Bernese GPS Software Version 5.0 - Bernese GNSS Software

6. Data Preprocessing
result in large RMS errors of the other parameters estimated in GPSEST. There is still the
chance that the problem is actually not a cycle slip, but an outlier, and that only one or
a few observations are corrupted. If the cycle slip problem appears in the epoch-difference
between the epochs t1 and t2, the first corrective action is usually to mark (i.e., not use) the
observation stemming from epoch t2 (“Enable outlier rejection” in panel “MAUPRP 9: Outlier
Rejection / Ambiguity Setting”) and to try the same tests using the epoch-difference between
the epochs t1 and t3 and possibly t1 and t4 etc. Of course, there is a parameter which limits
the length of the interval [t1,tx]. It is specified by option “Mark consecutive outliers up to a time
interval”.
Small cycle slips in the data (up to about 10 cycles) might not be real but due to a high
noise level (e.g., for low elevation data). To reduces the probability that such cycle slips are
corrected the user may specify a minimum slip size in option “Minimum size of accepted cycle
slip correction”. If b1p, b2pq, and b5q are all smaller than this value the cycle slip is considered as
an outlier and is marked. With the option “Do not accept cycle slip corrections” the correction
of cycle slips may generally be suppressed. This is recommended when processing zerodifference
files because the introduction of the satellite clocks adds additional noise.
If you have to rerun MAUPRP for a set of observation files and you had cycle slip correction
enabled, you have to rebuilt the observation files first using SNGDIF for single-difference
files or RXOBV3, CODSPP for zero-difference files.
Cycle Slip Detection: Single Band Algorithm
If the screening mode L1, L2, or BOTH is selected in option “Screening mode, frequency to check”
of input panel “MAUPRP 3: General Options”, MAUPRP does not create any linear combination
of the measurements. The value m is computed as
m = r1 or m = f2 2
f 2 1
and only the condition (6.8) is tested (and not the condition (6.6)).
r2
(6.11)
For short baselines (< 10 km) the method BOTH is preferable because of the higher noise
level of the ionosphere-free linear combination L3 used in the COMBINED mode for the cycle
slip detection. For longer baselines the COMBINED mode is mandatory as only there the
ionosphere-free linear combination L3 of the L1 and L2 observations is used. The BOTH mode
actually consists only of the single frequency preprocessing for L1 and L2 independently.
Zero-difference files and observation files from kinematic stations can only be screened in
the COMBINED mode.
6.5.4 Clock Events in Preprocessing of Zero-Difference Files
In principle jumps in the receiver clock are uncritical. This is true if such events are treated
in a consistent way in the RINEX files. They affect the observation epoch, the code, and the
phase measurements in a similar way. To synchronize the receiver clocks program CODSPP
needs to run before MAUPRP is executed.
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