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
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