[postgis-users] Intersection problem

[Nicolas Ribot]

> Hello!
>
> Doing some intersection with Postgis version 1.1.6-2, I'm facing a very strange problem (at least for me)
>
> Two Polygons are passing all possible tests I'm able to do, but once it comes to compute the
> "Intersection", an error is thrown while the "Intersects" was ok.
>
> You find here the data in question.
>
> If somebody would have an idea of what is going on, any hint is more than welcome !
>

Hello Quentin,

What's the error message you see ?
Testing your polygons in Postgis 1.1.3, geos 2.2.1, I can produce a
valid intersection (see attached image).
Aslo, you may want to try to reduce the coordinates precision by using
the snaptogrip() function according to the data precision.

Spatial operators like intersects, overlaps, etc. are robust in
postgis. They always return the correct result.
constructive fonctions like intersection, geomunion, etc. on the other
side, may fail in some particular cases.
The lastest GEOS release corrects a lot of errors. You may want to
upgrade to this version if your problem is still here after a call to
snaptogrid().

Nicolas
Nicolas
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