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

Brent Fraser bfraser at geoanalytic.com
Wed Mar 2 10:42:30 PST 2011


   Hopefully your expectations aren't too high.  Here it is...

Best Regards,
Brent Fraser

On 3/2/2011 11:34 AM, Tyler Mitchell wrote:
> Brent, I'm sure a few of us are interested  - sounds good!  :)
> Tyler
> 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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