The ST_Transform method transforms geometry-expression from its spatial reference system
to the specified spatial reference system using the transform definition of
both spatial reference systems. The transformation is performed using the PROJ.4 library.
ST_Transform is required to move between different coordinate systems.
For example, use can use ST_Transform to transform a geometry
which uses latitude and longitude to a geometry with the
SRID 3310 "NAD83 / California Albers". The "NAD83 / California Albers"
spatial reference system is a planar projection for California data
which uses the Albers projection algorithm and metres for its linear
unit of measure.
Transformations from a lat/long system to a Cartesian system can be problematic for polar points. If the database server is
unable to transform a point close to the North or South pole, the latitude value of the point is shifted a small distance
(slightly more than 1e-10 radians) away from the pole, and along the same longitude, so that the transformation can succeed.
If you are transforming a geometry between two spatial reference systems
that have the same coordinate system, you can use the ST_SRID method instead of
The following example returns the result Point (184755.86861 -444218.175691).
It transforms a point in Los Angeles which is specified in
longitude and latitude to the projected planar SRID 3310
("NAD83 / California Albers").
This example assumes that the 'st_geometry_predefined_srs' feature has
been installed by the sa_install_feature system procedure.
SELECT NEW ST_Point( -118, 34, 4326 ).ST_Transform( 3310 )