```

```

## 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) and reports the area, volume, and maximum mean
height (volume/area).  Alternatively, specify a range of contours to be
tried  and grdvolume will determine the volume and area inside the con-
tour for all contour values. The contour that produced the maximum mean
height  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     xmin, xmax, ymin, and ymax specify the Region of  interest.  For
geographic  regions,  these  limits  correspond  to  west, east,
south, and north and you may specify them in decimal degrees  or
in  [+-]dd:mm[:ss.xxx][W|E|S|N]  format.  Append r if lower left
and upper right map coordinates are given instead of  wesn.  The
two  shorthands  -Rg  -Rd  stand  for  global  domain  (0/360 or
-180/+180 in longitude respectively, with -90/+90 in  latitude).
For  calendar time coordinates you may either give relative time
(relative  to  the  selected  TIME_EPOCH  and  in  the  selected
TIME_UNIT;  append  t  to  -JX|x),  or absolute time of the form
[date]T[clock] (append T to -JX|x). At least  one  of  date  and
clock must be present; the T is always required. The date string
must be of the form [-]yyyy[-mm[-dd]]  (Gregorian  calendar)  or
yyyy[-Www[-d]]  (ISO week calendar), while the clock string must
be of the form hh:mm:ss[.xxx]. The use of delimiters  and  their
type  and  positions must be as indicated (however, input/output
and plotting formats are flexible).

-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), use

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 contours in the previous exam-
ple, use

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

```

```       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.

GMT4.0                            1 Oct 2004                      GRDVOLUME(l)
```

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