[postgis-users] Unique Coverage

[Paragon Corporation]

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: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] 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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