ST_Is3d function

The ST_Is3d function takes a geometry as an input parameter and returns 1 if the specified geometry has Z coordinates. Otherwise, 0 (zero) is returned.

If the specified geometry is null or is empty, then null is returned.

Syntax

Parameter

geometry: A value of type ST_Geometry or one of its subtypes that represents the geometry that is to be tested for the existence of Z coordinates.

Return type

INTEGER

Example

In this example, several geometries are created with and without Z coordinates and M coordinates (measures). ST_Is3d is then used to determine which of them contain Z coordinates.


CREATE TABLE sample_geoms (id INTEGER, geometry ST_Geometry)

INSERT INTO sample_geoms VALUES
       (1, ST_Geometry('point EMPTY',0))

INSERT INTO sample_geoms VALUES
       (2, ST_Geometry('polygon((40 120, 90 120, 90 150, 40 150, 40 120))' ,0))

INSERT INTO sample_geoms VALUES
       (3, ST_Geometry('multipoint m (10 10 5, 50 10 6, 10 30 8)' ,0))

INSERT INTO sample_geoms VALUES
       (4, ST_Geometry('linestring z (10 10 166, 20 10 168)',0))

INSERT INTO sample_geoms VALUES
       (5, ST_Geometry('point zm (10 10 16 30)' ,0))


SELECT id, ST_Is3d(geometry)  Is_3D
FROM sample_geoms

Results:


ID          IS_3D
----------- -----------
          1           0
          2           0
          3           0
          4           1
          5           1