[postgis-users] Re: GeometryCollection Intersection

Markus Schneider schneider at lat-lon.de
Mon Jun 2 06:29:05 PDT 2008


thanks for the info.

Martin Davis wrote:
> Yes, that's correct, the geometry relationship predicates are not
> available for GeometryCollections.  The reason for this is that because
> GC's have very loose semantics (e.g. polygons can cross one another
> being the main one) it's not possible to robustly & exactly evaluate
> some predicates in certain situations.
> I guess intersection can always be evaluated correctly, however.  With
> the new work on prepared geometry, we perhaps could look at widening the
> scope a bit. (This might even be supported right now - I can't remember
> offhand).

Best regards,

Markus Schneider

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