[GRASS-user] Calculate the average slope by unit

[Hamish]

Jon wrote:
> I would like to calculate the average slope by square kilometer
> for a giving area. I have a raster of the considere area with
> the altitude. So my plan is to create a grid of square of 1 km²
> and to calculate for each square the average slope.
> 
> My main problem is that I don"t have any idea how to make
> it with grass.

- make a slope map from the DEM with r.slope.aspect at the same
resolution and bounds as the DEM. (run 'g.region rast=dem' first)

- make the grid with v.mkgrid, with box=1000,1000 (assuming the
location is meters-based)

- draw a 1 km x 1 km grid (d.grid), and overlay the v.mkgrid
vector map (area fill = none, or only display boundary features,
colored red or so) just to verify where it will be and what it
will look like.

- run v.rast.stats to calculate stats for each grid box, and
upload to that area's attribute table.


> Could someone give some tips?
> I put the raster i use at the following adress:
> http://www.megaupload.com/?d=IWRZC0HH


Hamish