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

[My Pid]

thanks for the answers !

The provided links really helped me to see that my own algorithm had a
strange behavior...

I am probably going to use the convexHull function !

regards,
Nick


2009/2/12 Nico Mandery <nico.mandery at geops.de>

> 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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