Provided by: gmt-common_5.4.5+dfsg-2_all bug


       mgd77convert - Convert MGD77 data to other file formats


       mgd77convert NGDC-ids  -Fa|c|m |t
        -T[+]a|c|m|t [  -C ] [  -D ] [  -L[w][e][+] ] [  -V[level] ]

       Note: No space is allowed between the option flag and the associated arguments.


       mgd77convert  reads versions of MGD77 files and writes the same data in (probably) another
       format to a new file in the current directory.  Both pre- and post-Y2K MGD77  formats  can
       be processed.


              Can be one or more of five kinds of specifiers:

              1. 8-character NGDC IDs, e.g., 01010083, JA010010etc., etc.

              2. 2-character agency codes which will return all cruises from each agency.

              3. 4-character  <agency><vessel>  codes,  which  will return all cruises from those

              4. =list, where list is a table with NGDC IDs, one per line.

              5. If nothing is specified we return all cruises in the data base.

              (See mgd77info -L for agency and vessel codes). If no file extension is given  then
              we  search  for files with one of the four known extensions.  The search order (and
              the extensions) tried is MGD77+ (".nc"), MGD77T (".m77t"), MGD77  (".mgd77"  )  and
              plain  text  file  (".dat").   Use  -I  to ignore one or more of these file types).
              Cruise files will be looked for first in the current directory and  second  in  all
              directories  listed  in  $MGD77_HOME/mgd77_paths.txt  [If $MGD77_HOME is not set it
              will default to $GMT_SHAREDIR/mgd77].

       -Fa|c|m |t
              Specifies the format of the input (From) files. Choose from a  for  standard  MGD77
              ASCII  table  (with  extension  .mgd77),  c  for the new MGD77+ netCDF format (with
              extension .nc), m for the new MGD77T format (extension .m77t) and  t  for  a  plain
              ASCII  tab-separated  table  dump  (with  extension  .dat).  Use -FC to recover the
              original MGD77 setting from the MGD77+ file [Default will apply any E77 corrections
              encoded in the file].

       -T[+]a|c|m |t
              Specifies  the  format  of  the output (To) files. Choose from a for standard MGD77
              ASCII table (with extension .mgd77), c for  the  new  MGD77+  netCDF  format  (with
              extension  .nc),  m  for  the new MGD77T format (extension .m77t) and t for a plain
              ASCII tab-separated table dump (with extension .dat). We will refuse to create  the
              file(s)  if they already exist in the current directory. Prepend + to override this


       -C     Convert from NGDC two-file data sets *.h77, *.a77 to single file *.mgd77. No  other
              options  (except  -V)  are  allowed.  Give  one or more names of *.h77 files, *.a77
              files, or just the file prefixes.

       -D     By default, the storage types used in a  MGD77+  netCDF  file  greatly  exceed  the
              precision  imposed by the ASCII MGD77 format. However, for the five items faa, eot,
              mag, diur and msd we use 2-byte integers with implied precisions of 0.1  mGal,  0.1
              nTesla,  and  1  m  as in the MGD77 format. It is possible that at some point these
              items will need to be stored as 4-byte ints which  would  allow  precisions  of  10
              fTesla,  1  nGal,  and  0.01  mm,  respectively. This option activates such storage
              [Default uses 2-byte integers].

              Set the level of verification reporting [none]  and  where  to  send  such  reports
              [stderr].  Append a combination of w for warnings, e for errors, and + to send such
              log information to stdout.

       -V[level] (more ...)
              Select verbosity level [c].

       -^ or just -
              Print a short message about the syntax of the command, then exits (NOTE: on Windows
              just use -).

       -+ or just +
              Print  an  extensive  usage  (help)  message,  including  the  explanation  of  any
              module-specific option (but not the GMT common options), then exits.

       -? or no arguments
              Print a complete usage (help) message, including the explanation  of  all  options,
              then exits.


       To convert a large set of a77,h77 pairs to proper mgd77 files, try

              gmt mgd77convert -C *.h77

       To  convert  01010047.mgd77  and  01010008.mgd77  to new netCDF .nc files, and capture all
       verification messages, try

              gmt mgd77convert 01010047 01010008 -Fa -Tc -V -Lew+ > log.lis

       To convert back to MGD77 ASCII and make sure it is identical to  the  original
       file, try (Bourne shell syntax)

              orig=`gmt mgd77path 01010047 -Ic`
              gmt mgd77convert 01010047 -Fc -Ta -V
              diff $orig 01010047.mgd77

       To convert to a plain ASCII table for manual editing, overwriting any existing
       table, try

              gmt mgd77convert 01010047 -Fc -T+t -V

       To recover the original NGDC MGD77 version of and ignore any E77  corrections,

              gmt mgd77convert 01020051 -FC -Ta -V


       mgd77convert  handles  four  different  formats.   (1) NGDC has now started to use the new
       tab-delimited version of the MGD77 data format, called MGD77T.  In  addition  to  all  the
       info  in  old  MGD77  files  it  contains  a  few  more  quality  flags for grav, mag, and
       bathymetry.  (2) The MGD77+ netCDF format was developed to facilitate  the  use  of  MGD77
       data  by scientists. It contains all the information of the original MGD77 file and if you
       convert back and forth you end up with the original. However,  file  sizes  are  typically
       ~30%  of  the  original ASCII format and is much faster to operate on. (3) The MGD77 ASCII
       tables are the traditional standard for distribution of underway geophysical data  to  and
       from  the  NGDC data center, now superseded by MGD77T.  Normally, only the ship-operations
       people and the cruise PI might be involved in making an MGD77 ASCII file for  transmission
       to  NGDC;  users  are  more  interested  in  reading  such  files.  (4)  The  plain  ASCII
       tab-separated dump is available for users who need to manually edit the content of a MGD77
       file.   This is usually easier to do when the columns are tab-separated than when they are
       all crunched together in the MGD77 punch-card format.


       The MGD77+ netCDF files  are  CF-1.0  and  COARDS  compliant  and  can  be  examined  with
       general-purpose tools such as ncBrowse and ncView.


       mgd77manage, mgd77list, mgd77info, mgd77track x2sys_init


       ncBrowse,        see       ncView,       see The  Marine  Geophysical  Data  Exchange
       Format - "MGD77", see


       2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe