[postgis-users] beginner questions re. SRID

Rick Schumeyer rschumeyer at ieee.org
Fri Oct 21 06:37:25 PDT 2005

I'm a postgis beginner and I hope the list can bear with me as I ask some
newbie questions.


My current questions are all about the SRID.


Is there a more human-readable table that contains the SRIDs and


Are the SRIDs always the same?  For example, SRID 2959 on my system is UTM
zone 18 with the GRS80 ellipse.  Is this always SRID 2959 for everybody?


The documentation includes this example:


CREATE TABLE parks ( PARK_ID int4, PARK_NAME varchar(128), PARK_DATE date,
PARK_TYPE varchar(2) );
SELECT AddGeometryColumn('parks', 'park_geom', 128, 'MULTIPOLYGON', 2 );
This column has an SRID of 128?  Does this mean that only objects with
SRID=128 can be inserted in the column?  I thought you included an SRID when
you INSERT an object?
How does postgis use the SRID internally?  Can it properly compare an object
with one SRID with an object with a different SRID?
Finally, if I have missed some documentation that explains this, please
point me in that direction!


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