[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
>
> #       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
```