ST_NDims

ST_NDims returns the coordinate dimension of a geometry. ST_NDims doesn't consider the topological dimension of a geometry. Instead, it returns a constant value depending on the dimension of the geometry.

Syntax

ST_NDims(geom)

Arguments

geom

A value of data type GEOMETRY or an expression that evaluates to a GEOMETRY type.

Return type

INTEGER representing the inherent dimension of geom.

If geom is null, then null is returned.

The values returned are as follows.

Returned value	Dimension of input geometry
2	2D
3	3DZ or 3DM
4	4D

Examples

The following SQL returns the number of dimensions of a 2D linestring.

SELECT ST_NDims(ST_GeomFromText('LINESTRING(0 0,1 1,2 2,0 0)'));

st_ndims
-------------
 2               

The following SQL returns the number of dimensions of a 3DZ linestring.

SELECT ST_NDims(ST_GeomFromText('LINESTRING Z(0 0 3,1 1 3,2 2 3,0 0 3)'));

st_ndims
-------------
 3               

The following SQL returns the number of dimensions of a 3DM linestring.

SELECT ST_NDims(ST_GeomFromText('LINESTRING M(0 0 4,1 1 4,2 2 4,0 0 4)'));

st_ndims
-------------
 3               

The following SQL returns the number of dimensions of a 4D linestring.

SELECT ST_NDims(ST_GeomFromText('LINESTRING ZM(0 0 3 4,1 1 3 4,2 2 3 4,0 0 3 4)'));

st_ndims
-------------
 4