1GRDCLIP(1) Generic Mapping Tools GRDCLIP(1)
2
6 grdclip - Clipping of range in grid files.
7
9 grdclip input_file.grd -Goutput_file.grd [ -Sahigh/above ] [
10 -Sblow/below ] [ -V ]
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13 grdclip will set values < low to below and/or values > high to above.
14 Useful when you want all of a continent or an ocean to fall into one
15 color or grayshade in image processing, or clipping of the range of
16 data values is required. above/below can be any number or NaN (Not a
17 Number). You must choose at least one of -Sa or -Sb.
18 input_file.grd
20 The input 2-D binary grid file.
21 -G output_file.grd is the modified output grid file.
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25 -Sa Set all data[i] > high to above.
26 -Sb Set all data[i] < low to below.
28 -V Selects verbose mode, which will send progress reports to stderr
30 [Default runs "silently"].
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33 By default GMT writes out grid as single precision floats in a COARDS-
34 complaint netCDF file format. However, GMT is able to produce grid
35 files in many other commonly used grid file formats and also facili‐
36 tates so called "packing" of grids, writing out floating point data as
37 2- or 4-byte integers. To specify the precision, scale and offset, the
38 user should add the suffix =id[/scale/offset[/nan]], where id is a two-
39 letter identifier of the grid type and precision, and scale and offset
40 are optional scale factor and offset to be applied to all grid values,
41 and nan is the value used to indicate missing data. When reading
42 grids, the format is generally automatically recognized. If not, the
43 same suffix can be added to input grid file names. See grdreformat(1)
44 and Section 4.17 of the GMT Technical Reference and Cookbook for more
45 information.
46 When reading a netCDF file that contains multiple grids, GMT will read,
48 by default, the first 2-dimensional grid that can find in that file. To
49 coax GMT into reading another multi-dimensional variable in the grid
50 file, append ?varname to the file name, where varname is the name of
51 the variable. Note that you may need to escape the special meaning of ?
52 in your shell program by putting a backslash in front of it, or by
53 placing the filename and suffix between quotes or double quotes. The
54 ?varname suffix can also be used for output grids to specify a variable
55 name different from the default: "z". See grdreformat(1) and Section
56 4.18 of the GMT Technical Reference and Cookbook for more information,
57 particularly on how to read splices of 3-, 4-, or 5-dimensional grids.
58
60 To set all values > 70 to NaN and all values < 0 to 0 in file data.grd:
61 grdclip data.grd -Gnew_data.grd -Sa70/NaN -Sb0/0 -V
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65 GMT(1), grdlandmask(1), grdmask(1), grdmath(1), grd2xyz(1), xyz2grd(1)
66GMT 4.3.1 15 May 2008 GRDCLIP(1)