What you say is true - people should use globally consistent means of naming their coordinate systems, but I end up with a lot of data that has little or no coordinate information, and often one ends up having to make an educated guess, for example that the data is projected tmerc lon0=29. And you know little more than that. By the time this data reaches me, I have no choice but to make up an arbitrary coordinate system for it and get it into a PostGIS DB.
Ideally, I would like to go back to the original source, educate the people about coordinate systems, and get them to manage this stuff properly, but that's just not feasible. As far as I understand, a SRID in a PostGIS DB is not intended to be globally unique. I know the standard PostGIS spatial_ref_sys table is populated such that the SRID and the EPSG codes are identical, but this is not a requirement. In fact, one could argue that they should intentionally be different, to prevent people mistaking one for the other. Anyway, the status quo is OK for me. Just wanted to voice the issue. Ben H -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ben Madin Sent: Monday, January 11, 2010 3:47 AM To: PostGIS Users Discussion Subject: Re: [postgis-users] Should spatial_ref_sys.srid not be auto increment? G'day Ben, On 11/01/2010, at 4:26 , Ben Harper wrote: > Wouldn't it be the right thing to have spatial_ref_sys.srid be an auto > increment field? I would guess it should be unique (and possibly even a primary key?), but I don't think auto-increment makes sense - better to have a system where people could provide new (or at least useful) projection information into a standard repository, and then they could be assigned a standard number. You might want to look at this : http://www.spatialreference.org/ and if you want to contribute to epsg lists I think you go here: http://www.epsg.org/Geodetic.html cheers Ben _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
