[mapserver-users] Displaying overlapping linestrings

[Stephen Woodbridge]

On 1/24/2013 11:13 AM, Jan Hartmann wrote:
> Does anyone know a trick to do this:
>
> I'm making geographical indexes for the map series in our map library.
> Each map sheets is displayed as a polygonal linestring, based on its
> corner coordinates. Lots of sheets have exactly the same boundaries, so
> it's not clear where a polygon indicates just one map sheet of several.
> It's easy, of course, to write a PostGIS query to return a different
> color code when map boundaries exactly coincide, but I was wondering
> whether something like that could be done by mapserver on its own, like
> XOR-ing a line with what is already there. Any ideas?

Hi Jan,

For polygons you could use a small negative buffer to shrink the polygon 
slightly. You can do this in postgis, and you might be able to do it 
with mapserver if geos is compiled in. See:

http://mapserver.org/development/rfc/ms-rfc-48.html

Steve W