Steve, I think I've done something similar with ST_ConvexHull( ), where I had a data set full of LINESTRING geometries and wanted to ConvexHull them into as many separate polygons as there are unique sets of values for two or three attributes stored on the objects. paraphrased below to obscure original detail:
SELECT ST_ConvexHull ( ST_Collect ( the_geom ) ) AS poly, table1.attr1, table1.attr2, table1.attr3 FROM table1, table2 WHERE some condition AND some other condition AND GROUP BY table1.attr1, table1.attr2, table1.attr3; I think in your case if you could do something like this or similar? select func_returning_dist_as_one_of_5_ranges(the_distance) AS range, ST_ConvexHull ( ST_Collect ( the_geom ) ) AS poly from table where.... GROUP BY range; 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
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