Bernese GPS Software Version 5.0 - Bernese GNSS Software

6. Data Preprocessing
no loss of signal lock occurs. A loss of lock causes a jump in the instantaneous accumulated
phase by an integer number of cycles. If there is a difference
n i Fk (t2) − n i Fk (t1) = 0 (6.2)
we say that a cycle slip occurred between time t1 and t2. There are several possible causes
for cycle slips:
• obstruction of the satellite signal due to trees, buildings, etc.,
• low signal-to-noise ratio due to rapidly changing ionospheric conditions, multipath,
high receiver dynamics, or low satellite elevation,
• failure in the receiver software, and
• malfunctioning of the satellite oscillator.
In Version 5.0 of the Bernese GPS Software the detection of cycle slips may be done on
RINEX level using the program RNXSMT (see Section 6.2). The limitations are given by
the requirement of dual–frequency data and the accuracy of the code observation because
both observation types are used together.
Using program MAUPRP (”Menu>Processing>Phase preprocessing”) cycle slips in the phase observations
can be identified more reliably 1 . The program does not need code observations to screen
the phase measurements. It is able to preprocess zero-difference as well as single-difference
observation files, forming and analyzing different linear combinations of phase observations.
In the case of zero-difference observation files it is necessary to introduce excellent high-rate
satellite clocks (accuracy < 0.1 ns; same sampling as data) to obtain reliable results. In any
case precise satellite orbits and sub-meter-accuracy station coordinates are required.
MAUPRP screens GPS, GLONASS, and GNSS (GPS and GLONASS) observation files. The
program either assumes that the wide-lane combination is not corrupted by cycle slips (this
is true if the preprocessing program RNXSMT was used before) or it looks for wide-lane
cycle slips, too.
The following tasks are accomplished by program MAUPRP:
(1) Mark observations due to the following reasons in order to exclude them from the preprocessing
and the data analysis (options in panel “MAUPRP 4: Marking of Observations”):
• observations at low satellite elevation,
• epochs with unpaired observations (L1 without L2 or vice versa),
• small pieces of observations.
(2) Perform a non-parametric screening to identify big outliers.
(3) Compute an epoch-difference solution as a reference for the cycle slip detection.
(4) Check all the observations and find the time intervals [t1,t2] which are corrupted by
cycle slips.
1 Although MAUPRP stands for Manual and AUtomatic PReProcessing the manual mode is no longer
available in Version 5.0 .
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