[postgis-users] srid for epsg 26915

[Paul Ramsey]

There's no such thing as a PostGIS SRID, the SRID only has true
meaning local to a database instance. Now, because we happen to
install a spatial_ref_sys.sql file which not only has SRID values but
makes them identical to the EPSG numbers, there is an assumption that
the SRID == EPSG number, but that's not required at all. We could
equally have numbered them starting from 1. The auth_name and
auth_srid columns give the "true" external numbers, but the internal
srid column is only really valid inside the database. That's why a
program reading from PostGIS, to work properly, takes the SRID value
from geometry_columns, and looks up either the auth_srid, or the
srtext, and uses that definition information to apply an SRS to
geometry.

Best,

Paul

On Wed, Sep 22, 2010 at 10:36 AM, David Fawcett <david.fawcett at gmail.com> wrote:

> Maybe there is a need for another line on the spatialreference.org
> page for 'PostGIS SRID' ?