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

[Micha Silver]

On Tue, 28 Jul 2009 11:24:19 -0700 (PDT)
daljeet <sachdev_dj at yahoo.com> wrote:

> 
> 
> 
> //d.vect Ind_rain_orig
> //The  Ind_rain_orig looks like this - when the region is set to
> vector of Kerala
> //g.region vect=ker_rain_v
> 
> http://n2.nabble.com/file/n3345107/Ind_rain_orig_reg_ker.png 
> 
> 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
> 
> http://n2.nabble.com/file/n3345107/Ind_rain_orig_reg_adm2.png 
> 

Since you seem to have a rigid matrix of data points, what's the
purpose of the voronoi polygons??
Can't you just run v.surf.rst to get a rain_info raster surface, then
r.contour to make your isohyetal lines? Finallly v.rast.stats will add
columns to the vector table with all the rainfall statistics.


 
> Thanks
> Daljeet
> 
> 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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> > 
> > 
>