R.terraflow outputs catchments around sinks in the dem. R.watershed
should be making huge delineations in comparison.
Mark
On Feb 2, 2009, at 11:40 AM, Markus Metz <markus.metz.gisw...@googlemail.com
> wrote:
Georg Kaspar wrote:
If these lakes have an outflow, i.e. water is leaving these lakes,
the
results will be more realistic when you omit the depression input to
r.watershed and only use the (not filled) DEM.
If you are talking about the basins output having NULL values around
these depression, this is because your basin threshold value was too
high, set it to a lower value. Check the current flow accumulation
output for a reasonable threshold.
so, my accumulation map contains values from -144714 to 58920 with
a majority of cells between 0-100. what would be an appropriate
threshold value?
You can try standard deviation of flow accumulation (r.univar -g).
I already tried 5000 and it looked similar to the output I received
from r.terraflow,
The basins of r.watershed look similar to the basins of r.terraflow?
but when running r.watershed with depression input I still receive
those null()-areas...
... in the basins output I assume. If you really want to treat lakes
as real depressions, i.e. water is not supposed to leave these
lakes, then there will always be NULL areas around the lakes unless
you set the threshold to something much smaller than 100, but then
the stream segments and basins become meaningless because there are
too many...
by the way, this is what my region looks like:
GRASS 6.2.3
Rather use 6.4.0RC3 instead of 6.2.3, you should get a couple of
nice surprises...
[...]
cells: 466400
Not that many cells, should take just a few seconds to get the
basins (with 6.4.0RC3).
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