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 speci­
       fied by the given contour (or zero if not given).   Alter­
       natively, specify a range of contours to be tried and grd­
       volume will determine the volume and area inside the  con­
       tour 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.
              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 con­
              tour 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 min­
              utes  [and  seconds],  use  the  dd:mm[:ss] format.
              Append r if lower left and upper right map  coordi­
              nates 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(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.



                            1 Mar 2002               GRDVOLUME(l)

Man(1) output converted with man2html