SEPTENTRIO PolaRx5TR, Reference Manual

Page: 408 / 512

4 SBF Reference
PVTResiduals
Number: 4009
"OnChange"
interval: default PVT output rate (see 4.1.8)
This block contains the residuals of all measurements used in PVT solution computed at
the epoch specified in the
TOW
and
WNc
fields. The PVT solution itself can be found in the
PVTCartesian
or
PVTGeodetic
blocks.
For each measurement from each satellite and each modulation used in the PVT solu-
tion, detailed PVT residual information is output for each observable type (code phase,
carrier phase and Doppler):
• a-posteriori measurement residual (
e
i
)
• absolute value of the
w
-test statistic (
w
i
)
• Minimal detectable bias (MDB).
In case of multi-base differential operation, a set of residuals is provided for all base stations.
This block uses a two-level sub-block structure analogous to that of the
MeasEpoch
block. It contains one
SatSignalInfo
sub-block for each satellite/signal type pair used
in the PVT or attitude computation. Each
SatSignalInfo
sub-block contains a number
of
ResidualInfo
sub-blocks, each of them containing the residuals of a given observable
type.
The standard deviation of the residual (
σ
e
) for satellite
i
and the "a priori" measure-
ment standard deviation (
σ
y
) can be computed from
e
i
,
w
i
and MDB by using the following
formulas (see also section 2.7):
σ
e
i
=
| e
i
|
w
i
and
σ
y
i
=
s
MDB
√
λ
0
.
σ
e
i
where
λ
0
is the non-centrality parameter and:
p
λ
0
=
√
2[erfinv(1
−
P
fa
) + erfinv(1
−
2 P
md
)]
with
P
fa
and
P
md
being the probability of false alarm and of missed detection respectively, as
set by the
setRAIMLevels
command, and the "
erfinv
" function being the inverse error
function. The output of
erfinv(x)
is the value
y
that satisfies the following equality:
x =
2
√
π
Z
y
0
e
− t
2
dt
This block can be used to monitor the quality of the measurements. Under normal circum-
stances, the residuals lie within -2 and +2 times the a-priori variance of the corresponding
measurements.
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