[postgis-users] RV: Distance Function

[Paul Ramsey]

Dan R Greening wrote:
 > t complains that the && operator is trying to compute overlap from two
> different geometries.  But shouldn't it just perform a projection to make it
> work?  Do I need to project this explicitly?  

Yes, you do need to project explicitly. Given that we have proj, it is 
possible we could now simply do the conversion as required (as a recall, 
the check was included in postgis post-srid support, but pre-proj support).

> And what if I project to some
> geometry that requires additional parameters, such as referenced here:
> http://xserve.flids.com/pipermail/proj/2004-June/000086.html  

EPSG numbers are supposed to include *all* information about a srs, 
including datum information. If you find your EPSG information is not 
sufficient, it is probably because the info in spatial_ref_sys is not 
actually correct. As a stopgap, simply update the proj4text attribute in 
your spatial_ref_sys entry to include the extra information you want (in 
the example you cite, it is datum transform parameters, to_wgs84)

Paul