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

Tyler Mitchell tmitchell at osgeo.org
Wed Mar 2 10:34:45 PST 2011

Brent, I'm sure a few of us are interested  - sounds good!  :)


On 2011-03-02, at 8:28 AM, Dan Putler wrote:

> Hi Brent,
> I can compile C++, and I'm interested. Is it possible to access the code?
> Dan
> On 03/02/2011 07:04 AM, Brent Fraser wrote:
>> Dan,
>>    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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