[OSGeo-Discuss] Command line tool for dissolving polygon boundaries

Brent Fraser bfraser at geoanalytic.com
Wed Mar 2 07:04:00 PST 2011


   I've got some C++ code that uses GDAL (with a GEOS Union call) to 
dissolve polygons based on an attribute.  If you can compile C++ code on 
Linux, you're welcome to it.

Best Regards,
Brent Fraser

On 3/2/2011 12:31 AM, Dan Putler wrote:
> Hi Paolo,
> Your point is well taken. What seem to be the best solutions involve 
> reading in a shapefile and then writing out a new one. I was starting 
> to lean toward either PostGIS or Spatialite by using a SQL script 
> sourced within the relevant cli shell since my guess was that they 
> would scale much better than any Python code I was likely to write. I 
> think I could automate things more with GRASS shell scripts than with 
> SQL scripts (there are over 3000 counties in the US). The geometry 
> cleaning GRASS does is a two edged sword, having all the benefits you 
> indicate, but at the cost of increased processing time. However, my 
> guess is that the benefits of the cleaning are worth the cost.
> Thanks for your advise.
> Dan
> On 03/01/2011 10:57 PM, Paolo Cavallini wrote:
>> Il giorno mar, 01/03/2011 alle 23.25 +0100, Paolo Corti ha scritto:
>>> Your only option here could be to use GRASS, but as far as I know you
>>> need to import your shapefile to the GRASS database, use a GRASS
>>> command (v.reclass [0]) and export back to shapefile the result, so it
>>> is not very direct.
>> Not very direct, but it's only one more command (v.in.ogr), with the
>> additional bonus that importing into GRASS you can clean up invalid
>> topologies, close empty gaps, remove unwanted overlaps, etc.
>> All the best.
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