[GRASS-user] Area weighting for vectors

[Micha Silver]

On 11/03/2010 04:55 PM, Hanlie Pretorius wrote:
> Hi,
>
> I need to add some attributes from a soil polygon layer to a catchment
> polygon layer using area weighting. In other words, the contribution
> of the soil layer needs to be weighted by the amount with which its
> polygons overlap the catchment polygons.
>
> For example, suppose I want to weight soil infiltration rates. 30% of
> a catchment polygon overlaps with soil type 1 and 70% overlaps with
> soil type 2. Now I want a new attribute in the catchment polygon that
> takes 30% of the infiltration rate of soil type 1 and adds it to 70%
> of the infiltration rate of soil type 2.
>
> How can I do this in GRASS?
>    

The most straight forward way is using v.rast.stats. This module adds to 
a vector attribute table the univariate statistics from a raster. So 
you'll first convert the soil map to raster, then run v.rast.stats using 
the catchment polygons as the vector and the soil infiltration as the 
raster.

> Thanks
> Hanlie
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>    


-- 
Micha Silver
Arava Development Co. +972-52-3665918
http://surfaces.co.il