ST_ZMin

Syntax

float ST_ZMin(box3d aGeomorBox2DorBox3D)

Parameters

Usage notes

• The parameter type is defined as box3d, but auto-casting lets the function accept Box2D and geometry objects as well. String representations of Box2D and geometry objects are not supported by auto-casting — pass them with an explicit cast instead.

• ST_ZMin preserves z-coordinates and does not drop them from 3D objects.

• ST_ZMin supports circular strings and curves.

Examples

Get the minimum z-coordinate of a LineString

Pass a geometry object using the ::geometry cast:

SELECT ST_ZMin('LINESTRING(0 1 2,3 4 5)'::geometry);
 st_zmin
---------
       2
(1 row)

Get the minimum z-coordinate of a BOX3D

Pass a BOX3D literal directly:

SELECT ST_ZMin('BOX3D(1 2 3,4 5 6)'::box3d);
 st_zmin
---------
       3
(1 row)

Get the minimum z-coordinate of a CircularString

SELECT ST_ZMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
 st_zmin
---------
       1
(1 row)

String literals without a cast fail

Passing a plain string without an explicit cast raises a parser error because auto-casting does not apply to string representations:

-- This does NOT work
SELECT ST_ZMin('LINESTRING(0 1 2,3 4 5)');
-- ERROR:  BOX3D parser - doesn't start with BOX3D(

Use ST_GeomFromEWKT or an explicit ::geometry cast to avoid this error:

SELECT ST_ZMin(ST_GeomFromEWKT('LINESTRING(0 1 2,3 4 5)'));
 st_zmin
---------
       2
(1 row)

Related functions

• [ST_ZMax](): Returns the maximum z-coordinate of a bounding box.

• [ST_XMin](): Returns the minimum x-coordinate of a bounding box.

• [ST_XMax](): Returns the maximum x-coordinate of a bounding box.

• [ST_YMin](): Returns the minimum y-coordinate of a bounding box.

• [ST_YMax](): Returns the maximum y-coordinate of a bounding box.