Hi Daniel,<br><br>Well, r.watershed does have a logic behind the way in the numbering scheme. What you can do is wait for r.watershed to end and then using its watersheds delimit the r.terraflow watersheds.<br>By the way, if you want to delineate the watersheds, it's better to run r.watershed on smaller areas (and using a larger threshold) a couple of times; you'd only have to wait at most a couple of hours. Then patch the maps and create your watersheds (using also r.terraflow's output); I did this for a 9600 km2 basin.<br><br>Jaime<br><br><b><i>Daniel Victoria <daniel.victoria@gmail.com></i></b> escribió:<blockquote class="replbq" style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"> I tried searching through the mailing list for something about<br>r.terraflow and the logic in the numbering scheme but could not find<br>anything. Could some kind soul brieflly explain the logic behind it?<br><br> I did find a message between Dylan and
Hamish last year about joining<br>the basins output from r.terraflow. Basically trya mixture of r.drain,<br>v.extract or r.flow..<br><br>http://article.gmane.org/gmane.comp.gis.grass.user/15113/match=terraflow+logical<br><br>Hamish, have you tried using r.drain to connect the smaller basins?<br><br>I tough about using r.terraflow with the D8 option and the use the<br>flow direction output with r.water.outlet. Is that possible?<br>Unfortunatelly I can't test it here because r.watershed is still<br>running (+2 days) and I don't want to stop the process now that it<br>reached 50%...<br><br>Cheers<br>Daniel<br><br>On Dec 28, 2007 7:12 AM, Hamish <hamish_b@yahoo.com> wrote:<br>> Daniel Victoria wrote:<br>> > > I trying to delineate watersheds for several points in a very big<br>> > > DEM<br>> > ><br>> > > | Data Type: CELL |<br>> > > | Rows: 4803 |<br>> > > | Columns: 5172 |<br>> > > | Total Cells:
24841116<br>> > ><br>> > > I've successfully ran r.terraflow on the DEM but now I'm stuck.<br>> > > How do I get the watershed area for my points of interest? I've<br>> > > tried using the direction map produced with r.water.outlet but it<br>> > > did not work (I used MFD flow calculation).<br>> > ><br>> > > Also, from what I understood, the sink watershed map is suposed to<br>> > > be the watersheds delineated by the terraflow module, is that<br>> > > correct?<br>><br>> Near-to, but not exactly.<br>><br>> > > Anyway, I think I'll let r.watershed run for the night<br>><br>> For a region that big r.watershed will take a long time to finish, but<br>> it can be worth the wait. IIRC you get more accurate results from<br>> r.watershed than from r.terraflow. (see historical post by ?<br>> Helena/Laura/Charles?)<br>><br>> The hardest part with r.watershed is
getting the threshold setting near<br>> to the scale you wish to work with.<br>><br>> For watershed delimination see (new) examples here:<br>> http://grass.ibiblio.org/grass63/manuals/html63_user/r.watershed.html<br>> http://grass.gdf-hannover.de/wiki/Psmap_flooding_example<br>><br>><br>> Jaime Carrera wrote:<br>> > > that's right; you end up with a lot of sub-basins, which you can<br>> > > aggregate according to your need. They are numbered on a logical<br>> > > sequence, so it's really easy to aggregate them with r.mapcalc;<br>> > > just check where a key outlet is and go upstream from there.<br>><br>> Daniel:<br>> > Well, I think that something has gone wrong then because the basin<br>> > numbering does not seam to be in a logical sequence. Or I have not<br>> > understood what is the logic in the numbering sequence.<br>><br>> AFAIR Jamie is correct, there is some logical sequence
there. I don't<br>> see much about it in the help page but if you search the mailing list<br>> archive or source code you can find it.<br>><br>> > Just for the record, here is my g.region -p output:<br>> ...<br>> > nsres: 899.99917697<br>> > ewres: 899.9166173<br>> > rows: 4803<br>> > cols: 5172<br>> ...<br>> > The resolution is strange because the DEM was projected from a 30<br>> > arcsec latlon map. I tried to set it to 900 meters but the output was<br>> > like this...<br>><br>> I think there is a way to have r.proj use the target location's region<br>> setting (region cropping flag?). The ugly way to clean the resolution<br>> is to force a 900m res with 'g.region res=900 -a'<br>><br>><br>><br>> good luck,<br>> Hamish<br>><br>><br>><br>> ____________________________________________________________________________________<br>> Never miss a
thing. Make Yahoo your home page.<br>> http://www.yahoo.com/r/hs<br>><br>><br>_______________________________________________<br>grass-user mailing list<br>grass-user@lists.osgeo.org<br>http://lists.osgeo.org/mailman/listinfo/grass-user<br></hamish_b@yahoo.com></blockquote><br><p> 
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