ST_IsClosed

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

	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