[postgis-users] Newbie questions: SRIDs, function return values

Paul Ramsey pramsey at cleverelephant.ca
Thu May 15 07:57:25 PDT 2008

The danger of this approach is that it falls apart as people start
pushing the limits...

select blah from a, b where st_dwithin(st_utm(a.geom),st_utm(b.goem),100)

It's a pandora's box... as are all things geodetic


On Thu, May 15, 2008 at 7:45 AM, Markus Schaber <schabi at logix-tt.com> wrote:
> Hi, Paul,
> "Paul Ramsey" <pramsey at cleverelephant.ca> wrote:
>> There's no universal answer to this, but I have long thought that a
>> simple answer suitable for may people would be a ST_UTM(geom) wrapper
>> on transform that picks the appropriate UTM zone for a given geometry.
>> It would work perfectly well for any collection of small objects. It
>> would fall apart for larger things like states and countries that are
>> of similar size to a UTM zone.
> The function could simply use the centroid of the bounding box, that
> shoul be fast enough.
> Regards,
> Markus
> --
> Markus Schaber | Logical Tracking&Tracing International AG
> Dipl. Inf.     | Software Development GIS
> Fight against software patents in Europe! www.ffii.org
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