The above rules for the identification of data series
and that of initialization of the differential operations are
the same as those of the Compact RINEX version 1.0
format. There is, however, one subtle but significant
difference concerning the handling of the LLI and signal
strength flags (the category D series). In the case of
Compact RINEX version 1.0, these data are set for each
data type separately and the initialization of the differential
operation is triggered by that of the corresponding
observation record (the category C series) of the
corresponding satellite. The version 1.0 format is, therefore,
not capable of handling only–flag data (without an
observation field). The version 3.0 format is improved to
solve this defect: a category D series is defined not for each
data type but for all data types bundled as described
previously and the initialization for the category D series is
triggered independently of that for the category C series. 
