Open AccessA Method to Accelerate the Convergence of Satellite Clock Offset Estimation Considering the Time-Varying Code Biases
Author(s) -
Shuai Liu,
Yunbin Yuan
Publication year - 2021
Publication title -
remote sensing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.285
H-Index - 124
ISSN - 2072-4292
DOI - 10.3390/rs13142714
Subject(s) - computer science , precise point positioning , convergence (economics) , code (set theory) , offset (computer science) , satellite , utc offset , filter (signal processing) , real time computing , algorithm , global positioning system , telecommunications , gnss applications , physics , set (abstract data type) , computer vision , astronomy , economics , programming language , economic growth
Continuous and stable precision satellite clock offsets are an important guarantee for real-time precise point positioning (PPP). However, in real-time PPP, the estimation of a satellite clock is often interrupted for various reasons such as network fluctuations, which leads to a long time for clocks to converge again. Typically, code biases are assumed to stay constant over time in clock estimation according to the current literature. In this contribution, it is shown that this assumption reduces the convergence speed of estimation, and the satellite clocks are still unstable for several hours after convergence. For this reason, we study the influence of different code bias extraction schemes, that is, taking code biases as constants, extracting satellite code biases (SCBs), extracting receiver code biases (RCBs) and simultaneously extracting SCBs and RCBs, on satellite clock estimation. Results show that, the time-varying SCBs are the main factors leading to the instability of satellite clocks, and considering SCBs in the estimation can significantly accelerate the filter convergence and improve the stability of clocks. Then, the products generated by introducing SCBs in the clock estimation based on undifferenced observations are applied to PPP experiments. Compared with the original undifferenced model, clocks estimated using the new method can significantly accelerate the convergence speed of PPP and improve the positioning accuracy, which illustrates that our estimated clocks are effective and superior.