ST_ReducePrecision
Name
ST_ReducePrecision — Returns a valid geometry with points rounded to a grid tolerance.
Synopsis
geometry
ST_ReducePrecision
(
geometry
g
, float8
gridsize
)
;
Description
Returns a valid geometry with all points rounded to the provided grid tolerance, and features below the tolerance removed.
Unlike ST_SnapToGrid the returned geometry will be valid, with no ring self-intersections or collapsed components.
Precision reduction can be used to:
-
match coordinate precision to the data accuracy
-
reduce the number of coordinates needed to represent a geometry
-
ensure valid geometry output to formats which use lower precision (e.g. text formats such as WKT, GeoJSON or KML when the number of output decimal places is limited).
-
export valid geometry to systems which use lower or limited precision (e.g. SDE, Oracle tolerance value)
Availability: 3.1.0 - requires GEOS >= 3.9.0.
Examples
SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 0.1));
st_astext
-----------------
POINT(1.4 19.3)
SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 1.0));
st_astext
-------------
POINT(1 19)
SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 10));
st_astext
-------------
POINT(0 20)
Precision reduction can reduce number of vertices
SELECT ST_AsText(ST_ReducePrecision('LINESTRING (10 10, 19.6 30.1, 20 30, 20.3 30, 40 40)', 1));
st_astext
-------------
LINESTRING (10 10, 20 30, 40 40)
Precision reduction splits polygons if needed to ensure validity
SELECT ST_AsText(ST_ReducePrecision('POLYGON ((10 10, 60 60.1, 70 30, 40 40, 50 10, 10 10))', 10));
st_astext
-------------
MULTIPOLYGON (((60 60, 70 30, 40 40, 60 60)), ((40 40, 50 10, 10 10, 40 40)))