Oh, I missed your certain % comment. You would use something like this in your base query:
Area2d(intersection(a.the_geom,b.the_geom)) / area2d(a.the_geom) as pct_cover And then filter out ones whose pct_cover met your threshold. r.b. Robert W. Burgholzer Surface Water Modeler Office of Water Supply and Planning Virginia Department of Environmental Quality [EMAIL PROTECTED] 804-698-4405 Open Source Modeling Tools: http://sourceforge.net/projects/npsource/ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Martin Davis Sent: Thursday, September 25, 2008 8:13 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] Deleting an arbitrary polygon AFAIK there is no way to do this in a single pass. One way to do it iteratively is: - add a column which will flag features which are "nonoverlapping" (and which will be kept) - choose one feature and flag it as nonoverlapping - iterate { - delete all features which overlap some "nonoverlapping" feature - pick an unmarked feature and flag it as "nonoverlapping" - exit if all features are flagged as "nonoverlapping" } This is probably going to be slow... Dylan Lorimer wrote: > Hey PostGIS Friends, here's a problem that's stumping me, hoping you can help: > > I have a bunch of polygons, many of which overlap with each other. I > would like to trim down the set of polygons to only those that do not > overlap. I'm not particular about which I delete, so long as they > overlap by a certain %. > > Any thoughts on how to do this? I was trying for a self join but can't > figure out how to not to delete all polygons that overlap. > > Cheers, > dylan > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > > -- Martin Davis Senior Technical Architect Refractions Research, Inc. (250) 383-3022 _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
