G2IDS
 
     G2IDS is a list of integers that are encoded into the GRIB2 
     Identification Section ( Section 1 ) that identifies the source and
     type of data packed in the GRIB2 message:
 
        Orig center ; sub-center ; master tables vers ; local tables ver ;
        Significance of reference time ; status of data ; type of data
 
     The Originating Center id  can be found in WMO Common Code Table C-1.
     The default is 7 = "NCEP".

     The sub-center is defined by the originating center.
 
     The current WMO master table version number is 2.

     Local table version numbers are defined by the originating center.

     The significance of the referece time is defined in GRIB2 Code Table 1.2:
             0   = Analysis 
             1   = Start of forecast (default)
             2   = Verifying time of forecast 
             3   = Observation time 
             255 = Missing

     The production status of data is defined in GRIB2 Code Table 1.3:
             0   = Operational products  (default)
             1   = Operational test products 
             2   = Research products 
             3   = Re-analysis products 
             255 = Missing

     The type of data is defined in GRIB2 Code Table 1.4:
             0   = Analysis products 
             1   = Forecast products  (default)
             2   = Analysis and forecast products 
             3   = Control forecast products 
             4   = Perturbed forecast products 
             5   = Control and perturbed forecast products 
             6   = Processed satellite observations 
             7   = Processed radar observations 
             255 = Missing