[postgis-users] Build polygons from points

[Kevin Neufeld]

PostGIS offers a ConvexHull(geometry) method. In conjunction with the 
Collect() method, you could...

SELECT ConvexHull(Collect(the_geom)) FROM my_point_table;

to get a polygon or envelope of all your points.

(Check out http://en.wikipedia.org/wiki/Convex_hull for a definition).

Cheers,
-- Kevin

Rob Tester wrote:
> Check out the CGAL lib. It should be able to do what you ask. 
>
> http://www.cgal.org/
>
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of galen
> Sent: Tuesday, January 30, 2007 12:47 PM
> To: postgis-users at postgis.refractions.net
> Subject: [postgis-users] Build polygons from points
>
>
> Say I have 500 points that represent an area and I'm hoping to build a
> polygon out of those points.  Is there a good function to do this in postgis
> or a good program that anyone has written that can accommodate this?
> Obviously there is no "perfect" method of building polygons from points, but
> a function that accepted some inputs (like concavity 0-10 or something,
> similar to the way Simplify works?) would seemingly help me refine the
> "perfect' method for my purposes.
>
> Thanks,
> Galen
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