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

[Paul Ramsey]

G definitionally does not overlap itself if it is a 
geometrycollection??? Maybe this was a typo and not an actual decision 
on the part of the drafters?

On Tuesday, April 8, 2003, at 01:51 PM, Martin Davis wrote:

> 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
>>
>>
>>
>>
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>
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      Paul Ramsey
      Refractions Research
      Email: pramsey at refractions.net
      Phone: (250) 885-0632