1GRDVOLUME(1) GMT GRDVOLUME(1)
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6 grdvolume - Calculate grid volume and area constrained by a contour
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9 grdvolume grdfile [ -Ccval or -Clow/high/delta or -Crlow/high or
10 -Crcval] [ -Lbase ] [ -Rregion ] [ -S[unit] ] [ -T[c|h] ] [
11 -V[level] ] [ -Zfact[/shift] ] [ -fflags ] [ -oflags ]
12 Note: No space is allowed between the option flag and the associated
14 arguments.
15
17 grdvolume reads a 2-D grid file and calculates the volume contained
18 between the surface and the plane specified by the given contour (or
19 zero if not given) and reports the area, volume, and maximum mean
20 height (volume/area). Alternatively, specify a range of contours to be
21 tried and grdvolume will determine the volume and area inside the con‐
22 tour for all contour values. Using -T, the contour that produced the
23 maximum mean height (or maximum curvature of heights vs contour value)
24 is reported as well. This feature may be used with grdfilter in design‐
25 ing an Optimal Robust Separator [Wessel, 1998].
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28 grdfile
29 The name of the input 2-D binary grid file. (See GRID FILE FOR‐
30 MAT below.)
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33 -Ccval or -Clow/high/delta or -Crlow/high or -Crcval
34 find area, volume and mean height (volume/area) inside the cval
35 contour. Alternatively, search using all contours from low to
36 high in steps of delta. [Default returns area, volume and mean
37 height of the entire grid]. The area is measured in the plane of
38 the contour. The Cr form on the other hand computes the volume
39 between the grid surface and the plans defined by low and high,
40 or below cval and grid's minimum. Note that this is an outside
41 volume whilst the other forms compute an inside (below the sur‐
42 face) area volume. Use this form to compute for example the vol‐
43 ume of water between two contours.
44 -Lbase Also add in the volume from the level of the contour down to
46 base [Default base is contour].
47 -S[unit]
49 For geographical grids, append a unit from e|f|k|M|n|u [Default
50 is meter (e)].
51 -T[c|h]
53 Determine the single contour that maximized the average height
54 (= volume/area). Select -Tc to use the maximum curvature of
55 heights versus contour value rather than the contour with the
56 maximum height to pick the best contour value (requires -C).
57 -Rxmin/xmax/ymin/ymax[+r][+uunit] (more ...)
59 Specify the region of interest.
60 -V[level] (more ...)
62 Select verbosity level [c].
63 -Zfact[/shift]
65 Optionally subtract shift before scaling data by fact. [Default
66 is no scaling]. (Numbers in -C, -L refer to values after this
67 scaling has occurred).
68 -f[i|o]colinfo (more ...)
70 Specify data types of input and/or output columns.
71 -ocols[,...] (more ...)
73 Select output columns (0 is first column).
74 -^ or just -
76 Print a short message about the syntax of the command, then
77 exits (NOTE: on Windows just use -).
78 -+ or just +
80 Print an extensive usage (help) message, including the explana‐
81 tion of any module-specific option (but not the GMT common
82 options), then exits.
83 -? or no arguments
85 Print a complete usage (help) message, including the explanation
86 of all options, then exits.
87
89 By default GMT writes out grid as single precision floats in a
90 COARDS-complaint netCDF file format. However, GMT is able to produce
91 grid files in many other commonly used grid file formats and also
92 facilitates so called "packing" of grids, writing out floating point
93 data as 1- or 2-byte integers. (more ...)
94
96 To determine the volume in km^3 under the surface hawaii_topo.nc
97 (height in km), use
98 gmt grdvolume hawaii_topo.nc -Sk
100 To find the volume between the surface peaks.nc and the contour z = 250
102 m in meters, use
103 gmt grdvolume peaks.nc -Se -C250
105 To search for the contour, between 100 and 300 in steps of 10, that
107 maximizes the ratio of volume to surface area for the file peaks.nc,
108 use
109 gmt grdvolume peaks.nc -C0/300/10 -Th > results.d
111 To see the areas and volumes for all the contours in the previous exam‐
113 ple, use
114 gmt grdvolume peaks.nc -C100/300/10 > results.d
116 To find the volume of water in a lake with its free surface at 0 and
118 max depth of 300 meters, use
119 gmt grdvolume lake.nc -Cr-300/0
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123 1. For geographical grids we convert degrees to "Flat Earth" distances
124 in meter. You can use -S to select another distance unit. The area
125 is then reported in this unit squared while the volume is reported
126 in unit^2 * z_unit quantities.
127 2. grdvolume distinguishes between gridline and pixel-registered grids.
129 In both cases the area and volume are computed up to the grid bound‐
130 aries. That means that in the first case the grid cells on the
131 boundary only contribute half their area (and volume), whereas in
132 the second case all grid cells are fully used. The exception is when
133 the -C flag is used: since contours do not extend beyond the outer‐
134 most grid point, both grid types are treated the same. That means
135 the outer rim in pixel oriented grids is ignored when using the -C
136 flag.
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139 gmt, grdfilter, grdmask, grdmath
140
142 Wessel, P., 1998, An empirical method for optimal robust
143 regional-residual separation of geophysical data, Math. Geol., 30(4),
144 391-408.
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147 2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
1485.4.5 Feb 24, 2019 GRDVOLUME(1)