thanks for the answers !<br><br>The provided links really helped me to see that my own algorithm had a strange behavior...<br><br>I am probably going to use the convexHull function !<br><br>regards,<br>Nick<br><br><br><div class="gmail_quote">
2009/2/12 Nico Mandery <span dir="ltr"><<a href="mailto:nico.mandery@geops.de">nico.mandery@geops.de</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
In regards to a convcave hull you might want to check this thread:<br>
<a href="http://www.mail-archive.com/postgis-users@postgis.refractions.net/msg05979.html" target="_blank">http://www.mail-archive.com/postgis-users@postgis.refractions.net/msg05979.html</a><br>
<br>
nico<br>
<br>
<a href="mailto:nicklas.aven@jordogskog.no">nicklas.aven@jordogskog.no</a> schrieb:<br>
<div class="Ih2E3d">> Hallo<br>
><br>
> you can read about it here:<br>
> <a href="http://www.postgis.org/documentation/manual-svn/ST_ConvexHull.html" target="_blank">http://www.postgis.org/documentation/manual-svn/ST_ConvexHull.html</a><br>
> 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.<br>
><br>
> /Nicklas<br>
><br>
><br>
><br>
> 2009-02-12 My Pid wrote:<br>
><br>
> Hello,<br>
>> I am really a newbie in the postgis world.<br>
>><br>
>> I am a developper for <a href="http://www.openbmap.org/" target="_blank">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>
</div>>> <a href="http://realtimeblog.free.fr/cell_map.php?mcc=208&mnc=1&lac=14592&cellid=62403&display=Display" target="_blank">http://realtimeblog.free.fr/cell_map.php?mcc=208&mnc=1&lac=14592&cellid=62403&display=Display</a><br>
<div class="Ih2E3d">>><br>
>><br>
>><br>
>> Is it possible to use postgis functions to generate this kind of envelope ?<br>
>><br>
>> regards,<br>
>> Nick<br>
>><br>
>><br>
</div>>> ------------------------------------------------------------------------<br>
>><br>
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