

Examples

SELECT ST_AsText(ST_Multi(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
			743265 2967450,743265.625 2967416,743238 2967416))')));
			st_astext
			--------------------------------------------------------------------------------------------------
			MULTIPOLYGON(((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,
			743238 2967416)))
			(1 row)
			

See Also

ST_AsText


Name

ST_Normalize — Return the geometry in its canonical form.

Synopsis

geometry ST_Normalize ( geometry geom ) ;

Description

Returns the geometry in its normalized/canonical form. May reorder vertices in polygon rings, rings in a polygon, elements in a multi-geometry complex.

Mostly only useful for testing purposes (comparing expected and obtained results).

Examples

SELECT ST_AsText(ST_Normalize(ST_GeomFromText(
  'GEOMETRYCOLLECTION(
    POINT(2 3),
    MULTILINESTRING((0 0, 1 1),(2 2, 3 3)),
    POLYGON(
      (0 10,0 0,10 0,10 10,0 10),
      (4 2,2 2,2 4,4 4,4 2),
      (6 8,8 8,8 6,6 6,6 8)
    )
  )'
)));
                                                                     st_astext
----------------------------------------------------------------------------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(POLYGON((0 0,0 10,10 10,10 0,0 0),(6 6,8 6,8 8,6 8,6 6),(2 2,4 2,4 4,2 4,2 2)),MULTILINESTRING((2 2,3 3),(0 0,1 1)),POINT(2 3))
(1 row)
			

See Also

ST_Equals ,


Name

ST_RemovePoint — Remove point from a linestring.

Synopsis

geometry ST_RemovePoint ( geometry linestring , integer offset ) ;

Description

Remove a point from a linestring, given its 0-based index. Useful for turning a closed ring into an open line string

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

Examples

--guarantee no LINESTRINGS are closed
--by removing the end point.  The below assumes the_geom is of type LINESTRING
UPDATE sometable
	SET the_geom = ST_RemovePoint(the_geom, ST_NPoints(the_geom) - 1)
	FROM sometable
	WHERE ST_IsClosed(the_geom) = true;
		

Name

ST_Reverse — Return the geometry with vertex order reversed.

Synopsis

geometry ST_Reverse ( geometry g1 ) ;

Description

Can be used on any geometry and reverses the order of the vertexes.

Enhanced: 2.4.0 support for curves was introduced.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Examples

SELECT ST_AsText(the_geom) as line, ST_AsText(ST_Reverse(the_geom)) As reverseline
FROM
(SELECT ST_MakeLine(ST_MakePoint(1,2),
		ST_MakePoint(1,10)) As the_geom) as foo;
--result
		line         |     reverseline
---------------------+----------------------
LINESTRING(1 2,1 10) | LINESTRING(1 10,1 2)

Name

ST_Rotate — Rotate a geometry rotRadians counter-clockwise about an origin.

Synopsis

geometry ST_Rotate ( geometry geomA , float rotRadians ) ;

geometry ST_Rotate ( geometry geomA , float rotRadians , float x0 , float y0 ) ;

geometry ST_Rotate ( geometry geomA , float rotRadians , geometry pointOrigin ) ;

Description

Rotates geometry rotRadians counter-clockwise about the origin. The rotation origin can be specified either as a POINT geometry, or as x and y coordinates. If the origin is not specified, the geometry is rotated about POINT(0 0).

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 additional parameters for specifying the origin of rotation were added.

Availability: 1.1.2. Name changed from Rotate to ST_Rotate in 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

--Rotate 180 degrees
SELECT ST_AsEWKT(ST_Rotate('LINESTRING (50 160, 50 50, 100 50)', pi()));
               st_asewkt
---------------------------------------
 LINESTRING(-50 -160,-50 -50,-100 -50)
(1 row)

--Rotate 30 degrees counter-clockwise at x=50, y=160
SELECT ST_AsEWKT(ST_Rotate('LINESTRING (50 160, 50 50, 100 50)', pi()/6, 50, 160));
                                 st_asewkt
---------------------------------------------------------------------------
 LINESTRING(50 160,105 64.7372055837117,148.301270189222 89.7372055837117)
(1 row)

--Rotate 60 degrees clockwise from centroid
SELECT ST_AsEWKT(ST_Rotate(geom, -pi()/3, ST_Centroid(geom)))
FROM (SELECT 'LINESTRING (50 160, 50 50, 100 50)'::geometry AS geom) AS foo;
                           st_asewkt
--------------------------------------------------------------
 LINESTRING(116.4225 130.6721,21.1597 75.6721,46.1597 32.3708)
(1 row)
		

Name

ST_RotateX — Rotate a geometry rotRadians about the X axis.

Synopsis

geometry ST_RotateX ( geometry geomA , float rotRadians ) ;

Description

Rotate a geometry geomA - rotRadians about the X axis.

[Note]

ST_RotateX(geomA, rotRadians) is short-hand for ST_Affine(geomA, 1, 0, 0, 0, cos(rotRadians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0) .

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from RotateX to ST_RotateX in 1.2.2

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

--Rotate a line 90 degrees along x-axis
SELECT ST_AsEWKT(ST_RotateX(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
		 st_asewkt
---------------------------
 LINESTRING(1 -3 2,1 -1 1)

Name

ST_RotateY — Rotate a geometry rotRadians about the Y axis.

Synopsis

geometry ST_RotateY ( geometry geomA , float rotRadians ) ;

Description

Rotate a geometry geomA - rotRadians about the y axis.

[Note]

ST_RotateY(geomA, rotRadians) is short-hand for ST_Affine(geomA, cos(rotRadians), 0, sin(rotRadians), 0, 1, 0, -sin(rotRadians), 0, cos(rotRadians), 0, 0, 0) .

Availability: 1.1.2. Name changed from RotateY to ST_RotateY in 1.2.2

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

--Rotate a line 90 degrees along y-axis
 SELECT ST_AsEWKT(ST_RotateY(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
		 st_asewkt
---------------------------
 LINESTRING(3 2 -1,1 1 -1)

Name

ST_RotateZ — Rotate a geometry rotRadians about the Z axis.

Synopsis

geometry ST_RotateZ ( geometry geomA , float rotRadians ) ;

Description

Rotate a geometry geomA - rotRadians about the Z axis.

[Note]

This is a synonym for ST_Rotate

[Note]

ST_RotateZ(geomA, rotRadians) is short-hand for SELECT ST_Affine(geomA, cos(rotRadians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0, 1, 0, 0, 0) .

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from RotateZ to ST_RotateZ in 1.2.2

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

--Rotate a line 90 degrees along z-axis
SELECT ST_AsEWKT(ST_RotateZ(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
		 st_asewkt
---------------------------
 LINESTRING(-2 1 3,-1 1 1)

 --Rotate a curved circle around z-axis
SELECT ST_AsEWKT(ST_RotateZ(the_geom, pi()/2))
FROM (SELECT ST_LineToCurve(ST_Buffer(ST_GeomFromText('POINT(234 567)'), 3)) As the_geom) As foo;

													   st_asewkt
----------------------------------------------------------------------------------------------------------------------------
 CURVEPOLYGON(CIRCULARSTRING(-567 237,-564.87867965644 236.12132034356,-564 234,-569.12132034356 231.87867965644,-567 237))


Name

ST_Scale — Scale a geometry by given factors.

Synopsis

geometry ST_Scale ( geometry geomA , float XFactor , float YFactor , float ZFactor ) ;

geometry ST_Scale ( geometry geomA , float XFactor , float YFactor ) ;

geometry ST_Scale ( geometry geom , geometry factor ) ;

Description

Scales the geometry to a new size by multiplying the ordinates with the corresponding factor parameters.

The version taking a geometry as the factor parameter allows passing a 2d, 3dm, 3dz or 4d point to set scaling factor for all supported dimensions. Missing dimensions in the factor point are equivalent to no scaling the corresponding dimension.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.2.0 support for scaling all dimension (geometry parameter) was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports M coordinates.

Examples

--Version 1: scale X, Y, Z
SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 0.75, 0.8));
			  st_asewkt
--------------------------------------
 LINESTRING(0.5 1.5 2.4,0.5 0.75 0.8)

--Version 2: Scale X Y
 SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 0.75));
			st_asewkt
----------------------------------
 LINESTRING(0.5 1.5 3,0.5 0.75 1)

--Version 3: Scale X Y Z M
 SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)'),
   ST_MakePoint(0.5, 0.75, 2, -1)));
			       st_asewkt
----------------------------------------
 LINESTRING(0.5 1.5 6 -4,0.5 0.75 2 -1)



Name

ST_Segmentize — Return a modified geometry/geography having no segment longer than the given distance.

Synopsis

geometry ST_Segmentize ( geometry geom , float max_segment_length ) ;

geography ST_Segmentize ( geography geog , float max_segment_length ) ;

Description

Returns a modified geometry having no segment longer than the given max_segment_length . Distance computation is performed in 2d only. For geometry, length units are in units of spatial reference. For geography, units are in meters.

Availability: 1.2.2

Enhanced: 2.3.0 Segmentize geography now uses equal length segments

Enhanced: 2.1.0 support for geography was introduced.

Changed: 2.1.0 As a result of the introduction of geography support: The construct SELECT ST_Segmentize('LINESTRING(1 2, 3 4)',0.5); will result in ambiguous function error. You need to have properly typed object e.g. a geometry/geography column, use ST_GeomFromText, ST_GeogFromText or SELECT ST_Segmentize('LINESTRING(1 2, 3 4)'::geometry,0.5);

[Note]

This will only increase segments. It will not lengthen segments shorter than max length

Examples

SELECT ST_AsText(ST_Segmentize(
ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
		,5)
);
st_astext
--------------------------------------------------------------------------------------------------
MULTILINESTRING((-29 -27,-30 -29.7,-34.886615700134 -30.758766735029,-36 -31,
-40.8809353009198 -32.0846522890933,-45 -33),
(-45 -33,-46 -32))
(1 row)

SELECT ST_AsText(ST_Segmentize(ST_GeomFromText('POLYGON((-29 28, -30 40, -29 28))'),10));
st_astext
-----------------------
POLYGON((-29 28,-29.8304547985374 37.9654575824488,-30 40,-29.1695452014626 30.0345424175512,-29 28))
(1 row)

			

Name

ST_SetPoint — Replace point of a linestring with a given point.

Synopsis

geometry ST_SetPoint ( geometry linestring , integer zerobasedposition , geometry point ) ;

Description

Replace point N of linestring with given point. Index is 0-based.Negative index are counted backwards, so that -1 is last point. This is especially useful in triggers when trying to maintain relationship of joints when one vertex moves.

Availability: 1.1.0

Updated 2.3.0 : negative indexing

This function supports 3d and will not drop the z-index.

Examples

--Change first point in line string from -1 3 to -1 1
SELECT ST_AsText(ST_SetPoint('LINESTRING(-1 2,-1 3)', 0, 'POINT(-1 1)'));
	   st_astext
-----------------------
 LINESTRING(-1 1,-1 3)

---Change last point in a line string (lets play with 3d linestring this time)
SELECT ST_AsEWKT(ST_SetPoint(foo.the_geom, ST_NumPoints(foo.the_geom) - 1, ST_GeomFromEWKT('POINT(-1 1 3)')))
FROM (SELECT ST_GeomFromEWKT('LINESTRING(-1 2 3,-1 3 4, 5 6 7)') As the_geom) As foo;
	   st_asewkt
-----------------------
LINESTRING(-1 2 3,-1 3 4,-1 1 3)

SELECT ST_AsText(ST_SetPoint(g, -3, p))
FROM ST_GEomFromText('LINESTRING(0 0, 1 1, 2 2, 3 3, 4 4)') AS g
	, ST_PointN(g,1) as p;
	   st_astext
-----------------------
LINESTRING(0 0,1 1,0 0,3 3,4 4)

			

Name

ST_SetSRID — Set the SRID on a geometry to a particular integer value.

Synopsis

geometry ST_SetSRID ( geometry geom , integer srid ) ;

Description

Sets the SRID on a geometry to a particular integer value. Useful in constructing bounding boxes for queries.

[Note]

This function does not transform the geometry coordinates in any way - it simply sets the meta data defining the spatial reference system the geometry is assumed to be in. Use ST_Transform if you want to transform the geometry into a new projection.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves

Examples

-- Mark a point as WGS 84 long lat --

SELECT ST_SetSRID(ST_Point(-123.365556, 48.428611),4326) As wgs84long_lat;
-- the ewkt representation (wrap with ST_AsEWKT) -
SRID=4326;POINT(-123.365556 48.428611)
			

-- Mark a point as WGS 84 long lat and then transform to web mercator (Spherical Mercator) --

SELECT ST_Transform(ST_SetSRID(ST_Point(-123.365556, 48.428611),4326),3785) As spere_merc;
-- the ewkt representation (wrap with ST_AsEWKT) -
SRID=3785;POINT(-13732990.8753491 6178458.96425423)
			

Name

ST_SnapToGrid — Snap all points of the input geometry to a regular grid.

Synopsis

geometry ST_SnapToGrid ( geometry geomA , float originX , float originY , float sizeX , float sizeY ) ;

geometry ST_SnapToGrid ( geometry geomA , float sizeX , float sizeY ) ;

geometry ST_SnapToGrid ( geometry geomA , float size ) ;

geometry ST_SnapToGrid ( geometry geomA , geometry pointOrigin , float sizeX , float sizeY , float sizeZ , float sizeM ) ;

Description

Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive points falling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type. Collapsed geometries in a collection are stripped from it. Useful for reducing precision.

Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, must be a point) and cell sizes. Specify 0 as size for any dimension you don't want to snap to a grid.

[Note]

The returned geometry might lose its simplicity (see ST_IsSimple ).

[Note]

Before release 1.1.0 this function always returned a 2d geometry. Starting at 1.1.0 the returned geometry will have same dimensionality as the input one with higher dimension values untouched. Use the version taking a second geometry argument to define all grid dimensions.

Availability: 1.0.0RC1

Availability: 1.1.0 - Z and M support

This function supports 3d and will not drop the z-index.

Examples

--Snap your geometries to a precision grid of 10^-3
UPDATE mytable
   SET the_geom = ST_SnapToGrid(the_geom, 0.001);

SELECT ST_AsText(ST_SnapToGrid(
			ST_GeomFromText('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'),
			0.001)
		);
			  st_astext
-------------------------------------
 LINESTRING(1.112 2.123,4.111 3.237)
 --Snap a 4d geometry
SELECT ST_AsEWKT(ST_SnapToGrid(
	ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 2.3456 1.11111,
		4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)'),
 ST_GeomFromEWKT('POINT(1.12 2.22 3.2 4.4444)'),
 0.1, 0.1, 0.1, 0.01) );
								  st_asewkt
------------------------------------------------------------------------------
 LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)


--With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m and z the same
SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 3 2.3456,
		4.111111 3.2374897 3.1234 1.1111)'),
	   0.01)      );
						st_asewkt
---------------------------------------------------------
 LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)

		

Name

ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.

Synopsis

geometry ST_Snap ( geometry input , geometry reference , float tolerance ) ;

Description

Snaps the vertices and segments of a geometry another Geometry's vertices. A snap distance tolerance is used to control where snapping is performed. The result geometry is the input geometry with the vertices snapped. If no snapping occurs then the input geometry is returned unchanged.

Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (which cause problems during noding and intersection calculation).

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided using heuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.

[Note]

The returned geometry might lose its simplicity (see ST_IsSimple ) and validity (see ST_IsValid ).

Availability: 2.0.0 requires GEOS >= 3.3.0.

Examples

A multipolygon shown with a linestring (before any snapping)

A multipolygon snapped to linestring to tolerance: 1.01 of distance. The new multipolygon is shown with reference linestring

SELECT ST_AsText(ST_Snap(poly,line, ST_Distance(poly,line)*1.01)) AS polysnapped
FROM (SELECT
   ST_GeomFromText('MULTIPOLYGON(
     ((26 125, 26 200, 126 200, 126 125, 26 125 ),
      ( 51 150, 101 150, 76 175, 51 150 )),
      (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line

	) As foo;

                             polysnapped
---------------------------------------------------------------------
 MULTIPOLYGON(((26 125,26 200,126 200,126 125,101 100,26 125),
 (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
				

A multipolygon snapped to linestring to tolerance: 1.25 of distance. The new multipolygon is shown with reference linestring

SELECT ST_AsText(
    ST_Snap(poly,line, ST_Distance(poly,line)*1.25)
  ) AS polysnapped
FROM (SELECT
  ST_GeomFromText('MULTIPOLYGON(
    (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
      ( 51 150, 101 150, 76 175, 51 150 )),
      (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line

	) As foo;

                             polysnapped
---------------------------------------------------------------------
MULTIPOLYGON(((5 107,26 200,126 200,126 125,101 100,54 84,5 107),
(51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
				

The linestring snapped to the original multipolygon at tolerance 1.01 of distance. The new linestring is shown with reference multipolygon

SELECT ST_AsText(
   ST_Snap(line, poly, ST_Distance(poly,line)*1.01)
  ) AS linesnapped
FROM (SELECT
  ST_GeomFromText('MULTIPOLYGON(
     ((26 125, 26 200, 126 200, 126 125, 26 125),
      (51 150, 101 150, 76 175, 51 150 )),
      ((151 100, 151 200, 176 175, 151 100)))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
	) As foo;

              linesnapped
----------------------------------------
 LINESTRING(5 107,26 125,54 84,101 100)
				

The linestring snapped to the original multipolygon at tolerance 1.25 of distance. The new linestring is shown with reference multipolygon

SELECT ST_AsText(
 ST_Snap(line, poly, ST_Distance(poly,line)*1.25)
  ) AS linesnapped
FROM (SELECT
  ST_GeomFromText('MULTIPOLYGON(
     (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
      (51 150, 101 150, 76 175, 51 150 )),
      ((151 100, 151 200, 176 175, 151 100 )))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
	) As foo;
              linesnapped
---------------------------------------
LINESTRING(26 125,54 84,101 100)
				

Name

ST_Transform — Return a new geometry with its coordinates transformed to a different spatial reference.

Synopsis

geometry ST_Transform ( geometry g1 , integer srid ) ;

geometry ST_Transform ( geometry geom , text to_proj ) ;

geometry ST_Transform ( geometry geom , text from_proj , text to_proj ) ;

geometry ST_Transform ( geometry geom , text from_proj , integer to_srid ) ;

Description

Returns a new geometry with its coordinates transformed to a different spatial reference system. The destination spatial reference to_srid may be identified by a valid SRID integer parameter (i.e. it must exist in the spatial_ref_sys table). Alternatively, a spatial reference defined as a PROJ.4 string can be used for to_proj and/or from_proj , however these methods are not optimized. If the destination spatial reference system is expressed with a PROJ.4 string instead of an SRID, the SRID of the output geometry will be set to zero. With the exception of functions with from_proj , input geometries must have a defined SRID.

ST_Transform is often confused with ST_SetSRID(). ST_Transform actually changes the coordinates of a geometry from one spatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the geometry.

[Note]

Requires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiled in.

[Note]

If using more than one transformation, it is useful to have a functional index on the commonly used transformations to take advantage of index usage.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Enhanced: 2.3.0 support for direct PROJ.4 text was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.6

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Examples

Change Massachusetts state plane US feet geometry to WGS 84 long lat

SELECT ST_AsText(ST_Transform(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
	743265 2967450,743265.625 2967416,743238 2967416))',2249),4326)) As wgs_geom;

 wgs_geom
---------------------------
 POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
-71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.177684
8522251 42.3902896512902));
(1 row)

--3D Circular String example
SELECT ST_AsEWKT(ST_Transform(ST_GeomFromEWKT('SRID=2249;CIRCULARSTRING(743238 2967416 1,743238 2967450 2,743265 2967450 3,743265.625 2967416 3,743238 2967416 4)'),4326));

				 st_asewkt
--------------------------------------------------------------------------------------
 SRID=4326;CIRCULARSTRING(-71.1776848522251 42.3902896512902 1,-71.1776843766326 42.3903829478009 2,
 -71.1775844305465 42.3903826677917 3,
 -71.1775825927231 42.3902893647987 3,-71.1776848522251 42.3902896512902 4)

		

Example of creating a partial functional index. For tables where you are not sure all the geometries will be filled in, its best to use a partial index that leaves out null geometries which will both conserve space and make your index smaller and more efficient.

CREATE INDEX idx_the_geom_26986_parcels
  ON parcels
  USING gist
  (ST_Transform(the_geom, 26986))
  WHERE the_geom IS NOT NULL;
		

Examples of using PROJ.4 text to transform with custom spatial references.

-- Find intersection of two polygons near the North pole, using a custom Gnomic projection
-- See http://boundlessgeo.com/2012/02/flattening-the-peel/
 WITH data AS (
   SELECT
     ST_GeomFromText('POLYGON((170 50,170 72,-130 72,-130 50,170 50))', 4326) AS p1,
     ST_GeomFromText('POLYGON((-170 68,-170 90,-141 90,-141 68,-170 68))', 4326) AS p2,
     '+proj=gnom +ellps=WGS84 +lat_0=70 +lon_0=-160 +no_defs'::text AS gnom
 )
 SELECT ST_AsText(
   ST_Transform(
     ST_Intersection(ST_Transform(p1, gnom), ST_Transform(p2, gnom)),
   gnom, 4326))
 FROM data;
                                          st_astext
 --------------------------------------------------------------------------------
  POLYGON((-170 74.053793645338,-141 73.4268621378904,-141 68,-170 68,-170 74.053793645338))
		

Configuring transformation behaviour

Sometimes coordinate transformation involving a grid-shift can fail, for example if PROJ.4 has not been built with grid-shift files or the coordinate does not lie within the range for which the grid shift is defined. By default, PostGIS will throw an error if a grid shift file is not present, but this behaviour can be configured on a per-SRID basis either by testing different to_proj values of PROJ.4 text, or altering the proj4text value within the spatial_ref_sys table.

For example, the proj4text parameter +datum=NAD87 is a shorthand form for the following +nadgrids parameter:

+nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat

The @ prefix means no error is reported if the files are not present, but if the end of the list is reached with no file having been appropriate (ie. found and overlapping) then an error is issued.

If, conversely, you wanted to ensure that at least the standard files were present, but that if all files were scanned without a hit a null transformation is applied you could use:

+nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null

The null grid shift file is a valid grid shift file covering the whole world and applying no shift. So for a complete example, if you wanted to alter PostGIS so that transformations to SRID 4267 that didn't lie within the correct range did not throw an ERROR, you would use the following:

UPDATE spatial_ref_sys SET proj4text = '+proj=longlat +ellps=clrk66 +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null +no_defs' WHERE srid = 4267;

Name

ST_Translate — Translate a geometry by given offsets.

Synopsis

geometry ST_Translate ( geometry g1 , float deltax , float deltay ) ;

geometry ST_Translate ( geometry g1 , float deltax , float deltay , float deltaz ) ;

Description

Returns a new geometry whose coordinates are translated delta x,delta y,delta z units. Units are based on the units defined in spatial reference (SRID) for this geometry.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

Move a point 1 degree longitude

	SELECT ST_AsText(ST_Translate(ST_GeomFromText('POINT(-71.01 42.37)',4326),1,0)) As wgs_transgeomtxt;

	wgs_transgeomtxt
	---------------------
	POINT(-70.01 42.37)
		

Move a linestring 1 degree longitude and 1/2 degree latitude

SELECT ST_AsText(ST_Translate(ST_GeomFromText('LINESTRING(-71.01 42.37,-71.11 42.38)',4326),1,0.5)) As wgs_transgeomtxt;
		   wgs_transgeomtxt
	---------------------------------------
	LINESTRING(-70.01 42.87,-70.11 42.88)
		

Move a 3d point

SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
	st_asewkt
	---------
	POINT(5 12 3)
		

Move a curve and a point

SELECT ST_AsText(ST_Translate(ST_Collect('CURVEPOLYGON(CIRCULARSTRING(4 3,3.12 0.878,1 0,-1.121 5.1213,6 7, 8 9,4 3))','POINT(1 3)'),1,2));
														 st_astext
------------------------------------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(CURVEPOLYGON(CIRCULARSTRING(5 5,4.12 2.878,2 2,-0.121 7.1213,7 9,9 11,5 5)),POINT(2 5))

Name

ST_TransScale — Translate a geometry by given factors and offsets.

Synopsis

geometry ST_TransScale ( geometry geomA , float deltaX , float deltaY , float XFactor , float YFactor ) ;

Description

Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.

[Note]

ST_TransScale(geomA, deltaX, deltaY, XFactor, YFactor) is short-hand for ST_Affine(geomA, XFactor, 0, 0, 0, YFactor, 0, 0, 0, 1, deltaX*XFactor, deltaY*YFactor, 0) .

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_AsEWKT(ST_TransScale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 1, 1, 2));
		  st_asewkt
-----------------------------
 LINESTRING(1.5 6 3,1.5 4 1)


--Buffer a point to get an approximation of a circle, convert to curve and then translate 1,2 and scale it 3,4
  SELECT ST_AsText(ST_Transscale(ST_LineToCurve(ST_Buffer('POINT(234 567)', 3)),1,2,3,4));
														  st_astext
------------------------------------------------------------------------------------------------------------------------------
 CURVEPOLYGON(CIRCULARSTRING(714 2276,711.363961030679 2267.51471862576,705 2264,698.636038969321 2284.48528137424,714 2276))

8.7. Geometry Outputs

ST_AsBinary — Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
ST_AsEncodedPolyline — Returns an Encoded Polyline from a LineString geometry.
ST_AsEWKB — Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.
ST_AsEWKT — Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
ST_AsGeoJSON — Return the geometry as a GeoJSON element.
ST_AsGML — Return the geometry as a GML version 2 or 3 element.
ST_AsHEXEWKB — Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.
ST_AsKML — Return the geometry as a KML element. Several variants. Default version=2, default precision=15
ST_AsLatLonText — Return the Degrees, Minutes, Seconds representation of the given point.
ST_AsSVG — Returns a Geometry in SVG path data given a geometry or geography object.
ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
ST_AsTWKB — Returns the geometry as TWKB, aka "Tiny Well-Known Binary"
ST_AsX3D — Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
ST_GeoHash — Return a GeoHash representation of the geometry.
ST_AsGeobuf — Return a Geobuf representation of a set of rows.
ST_AsMVTGeom Transform a geometry into the coordinate space of a Mapbox Vector Tile.
ST_AsMVT Return a Mapbox Vector Tile representation of a set of rows.

Name

ST_AsBinary — Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.

Synopsis

bytea ST_AsBinary ( geometry g1 ) ;

bytea ST_AsBinary ( geometry g1 , text NDR_or_XDR ) ;

bytea ST_AsBinary ( geography g1 ) ;

bytea ST_AsBinary ( geography g1 , text NDR_or_XDR ) ;

Description

Returns the Well-Known Binary representation of the geometry. There are 2 variants of the function. The first variant takes no endian encoding parameter and defaults to server machine endian. The second variant takes a second argument denoting the encoding - using little-endian ('NDR') or big-endian ('XDR') encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

[Note]

The WKB spec does not include the SRID. To get the WKB with SRID format use ST_AsEWKB

[Note]

ST_AsBinary is the reverse of ST_GeomFromWKB for geometry. Use ST_GeomFromWKB to convert to a postgis geometry from ST_AsBinary representation.

[Note]

The default behavior in PostgreSQL 9.0 has been changed to output bytea in hex encoding. ST_AsBinary is the reverse of ST_GeomFromWKB for geometry. If your GUI tools require the old behavior, then SET bytea_output='escape' in your database.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 support for higher coordinate dimensions was introduced.

Enhanced: 2.0.0 support for specifying endian with geography was introduced.

Availability: 1.5.0 geography support was introduced.

Changed: 2.0.0 Inputs to this function can not be unknown -- must be geometry. Constructs such as ST_AsBinary('POINT(1 2)') are no longer valid and you will get an n st_asbinary(unknown) is not unique error . Code like that needs to be changed to ST_AsBinary('POINT(1 2)'::geometry); . If that is not possible, then install legacy.sql .

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.37

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

		   st_asbinary
--------------------------------
\001\003\000\000\000\001\000\000\000\005
\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000
\000\000\000\360?\000\000\000\000\000\000
\360?\000\000\000\000\000\000\360?\000\000
\000\000\000\000\360?\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000
(1 row)
SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
		   st_asbinary
--------------------------------
\000\000\000\000\003\000\000\000\001\000\000\000\005\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000
\000\000\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
(1 row)

Name

ST_AsEncodedPolyline — Returns an Encoded Polyline from a LineString geometry.

Synopsis

text ST_AsEncodedPolyline ( geometry geom , integer precision=5 ) ;

Description

Returns the geometry as an Encoded Polyline. This is a format very useful if you are using google maps

Availability: 2.2.0

Examples

Basic

	SELECT ST_AsEncodedPolyline(GeomFromEWKT('SRID=4326;LINESTRING(-120.2 38.5,-120.95 40.7,-126.453 43.252)'));
	--result--
	|_p~iF~ps|U_ulLnnqC_mqNvxq`@
	

Use in conjunction with geography linestring and geography segmentize, and put on google maps

-- the SQL for Boston to San Francisco, segments every 100 KM
	SELECT ST_AsEncodedPolyline(
		ST_Segmentize(
			ST_GeogFromText('LINESTRING(-71.0519 42.4935,-122.4483 37.64)'),
				100000)::geometry) As encodedFlightPath;

javascript will look something like this where $ variable you replace with query result

<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?libraries=geometry"></script>
<script type="text/javascript">
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Name

ST_AsEWKB — Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.

Synopsis

bytea ST_AsEWKB ( geometry g1 ) ;

bytea ST_AsEWKB ( geometry g1 , text NDR_or_XDR ) ;

Description

Returns the Well-Known Binary representation of the geometry with SRID metadata. There are 2 variants of the function. The first variant takes no endian encoding parameter and defaults to little endian. The second variant takes a second argument denoting the encoding - using little-endian ('NDR') or big-endian ('XDR') encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

[Note]

The WKB spec does not include the SRID. To get the OGC WKB format use ST_AsBinary