Hi all,
I used r.watershed on a small test-region an all I produce
for accumulation and flow-direction was -1 on the whole area
except on the border-cells. Whats wrong?
Curiously is that the first time I tried on my equal-area projection
everything seemed normal. Before on ll it was wrong and after on that
laea-projection it was like mentioned.
I tried on grass63 and on grass64 (and different thresholds, new
output-names...). Both the same. (On opensuse 11.1 64)
r.watershed elevation=etopo1_fil@achim depression=etopo1_fil@achim
threshold=100000 accumulation=r_watershed_etopo1_accu
drainage=r_watershed_etopo1_dir basin=r_watershed_etopo1_basin
stream=r_watershed_etopo1_stream half.basin=r_watershed_etopo1_halfbasin
visual=r_watershed_etopo1_visual
length.slope=r_watershed_etopo1_lenghtslope
slope.steepness=r_watershed_etopo1_slopesteepness --overwrite
Can anyone help?
Best regards
Achim
achim wrote:
Hi all,
I used r.watershed on a small test-region an all I produce
for accumulation and flow-direction was -1 on the whole area
except on the border-cells. Whats wrong?
Curiously is that the first time I tried on my equal-area projection
everything seemed normal. Before on ll it was wrong and after on that
laea-projection it was like mentioned.
I tried on grass63 and on grass64 (and different thresholds, new
output-names...). Both the same. (On opensuse 11.1 64)
May be you need to run
g.region rast=etopo1_fil
first?
You can not use the same raster as elevation and as depression, this will give the you results you observed, nonsense results.
The name etopo_fil suggests that you filled the elevation map first before using it as input for r.watershed. This can heavily distort flow accumulation and flow direction output, the input elevation map *must not* be filled for r.watershed. Input depression is only needed if there are real depressions in the area, depressions without outflow. The Dead Sea is such a real depression, ordinary lakes are not, they usually have an outflow.
More details are in the help page:
http://grass.osgeo.org/grass64/manuals/html64_user/r.watershed.html
Good luck,
Markus M
r.watershed elevation=etopo1_fil@achim depression=etopo1_fil@achim
threshold=100000 accumulation=r_watershed_etopo1_accu
drainage=r_watershed_etopo1_dir basin=r_watershed_etopo1_basin
stream=r_watershed_etopo1_stream half.basin=r_watershed_etopo1_halfbasin
visual=r_watershed_etopo1_visual
length.slope=r_watershed_etopo1_lenghtslope
slope.steepness=r_watershed_etopo1_slopesteepness --overwrite
Can anyone help?
Best regards
Achim
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grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
That helped!
Thank you very much.
I thought that in depression-input zero means depressions (like in
r.terraflow, which does not produce that good results).
Thanks,
achim
Btw: I suggest oceans as real sinks. Think thats ok... 
the Problem was as you s
Markus Metz schrieb:
achim wrote:
Hi all,
I used r.watershed on a small test-region an all I produce
for accumulation and flow-direction was -1 on the whole area
except on the border-cells. Whats wrong?
Curiously is that the first time I tried on my equal-area projection
everything seemed normal. Before on ll it was wrong and after on that
laea-projection it was like mentioned.
I tried on grass63 and on grass64 (and different thresholds, new
output-names...). Both the same. (On opensuse 11.1 64)
May be you need to run
g.region rast=etopo1_fil
first?
You can not use the same raster as elevation and as depression, this
will give the you results you observed, nonsense results.
The name etopo_fil suggests that you filled the elevation map first
before using it as input for r.watershed. This can heavily distort flow
accumulation and flow direction output, the input elevation map *must
not* be filled for r.watershed. Input depression is only needed if there
are real depressions in the area, depressions without outflow. The Dead
Sea is such a real depression, ordinary lakes are not, they usually have
an outflow.
More details are in the help page:
http://grass.osgeo.org/grass64/manuals/html64_user/r.watershed.html
Good luck,
Markus M
r.watershed elevation=etopo1_fil@achim depression=etopo1_fil@achim
threshold=100000 accumulation=r_watershed_etopo1_accu
drainage=r_watershed_etopo1_dir basin=r_watershed_etopo1_basin
stream=r_watershed_etopo1_stream half.basin=r_watershed_etopo1_halfbasin
visual=r_watershed_etopo1_visual
length.slope=r_watershed_etopo1_lenghtslope
slope.steepness=r_watershed_etopo1_slopesteepness --overwrite
Can anyone help?
Best regards
Achim
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
achim wrote:
That helped!
Thank you very much.
I thought that in depression-input zero means depressions (like in
r.terraflow, which does not produce that good results).
From the help page: "Any non-zero values indicate depressions."
Thanks,
achim
Btw: I suggest oceans as real sinks. Think thats ok...
It's easier, faster and safer to mask out oceans (create an ocean mask or set elevation map cells to NULL for oceans)