[postgis-users] SRID and EPSG

António Pestana afsm.pestana at gmail.com
Mon May 26 16:24:20 PDT 2008

As a teacher of Surveying and GIS I give my vote to Andy's suggestion.
Nevertheless I must say that I suspect that the misunderstanding of geodesic
and cartographic reference systems concepts is one of the most important
causes of error when working with GIS. For the average user I think that it
would be most interesting to pick and use a reference system from an
up-to-date "standard", like EPSG last version, so the automatic conversion
process Markus suggested is a very appealing idea.

Regards to all


2008/5/26 Andy Anderson <aanderson at amherst.edu>:

>  António Pestana <afsm.pestana at gmail.com> wrote:
>> What about http://www.epsg.org/databases/Discv6_15sql-PosgreSql.html ? Is
>>> it
>>> of any use? I'm really new to PostgreSQL and PostGIS, so may be this is a
>>> really dumb question...
> On May 26, 2008, at 3:04 PM, Markus Schaber wrote:
>> The EPSG database contains a rather complex relational structure of
>> different tables describing reference systems, projections etc.
>> This relationals tructure was originally delivered as access file, but
>> additional delivery formats (like PostgreSQL SQL dump) have been added.
>> The PostGIS spatial_ref_sys table itsself contains a "flattened" view
>> of some aspects of that relational model.
>> So the EPSG database cannot be loaded as spatial_ref_sys table, but
>> maybe an automatic conversion process could be developed.
> Might it be useful to implement that relational table in PostGIS, along
> with functions that combine them to build a spatial reference? This might
> make it more usable in situations where you want to build your own (give me
> the WGS 84 datum, a Lambert conformal conic with such-and-such standard
> parallels, and a coordinate origin at this point). Or is that just too
> uncommon and complicated for most users?
> The current SRID table would still exist but be built at install time, of
> course.
> -- Andy
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