[postgis-users] How to extract multiple convex hulls from a query?

[Stephen Woodbridge]

Hi all,

I am trying to construct multiple convex hulls from a series of point 
where  I have an attribute dist for each point.

What I want is to generate convex hulls for expanding rings where dist 
<= slice up to some max_dist.

So if slice=100 and max_dist=500, then each hull would be:

1. all points <= 100
2. all points <= 200
3. all points <= 300
4. all points <= 400
5. all points <= 500

So I have a procedure that generates the points and is fairly costly to 
run. I would like to run it once and extract all the hulls in a single 
pass if possible.

I'm currently running postgresql 8.3 and "POSTGIS="1.5.1" 
GEOS="3.2.0-CAPI-1.6.0" PROJ="Rel. 4.6.1, 21 August 2008" 
LIBXML="2.6.32" USE_STATS"

Any thoughts or snippets would be appreciated.

Thanks,
   -Steve