1MGD77CONVERT(1) Generic Mapping Tools MGD77CONVERT(1)
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6 mgd77convert - Translate between different formats of MGD77 files
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9 mgd77convert NGDC-ids -Fa|b|t -T[+]a|b|t [ -L[w][e][+] ] [ -V ] [ -4 ]
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12 mgd77convert reads versions of MGD77 files and writes the same data in
13 (probably) another format to a new file in the current directory.
14 NGDC-ids
16 Can be one or more of five kinds of specifiers:
17 1) 8-character NGDC IDs, e.g., 01010083, JA010010etc., etc.
18 2) 2-character <agency> codes which will return all cruises from
19 each agency.
20 3) 4-character <agency><vessel> codes, which will return all
21 cruises from those vessels.
22 4) =<list>, where <list> is a table with NGDC IDs, one per line.
23 5) If nothing is specified we return all cruises in the data
24 base.
25 (See mgd77info -F for agency and vessel codes). The ".mgd77" or
26 ".nc" extensions will automatically be appended, if needed (use
27 -I to ignore certain file types). Cruise files will be looked
28 for first in the current directory and second in all directories
29 listed in $MGD77_HOME/mgd77_paths.txt [If $MGD77_HOME is not set
30 it will default to $GMT_SHAREDIR/mgd77].
31 -F Specifies the format of the input (From) files. Choose from a
33 for standard MGD77 ASCII table (with extension .mgd77), b for
34 the new MGD77+ netCDF format (with extension .nc), and t for a
35 plain ASCII tab-separated table dump (with extension .dat). Use
36 -FC to recover the original MGD77 setting from the MGD77+ file
37 [Default will apply any E77 corrections encoded in the file].
38 -T Specifies the format of the output (To) files. Choose from a
40 for standard MGD77 ASCII table (with extension .mgd77), c for
41 the new MGD77+ netCDF format (with extension .nc), and t for a
42 plain ASCII tab-separated table dump (with extension .dat). We
43 will refuse to create the file(s) if they already exist in the
44 current directory. Prepend + to override this policy.
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47 No space between the option flag and the associated arguments.
48 -L Set the level of verification reporting [none] and where to send
50 such reports [stderr]. Append a combination of w for warnings,
51 e for errors, and + to send such log information to stdout.
52 -V Selects verbose mode, which will send progress reports to stderr
54 [Default runs "silently"].
55 -4 By default, the storage types used in a MGD77+ netCDF file
57 greatly exceed the precision imposed by the ASCII MGD77 format.
58 However, for the five items faa, eot, mag, diur and msd we use
59 2-byte integers with implied precisions of 0.1 mGal, 0.1 nTesla,
60 and 1 m as in the MGD77 format. It is possible that at some
61 point these items will need to be stored as 4-byte ints which
62 would allow precisions of 1 fTesla, 1 nGal, and 0.01 mm, respec‐
63 tively. This option activates such storage [Default uses 2-byte
64 integers].
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67 To convert 01010047.mgd77 and 01010008.mgd77 to new netCDF .nc files,
68 and capture all verification messages, try
69 mgd77convert 01010047 01010008 -Fa -Tc -V -Lew+ > log.lis
71 To convert 01010047.nc back to MGD77 ASCII and make sure it is identi‐
73 cal to the original file, try (Bourne shell syntax)
74 orig=`mgd77path 01010047 -Ic`
76 mgd77convert 01010047 -Fc -Ta -V
77 diff $orig 01010047.mgd77
78 To convert 01010047.nc to a plain ASCII table for manual editing, over‐
80 writing any existing table, try
81 mgd77convert 01010047 -Fc -T+t -V
83 To recover the original NGDC MGD77 version of 01020051.nc and ignore
85 any E77 corrections, use
86 mgd77convert 01020051 -FC -Ta -V
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89 mgd77convert handles three different formats. (1) The MGD77 ASCII
90 tables are the established standard for distribution of underway geo‐
91 physical data to and from the NGDC data center. Normally, only the
92 ship-operations people and the cruise PI might be involved in making an
93 MGD77 ASCII file for transmission to NGDC; users are more interested in
94 reading such files. (2) The MGD77+ netCDF format was developed to fas‐
95 cilitate the use of MGD77 data by scientists. It contains all the
96 information of the original MGD77 file and if you convert back and
97 forth you end up with the original. However, file sizes are typically
98 ~30% of the original ASCII format and is much faster to operate on. (3)
99 The plain ASCII tab-separated dump is available for users who need to
100 manually edit the content of a MGD77 file. This is usually easier to
101 do when the columns are tab-separated than when they are all crunched
102 together in the MGD77 punch-card format.
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105 The MGD77+ netCDF files are CF-1.0 and COARDS compliant and can be
106 examined with general-purpose tools such as ncBrowse and ncView.
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109 mgd77manage(1), mgd77list(1), mgd77sample(1), mgd77track(1)
110 x2sys_init(1)
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113 Wessel, P., and W. H. F. Smith, 2005, The Generic Mapping Tools (GMT)
114 version 4.1 Technical Reference & Cookbook, SOEST/NOAA.
115 Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic
116 Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579.
117 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
118 ping Tools Released, EOS Trans., AGU, 76 (33), p. 329.
119 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
120 ping Tools Released, http://www.agu.org/eos_elec/95154e.html, Copyright
121 1995 by the American Geophysical Union.
122 Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Dis‐
123 play Data, EOS Trans., AGU, 72 (41), p. 441.
124 ncBrowse, see http://www.epic.noaa.gov/java/ncBrowse/
125 ncView, see http://meteora.ucsd.edu/~pierce/ncview_home_page.html
126 The Marine Geophysical Data Exchange Format - "MGD77", see
127 http://www.ngdc.noaa.gov/mgg/dat/geodas/docs/mgd77.txt
128GMT 4.3.1 15 May 2008 MGD77CONVERT(1)