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<p>Dear Ming,</p>
<p>what function are you using to derive the streams in GRASS?</p>
<p>The reason is probably that GRASS and ArcGIS use different
algorithms to obtain the streams from the dem. As far as I
remember (but I might be wrong) ArcGIS uses SFD while GRASS
(r.stream.extract) uses MFD (i.e. single vs. multiple flow
directions).</p>
<p>So, if you want to get exactly the same streams you need to find
out how ArcGIS does it and try to set the parameters in GRASS
accordingly (of possible).</p>
<p>Additionally, flat areas are usually difficult for all
algorithms.<br>
</p>
<p>Best,</p>
<p>Mira<br>
</p>
<div class="moz-cite-prefix">On 17/02/2021 16.23, ming han wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAD+uAWjLS8dvajrus2Xwv_iPhq04Wha=4WQ0C=0v9Lb0vHhDMA@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Hi Everyone
<div> </div>
<div> I just notice that streams from GRASS are inconsistent
with streams obtained from ArcGIS sometimes, when there is a
flat or low slope dem region such as lakes. </div>
<div> </div>
<div> As shown in the following figure, there is a sharp turn
from streams derived from GRASS. </div>
<div><br>
</div>
<div> I love GRASS and I am a GRASS user, I am asking this
because the DEM that I am using is MERIT hydrological
pre-conditioned DEM. I guess they are using ArcGIS. </div>
<div><br>
</div>
<div> I just want to get a consistent stream network with the
stream network provided by MERIT. </div>
<div> </div>
<div> Is there any solution for this?</div>
<div><br>
</div>
<div>Many thanks</div>
<div>Ming </div>
<div><br>
</div>
<div> </div>
<img src="cid:part1.0B7CF84E.BB8FA8CE@uni-landau.de"
alt="image.png" class="" width="542" height="435"><br>
</div>
<br>
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</blockquote>
<pre class="moz-signature" cols="72">--
Dr. Mira Kattwinkel
Quantitative Landscape Ecology
iES Landau, Institute for Environmental Sciences
University of Koblenz-Landau
Fortstraße 7
76829 Landau
Germany
Phone: + 49 6341 280-31553
Office: Building I, Room 2.02</pre>
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