This topic describes the ST_NDims function. This function returns the coordinate dimension of the input geometry object.

Syntax

integer  ST_NDims(geometry  g1);

Parameters

Parameter Description
g1 The geometry object that you want to specify.

Description

  • This function returns different coordinate dimensions when you specify different types of geometry objects.
    • If you specify a 2D object, this function returns the coordinate dimension in the (X,Y) format.
    • If you specify a 3D object, this function returns the coordinate dimension in the (X,Y,Z) or (X,Y,M) format.
    • If you specify a 4D object, this function returns the coordinate dimension in the (X,Y,Z,M) format.
  • This function supports 3D objects and does not delete z coordinates.

Examples

  • Results returned by specifying a 2D object:
    SELECT ST_NDims('POINT(0 1)'::geometry);
 st_ndims
----------
        2
(1 row)
  • Results returned by specifying a 3DM object and a 3DZ object:
    SELECT ST_NDims('POINT(0 1 2)'::geometry) as _3DZ,ST_NDims('POINTM(0 1 2)'::geometry) as _3DM;
 _3dz | _3dm
------+------
    3 |    3
(1 row)
  • Results returned by specifying a 4D object:
    SELECT ST_NDims('POINT(0 1 2 3)'::geometry);
 st_ndims
----------
        4
(1 row)