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

Dan Putler dan.putler at sauder.ubc.ca
Tue Mar 1 23:31:54 PST 2011

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.


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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