[geos-devel] BUG: relate(g1,g2) crashes with GEOMETRYCOLLECTION?

[Martin Davis]

Nope - if you look at the spec it clearly spells out that A and B overlap *only* if A intersects exterior(B) or vice-versa.  They clearly intended the answer to be FALSE if the geometries were the same.

Martin Davis, Senior Technical Architect
Vivid Solutions Inc.
Suite #1A-2328 Government Street   Victoria, B.C.   V8T 5G5
Phone: (250) 385 6040    Fax: (250) 385 6046
EMail: mbdavis at vividsolutions.com  Web: www.vividsolutions.com


> -----Original Message-----
> From: Martin Davis 
> Sent: Tuesday, April 08, 2003 1:52 PM
> To: GEOS Development List
> Subject: RE: [geos-devel] BUG: relate(g1,g2) crashes with
> GEOMETRYCOLLECTION?
> 
> 
> Yep, overlaps(G,G) = false according to the OGC spec.  This 
> may be a bit counter-intuitive.  Not sure what the rationale 
> behind this decision was. 
> 
> I usually use A.relate(B, "T********") to determine if things 
> overlap "properly".
> 
> Martin Davis, Senior Technical Architect
> Vivid Solutions Inc.
> Suite #1A-2328 Government Street   Victoria, B.C.   V8T 5G5
> Phone: (250) 385 6040    Fax: (250) 385 6046
> EMail: mbdavis at vividsolutions.com  Web: www.vividsolutions.com
> 
> 
> > -----Original Message-----
> > From: David Blasby [mailto:dblasby at refractions.net]
> > Sent: Tuesday, April 08, 2003 1:43 PM
> > To: GEOS Development List
> > Subject: Re: [geos-devel] BUG: relate(g1,g2) crashes with
> > GEOMETRYCOLLECTION?
> > 
> > 
> > Martin Davis wrote:
> > 
> > >Yep.  Neither GEOS nor JTS support GeometryCollections as 
> > arguments to relate.  This is partly because the semantics 
> > aren't very well defined, and partly because the obvious 
> > semantics [ X.relate(GC) = X.relate(union(GC.components) ] 
> > would make the operation non-robust.
> > >
> > >That said, we or you could always implement the above 
> > semantics fairly easily...
> > >
> > Its unfortunate that the spec doesnt tell you what to do in 
> > the case of 
> > GEOMETRYCOLLECTIONs.
> > 
> > I've also noticed that overlaps(g,g) is FALSE!
> > 
> > dave
> > 
> > 
> > 
> > 
> > _______________________________________________
> > geos-devel mailing list
> > geos-devel at geos.refractions.net
> > http://geos.refractions.net/mailman/listinfo/geos-devel
> > 
> 
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