Bernese GPS Software Version 5.0 - Bernese GNSS Software

6.4.2 Strategies for Baseline Definition
6.5 Preprocessing Phase Observations
Usually, we use the number of observations as optimization criterion. The baselines are
created taking into account the number of common observations for the associated stations.
From all possible combinations, a set of baselines with maximum common observations is
chosen. The number of observations are scaled to a sampling rate of one minute and to one
frequency when the set of baselines is selected in order to treat all zero-difference files in
the same way.
Another possibility is to use the baseline length as a criterion to create the set of shortest
baselines. This could be useful if you want to create the same set of baselines for each session
(assuming, the same stations are observing in each session). The strategy can only be used
if the observations from all stations cover the same time interval. The baseline length is
an important criterion for ambiguity resolution. If the number of observations is used as a
criterion, the program will not create very long baselines, either.
For both strategies you have the possibility to specify “Predefined baselines” from a baseline
definition file (see Section 22.8.15 for a description). The predefined baselines are created
in any case. Additional baselines are built using the selected strategy to complete the set
of baselines.
Using the STAR strategy the baselines are built by connecting one reference station with
all remaining stations. You may select the reference station manually in the input panel
(option “Reference station for STAR strategy” in panel “SNGDIF 1: Observation File Selection”).
Otherwise the reference station will be selected automatically in a way that the sum of the
length of all baselines is minimized.
You can also select the stations for a baseline manually in the input panel or select the
stations for the baselines to be created by a baseline definition file. SNGDIF may create a
list of the formed baselines in a file which may be introduced as baseline definition file in
another run of the program. This allows, e.g., to recreate the same baselines for another day.
This possibility may be used to create the same baselines from phase and code observations
which is necessary if you use the Melbourne-Wübbena linear combination, e.g., for the
ambiguity resolution. In a first step the baselines for the phase measurements are created
optimizing the number of observations and are then stored in a baseline definition file. In
the second step the same baselines are formed for the code observations by introducing this
file as “Predefined baselines”.
6.5 Preprocessing Phase Observations (MAUPRP)
It was stated in Section 2.3 that the receivers can measure the difference between the phase of
the satellite transmitted carrier and the phase of the receiver generated replica of the signal.
This measurement yields a value between 0 and 1 cycle (0 and 2π). After turning on the
receiver an integer counter is initialized. During tracking, the counter is incremented by one
whenever the fractional phase changes from 2π to 0. Thus, for every epoch the accumulated
phase is the sum of the directly measured fractional phase and the integer count. The initial
integer number ni Fk of cycles between the satellite i and receiver k is unknown and has to
be estimated (see Eqns. (2.34)). This initial phase ambiguity remains the same as long as
Bernese GPS Software Version 5.0 Page 115