[GRASS-user] Thiessen Polygons

[Dylan Beaudette]

On Wed, Feb 11, 2009 at 5:03 PM, Dylan Beaudette
<debeaudette at ucdavis.edu> wrote:
> On Wednesday 11 February 2009, MORREALE Jean Roc wrote:
>> Hamish a écrit :
>> > Kurt Springs wrote:
>> >> Does anyone know how to do Thiessen Polygons in GRASS?
>> >>
>> >> I need to use them around various types of megalithic tomb
>> >> sites that are in point vector files.
>> >
>> > v.voronoi
>> >
>> >
>> > there is some replacement test code to look at in grass-addons as well:
>> >  http://trac.osgeo.org/grass/browser/grass-addons/vector/voronoi
>>
>> While we are on this topic, is there a way to get a weigthed voronoi
>> diagram using grass ?
>>
>> The ability to rank a point to tune the area's influence would be great,
>> for that purpose I've been using an arcgis'extension* but with grass it
>> is not possible**. Is there a way to get a similar result ?
>>
>> *http://www.geog.unt.edu/~pdong/software.htm
>> **http://osdir.com/ml/gis.grass.user/2004-04/msg00036.html
>>
>> Regards,
>> MORREALE Jean Roc
>

Now that I have read about 'weighted voronoi diagrams', I wonder if a
combination of r.cost + r.mapcalc would solve this problem. Something
along those lines is demonstrated here:

http://casoilresource.lawr.ucdavis.edu/drupal/node/288

This example isn't quite what is requested, although using r.cost with
start=point_i, and stop=neighbor_points (derived from v.delaunay /
v.distance?) may work. It would then be a little more work to convert
the weighted-distance rasters into polygons, and link back to the
original attribute tables... but (hopefully) not outside the realm of
possibility via a script.


Cheers,

Dylan