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|c|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. Both
14 pre- and post-Y2K MGD77 formats can be processed.
15 NGDC-ids
17 Can be one or more of five kinds of specifiers:
18 1) 8-character NGDC IDs, e.g., 01010083, JA010010etc., etc.
19 2) 2-character <agency> codes which will return all cruises from
20 each agency.
21 3) 4-character <agency><vessel> codes, which will return all
22 cruises from those vessels.
23 4) =<list>, where <list> is a table with NGDC IDs, one per line.
24 5) If nothing is specified we return all cruises in the data
25 base.
26 (See mgd77info -L for agency and vessel codes). The ".mgd77" or
27 ".nc" extensions will automatically be appended, if needed (use
28 -I to ignore certain file types). Cruise files will be looked
29 for first in the current directory and second in all directories
30 listed in $MGD77_HOME/mgd77_paths.txt [If $MGD77_HOME is not set
31 it will default to $GMT_SHAREDIR/mgd77].
32 -F Specifies the format of the input (From) files. Choose from a
34 for standard MGD77 ASCII table (with extension .mgd77), c for
35 the new MGD77+ netCDF format (with extension .nc), and t for a
36 plain ASCII tab-separated table dump (with extension .dat). Use
37 -FC to recover the original MGD77 setting from the MGD77+ file
38 [Default will apply any E77 corrections encoded in the file].
39 -T Specifies the format of the output (To) files. Choose from a
41 for standard MGD77 ASCII table (with extension .mgd77), c for
42 the new MGD77+ netCDF format (with extension .nc), and t for a
43 plain ASCII tab-separated table dump (with extension .dat). We
44 will refuse to create the file(s) if they already exist in the
45 current directory. Prepend + to override this policy.
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48 No space between the option flag and the associated arguments.
49 -L Set the level of verification reporting [none] and where to send
51 such reports [stderr]. Append a combination of w for warnings,
52 e for errors, and + to send such log information to stdout.
53 -V Selects verbose mode, which will send progress reports to stderr
55 [Default runs "silently"].
56 -4 By default, the storage types used in a MGD77+ netCDF file
58 greatly exceed the precision imposed by the ASCII MGD77 format.
59 However, for the five items faa, eot, mag, diur and msd we use
60 2-byte integers with implied precisions of 0.1 mGal, 0.1 nTesla,
61 and 1 m as in the MGD77 format. It is possible that at some
62 point these items will need to be stored as 4-byte ints which
63 would allow precisions of 1 fTesla, 1 nGal, and 0.01 mm, respec‐
64 tively. This option activates such storage [Default uses 2-byte
65 integers].
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68 To convert 01010047.mgd77 and 01010008.mgd77 to new netCDF .nc files,
69 and capture all verification messages, try
70 mgd77convert 01010047 01010008 -Fa -Tc -V -Lew+ > log.lis
72 To convert 01010047.nc back to MGD77 ASCII and make sure it is identi‐
74 cal to the original file, try (Bourne shell syntax)
75 orig=`mgd77path 01010047 -Ic`
77 mgd77convert 01010047 -Fc -Ta -V
78 diff $orig 01010047.mgd77
79 To convert 01010047.nc to a plain ASCII table for manual editing, over‐
81 writing any existing table, try
82 mgd77convert 01010047 -Fc -T+t -V
84 To recover the original NGDC MGD77 version of 01020051.nc and ignore
86 any E77 corrections, use
87 mgd77convert 01020051 -FC -Ta -V
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90 mgd77convert handles three different formats. (1) The MGD77 ASCII
91 tables are the established standard for distribution of underway geo‐
92 physical data to and from the NGDC data center. Normally, only the
93 ship-operations people and the cruise PI might be involved in making an
94 MGD77 ASCII file for transmission to NGDC; users are more interested in
95 reading such files. (2) The MGD77+ netCDF format was developed to fas‐
96 cilitate the use of MGD77 data by scientists. It contains all the
97 information of the original MGD77 file and if you convert back and
98 forth you end up with the original. However, file sizes are typically
99 ~30% of the original ASCII format and is much faster to operate on. (3)
100 The plain ASCII tab-separated dump is available for users who need to
101 manually edit the content of a MGD77 file. This is usually easier to
102 do when the columns are tab-separated than when they are all crunched
103 together in the MGD77 punch-card format.
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106 The MGD77+ netCDF files are CF-1.0 and COARDS compliant and can be
107 examined with general-purpose tools such as ncBrowse and ncView.
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110 mgd77manage(1), mgd77list(1), mgd77sample(1), mgd77track(1)
111 x2sys_init(1)
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114 Wessel, P., and W. H. F. Smith, 2009, The Generic Mapping Tools (GMT)
115 version 4.5.0 Technical Reference & Cookbook, SOEST/NOAA.
116 Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic
117 Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579.
118 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
119 ping Tools Released, EOS Trans., AGU, 76 (33), p. 329.
120 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
121 ping Tools Released, http://www.agu.org/eos_elec/95154e.html, Copyright
122 1995 by the American Geophysical Union.
123 Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Dis‐
124 play Data, EOS Trans., AGU, 72 (41), p. 441.
125 ncBrowse, see http://www.epic.noaa.gov/java/ncBrowse/
126 ncView, see http://meteora.ucsd.edu/~pierce/ncview_home_page.html
127 The Marine Geophysical Data Exchange Format - "MGD77", see
128 http://www.ngdc.noaa.gov/mgg/dat/geodas/docs/mgd77.txt
129GMT 4.5.6 10 Mar 2011 MGD77CONVERT(1)