Thank you, this actually worked. As I actually wanted the value in meters what I did was to create a very hi-res grid with 20 meter resolution and then assign the value 400 in the rasterisation of the vector, to finally resample.
A direct rasterisation of the vector using the area column as attribute as previously suggested instead didn't work. Many thanks, Antonello 2012/6/12 Micha Silver <[email protected]> > On 12/06/2012 10:18, Antonello Lobianco wrote: > > Hello everybody on the list! > > I am a "occasional" grass gis user and I'm stuck with a relatively > simple task: I have a high-res vector layer describing only one category > (Corine Land Cover map for "broad-leaved forests", 311) and I want to > rasterise it in a low-res 8-by-8 km raster map where the value stored on > each cell is the area (or, that's the same, the share of the area) that the > vector cover within that cell. > So each pixel/cell would have a value ranging from 0 (no broad-leaved > forest at all) to 64 (all the area of the pixel is covered by > broaded-leaved forests). > I already managed to get the region with the right cell dimension, add the > area geometry to the vector and load it in grass, but I don't know now how > to rasterize it (v.to.raster seems to me to not offer the option to put the > area, but only a specific catgegory, but maybe I am wrong??). > > > I'm not sure what your final goal is, but you can do what you've described > as follows: > > # First set resolution to 1 km > g.region -p res=1000 > # Now rasterize the vector > v.to.rast broad_leaf_vector out=broad_leaf_1km type=area use=val val=1 > # THis will give you as raster of 1km X 1km with values of 1 where the > original vector covered, and null otherwise > # Now change resolution to 8km and use r.resamp.stats to resample to your > courser region: > g.region -p res=8000 > # Use the "sum" method of r.resamp.stats to get the values for the new, > coarse raster > r.resamp.stats broad_leaf_1km out=broad_leaf_8km method=sum > # Should leave you with a new raster of res 8km, and with values 0-64 > > HTH, > Micha > > Thank you for any hint you could provide me. > > Antonello > > > -- > Antonello Lobianco > INRA, Laboratoire d'Economie Forestière > 14 Rue Girardet - 54000 Nancy, France > Tel: +33.652392310 > Email: [email protected] > http://antonello.lobianco.org > > This mail was received via Mail-SeCure System. > > > _______________________________________________ > grass-user mailing > [email protected]http://lists.osgeo.org/mailman/listinfo/grass-user > > > This mail was received via Mail-SeCure System. > > > > > > -- > Micha Silver052-3665918 > > -- Antonello Lobianco INRA, Laboratoire d'Economie Forestière 14 Rue Girardet - 54000 Nancy, France Tel: +33.652392310 Email: [email protected] http://antonello.lobianco.org
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