[postgis-devel] Two geometries intersects but intersection is empty

Martin Davis mbdavis at refractions.net
Thu Jun 3 09:15:30 PDT 2010


Can you post the case?

This can happen because the intersects predicate test is more accurate 
than the intersection computation.  (Technically speaking, it's possible 
to detect that two segments intersect, but be unable to compute an 
accurate point that represents the intersection).

Pierre Racine wrote:
> Hi,
>
> Is it possible that st_intersects returns true on two geometries but their st_intersection returns "GEOMETRYCOLLECTION EMPTY"?
>
> I have a nice case here...
>
> Pierre
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022




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