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

[Michael Fuhr]

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