Hi Rich,<div><br></div><div>AFAIK (but surely Markus Metz will give an insight) r.stream.extract must run with flow accumulation produced by r.watershed. In order to use a weighted flow accumulation, I would produce it using the r.watershed command with the option "flow", instead of mapcalc.</div>
<div><br></div><div>HTH</div><div>madi<br><br><div class="gmail_quote">On Thu, Apr 5, 2012 at 11:29 PM, Rich Shepard <span dir="ltr"><<a href="mailto:rshepard@appl-ecosys.com" target="_blank">rshepard@appl-ecosys.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> I'm learning to use r.stream.extract by following the detailed example on<br>
the manual page. The last two steps are to extract steam maps using both<br>
weighted and unweighted accumulation maps. The example syntax is:<br>
<br>
# extract streams<br>
r.stream.extract elevation=elevation.10m@<u></u>PERMANENT \<br>
accumulation=elevation.10m.<u></u>acc.weighed \<br>
threshold=1000 \<br>
stream_rast=elevation.10m.<u></u>streams<br>
<br>
And the example syntax to create the weighted flow accumulation map is:<br>
<br>
# weigh accumulation map<br>
r.mapcalc "elevation.10m.acc.weighed = elevation.10m.acc * weight"<br>
<br>
For one of my sub-watersheds I ran the following:<br>
<br>
r.mapcalc "dem10m.acc.weighted = dem10m.acc * weight"<br>
<br>
(all on one line but it may wrap to two lines when you view it).<br>
<br>
I check that this worked properly by displaying demm10m.avg on d.mon x0, then<br>
displaying dem10m.acc.weighted on the same monitor. The two maps are congruent. So,<br>
when I run r.stream.extract I get an error that the accumulation map does<br>
not match the elevation map from which r.mapcalc created it:<br>
<br>
r.stream.extract elevation=dem10m.avg accumulation=dem10m.acc.<u></u>weighted threshold=1000 stream_rast=dem10m.streams<br>
<br>
(NOTE: again, all on one line, but may display on two lines.)<br>
<br>
Load input maps and get start points...<br>
ERROR: Accumulation map does not match elevation map!<br>
<br>
There is no error with the unweighted accumulation map (dem10m.acc).<br>
<br>
I'm not seeing why this error is generated, and need to understand why so<br>
I can model a dozen or so small basins.<br>
<br>
TIA,<br>
<br>
Rich<br>
<br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br>Ing. Margherita Di Leo, Ph.D.<br>
</div>