[GRASS-user] calculate the volume of a DEM with r.volume
marion-brunet at sfr.fr
marion-brunet at sfr.fr
Sun Jul 15 04:52:29 PDT 2018
<span style="font-family:arial,helvetica,sans-serif; font-size:12px">Hi,<br>
<br>
Thank you for the clarification on the clumps, it makes more sense for me now.<br>
<br>
However you said :</span><br>
<br>
"Ideally, the clump option of r.volume should be optional. You could file<br>
an enhancement wish on trac for that.<span style="font-family:arial,helvetica,sans-serif; font-size:12px">"<br>
<br>
But I don't really understand what you mean by "an enhancement wish on trac for that", could you explain it a bit more ?<br>
<br>
I tried doing both r.volume and multiplying the sum by the cell size, and I have approximately the same results, but there a are some little differences. I think it is because, with the second method, I rounded up the results I had, because there were too many digits, so I might I lost some precision in my results.<br>
<br>
Marion</span><br>
<div class="gl_quote" style="margin-top: 20px; padding-top: 5px;">De : "Moritz Lennert"<br>
A : marion-brunet at sfr.fr,"Markus Neteler" ,"grass-user"<br>
Envoyé: vendredi 13 juillet 2018 17:41<br>
Objet : Re: [GRASS-user] calculate the volume of a DEM with r.volume<br>
<div class="gl_quoted">On 13/07/18 09:51, marion-brunet at sfr.fr wrote:<br>
> Hello,<br>
><br>
> I am working on Windows and I tried using GRASS 7.2.2, GRASS 7.4.0 and<br>
> GRASS 7.4.1 to see if there is any difference, but it is always the same.<br>
><br>
> I have a ratser map calleddec-juin<br>
> First I didr.clump input=dec-juin at 1217_Interpo0618 output=test<br>
> to get the clumps<br>
> Then I didr.volume input=dec-juin at 1217_Interpo0618<br>
> clump=test at 1217_Interpo0618<br>
> to have the volume.<br>
<br>
<br>
If dec-juin at 1217_Interpo0618 contains your DEM difference, than you will<br>
have different values for each pixel and clumping the map will results<br>
in almost as many clumps as pixels. The clumps are meant to be used to<br>
delineate specific areas for which you want the volume. If you want the<br>
total volume of the entire computational region, you can just create a<br>
map with r.mapcalc like this:<br>
<br>
r.mapcalc "clump = 1"<br>
<br>
and then run<br>
<br>
r.volume input=dec-juin at 1217_Interpo0618 clump=clump<br>
<br>
which should give you the total volume.<br>
<br>
Ideally, the clump option of r.volume should be optional. You could file<br>
an enhancement wish on trac for that.<br>
<br>
Then again, as Micha has already explained, you can get the same result<br>
simply doing<br>
<br>
r.sum dec-juin at 1217_Interpo0618<br>
<br>
and then multply the result by the area of your pixels (ewres*nsres).<br>
<br>
Moritz<br>
<br>
> The result I have is:<br>
><br>
> (Fri Jul 13 14:12:45 2018)<br>
> r.volume input=dec-juin at 1217_Interpo0618 clump=test at 1217_Interpo0618<br>
> Volume report on data from using clumps on<br>
> raster map<br>
> Category Average Data # Cells Centroid Total<br>
> Number in clump Total in clump Easting Northing Volume<br>
> -----------------------------------------------------------------------------<br>
> 1 -8.02 -72 9 191262.28 1222178.97<br>
> -22.59<br>
> 2 -9.02 -622 69 191265.64 1222177.29<br>
> -194.78<br>
> 3 -8.04 -394 49 191268.44 1222176.73<br>
> -123.30<br>
> 4 -7.08 -276 39 191271.23 1222177.85<br>
> -86.46<br>
> 5 -5.94 -427 72 191274.59 1222176.73<br>
> -133.75<br>
> 6 -4.30 -275 64 191285.22 1222178.97<br>
> -86.09<br>
> 7 -5.10 -2714 532 191288.58 1222174.50<br>
> -849.47<br>
> 8 -0.60 -7 12 191221.43 1222177.29<br>
> -2.27<br>
> 9 -8.95 -1030 115 191230.39 1222176.17<br>
> -322.31<br>
> 10 -10.06 -1217 121 191245.49 1222175.61<br>
> -380.88<br>
> 11 -10.93 -1956 179 191249.97 1222177.29<br>
> -612.34<br>
> 12 -10.24 -645 63 191259.48 1222175.61<br>
> -201.92<br>
> 13 -7.05 -621 88 191329.43 1222177.29<br>
> -194.28<br>
> 14 -7.51 -60 8 191336.14 1222177.29<br>
> -18.81<br>
> 15 -7.47 -30 4 191337.26 1222177.29<br>
> -9.35<br>
> 16 -8.04 -322 40 191340.06 1222177.29<br>
> -100.63<br>
> 17 -8.99 -108 12 191343.98 1222177.29<br>
> -33.78<br>
> 18 4.98 45 9 191182.26 1222175.05<br>
> 14.03<br>
> etc<br>
> etc<br>
> 24458 -5.50 -22 4 191397.13 1221585.50<br>
> -6.88<br>
> 24459 -5.51 -33 6 191378.11 1221584.39<br>
> -10.34<br>
> 24460 -5.52 -11 2 191380.91 1221584.39<br>
> -3.45<br>
> 24461 -5.27 -30348 5764 191309.84 1221601.17<br>
> -9498.51<br>
> 24462 -5.49 -38 7 191358.53 1221582.15<br>
> -12.02<br>
> 24463 -5.49 -22 4 191363.56 1221583.83<br>
> -6.87<br>
> 24464 -5.48 -11 2 191385.38 1221583.83<br>
> -3.43<br>
> 24465 -5.49 -11 2 191387.06 1221583.83<br>
> -3.44<br>
> 24466 -5.50 -11 2 191388.74 1221583.83<br>
> -3.44<br>
> 24467 -5.50 -22 4 191360.20 1221582.71<br>
> -6.88<br>
> 24468 -5.92 -523187 88358 191241.58 1221675.00<br>
> -163750.63<br>
> (Fri Jul 13 14:13:03 2018) La commande s'est terminée (18 sec)<br>
><br>
> As you can see, I have nothing at the end of the command... But I know<br>
> it is finished, because when I created the clumps it said that it<br>
> created 24468 clumps.<br>
> Do you need any more information?<br>
><br>
><br>
> Thank you very much<br>
> De : "Markus Neteler"<br>
> A : marion-brunet at sfr.fr,"grass-user"<br>
> Envoyé: jeudi 12 juillet 2018 16:43<br>
> Objet : Re: [GRASS-user] calculate the volume of a DEM with r.volume<br>
> Hello Marion,<br>
><br>
> On Wed, Jul 11, 2018 at 10:32 AM, > > wrote:<br>
> > Hello,<br>
> ><br>
> > I tried using r.volume as you suggested. According to the<br>
> documentation it<br>
> > is suitable for what I am trying to do.<br>
> ><br>
> > However, when I use it, I don't have the "Total volume" line at the<br>
> end of<br>
> > the report, like it is shown in the documentation. I just have the total<br>
> > volume of each clump, but not of all the clumps... Has it ever<br>
> happened to<br>
> > you when using this command?<br>
><br>
> That's weird! Which version/operating system do you use?<br>
><br>
> > in the command line<br>
> ><br>
> > I simply wroter.volume input=difference clump=clump in the command line<br>
><br>
><br>
> Here on command line:<br>
><br>
> GRASS 7.4.1svn (nc_spm_08_grass7):~ > g.region raster=elevation<br>
> GRASS 7.4.1svn (nc_spm_08_grass7):~ > r.volume input=elevation<br>
> clump=geology_30m<br>
> 100%<br>
><br>
> Volume report on data from using clumps on<br>
> raster map<br>
><br>
> Category Average Data # Cells Centroid Total<br>
> Number in clump Total in clump Easting Northing Volume<br>
> -----------------------------------------------------------------------------<br>
> 217 118.93 86288828 725562 635325.00 221535.00<br>
> 8628882798.63<br>
> 262 108.97 21650560 198684 638935.00 222495.00<br>
> 2165056037.02<br>
> 270 92.23 63578874 689373 642405.00 221485.00<br>
> 6357887443.53<br>
> 405 132.96 33732662 253710 631835.00 224095.00<br>
> 3373266208.59<br>
> 583 139.35 3011288 21609 630205.00 224665.00<br>
> 301128821.55<br>
> 720 124.30 599618 4824 634075.00 227995.00<br>
> 59961816.06<br>
> 766 132.43 936791 7074 631425.00 227845.00<br>
> 93679120.08<br>
> 862 118.31 7302317 61722 630505.00 218885.00<br>
> 730231746.74<br>
> 910 94.20 4235816 44964 639215.00 216365.00<br>
> 423581613.11<br>
> 921 135.22 1693985 12528 630755.00 215445.00<br>
> 169398523.05<br>
> 945 127.24 1145 9 630015.00 215015.00<br>
> 114512.03<br>
> 946 89.91 365748 4068 639085.00 215255.00<br>
> 36574833.85<br>
> 948 129.02 112632 873 630185.00 215115.00<br>
> 11263181.57<br>
> -----------------------------------------------------------------------------<br>
> Total Volume =<br>
> 22351026655.81<br>
> ... which looks ok.<br>
> Can you say a bit more about your system?<br>
> Markus<br>
><br>
><br>
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><br>
</div>
<div class="gl_quoted"> </div>
</div>
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