Its supposed to merge and dissolve boundaries where as ST_Collect just collects the geometries into one record.
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of erik Sent: Monday, August 18, 2008 10:48 AM To: PostGIS Users Discussion Subject: Re: [postgis-users] PostGIS 1.3.3 on Windows XP Unstable Isn't a Union supposed to merge all polygons in one? The only thing I get to do this in ArcView is the "Merge" and that's also the functionality I get from ST_Union. Btw, for ST_Union'ing many complex polygons I'm using CascadedUnion as written here: http://postgis.refractions.net/pipermail/postgis-users/2007-December/017 995.html. On Mon, Aug 18, 2008 at 4:12 PM, Bresnahan, Mike <[EMAIL PROTECTED]> wrote: > How the hell do you get it to do a real union? Heh. Intuitive ArcMap is not. It took me forever to figure it out as well. You can do a union a couple different ways. The way that seemed to work the best for this is to: 1) Run ArcMap 2) Add the shapefile to your map 3) Open the edit toolbar. 4) Click on Start Editing. 5) Select the entire dataset by left clicking and then dragging a rectangle around the geometry. 6) Select Union from the menu on the edit toolbar. You should see the union happen right before your eyes. I think I tried the Union Tool like you did and didn't get what I expected. I think it just did a union on each individual feature instead of doing an aggregate union. _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ----------------------------------------- The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer.
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