If two geometries overlap, which one would you take? I assume you would leave all out of an overlapping set except for one or would you be taking the non-overlapping sections? Thanks, Regina
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dylan Lorimer Sent: Friday, May 02, 2008 7:29 PM To: PostGIS Users Discussion Subject: [postgis-users] Unique Coverage Hi PostGIS Users, Have what I hope is a simple problem that I'm not sure how to solve with PostGIS. I think I need to do a self-join on 0 overlap, but I'm just not certain. Given a number of polygons, some overlapping, some not, I want to produce the geometries of all non-overlapping areas...ie all unique "pixels". This has specifically to do with catalogs of overlapping imagery over an area, where I have polygons for each scene and want to compute unique pixels. Would I join a table with itself to achieve this? Cheers, dylan
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