[postgis-users] compute "difference" between two roads

[c. m.]

hi michael,
thanks a lot that you're trying to help me. i'm quite new to the whole 
thing. do you mean small db table's e.g. concerning one street?

cesare


>From: Michael Fuhr <mike at fuhr.org>
>Reply-To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
>To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
>Subject: Re: [postgis-users] compute "difference" between two roads
>Date: Fri, 8 Sep 2006 05:30:49 -0600
>
>On Fri, Sep 08, 2006 at 09:38:23AM +0200, c. m. wrote:
> > i'm using the navteq data set, postgis/postgres and the uml
> > mapserver. Actually I have created a table with forest streets and
> > one with side streets. forest streets are a subset of side streets,
> > i.e. a forest street is also a side street. now I want to
> > geometrically compute the difference of the two (side - forest
> > streets) to get an adjacent side streets table (layer)  to be able
> > to display them properly and independently on the mapserver. as a
> > result I always get the entire side street and not the difference
> > between the two areas/lines...unfortunately it doesn't work and I
> > can't understand why.
>
>Could you post a couple of geometries along with the difference
>you get?
>
>--
>Michael Fuhr
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