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

[Martin Davis]

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
>