Bernese GPS Software Version 5.0 - Bernese GNSS Software

7.4 Weighting and Correlations
• the geometric part of the phase windup [Wu et al., 1993] for phase observations.
One part considers the effect of varying relative geometry of receiver and satellite.
Another part is the contribution originating from the satellite’s attitude. The latter
one can be fully absorbed by the satellite clock corrections. 1
7.4 Weighting and Correlations
7.4.1 A Priori Sigma of Unit Weight
The RMS of unit weight usually refers to the phase weight of the zero-difference L1 phase
observable at the zenith, if elevation-dependent weighting is enabled (see next section)
or averaged over all zenith angles if no elevation-dependent weighting is enabled. The a
priori weights wp and wc for the L1 phase and code observable are defined in the file
${X}/GEN/CONST. as wc/wp = 10 −4 , i.e.,
σc
σp
= 100 (7.13)
where σc and σp represent the measurement noise for pseudorange and phase observations
respectively.
The a priori sigma specified in panel “GPSEST 3.1: General Options 1” should approximately
agree with the actual measurement noise of the one-way L1 phase observations (the a
posteriori sigma of unit weight given in the GPSEST output file). The value of this sigma
is used for scaling of any a priori sigmas used to constrain specific parameters whereas the
σ in Eqn. (7.1) is the σp as defined in ${X}/GEN/CONST. and not the user-specified a priori
sigma. Therefore, when changing the a priori sigma, you also change the strength of the
defined a priori constraints. The default value is 0.001 m if elevation-dependent weighting
is enabled.
7.4.2 Station-Specific Weighting of Observations
Station-specific weighting of observations may make sense for pseudo-range measurements
if data from different receivers are processed in one run because the noise level for this
observable depends on the receiver.
The weighting is performed by so-called sigma factors that scale the a priori sigma used for
weighting the observations. The same factors are used for rescaling the edit level for code
observations in the zero difference processing mode (see option “Maximum tolerated O-C term”
in panel “GPSEST 3.2: General Options 2”). In this case, however, values below unity are set
to unity.
The station sigma factors are contained in a file (see Section 22.8.14) that may be specified
in option “Station sigma factors” in panel “GPSEST 1.2: Input Files 2”. For each station, the file
1 The originally released Version 5.0 of Bernese GPS Software considers only the geometrical part. With
an update published in November 2006 the observations you may choose whether you want to correct
for the geometrical part, the total effect or ignore the effect. We refer to the online help on the option
“Polarization effect” in panel “GPSEST 3.1: General Options 1” for more details.
Bernese GPS Software Version 5.0 Page 143