[GRASS-user] Determining area of poligon vector layer around circle of points in other vector layer

Rainer M Krug r.m.krug at gmail.com
Fri Jun 13 04:05:35 EDT 2008


Thanks - that sounds interesting. So there is no way of doing that
without a loop?

Rainer

On Thu, Jun 12, 2008 at 7:25 PM, Martin Wegmann
<wegmann at biozentrum.uni-wuerzburg.de> wrote:
> Hello Rainer,
>
> On Donnerstag, 12. Juni 2008 19:13:18 Rainer M Krug wrote:
>> Hi
>>
>> I have two vector layers - one with polygons and one with points, both
>> in UTM 34 S.
>>
>> Now I would like to calculate the area of the polygons in circles
>> around the points, i.e. how much area in a 500m circle around the
>> points is covered by the polygons, and store this in the attribute
>> table of the point layer.
>>
>> Is there any easy way of achieving this? If I simply buffer the
>> points, the circles overlap sometimes and form one polygon, and I want
>> to have the results for each point - so that doesn't work.
>
> perhaps if you create a loop:
>
> v.to.rast your points output=points use=cat
>
> max=`r.info -r "points" | grep max | cut -f2 -d=`
>
> COUNTER=`r.info -r "points" | grep min | cut -f2 -d=`
>
> while [ "$COUNTER" -le "$max" ]; do
>
>        r.mapcalc "tttemp_1 = if(points == "$COUNTER",1,null())"
>
>        r.buffer input=tttemp_1 output=tttemp_buffer distances=100 --o
>
> #       your query
> #       patch result with previous query
> #       redo it until all patches are analysed
>
>        let "COUNTER=COUNTER+1"
>
> done
>
>
> hope this helps, Martin
>
>
>



-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Plant Conservation Unit
Department of Botany
University of Cape Town
Rondebosch 7701
South Africa


More information about the grass-user mailing list