[postgis-users] Comparing Geometries with Different SRIDs

[Charlie Savage]

> The 2 point could be spatially equal given different SRIDS and
> coordinates if they were projected to a common SRID. So should geometry
> operators silently
> Call st_transform to make the righthand match the lefthand before
> comparing? This would be quite the expensive operation.

No. You can't automatically transform between different SRID values 
Think of the case of one geometry with an SRID value of 4326 and one 
with an SRID value of -1 (no coordinate system).

So different SRID values, then the geometries are not equal.  It is up 
to the user to transform geometries to the same SRID before calling 
ST_EQUALS.

Charlie
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