NAME

       mgd77togmt - Convert an MGD-77 ASCII file to a binary gmt file

SYNOPSIS

       mgd77togmt  [  -Llist  ]  [  mgd77file  ]  -Flegid  -Ystart_year  [  -Ainformation ] [ -Itime_increment ]
       [-T[offset]] [-W[cable_length]] [ -V ]

DESCRIPTION

       mgd77togmt 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 extension.

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 position.  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.  distance 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 ALSO

       dat2gmt(1), GMT(1)

REFERENCES

       Wessel,  P., and W. H. F. Smith, 2013, The Generic Mapping Tools (GMT) version 4.5.11 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 Mapping Tools Released, EOS Trans., AGU,
       76 (33), p. 329.
       Wessel,   P.,   and  W.  H.  F.  Smith,  1995,  New  Version  of  the  Generic  Mapping  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 Display 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 Geophysical 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 4.5.11                                         5 Nov 2013                                   MDG77TOGMT(1gmt)