[postgis-users] PostGIS 1.3.3 on Windows XP Unstable

[erik]

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/017995.html.




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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