Abstract
Due to different designs of receiver correlators and front ends, receiver-related pseudorange biases, called signal distortion biases (SDBs), exist. Ignoring SDBs that can reach up to 0.66 cycles and 10 ns in Melbourne-Wübbena (MW) and ionosphere-free (IF) combinations can negatively affect phase bias estimation. In this contribution, we investigate the SDBs and evaluate the impacts on wide-lane (WL) and narrow-lane (NL) phase bias estimations, and further propose an approach to eliminating these SDBs to improve phase bias estimation. Based on a large data set of 302 multi-global navigation satellite system (GNSS) experiment (MGEX) stations, including 5 receiver brands, we analyze the characteristics of these SDBs The SDB characteristics of different receiver types for different GNSS systems differ from each other. Compared to the global positioning system (GPS) and BeiDou navigation satellite system (BDS), SDBs of Galileo are not significant; those of BDS-3 are significantly superior to BDS-2; Septentrio (SEPT) receivers show the most excellent consistency among all receiver types. Then, we apply the corresponding corrections to phase bias estimation for GPS, Galileo and BDS. The experimental results reveal that the calibration can greatly improve the performance of phase bias estimation. For WL phase biases estimation, the consistencies of WL phase biases among different networks for GPS, Galileo, BDS-2 and BDS-3 improve by 89%, 77%, 76% and 78%, respectively. There are scarcely any improvements of the fixing rates for Galileo due to its significantly small SDBs, while for GPS, BDS-2 and BDS-3, the WL ambiguity fixing rates can improve greatly by 13%, 27% and 14% after SDB calibrations with improvements of WL ambiguity fixing rates, the corresponding NL ambiguity fixing rates can further increase greatly, which can reach approximately 16%, 27% and 22%, respectively. Additionally, after the calibration, both WL and NL phase bias series become more stable. The standard deviations (STDs) of WL phase bias series for GPS and BDS can improve by more than 46%, while those of NL phase bias series can yield improvements of more than 13%. Ultimately, the calibration can make more WL and NL ambiguity residuals concentrated in ranges within ±0.02 cycles. All these results demonstrate that SDBs for phase bias estimation cannot be ignored and must be considered when inhomogeneous receivers are used.
Highlights
Precise point positioning (PPP) is a high-precision positioning technique that can achieve centimeter-level positioning with a single receiver [1]
The standard deviations (STDs) of WL phase bias series for global positioning system (GPS), Galileo, BeiDou navigation satellite system (BDS)-2 and BDS-3 improve by approximately 55%, 7%, 47% and 46%, respectively, while those of NL phase bias series for GPS, BDS-2 and BDS-3 improve by approximately 13%, 35% and
Due to the difference of the correlator and the front-end design among different types of receivers, receiver related SDBs exist, which has great importance in GNSS precise data processing. In this contribution, based on a large data set from the MGEX network, we analyze the characteristics of SDBs and obtain the corresponding corrections by the calibration method proposed, and further apply them to WL and NL phase bias estimations
Summary
Precise point positioning (PPP) is a high-precision positioning technique that can achieve centimeter-level positioning with a single receiver [1]. Undifferenced ambiguities cannot be estimated as integers directly, limiting the application of PPP [2,3]. Several PPP ambiguity resolution (PPP-AR) approaches have been proposed and implemented [2,3,4,5,6]. Ge et al (2008) [4] utilized satellite phase biases to recover the ambiguity integer property. Laurichesse et al (2009) [5] and Collins et al (2008) [6]. Provided integer or decoupled clock products directly to users by absorbing narrow-lane (NL) phase biases into the satellite clocks. All three methods have been already proven equivalent in theory, but with different expressions [7,8,9]
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