ST_Dimension
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Name

ST_Dimension — Returns the topological dimension of a geometry.

Synopsis

integer ST_Dimension(geometry g);

Description

Return the topological 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 (e.g. for an empty GEOMETRYCOLLECTION) 0 is returned.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.2

[Note]

A TIN, including a closed TIN surface, is a surface geometry and has dimension 2. Use CG_MakeSolid to make the solid representation explicit; the resulting 3D solid has dimension 3. Solid geometry semantics, such as volume, are handled separately by the SQL/MM 3D solid functions (SQL-MM IEC 13249-3: 9.1).

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))');
1
SELECT ST_Dimension('TIN Z (((0 0 0,0 0 1,0 1 0,0 0 0)),((0 0 0,0 1 0,1 0 0,0 0 0)),((0 0 0,1 0 0,0 0 1,0 0 0)),((1 0 0,0 1 0,0 0 1,1 0 0)))');
2