Yes. This! What you wrote. But the issue is that r.water.outlet make basins based on SFD, right? What if there are 10,000 cells that feed into cell C at x,y, and then cell C feeds 49% (based on MFD) into the basin. These 10,000 cells are not included in the r.water.outlet basin, are they?
-k. Please excuse brevity. Sent from pocket computer with tiny non-haptic feedback keyboard. > On 31 Aug 2017, at 20:51, Micha Silver <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 >>>>> [email protected] >>>>> https://lists.osgeo.org/mailman/listinfo/grass-user >> >> >> >> >> _______________________________________________ >> grass-user mailing list >> [email protected] >> https://lists.osgeo.org/mailman/listinfo/grass-user > > -- > Micha Silver > Ben Gurion Univ. > Sde Boker, Remote Sensing Lab > cell: +972-523-665918
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