The ST_Transform function takes a geometry
and a spatial reference system identifier as input parameters and
transforms the geometry to be represented in the given spatial reference
system. Projections and conversions between different coordinate systems
are performed and the coordinates of the geometries are adjusted accordingly.

The
geometry can be converted to the specified spatial reference system only if the region covered by
the specified spatial reference system covers the location of the geometry. If either the
geometry's current spatial reference system or the specified spatial reference system is based on a
projected coordinate system, a reverse projection is performed to determine the geographic
coordinate system that underlies the projected one.

If the given geometry is null, then null will be returned.

This
function can also be called as a method.

Syntax

Parameters

geometry

A value of type ST_Geometry or one of its subtypes that represents
the geometry that is transformed to the spatial reference system identified
by srs_id.

srs_id

A value of type INTEGER that identifies the spatial reference
system for the resulting geometry.

If the transformation to the
specified spatial reference system cannot be performed because the
current spatial reference system of geometry is not compatible
with the spatial reference system identified by srs_id, then
an exception condition is raised (SQLSTATE 38SUC).

If srs_id does
not identify a spatial reference system listed in the catalog view
DB2GSE.ST_SPATIAL_REFERENCE_SYSTEMS, then an exception condition is
raised (SQLSTATE 38SU1).

Return type

db2gse.ST_Geometry

Examples

Example 1

The following example illustrates the use of ST_Transform to
convert a geometry from one spatial reference system to another.

First,
the state plane spatial reference system with an ID of 3 is created
using a call to db2se.

The SAMPLE_POINTS_SP table in state plane coordinates using that
spatial reference system.

The SAMPLE_POINTS_LL table using coordinates specified in latitude
and longitude.

SET CURRENT FUNCTION PATH = CURRENT FUNCTION PATH, db2gse
CREATE TABLE sample_points_sp (id INTEGER, geometry ST_Point)
CREATE TABLE sample_points_ll (id INTEGER, geometry ST_Point)
INSERT INTO sample_points_sp
VALUES (12457, ST_Point('point ( 567176.0 1166411.0)', 3) )
INSERT INTO sample_points_sp
VALUES (12477, ST_Point('point ( 637948.0 1177640.0)', 3) )
INSERT INTO sample_points_ll
VALUES (12457, ST_Point('point ( -74.22371600 42.03498700)', 1) )
INSERT INTO sample_points_ll
VALUES (12477, ST_Point('point ( -73.96293200 42.06487900)', 1) )

Then the ST_Transform function is used to convert the
geometries.

Example 2

This example converts points that are in latitude and longitude
coordinates to state plane coordinates.

SELECT id, CAST( ST_AsText( ST_Transform( geometry, 3) )
AS VARCHAR(100) ) STATE_PLANE
FROM sample_points_ll

Results:

ID STATE_PLANE
----------- -----------------------------------------
12457 POINT ( 567176.00000000 1166411.00000000)
12477 POINT ( 637948.00000000 1177640.00000000)

Example 3

This example converts points that are in state plane coordinates
to latitude and longitude coordinates.

SELECT id, CAST( ST_AsText( ST_Transform( geometry, 1) )
AS VARCHAR(100) ) LAT_LONG
FROM sample_points_sp

Results:

ID LAT_LONG
----------- ----------------------------------
12457 POINT ( -74.22371500 42.03498800)
12477 POINT ( -73.96293100 42.06488000)