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)