Micha, I was thinking the same... but the ultimate result wanted is still unclear; hope you are well!
Tom On Thu, Aug 31, 2017 at 2:51 PM Micha Silver <tsvi...@gmail.com> wrote: > I'm also not clear what you are asking. But risking a guess: > You could run r.water.outlet *1 time* to get the basin. Then use that > raster as a MASK, so that the next process will address only the pixels > within the basin. Now do a loop with r.univar on all 14,000 flow rasters, > and you'll get 14,000 results with total, min, max, mean, etc of the basin > pixels for each of the flow rasters. > > -- > Micha > > > On 08/31/2017 09:30 PM, Thomas Adams wrote: > > Ken, > > You "want 14,000 values" of what?? Your original email stated you were > "trying to determine flow past a drainage basin outlet" -- r.watershed does > NOT do this, if indeed this is what you want. And you say you have "14,000 > flow rasters to be used as input" -- what exactly are these 'flow rasters'; > what is your goal? I may not understand... > > Tom > > On Thu, Aug 31, 2017 at 2:24 PM, Ken Mankoff <mank...@gmail.com> wrote: > >> Hi Tom, >> >> I have 1 DEM and 14,000 flow rasters to be used as input. I want 14,000 >> values, one at a specific coordinate from each acc output. >> >> I can do this by running r.watershed 14,000 times. That is slow, unless >> I'm missing something (e.g. It works with I.group variables or Time Series >> data more efficiently). >> >> An alternative approach is possible if I knew the complete drainage basin >> *and* the fractional value of each cell that contributed to the basin. In >> this case I don't need to route. But basins from r.watershed or >> r.water.outlet, I think, use SFD not MFD (no cell is ever in 2 basins, are >> they?), and I don't know how to get the fractional contribution from each >> cell. >> >> -k. >> >> Please excuse brevity. Sent from pocket computer with tiny non-haptic >> feedback keyboard. >> >> On 31 Aug 2017, at 19:59, Thomas Adams <tea...@gmail.com> wrote: >> >> Ken, >> >> I'm confused about what you are trying to do with r.watershed, because >> the output from the module is: >> >> accumulation=name >> Name for output accumulation raster map >> Number of cells that drain through each cell >> tci=name >> Name for output topographic index ln(a / tan(b)) map >> spi=name >> Stream power index a * tan(b) >> Name for output raster map >> drainage=name >> Name for output drainage direction raster map >> basin=name >> Name for output basins raster map >> stream=name >> Name for output stream segments raster map >> half_basin=name >> Name for output half basins raster map >> Each half-basin is given a unique value >> length_slope=name >> Name for output slope length raster map >> Slope length and steepness (LS) factor for USLE >> slope_steepness=name >> Name for output slope steepness raster map >> Slope steepness (S) factor for USLE >> >> I think you want a hydrologic model, and r.watershed is NOT that. What >> are you trying to obtain? >> >> Tom >> >> >> >> >> On Thu, Aug 31, 2017 at 1:47 PM, Ken Mankoff <mank...@gmail.com> wrote: >> >>> Hi List, >>> >>> I'm trying to determine flow past a drainage basin outlet. The >>> complicating factor is that I need to do this each day for 40 years. If I >>> do "r.watershed" ~14,000 times I'll get the results, but it will take 3 >>> days. It seems that r.watershed is likely calculating many things each time >>> through the loop. Is there a more efficient way to this? A flag to >>> r.watershed that isn't documented? Something with time-series? >>> >>> Alternatively, because I only need the flow at the outlet, I could >>> calculate the basin, not route the flow, and instead sum the values in the >>> basin. I assume this would take seconds or minutes rather than days. In >>> this case I'm not sure of the best way to define the basin. I tried doing >>> r.water.outlet upstream from the outlet, but I think this uses SFD, which >>> means the basin may be significantly underestimated. >>> >>> I also tried inverting/flipping the DEM and then running r.watershed >>> with convergence=1, and a flow equal to 0 everywhere except 1000 at the >>> outlet (now the source due to the inversion) to see where it flooded >>> upstream (now downstream due to the inversion). This didn't seem to work... >>> because basins are filled and flow routes to the edge of the DEM, I could >>> not pick out the >>> >>> Any advice how to either a) efficiently route 14,000 FLOW rasters over 1 >>> DEM or b) determine the full basin will be much appreciated. >>> >>> Thanks, >>> >>> -k. >>> >>> _______________________________________________ >>> grass-user mailing list >>> grass-user@lists.osgeo.org >>> https://lists.osgeo.org/mailman/listinfo/grass-user >>> >> >> >> >> > > > > _______________________________________________ > grass-user mailing > listgrass-user@lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/grass-user > > > -- > Micha Silver > Ben Gurion Univ. > Sde Boker, Remote Sensing Lab > cell: +972-523-665918 > > -- Sent from Gmail Mobile
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