[postgis-users] PostGIS 1.3.3 on Windows XP Unstable

Obe, Regina robe.dnd at cityofboston.gov
Mon Aug 18 09:00:16 PDT 2008

Its supposed to merge and dissolve boundaries where as ST_Collect just
collects the geometries into one record.


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

On Mon, Aug 18, 2008 at 4:12 PM, Bresnahan, Mike
<Mike.Bresnahan at bestbuy.com> 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.
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