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.