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.fawc...@gmail.com> wrote: > Maybe there is a need for another line on the spatialreference.org > page for 'PostGIS SRID' ? _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users