NAME
grdvolume - Calculating volume under a surface within a con-
tour
SYNOPSIS
grdvolume grdfile [ -Ccval or -Clow/high/delta ] [ -Lbase ]
[ -Rwest/east/south/north[r] ] [ -S[k] ] [ -T ] [ -V[l] ] [
-Zfact[/delta] ]
DESCRIPTION
grdvolume reads a 2-D binary grd file and calculates the
volume contained between the surface and the plane specified
by the given contour (or zero if not given). Alternatively,
specify a range of contours to be tried and grdvolume will
determine the volume and area inside the contour for all
contour values. The contour that produced the maximum mean
height (volume/area) is reported as well. This feature may
be used with grdfilter in designing an Optimal Robust
Separator [Wessel, 1998].
grdfile
The name of the input 2-D binary grd file.
OPTIONS
No space between the option flag and the associated argu-
ments.
-C find area and volume inside the cval contour. Alterna-
tively, search using all contours from low to high in
steps of delta. [Default returns entire area and
volume of grid].
-L Also add in the volume from the level of the contour
down to base [Default base is contour].
-S Convert degrees to meters, append k for km [Default is
Cartesian].
-T Use curvature minimum rather than maximum height to
find best contour value (when contour search is
selected with -C).
-R west, east, south, and north specify the Region of
interest. To specify boundaries in degrees and minutes
[and seconds], use the dd:mm[:ss] format. Append r if
lower left and upper right map coordinates are given
instead of wesn.
-V Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"]. Append l to see
all the results for each contour level tested (when
contour search has been selected).
-Z Optionally subtract shift before scaling data by fact.
[Default is no scaling]. (Numbers in -C, -L refer to
values after this scaling has occurred).
EXAMPLES
To determine the volume in km^3 under the surface
hawaii_topo.grd (height in km), try
grdvolume hawaii_topo.grd -Sk
To find the volume between the surface peaks.grd and the
contour z = 250, use
grdvolume peaks.grd -Sk -C250
To search for the contour, between 100 and 300 in steps of
10, that maximizes the ratio of volume to surface area for
the file peaks.grd, use
grdvolume peaks.grd -Sk -C100/300/10 > results.d
SEE ALSO
gmt(l), grdfilter(l)
REFERENCES
Wessel, P., 1998, An empirical method for optimal robust
regional-residual separation of geophysical data, Math.
Geol., 30(4), 391-408.