[GRASSLIST:6387] Re: Computing polygon area after/during v.overlay

[Hamish]

> I have not been able to compute the area of vector polygons after a 
> v.overlay operation. Here's what I've done in the 6.0.0 release of 
> GRASS, running OS X 10.3.8:
...
>
> 4. Overlay the two vector files (v.overlay ainput=name2 atype=area 
> alayer=1 binput=esri92shp btype=area blayer=1 output=name2_overlay 
> operator=or olayer=1,0,0 )
> 
> All the data are lat-long format, as is the location. After the 
> v.overlay, I get topology and the .dbf file shows that I've 
> successfully merged the data, but I haven't found a way to compute the
> areas of each clipped polygon. Ultimately, I need to create weighted 
> averages (first by area, later by other variables) for each country.

d.vect overlay_output
d.what.vect

should show you the area quickly.


I think it is possible to make a report by using v.to.db. (same with line
length, ..)

examples from the help page:
  http://grass.ibiblio.org/grass60/manuals/html60_user/v.to.db.html

Printing reports

Report all area sizes of a map:
v.to.db -p soils option=area type=boundary units=h

Report all area sizes of a map, sorted by category number:
v.to.db -p soils option=area type=boundary units=h | sort -n



Hamish