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       r.volume  - Calculates the volume of data "clumps".
       Optionally produces a GRASS vector points map containing the calculated centroids of these


       raster, volume, clumps


       r.volume --help
       r.volume [-f] input=name  [clump=name]   [centroids=name]   [output=name]    [--overwrite]
       [--help]  [--verbose]  [--quiet]  [--ui]

           Generate unformatted report (items separated by colon)

           Allow output files to overwrite existing files

           Print usage summary

           Verbose module output

           Quiet module output

           Force launching GUI dialog

       input=name [required]
           Name of input raster map representing data that will be summed within clumps

           Name of input clump raster map
           Preferably the output of r.clump. If no clump map is given than MASK is used.

           Name for output vector points map to contain clump centroids

           Name for output file to hold the report
           If no output file given report is printed to standard output


       r.volume  is  a  tool  for  summing  cell values within clumps and calculating volumes and
       centroids of patches or clumps.

       r.volume generates a table containing the sum of all cells from a input raster map  sorted
       by  category  on  a  clump raster map, and optionally generates a vector points map of the
       centroids for each clump.  If a clump map is not specified, the current MASK is used.  The
       MASK  can  be  defined  by r.mask. The sum is multiplied by the area of a cell to give the
       volume occupied by that cell. See below for an example of the output table.


       If a clump map is not given and a MASK not set, the program exits with an error message.

       r.volume works in the current region and respects the current MASK.

       The centroid coordinates are the same as those stored  in  the  vector  map  (if  one  was
       requested  by  centroids  parameter).  They  are  guaranteed  to  fall  on  a  cell of the
       appropriate category, thus they are not always the true, mathematical centroid. They  will
       always fall at a cell center.

       Attribute table linked to the vector map with centroids contains several columns:

           ·   cat - category value (integer)

           ·   volume - volume value (double precision)

           ·   average - average value in the clump (double precision)

           ·   sum - sum of cell values in the clump (double precision)

           ·   count - number of cells with the category (integer)

       Vector  points  can  be  converted  directly  to  a  raster map with each point a separate
       category using

       By preprocessing the elevation raster map with r.mapcalc and  using  suitable  masking  or
       clump maps, very interesting applications can be done with r.volume.  Such as, calculating
       the volume of rock in a potential quarry; calculating cut/fill volumes for roads;  finding
       water volumes in potential reservoirs.


       The following report was generated by the command (North Carolina dataset):
       # set computational region
       g.region raster=elevation
       # compute volume
       r.volume input=elevation clump=geology_30m
       Volume report on data from <elevation> using clumps on <geology_30m> raster map
       Category   Average   Data   # Cells        Centroid             Total
       Number     in clump  Total  in clump   Easting     Northing     Volume
            217    118.93  86288828  725562   635325.00   221535.00    8628882798.63
            262    108.97  21650560  198684   638935.00   222495.00    2165056037.02
            270     92.23  63578874  689373   642405.00   221485.00    6357887443.53
            405    132.96  33732662  253710   631835.00   224095.00    3373266208.59
            583    139.35   3011288   21609   630205.00   224665.00     301128821.55
            720    124.30    599618    4824   634075.00   227995.00      59961816.06
            766    132.43    936791    7074   631425.00   227845.00      93679120.08
            862    118.31   7302317   61722   630505.00   218885.00     730231746.74
            910     94.20   4235816   44964   639215.00   216365.00     423581613.11
            921    135.22   1693985   12528   630755.00   215445.00     169398523.05
            945    127.24      1145       9   630015.00   215015.00        114512.03
            946     89.91    365748    4068   639085.00   215255.00      36574833.85
            948    129.02    112632     873   630185.00   215115.00      11263181.57
                                                       Total Volume = 22351026655.81
       The  Data  Total  column is the sum of the elevations for each in each of the fields.  The
       Total Volume is the sum multiplied by  the  east-west  resolution  times  the  north-south
       resolution. Note that the units on the volume may be difficult if the units of cell values
       on the input raster map and the resolution units differ.


        r.clump, r.mask, r.mapcalc


       Dr. James Hinthorne, Central Washington University GIS Laboratory, December 1988.
       Updated to GRASS 7 by Martin Landa, Czech Technical University in Prague, Czech Republic

       Last changed: $Date: 2014-12-19 22:17:36 +0100 (Fri, 19 Dec 2014) $


       Available at: r.volume source code (history)

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