[postgis-users] ST_ConcaveHull

[Ahmad Aburizaiza]

Try this.

Select ST_ConcaveHull(ST_Collect(the_geom)) FROM table;


*---------------------------------------------------------------------------
Ahmad Aburizaiza
PhD student at **George Mason University**
Geography and Geoinformation Science Department
Fairfax, VA, USA
Tel : +1-703-981-0354*



On Thu, Jul 7, 2011 at 10:44 AM, Brian Sanjeewa Rupasinghe <
jinkabs at gmail.com> wrote:

> Hi,
>
> I have a building polygon table and from the following query i get the
> polygon
> coordinates.
>
> select st_astext (st_geometryn(the_geom, 1))
> from building_poly;
>
> Now what i need is to get the concave hull of all polygon coordinates.
> I tried the following query but it does not work.
>
> SELECT ST_ConcaveHull(ST_Union(select st_astext (st_geometryn(the_geom,
> 1))
> from building_poly), 1)  As convexhull;
>
> How to correct it?
>
> Cheers, Sanjeewa.
>
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