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]. The area is measured in the plane of the countour.

       -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

       To see the areas and volumes for all the countours in the previous example, try

       grdvolume peaks.grd -Sk -Vl -C100/300/10 > results.d

SEE ALSO

       gmt(1gmt), grdfilter(1gmt)

REFERENCES

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

                                            1 Jan 2004                               GRDVOLUME(l)