[GRASS-user] Area weighting for vectors

[Hanlie Pretorius]

2010/11/3, Micha Silver <micha at arava.co.il>:
> 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, this worked.

Is there a reason (other than no one has had time to do it) that a
similar function doesn't exist for two vector layers?