https://orcid.org/0000-0001-8857-7530
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ABSTRACT
With the completion of Chinese BeiDou Navigation Satellite System (BDS), the world has begun to enjoy the Positioning, Navigation, and Timing (PNT) services of four Global Navigation Satellite Systems (GNSS). In order to improve the GNSS performance and expand its applications, Low Earth Orbit (LEO) Enhanced Global Navigation Satellite System (LeGNSS) is being vigorously advocated. Combined with high-, medium-, and low- earth orbit satellites, it can improve GNSS performance in terms of orbit determination, Precise Point Positioning (PPP) convergence time, etc. This paper comprehensively reviews the current status of LeGNSS, focusing on analyzing its advantages and challenges for precise orbit and clock determination, PPP convergence, earth rotation parameter estimation, and global ionosphere modeling. Thanks to the fast geometric change brought by LEO satellites, LeGNSS is expected to fundamentally solve the problem of the long convergence time of PPP without any augmentation. The convergence time can be shortened within 1 minute if appropriate LEO constellations are deployed. However, there are still some issues to overcome, such as the optimization of LEO constellation as well as the real time LEO precise orbit and clock determination.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
Raw data were generated at Tongji University. Derived data supporting the findings of this study are available at https://gnss.tongji.edu.cn/info/1023/1447.htm or from the corresponding author [email protected].
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Notes on contributors
Haibo Ge
Haibo Ge received his PhD degree at Tongji University. Now he is an assistant professor at college of surveying and geo-informatics, Tongji University. His research interests are orbit determination for high-, medium-, and low-orbit satellites and LEO-enhanced GNSS applications.
Bofeng Li
Bofeng Li obtained his B.Sc. and PhD both from and is now a Professor in Geodesy at Tongji University. He was appointed by ‘Young 1000-Talent’ program in 2013. His research interests include GNSS ambiguity resolution, precise orbit determination, real-time precise positioning as well as the mathematical Geodesy.
Song Jia
Song Jia is now a PhD student at Tongji University. Her researches mainly concentrate on earth rotation parameters determined from a combined processing of LEO- and ground-based GNSS observations.
Liangwei Nie
Liangwei Nie is now a PhD student in Geodesy at Technical University of Berlin. His research interests include precise orbit determination and precise clock estimation.
Tianhao Wu
Tianhao Wu is now a PhD student of Tongji University. His major research interest is precise orbit determination of LEO and GNSS satellites.
Zhe Yang
Zhe Yang obtained her PhD degree from The Hong Kong Polytechnic University in 2018, with dissertation research focusing on equatorial ionospheric plasma irregularities and associated scintillations of GNSS signals. She is now working as an Assistant Professor at College of Surveying and Geo-informatics, Tongji University. Her research interests are mainly in ionosphere remote sensing using multi-GNSS signals and ionospheric space weather impacts on GNSS.
Jingzhe Shang
Jingzhe Shang is now a Master student at Tongji University. His researches mainly concentrate on GNSS-based and LeGNSS-based global ionosphere modeling.
Yanning Zheng
Yanning Zheng is now a PhD student at Tongji University. His research interests include PPP, PPP-RTK, and LeGNSS.
Maorong Ge
Maorong Ge received his PhD degree in Geodesy at Wuhan University. He is now a professor at Technical University of Berlin and head of the GNSS real-time software group at the German Research Centre for Geosciences. His research interests are GNSS algorithms and software development.