Abstract
Many Beidou navigation satellite system (BDS) receivers or boards provide dual-frequency measurements to conduct precise positioning and navigation for low-power consumption. Cycle-slip processing is a primary work to guarantee consistent, precise positioning with the phase data. However, the cycle-slip processing of BDS dual-frequency phases still follows with those of existing GPS methods. For single-satellite data, cycle-slip detection (CSD) with the geometry-free phase (GF) is disturbed by severe ionospheric delay variations, while CSD or cycle-slip repair (CSR) with the Melbourne–Wubbena combination (MW) must face the risk of the tremendous disturbance from large pseudorange errors. To overcome the above limitations, a new cycle-slip repair method for BDS dual-frequency phases (BDCSR) is proposed: (1) An optimal model to minimize the variance of the cycle-slip calculation was established to the dual-frequency BDS, after correcting the ionospheric variation with a reasonable and feasible way. (2) Under the BDS dual-frequency condition, a discrimination function was built to exclude the adverse disturbance from the pseudorange errors on the CSR, according to the rankings of the absolute epoch-difference GFs calculated by the searched cycle-slip candidates after correcting the ionospheric variation. Subsequently, many compared CSR tests were implemented in conditions of low and medium elevations during strong geomagnetic storms. Comparisons from the results of different methods show that: (1) The variations of ionospheric delays are intolerable in the cycle-slip calculation during the geomagnetic storm, and the tremendous influence from the ionospheric variation should be corrected before calculating the cycle-slip combination with the BDS dual-frequency data. (2) Under the condition of real dual-frequency BDS data during the geomagnetic storm, the actual success rate of the conventional dual-frequency CSR (CDCSR) by employing the optimized combinations, but absenting from the discrimination function, is lower than that of BDCSR by about 2%; The actual success rate of the CSD with MW (MWCSD), is lower than that of BDCSR by about 2%. (3) After adding gross errors of 0.7 m to all real epoch-difference pseudoranges epoch-by-epoch, results of CDCSR and MWCSD showed many errors. However, BDCSR achieved a higher actual success rate than those of CDCSR and MWCSD, about 43% and 16%, respectively, and better performance of refraining the disturbance of large pseudorange error on the cycle-slip determination was achieved in the BDCSR methodology.
Highlights
Global navigation satellite system (GNSS) relies on using phase observations to provide precise services of positioning, timing, navigation, orbit determination, clock error estimation, and so on [1,2]
BDCSR achieved a higher actual success rate than those of conventional dual-frequency CSR (CDCSR) and MWCSD, about 43% and 16%, respectively, and better performance of refraining the disturbance of large pseudorange error on the cycle-slip determination was achieved in the BDCSR methodology
In response to the above limitations, this study proposed a cycle-slip repair method for Beidou navigation satellite system (BDS) dual-frequency phases (BDCSR) to overcome the adverse disturbances of severe ionospheric variations and large pseudorange errors on CSR
Summary
Global navigation satellite system (GNSS) relies on using phase observations to provide precise services of positioning, timing, navigation, orbit determination, clock error estimation, and so on [1,2]. The continuous phase observations without abnormal slips help to guarantee the consistency and convergence of the aforementioned precise services. When the phase observation was interrupted or relocked, cycle slips will appear in the phase data at the subsequent epoch. If the cycle slip is not correctly detected and reasonably handled, the results of GNSS precise services will be destroyed [3,4]. When more satellites experienced cycle slips at the same epoch, the initialization procedure would give rise to the extra costs of waiting for convergence and degrading of service accuracy [7].
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