July 16, 2018
                                                          W/EMC:VUONG

cnvgrib utility.

This command line utility program converts every GRIB
message in the input file from one GRIB edition to another.
It currently converts GRIB1 to GRIB2, and GRIB2 to GRIB1
using WMO master tables as well as various NCEP local tables.

The cnvgrib utility requires both the w3lib and g2lib
libraries.

We have added support for PNG and JPEG2000 image compression
algorithms within the GRIB2 standard.  If you would like
this converter to be able to utilize these new GRIB2 Templates,
then the g2lib must be compiled with this support enabled.
The README file included with the "g2lib" library 
describes how to compile that library to support PNG and
JPEG2000, and it also lists the external libraries that
are required.  These libraries, if desired, will have to linked 
in when creating the cnvgrib executable.



Usage: cnvgrib [-h] {-g12|-g21|-g22} [-m|-m0] [-nv]
               [{-p0|-p2|-p31|-p32|-p40|-p41}]  ingribfile   outgribfile
  

Usage: cnvgrib  -h  For helps and shows all options


cnvgrib:  version cnvgrib-3.1.1 
  
Must use one of the following options:
   -g12     converts GRIB1 to GRIB2
   -g21     converts GRIB2 to GRIB1
   -g22     converts GRIB2 to GRIB2  (used to change packing option)
  
Optional packing options: (for use with  -g12 and -g22 only)
   -p0      simple packing
   -p2      complex packing
   -p31     complex pack with 1st order diffs
   -p32     complex pack with 2nd order diffs
   -p40     JPEG2000 encoding
   -p41     PNG encoding
  
Other Optional options: 
   -nv      Do not combine U, V wind components
  
   Use missing value management instead of bitmap
   (ONLY valid with Complex Packing options: -p2, -p31 or -p32 )
  
   -m      Primary missing values included within the data values
   -m0     No explicit missing values included within the data values
   -mastertable_ver_x     Master Table version where x is number from 2 to 21