Re: Bugs in r.stream.extract
Huidae Cho <[email protected]>
| Newsgroups | gmane.comp.gis.grass.devel,gmane.comp.gis.grass.user |
|---|---|
| Message-ID | <CANEOyhopz7gzid3dahToFLAN5=6c8GRDTgf3Wg0d76=Jz8m3mw@mail.gmail.com> |
Ming, The discrepancy in flow accumulation between the two modules is explained in the r.accumulate manual at https://grass.osgeo.org/grass78/manuals/addons/r.accumulate.html. See Examples => Flow accumulation. Most likely, this is because of r.watershed's handling of border cells. Thanks, Huidae On Wed, Nov 25, 2020 at 7:17 AM ming han <[email protected]> wrote: > And another problem I got is that the flow accumulation I got from > r.accumulate and r.watershed is different when r.accumulate using flow > direction from r.watershed. Again is there anyway r.watershed supports > using flow direction, so we can get the consistent result. > > We need this when we need to adjust the flow direction from r.watershed > or r.stream.extract. and then we need to determine new flow accumulation > with an adjusted flow direction dataset. If the result is inconsistent, > not sure what is the solution is. > > Cheers > Ming > > ming han <[email protected]> 于2020年11月25日周三 上午6:38写道： > >> Hi Ken >> >> Many thanks for your reply, I think I made a mistake, the flow >> accumulation I provided to r.stream.extract did not match the DEM I >> provided in r.stream.extract. The streamline seems based on flow >> accumulation derived from the provided DEM. >> >> But, If I only want to use flow direction to drive streams, which >> function I should use? >> >> Is there any chance that r.stream.extract can use flow direction as >> inputs without DEM? >> >> Thanks >> Ming >> >> >> Ken Mankoff <[email protected]> 于2020年11月24日周二 上午7:07写道： >> >>> Hi Ming, >>> >>> On 2020-11-23 at 09:05 -08, ming han <[email protected]> wrote... >>> > Hope this email finds you well. I got a weird result when using >>> > r.stream.extract, as shown in the following figure. The back grids is >>> > the flow accumulation layer with a flow accumulation threshold larger >>> > than 1000. while the blue line is the stream generated by >>> > r.stream.extract. Why the stream from r.stream.extract did not follow >>> > flow accumulation results? And how to fix this problem? >>> >>> Is there any chance you can share the raster that includes this region >>> so I can examine it? And the exact command you ran? >>> >>> -k. >>> >>> _______________________________________________ > grass-dev mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/grass-dev > -- Huidae Cho, Ph.D., GISP GRASS GIS Developer https://idea.isnew.info _______________________________________________ grass-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-dev