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List:       grass-user
Subject:    [GRASS-user] drainage extraction - so homogeneous output across
From:       Milton Cezar Ribeiro <miltinho.astronauta () gmail ! com>
Date:       2009-12-28 20:39:27
Message-ID: 64f1583f0912281239h25089a4fre2e502e5111ad9f () mail ! gmail ! com
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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

[Attachment #5 (text/html)]

<div>Dear all,</div>
<div> </div>
<div>I extracted drainage from a large number of tiles of SRTM DEMs, for several</div>
<div>regions of Brazil. The regions have very different relief conditions,</div>
<div>ranging from almost flat to very inclined. I have some cartographic maps</div>
<div>at scale 1:50,000, and the (reference) densities ranges from 7 to 16%. </div>
<div>But I was surprise that using the command below the estimated drainage</div>
<div>is (on my point of view) very homogeneous, ranging from 3 to 4% only:</div>
<div> </div>
<div>r.watershed.exe -m --o memory=2048 elevation=srtm_map threshold=250 stream=srtm_map_drainage</div>
<div> </div>
<div>Why my output map is so homogeneous accross regions with</div>
<div>very different terrain conditions?</div>
<div> </div>
<div>Any hint are welcome.</div>
<div> </div>
<div>cheers</div>
<div> </div>
<div>milton</div>


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