[GRASS-user] Calculate the average slope by unit

[Markus Metz]

Hamish wrote:
> 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.
>
>
Simpler alternative with r.resamp.stats:
- get slope as described above
- set the region resolution to 1km
- run r.resamp.stats with slope as input and method=average

Markus M