[GRASS-user] drainage extraction - so homogeneous output across different relief conditions

[Milton Cezar Ribeiro]

Dear all,

I extracted drainage from a large number of tiles of SRTM DEMs, for several
regions of Brazil. The regions have very different relief conditions,
ranging from almost flat to very inclined. I have some cartographic maps
at scale 1:50,000, and the (reference) densities ranges from 7 to 16%.
But I was surprise that using the command below the estimated drainage
is (on my point of view) very homogeneous, ranging from 3 to 4% only:

r.watershed.exe -m --o memory=2048 elevation=srtm_map threshold=250
stream=srtm_map_drainage

Why my output map is so homogeneous accross regions with
very different terrain conditions?

Any hint are welcome.

cheers

milton
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20091228/e147c2fd/attachment.html