[GRASS-user] Personalised raster alghoritm (simple: area)

[Antonello Lobianco]

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 <micha at arava.co.il>

>  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: antonello.lobianco at nancy-engref.inra.fr
> http://antonello.lobianco.org
>
> This mail was received via Mail-SeCure System.
>
>
> _______________________________________________
> grass-user mailing listgrass-user at lists.osgeo.orghttp://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: antonello.lobianco at nancy-engref.inra.fr
http://antonello.lobianco.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20120612/055ebe5d/attachment.html>