GPACK

     GPACK is the packing type and the number of bits (or data precision)
     to be used to pack the grid data, separated with a slash:

	packing type / number of bits (NONE, GRIB, DIF)

	packing type / precision      (DEC)

     The valid packing types are:

	NONE	No packing 
	GRIB	Data is packed in GEMPAK GRIB format
	DEC	Data is packed in GEMPAK GRIB format
	DIF	Data is packed in GEMPAK DIF format

     If the packing type is DEC, the number of bits is replaced by the
     data precision.  The data will be scaled by 10**precision and rounded
     to the nearest integer.  The number of bits used to store the data
     will be the minimum number required to store the resulting integers.

     If the number of bits is less than 32, the packing type specified will 
     be used.  If no packing type is given, the data will be packed using 
     the GEMPAK GRIB scheme.

     In general, data should be stored using packing type GRIB with 16 bits,
     by specifying the precision in DEC or with no packing using type NONE.
     Care should be taken using the other packing options.

	Pack Type	Minimum		Maximum		Default
	  NONE		  32		  32		  32
	  DEC		  -5		   5		   2
	  DIF		   2		  32		  16
	  GRIB		   2		  32		  16

     The default data packing when GPACK is blank is GRIB/16.