A new automated cycle slip detection and repair method for a single dual-frequency GPS receiver |
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Authors: | Zhizhao Liu |
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Institution: | (1) Department of Geomatics Engineering, The University of Calgary, Calgary, Alberta, T2N 1N4, Canada; |
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Abstract: | This paper develops a new automated cycle slip detection and repair method that is based on only one single dual-frequency
GPS receiver. This method jointly uses the ionospheric total electron contents (TEC) rate (TECR) and Melbourne–Wübbena wide
lane (MWWL) linear combination to uniquely determine the cycle slip on both L1 and L2 frequencies. The cycle slips are inferred
from the information of ionospheric physical TECR and MWWL ambiguity at the current epoch and that at the previous epoch.
The principle of this method is that when there are cycle slips, the MWWL ambiguity will change and the ionospheric TECR will
usually be significantly amplified, the part of artificial TECR (caused by cycle slips) being significantly larger than the
normal physical TECR. The TECR is calculated based on the dual-frequency carrier phase measurements, and it is highly accurate.
We calculate the ionospheric change information (including TECR and TEC acceleration) using the previous epochs (30 epochs
in this study) and use the previous data to predict the TECR for the epoch needing cycle slip detection. If the discrepancy
is larger than our defined threshold 0.15 TECU/s, cycle slips are regarded to exist at that epoch. The key rational of method
is that during a short period (1.0 s in this study) the TECR of physical ionospheric phenomenon will not exceed the threshold.
This new algorithm is tested with eight different datasets (including one spaceborne GPS dataset), and the results show that
the method can detect and correctly repair almost any cycle slips even under very high level of ionospheric activities (with
an average Kp index 7.6 on 31 March 2001). The only exception of a few detected but incorrectly repaired cycle slip is due
to a sudden increased pseudorange error on a single satellite (PRN7) under very active ionosphere on 31 March 2001. This method
requires dual-frequency carrier phase and pseudorange data from only one single GPS receiver. The other requirement is that
the GPS data rate ideally is 1 Hz or higher in order to detect small cycle slips. It is suitable for many applications where
one single receiver is used, e.g. real-time kinematic rover station and precise point positioning. An important feature of
this method is that it performs cycle slip detection and repair on a satellite-by-satellite basis; thus, the cycle slip detection
and repair for each satellite are completely independent and not affected by the data of other satellites. |
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