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

[akrherz at iastate.edu]

Greetings,

Firstly, PostGIS continues to rock!  Thanks so much for this software...

My question is that I have a rivers linestring table and a political 
boundaries table (US counties) polygon.  I am wishing to extract the 
portion of the river geometry that lies along a county border.  Of course, 
these two layers don't have the same individual point precision, so I 
suspect some buffering, simplification is necessary.  I am not seeking 
anything exact, but something like if the river and a county border are 
within a few hundred meters of each other for some distance along the 
river and county border.

I can't seem to figure out which functions could accomplish this task, or 
if it is possible. Currently, I have no issue finding points of 
intersection, so perhaps that is part of the solution that is staring me 
in the face :)

Thanks!
   daryl