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<div align="left">I have been looking some more on this Hausdorff Distance. I'm afraid I have to take a step back. There are aspects that is not handled by my original idea and I can't see how to deal with it. The problem I didn't realize is that if the second geometry is "surrounding" the first, we have to search for the most far away point between the vertices. In the ordinary maxdistance-case we don't have to consider that and the maxdistance is always between two vertices. </div>
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<div align="left">/Nicklas</div>
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<div align="left"><br />
2009-07-09 Paragon Corporation wrote:<br />
<br />
Oh that's what that is. Hmm and I think its already ported to PostGIS,<br />
>though would be interesting to compare the speeds and results. Since the<br />
>current one in trunk is a GEOS call and Nicklas' would be a native PostGIS.<br />
><br />
>http://trac.osgeo.org/postgis/ticket/209 <br />
><br />
>Paul are you hmm planning add this to the manual -- I see you closed it? I<br />
>don't recall seeing it in the 1.5 docs or were we waiting for GEOS to be<br />
>patched first?<br />
><br />
>Thanks,<br />
>Regina<br />
><br />
><br />
>-----Original Message-----<br />
>From: postgis-devel-bounces@postgis.refractions.net<br />
>[mailto:postgis-devel-bounces@postgis.refractions.net] On Behalf Of Martin<br />
>Davis<br />
>Sent: Wednesday, July 08, 2009 6:14 PM<br />
>To: PostGIS Development Discussion<br />
>Subject: Re: [postgis-devel] st_dwithin, st_within, st_dcompletlywithin<br />
><br />
>That distance metric is known as the Hausdorff Distance. It's implemented<br />
>in JTS, and probably in GEOS as well.<br />
><br />
>nicklas.aven@jordogskog.no wrote:<br />
>><br />
>><br />
>> A function that gives the answer to for example:<br />
>> "How far away from France can you get in Belgia"<br />
>> To answer that we have to store compare the shortest distance to<br />
>> geometry2 from each vertex in geometry1 and finaly find wich vertex in<br />
>> geometry1 that has the highest "mindistance" to geometry2.<br />
>> Hope the idee is possible to understand. Is it of any use?<br />
><br />
>--<br />
>Martin Davis<br />
>Senior Technical Architect<br />
>Refractions Research, Inc.<br />
>(250) 383-3022<br />
><br />
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