[GRASS-user] how to calculate area of voronoi polygons considering the boundary of the catchment

daljeet sachdev_dj at yahoo.com
Tue Jul 28 14:24:19 EDT 2009

These white spots in the voronoi vector may be the cause. But i ran the
voronoi module on the "archsites" vector of the Spearfish60 dataset and its
runs fine. The cmd was

v.voronoi input="archsites" output="arch_voronoi"

The only difference is that the region of archsites has got less points 
(around 25) whereas in Ind_rain_orig the total points were 93,000. Can this
be an issue. Can you test the module at your end with less and huge data
points and see if you also get similar results in both the cases. This would
be a great help. 

Also, i checked and the data of rain fall on voronoi vector is NOT NULL on
these white spots (checked using v.what.vect).

//d.vect Ind_rain_orig
//The  Ind_rain_orig looks like this - when the region is set to vector of
//g.region vect=ker_rain_v


But when the region is set to Ind_adm2_v (whole  country) the image is like 
//g.region vect=Ind_adm2_v
//d.vect Ind_rain_orig



Moritz Lennert wrote:
> On 28/07/09 18:42, daljeet wrote:
>> Hi Moritz,
>> I am new to GRASS and the basic concepts of this field. Below, I tried my
>> best to share all the information. Please write if I have missed
>> anything.
> This is perfect, thanks !
>> //creating the voronoi
>> v.voronoi input="Ind_rain_orig" output="Ind_rain_ker_vor"
>> //display the voronoi
>> d.vect "Ind_rain_ker_vor"
>> http://n2.nabble.com/file/n3344342/Ind_rain_ker_vor.png 
> The problem is here, with v.voronoi, as you can see the white spots 
> here. What do the original points (Ind_rain_orig) look like ?
> I don't know the module well enough, but I think you might have hit a 
> bug there (I've just tried a simple example for myself and also get 
> weird white spots). Please file a report in the bug tracker.
>> //storing the area of each polygon to a csv file
>> v.report ker_rain_vor_over option=area units=k >ker_area.csv --o
> Note that you can use v.addcol and v.to.db upload the polygon areas to 
> the attribute table.
> Moritz
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