SEPTENTRIO PolaRx5TR, Reference Manual

Page: 302 / 512

4 SBF Reference
MeasEpoch
Number: 4027
"OnChange"
interval: internal measurement rate (receiver-type depen-
dent)
This block contains all the GNSS measurements (observables) taken at the time given by the
TOW
and
WNc
fields.
For each tracked signal, the following measurement set is available:
• the pseudorange
• the carrier phase
• the Doppler
• the C/N0
• the lock-time.
To decrease the block size, all the measurements from a given satellite are referenced to
one master measurement set. For instance, the L2 pseudorange (C2) is not much different
from the L1 pseudorange (C1), such that the difference between C2 and C1 is encoded,
instead of the absolute value of C2.
This is done by using a two-level sub-block structure. All the measurements from a
given satellite are stored in a
MeasEpochChannelType1
sub-block. The first part of this
sub-block contains the master measurements, encoded as absolute values. The second
part contains slave measurements, for which only the delta values are encoded in smaller
MeasEpochChannelType2
sub-blocks.
Every
MeasEpochChannelType1
sub-block contains a field "
N2
", which gives the number
of nested
MeasEpochChannelType2
sub-blocks. If there is only one signal tracked for a
given satellite, there are no slave measurements and
N2
is set to 0.
Decoding is done as follows:
1. Decode the master measurements and the
N2
value from the
MeasEpochChannelType1
sub-block.
2. If
N2
is not 0, decode the N2 nested
MeasEpochChannelType2
sub-blocks.
3. Go back to 1 till the
N1 MeasEpochChannelType1
sub-blocks have been decoded.
Note that measurements in this block are scrambled if the "Measurement Availability" per-
mission is not granted on your receiver. See also bit 7 of the
CommonFlags
field.
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