Code table 1 -- Flag indication relative to Sections 2 and 3
from the ECMWF publication "Binary data representation - FM 92 GRIB", May 1992


Bit       Value              Meaning
1       0       Section 2 omitted
        1       Section 2 Included
2       0       Section 3 omitted
        1       Section 3 included
3-8     0

Note: Bits enumerated from left to right.