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 con-
       tained 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  Carte-
              sian].

       -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(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.



GMT3.4.6                          1 Jan 2005                      GRDVOLUME(l)

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