[postgis-users] boundary or envelope of cloud of points

[Nico Mandery]

In regards to a convcave hull you might want to check this thread:
http://www.mail-archive.com/postgis-users@postgis.refractions.net/msg05979.html

nico

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