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mgd77convert(1)                       GMT                      mgd77convert(1)




NAME

       mgd77convert - Convert MGD77 data to other file formats


SYNOPSIS

       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.


DESCRIPTION

       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.


REQUIRED ARGUMENTS

       NGDC-ids
              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 vessels.

              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+ (a.nca), MGD77T (a.m77ta), MGD77 (a.mgd77a ) and plain
              text  file (a.data).  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-sep-
              arated  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-sep-
              arated  table dump (with extension .dat). We will refuse to cre-
              ate the file(s) if they already exist in the current  directory.
              Prepend + to override this policy.


OPTIONAL ARGUMENTS

       -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 pre-
              fixes.

       -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].

       -L[w][e][+]
              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 a|)
              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 explana-
              tion 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.


EXAMPLES

       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 01010047.nc back to MGD77 ASCII and make sure it is identi-
       cal 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 01010047.nc to a plain ASCII table for manual editing, over-
       writing any existing table, try

              gmt mgd77convert 01010047 -Fc -T+t -V

       To  recover  the  original NGDC MGD77 version of 01020051.nc and ignore
       any E77 corrections, use

              gmt mgd77convert 01020051 -FC -Ta -V


FILE FORMATS

       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 sci-
       entists. 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.


OTHER TOOLS

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


SEE ALSO

       mgd77manage(1), mgd77list(1), mgd77info(1), mgd77track x2sys_init(1)


REFERENCES

       ncBrowse,   see   http://www.epic.noaa.gov/java/ncBrowse/  ncView,  see
       http://meteora.ucsd.edu/~pierce/ncview_home_page/ The Marine  Geophysi-
       cal       Data       Exchange      Format      -      aMGD77a,      see
       http://www.ngdc.noaa.gov/mgg/dat/geodas/docs/mgd77.txt


COPYRIGHT

       2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe



5.4.2                            Jun 24, 2017                  mgd77convert(1)

gmt5 5.4.2 - Generated Thu Jun 29 14:06:23 CDT 2017
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