[gdal-dev] Re: [mapserver-users] converting a multi-thousand polygon shapefileinto a shapefile that just contains the exterior vertices

[Markus Neteler]

On Thu, Apr 30, 2009 at 6:27 AM, Rahkonen Jukka
<Jukka.Rahkonen at mmmtike.fi> wrote:
> Hi,
>
> What you want is the union of all the individual image polygons.  At least it can be made with GIS applications like QGis or OpenJUMP. I don't know of any tool that could do it directly from command line but such can exist, though.

GRASS can do that (GUI and command line):

1. assign a common attribute value to all polygons
2. perform a dissolve.

Manual:
http://grass.osgeo.org/grass64/manuals/html64_user/v.reclass.html
http://grass.osgeo.org/grass64/manuals/html64_user/v.dissolve.html

Best
Markus