[geos-devel] Re: [GEOS] #527: Union and UnaryUnion both fail at correctly node input lines

[Sandro Santilli]

On Tue, Apr 03, 2012 at 08:37:14AM +0200, Sandro Santilli wrote:
> On Mon, Apr 02, 2012 at 10:13:16PM -0700, Martin Davis wrote:
> > JTS uses the FastNodingValidator to check for correctly noded line
> > arrangements.  Basically it checks for any interior-interior segment
> > intersections, using indexing to speed things up.
> > 
> > And yes, the OGC operation semantics aren't fully capable when it
> > comes to more specific uses like checking noding.  That's one reason
> > I introduced the boundary-node rule.
> > 
> > The Polygonizer is fine with closed lines (as long as, as always,
> > the linework is FULLY noded).
> > 
> > This issue is just one more example of a robustness failure.
> 
> Do you think the use of a selected Noder might handle such cases
> better than relying on Union operation to do noding ?

I tried this. IteratedNoder succeeds at second iteration.

SimpleSnapRounder fails with:
 TopologyException: found endpt/interior pt intersection at index 1 :
                    pt 1.72506e+06 4.81909e+06

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