## NAME

          grdvolume - Calculating volume under a surface within a contour

## 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 arguments.

          -C   find area and volume inside the cval contour.  Alternatively,
               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, grdfilter

## REFERENCES

          Wessel, P., 1998, An empirical method for optimal robust regional-
          residual separation of geophysical data, Math. Geol., 30(4), 391-408.