r.volumegrass - Online in the Cloud

PROGRAM:

NAME

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

KEYWORDS

raster, volume, clumps

SYNOPSIS

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

Flags:
-f
Generate unformatted report (items separated by colon)

--overwrite
Allow output files to overwrite existing files

--help
Print usage summary

--verbose
Verbose module output

--quiet
Quiet module output

--ui
Force launching GUI dialog

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

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

centroids=name
Name for output vector points map to contain clump centroids

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

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 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.

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.

CENTROIDS
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 v.to.rast.

APPLICATIONS
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.

EXAMPLE

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.

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