[postgis-users] How to extract common linestring of polyon and linestring

[akrherz at iastate.edu]

On Wed, 11 Mar 2009, Stephen Woodbridge wrote:

> You might try something like:
>
> How about buffering the country polygon by your tolerance and then get 
> the results of the buffered country and the river.

Thanks so much, that got me pointed in the right direction.  What I 
settled on doing is:

  intersection(
       buffer(exteriorring(geometryn(n.geom,1)),0.02),
       r.geom
    )

So I turn the county polygon into an exteriorRing and then buffer it out a 
bit.  Then see what portions of the river intersect that buffered polygon.

thanks!
   daryl