I'd be suprised if one of the watershed models doesn't
provide this, but you should be able to get it easily
enough for any point on your DEM by computing the
slope of each cell with r.slope.aspect and storing
that in a slope_grid. Then use the following formula
in r.mapcalc (I think this will work):
area_grid = ewres()* nsres()/cos(slope_grid)
This gives you the surface area of each cell. Next use
this grid as the flow grid in r.watershed and create
the accumulation grid which should tally up the _true_
contributing area of each cell in your DEM. Use masks
if you are only interested in a sub-basin.
--- Rado Bonk <rado@cosmos.dsc.unomaha.edu> wrote:
Hi GRASSusers,
Is there a way to compute watershed surface area in
GRASS? In
mountain regions it differs a lot from that of
planimetric area.
-Rado Bonk
Rado Bonk
Geography and Geology
UNO, Nebraska, 68182-0199,
rado@cosmos.unomaha.edu
=====
--
David Finlayson
david_finlayson@yahoo.com
University of Washington
Box 351310
Seattle, WA 98195 - 1310
__________________________________________________
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There's a r.surf.area (at least in 5.0), but it has a couple problems
which I'm working on. Doesn't consider NULL area properly (it's
included) and only works with CELL rasters. I hope to get this fixed-up
for the upcoming release of GRASS 5.0 (stable).
On Mon, Oct 16, 2000 at 11:23:49PM -0700, David Finlayson wrote:
I'd be suprised if one of the watershed models doesn't
provide this, but you should be able to get it easily
enough for any point on your DEM by computing the
slope of each cell with r.slope.aspect and storing
that in a slope_grid. Then use the following formula
in r.mapcalc (I think this will work):
area_grid = ewres()* nsres()/cos(slope_grid)
This gives you the surface area of each cell. Next use
this grid as the flow grid in r.watershed and create
the accumulation grid which should tally up the _true_
contributing area of each cell in your DEM. Use masks
if you are only interested in a sub-basin.
--- Rado Bonk <rado@cosmos.dsc.unomaha.edu> wrote:
> Hi GRASSusers,
> Is there a way to compute watershed surface area in
> GRASS? In
> mountain regions it differs a lot from that of
> planimetric area.
>
> -Rado Bonk
>
> Rado Bonk
> Geography and Geology
> UNO, Nebraska, 68182-0199,
> rado@cosmos.unomaha.edu
>
=====
--
David Finlayson
david_finlayson@yahoo.com
University of Washington
Box 351310
Seattle, WA 98195 - 1310
__________________________________________________
Do You Yahoo!?
Yahoo! Messenger - Talk while you surf! It's FREE.
http://im.yahoo.com/
--
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