Bernese GPS Software Version 5.0 - Bernese GNSS Software

20.4 Description of the Processing Examples
20.4.2.5 Compute Ambiguity-Float Network Solution, Resolve Phase Ambiguities
The next processing steps are dedicated to ambiguity resolution. After computing a solution
with real valued ambiguities the QIF (quasi-ionosphere-free) strategy is used to resolve
ambiguities to their integer numbers.
#
# Compute ambiguity-float network solution, resolve phase ambiguities
# -------------------------------------------------------------------
401 ADDNEQ2 R2S_GEN ANY 1 331
402 GPSXTR R2S_GEN ANY 1 401
411 GPSQIFAP R2S_QIF ANY 1 402
412 GPSQIF_P R2S_QIF ANY 1 411
413 GPSXTR R2S_QIF ANY 1 412
PID 401 ADDNEQ2: A network solution with real valued ambiguities is computed baed
on normal equations stored in the GPSEST after the residual screening (PID 322).
Coordinates and troposphere estimates are saved for further use in the ambiguity
resolution step.
PID 402 GPSXTR: Creates a short overview of the float solution. It is included in the processing
summary (solution name P1 yyssss). The a posteriori rms error should be
not higher than about 1.4 mm.
PID 411 GPSQIFAP: Prepares the parallel execution of the ambiguity resolution steps. Program
BASLST is used to select baselines up to a maximum length of 2000 km. Only for
these baselines ambiguity resolution is attempted. This restriction is imposed because
for very long baselines the QIF resolution success rate drops and the probability of
wrongly resolved ambiguities rises. Please note that there are no baselines longer than
2000 km in this example campaign, however.
PID 412 GPSQIF P: One GPSEST is started for each baseline to be processed. Troposphere
estimates and coordinates from the float solution (PID 401) are introduced and fixed.
L1&L2 ambiguities are resolved simultaneously using the QIF strategy and are stored
in the observation header files.
PID 413 GPSXTR: Creates a summary of the previous step, listing, e.g., the percentage of
successfully resolved ambiguities. On the average, about 70% of ambiguities are resolved.
Note when processing your own data: On long baselines, large rms values for the
ambiguity float and fixed solutions do not necessarily indicate a problem, see Section
8.3.4.2.
Please note that the ambiguity resolution (GPSEST) runs baseline by baseline, independent
from the settings in variable V CLU . This is necessary due to the vast amount of stochastic
ionosphere parameters needed for the QIF strategy. Otherwise memory problems may arise.
Of course it is possible to use a different strategy or to include additional steps to resolve
remaining ambiguities based on other resolution strategies. Selection of the proper strategy
mainly depends on available observation data and network layout.
Bernese GPS Software Version 5.0 Page 443