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<div>Hallo </div>
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<div>you can read about it here:</div>
<div><a href="http://www.postgis.org/documentation/manual-svn/ST_ConvexHull.html">http://www.postgis.org/documentation/manual-svn/ST_ConvexHull.html</a></div>
<div>ST_ConvexHull will give you a better result but as you see in the documentation there is no function that gives a concave hull as you have in your example link.</div>
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<div>/Nicklas</div>
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<div><br />
<br />
2009-02-12 My Pid wrote:<br />
<br />
Hello,<br />
><br />
>I am really a newbie in the postgis world.<br />
><br />
>I am a developper for <a href="http://www.openbmap.org/">http://www.openbmap.org/</a> website<br />
>which identify GSM cell area from measures of GSM data<br />
>and GPS coordinates.<br />
><br />
>So I am planning to go from mysql to postgresql/postgis<br />
>and I am looking for a function that does the following:<br />
><br />
>I have a table containing the gps coordinates mentionned above.<br />
>I would like to generate a enveloppe or a boundary of the area<br />
> of the GSM cell.<br />
><br />
>What I have tried (among others)<br />
><br />
>SELECT ST_AsText(ST_Envelope(ST_Collect(gps_coordinates))) FROM "208_1_14592_gps";<br />
><br />
>with gps_coordinates - POINT geometry<br />
><br />
>It seems to output a 4 points polygons and I would like to get something like<br />
><br />
><a href="http://realtimeblog.free.fr/cell_map.php?mcc=208&mnc=1&lac=14592&cellid=62403&display=Display">http://realtimeblog.free.fr/cell_map.php?mcc=208&mnc=1&lac=14592&cellid=62403&display=Display</a><br />
><br />
><br />
><br />
>Is it possible to use postgis functions to generate this kind of envelope ?<br />
><br />
>regards,<br />
>Nick<br />
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