MDG77TOGMT(1) Generic Mapping Tools MDG77TOGMT(1)NAMEmgd77togmt - Convert an MGD-77 ASCII file to a binary gmt file
SYNOPSISmgd77togmt [ -Llist ] [ mgd77file ] -Flegid -Ystart_year [ -Ainforma‐
tion ] [ -Itime_increment ] [-T[offset]] [-W[cable_length]] [ -V ]
DESCRIPTIONmgd77togmt reads an ASCII MGD-77 format file [or standard input] and
creates a binary gmt file. The 16 header records specified in the
MGD-77 documentation may or may not be present. If two-way travel
times are available, mgd77togmt will convert those to corrected depths
using the Carter tables. Both old and new (Y2K-compliant) MGD-77 files
are supported.
-L Name of file with several records of the format mgd77file legid
start_year. For multiple files, use this option rather than the
-F -Y combination.
-Y The year of the first data point in the file. If not provided
and -L option not used, it tries to get it from a header file.
The header file must be in the same directory of the main file
and must have a name equal to the main but with a .h77 exten‐
sion.
OPTIONS
No space between the option flag and the associated arguments.
-A Set an optional 10 character information string to be stored in
the header [Default is blank].
-F Leg id that will be used in file name (legid.gmt). If not given,
it will be constructed from the mgd77file name plus the .gmt
extension.
-I Used for files where time is missing. The increment is used to
calculate fake times.
-T Extracts Total field instead of anomaly. Since F does not hold
in a 2 byte signed variable we subtract a constant [default =
40000] but you can provide another value in offset.
-W Take into account that the magnetometer is not at ship's posi‐
tion. cable_length is magnetometer tow distance [default = 200
meters]. If -W only is given (e.g., no cable_length) and like
with the -Y option, we try to get the tow distance from the
header file. Failing, defaults to 200 meters. Note that this
option will throw away the first points whose accumulated. dis‐
tance since the start of magnetic acquisition is less than
cable_length, and likewise for the end of the mag profile.
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
EXAMPLES
To create a gmt file from the ASCII file c2104.mgd77, run
mgd77togmt c2104.mgd77 -Y 1977
To create new gmt files from all the mgd77 files listed in list.d:
mgd77togmt-L list.d -V
SEE ALSOdat2gmt(1), GMT(1)REFERENCES
Wessel, P., and W. H. F. Smith, 2015, The Generic Mapping Tools (GMT)
version 4.5.14 Technical Reference & Cookbook, SOEST/NOAA.
Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic
Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579.
Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
ping Tools Released, EOS Trans., AGU, 76 (33), p. 329.
Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
ping Tools Released, http://www.agu.org/eos_elec/95154e.html, Copyright
1995 by the American Geophysical Union.
Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Dis‐
play Data, EOS Trans., AGU, 72 (41), p. 441.
MGD77 Task Group, 1977, The Marine Geophysical Data Exchange Format -
MGD77, Key to Geophysical Records documentation No. 10, National Geo‐
physical and Solar-Terrestrial Data Center, Boulder, CO.
Carter, D. J. T., Echo Sounding Correction Tables: Formerly Matthews'
Tables, 150 pp, Hydrographic Department, Ministry of Defense, Taunton,
Somerset, England, 1980.
GMT 4.5.14 1 Nov 2015 MDG77TOGMT(1)
