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:
(See mgd77info -L for agency and vessel codes). The ”.mgd77” or ”.nc” extensions will automatically be appended, if needed (use -I to ignore certain 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].
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 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 01010047.nc 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 01020051.nc and ignore any E77 corrections, use
gmt mgd77convert 01020051 -FC -Ta -V
mgd77convert handles three different formats. (1) The MGD77 ASCII tables are the established standard for distribution of underway geophysical data to and from the NGDC data center. 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. (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 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.
ncBrowse, see http://www.epic.noaa.gov/java/ncBrowse/ ncView, see http://meteora.ucsd.edu/~pierce/ncview_home_page/ The Marine Geophysical Data Exchange Format - “MGD77”, see http://www.ngdc.noaa.gov/mgg/dat/geodas/docs/mgd77.txt