[postgis-users] Polygons enclosing points

Rob Tester robtester at gmail.com
Fri Jul 6 06:25:12 PDT 2007

Checkout http://www.cgal.org they take the Delaunay triangulation and use it
to generate an alpha shape. The polygon produced from the alpha shape can be
concave or convex, it can also produce a multipolygon or polygons with holes
depending on the input points and the selected alpha value. The alpha shape
is a generalization an isn't perfect, but hard to determine what the optimal
shape from a collection of points would be anyway.  

If you want to go that route and use alpha shapes then look at
http://www.postlbs.org they have a simple implementation of the cgal alpha
shape 2d template for postgis. 


-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Nicolas
Sent: Friday, July 06, 2007 6:18 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Polygons enclosing points

> Dear all
> I have many points in a map layer which i want to surround with a polygon.
> Is there a way to automatically create optimum polygons that each enclose
> only one point and snap at their vertices?
> Thank you

I think a delaunay triangulation could do the trick.
Search this list for delaunay.
A thread like 'Voronoi / Dalaunay function (solved)' may be usefull.

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