1MDG77TOGMT(1) Generic Mapping Tools MDG77TOGMT(1)
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6 mgd77togmt - Convert an MGD-77 ASCII file to a binary gmt file
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9 mgd77togmt [ -Llist ] [ mgd77file ] -Flegid -Ystart_year [ -Ainforma‐
10 tion ] [ -Itime_increment ] [-T[<offset>]] [-W[<cable_length>]] [ -V ]
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13 mgd77togmt reads an ASCII MGD-77 format file [or standard input] and
14 creates a binary gmt file. The 16 header records specified in the
15 MGD-77 documentation may or may not be present. If two-way travel
16 times are available, mgd77togmt will convert those to corrected depths
17 using the Carter tables. Both old and new (Y2K-compliant) MGD-77 files
18 are supported.
19 -L Name of file with several records of the format mgd77file legid
21 start_year. For multiple files, use this option rather than the
22 -F -Y combination.
23 -Y The year of the first data point in the file. If not provided
25 and -L option not used, it tries to get it from a header file.
26 The header file must be in the same directory of the main file
27 and must have a name equal to the main but with a .h77 exten‐
28 sion.
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31 No space between the option flag and the associated arguments.
32 -A Set an optional 10 character information string to be stored in
34 the header [Default is blank].
35 -F Leg id that will be used in file name (legid.gmt). If not given,
37 it will be constructed from the mgd77file name plus the .gmt
38 extension.
39 -I Used for files where time is missing. The increment is used to
41 calculate fake times.
42 -T Extracts Total field instead of anomaly. Since F does not hold
44 in a 2 byte signed variable we subtract a constant [default =
45 40000] but you can provide another value in <offset>.
46 -W Take into account that the magnetometer is not at ship's posi‐
48 tion. <cable> is magnetometer tow distance [default = 200
49 meters]. If -W only is given (e.g. no <cable>) and like with
50 the -Y option, we try to get the tow distance from the header
51 file. Failing, defaults to 200 meters. Note that this option
52 will throw away the first points whose accumulated. distance
53 since the start of magnetic acquisition is less than cable.
54 length, and likewise for the end of the mag profile.
55 -V Selects verbose mode, which will send progress reports to stderr
57 [Default runs "silently"].
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60 To create a gmt file from the ASCII file c2104.mgd77, run
61 mgd77togmt c2104.mgd77 -Y1977
63 To create new gmt files from all the mgd77 files listed in list.d:
65 mgd77togmt -Llist.d -V
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69 dat2gmt(1), GMT(1)
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72 Wessel, P., and W. H. F. Smith, 2009, The Generic Mapping Tools (GMT)
73 version 4.5.0 Technical Reference & Cookbook, SOEST/NOAA.
74 Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic
75 Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579.
76 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
77 ping Tools Released, EOS Trans., AGU, 76 (33), p. 329.
78 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
79 ping Tools Released, http://www.agu.org/eos_elec/95154e.html, Copyright
80 1995 by the American Geophysical Union.
81 Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Dis‐
82 play Data, EOS Trans., AGU, 72 (41), p. 441.
83 MGD77 Task Group, 1977, The Marine Geophysical Data Exchange Format -
85 MGD77, Key to Geophysical Records documentation No. 10, National Geo‐
86 physical and Solar-Terrestrial Data Center, Boulder, CO.
87 Carter, D. J. T., Echo Sounding Correction Tables: Formerly Matthews'
89 Tables, 150 pp, Hydrographic Department, Ministry of Defense, Taunton,
90 Somerset, England, 1980.
91GMT 4.5.6 10 Mar 2011 MDG77TOGMT(1)