[postgis-users] Re: SRS WKT >>> srid?

Patrick pvanlaake at users.sourceforge.net
Wed Oct 19 01:36:24 PDT 2005

On 19-Oct-2005, Paul Ramsey <pramsey at refractions.net> ever so gracefully

> Generally, with some simple string comparisons and your eyes.

> No, it's not very efficient, but it is the standard, so it's not
> going anywhere.  If you need a nice normalized source of CRS
> information, the EPSG database from which our spatial_ref_sys
> contents are derived is the place to go.  Just google EPSG.


I know EPSG and I know it's normalized and it doesn't make any sense sending
me or anybody else there because everybody here wants to use PostGIS. And
string comparisons may be simple, but they are not efficient on about 4MB of
strings. I'll skip the thingy on my eyes, if you don't mind.

Insofar as standards go, OGC is an interoperability standard and it does not
prescribe any particular underlying format. It would be very valid to have
all the CRS information in a number of base tables and then a single view
that implements the OGC spatial_ref_sys table and which draws its
information from the base tables, assembling it into WKT using some
function. That would allow savvy programmers to efficiently query the CRS
components while still providing for the discovery and cataloguing services
that OGC mandates.

It would take quite some work to implement such an arrangement, but it would
most definitely not break any existing application code, as spatial_ref_sys
would not be expressed differently.

Just a thought,

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