NAME

       r.volume   -  Calculates the volume of data "clumps", and (optionally) produces a GRASS vector points map
       containing the calculated centroids of these clumps.

KEYWORDS

       raster, volume

SYNOPSIS

       r.volume
       r.volume help
       r.volume [-f] data=string  [clump=string]   [centroids=string]   [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -f
           Generate unformatted report

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       data=string
           Existing raster map representing data that will be summed within clumps

       clump=string
           Existing raster map, preferably the output of r.clump

       centroids=string
           Vector points map to contain clump centroids

DESCRIPTION

       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 data_map layer sorted by category on  a
       clump  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 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.

NOTES

       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.

EXAMPLE

       The  following report was generated by the command: (spearfish data base; fields.only is the fields layer
       without the National Forest category)

       r.volume data=elevation clump=fields.only centroids=field.centers

       Volume report on data from elevation using clumps on fields.only map
        Cat    Average   Data   # Cells        Centroid             Total
       Number  in clump  Total  in clump   Easting   Northing       Volume
           1   1181.09   75590      64   595500.00  4927700.00   755900000.00
           2   1163.50   69810      60   597100.00  4927700.00   698100000.00
           3   1146.83   34405      30   598300.00  4927700.00   344050000.00
           4   1193.20  366311     307   599400.00  4927300.00  3663110000.00
               .....
               .....
               .....
          60   1260.08  351563     279   603100.00  4921000.00  3515630000.00
          61   1213.93   35204      29   603700.00  4921500.00   352040000.00
          62   1207.71   33816      28   604100.00  4921500.00   338160000.00
                                                Total Volume = 67226740000.00
        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 e-w resolution times the n-s resolution.  Note that the units on the volume may
       be difficult if the units of cell values on the data_map layer and the resolution units differ.

   CENTROIDS
       The centroid coordinates are the same as those stored in the sites file (if one was requested).  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.

   FORMAT OF CENTROIDS table
       For  each  line  of  above  table the vector points table contains these columns: easting, northing, cat,
       volume, average, sum, count

       This can be converted directly to a raster map with each point a separate category using v.to.rast.

   APPLICATIONS
       By preprocessing the elevation layer 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.
       Data layers of other measures of real values.

AUTHOR

       Dr. James Hinthorne, Central Washington University GIS Laboratory
       December 1988.

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                     r.volume(1grass)