LEO enhanced Global Navigation Satellite System (LeGNSS) for real-time precise positioning services

Significance 

Lately there have been tremendous improvements in the Global Navigation Satellite Systems (GNSS). Going with the current trends, future demands for efficient and stable positioning, navigation and timing services are escalating globally. Unfortunately, applications of these systems have been limited by a number of drawbacks. For instance, the long initialization times in precise point positioning are attributed to lack of accurate atmospheric delay corrections. Consequently, they require dense network references that in most cases are not available in some areas such as deserts and oceans. This has led to the development of several approaches to enhance the orbit quality and precision of the satellites. Currently more than eighty satellites are available in service globally. However, the slow change in satellite geometry with respect to the ground station deteriorates the instantaneous initialization of the precise positioning. To this end, researchers have been looking for alternatives and have identified positioning, navigation, timing, remote sensing and communications (PNTRC) concept with different types of satellites based on the global navigation satellite systems constellations as well as low Earth orbit (LEO) constellations as a promising solution.

To this note, Tongji University researchers: Professor Bofeng Li, Yunzhong Shen, Dr. Haibo Ge, M.S. Liangwei Nie from the College of Surveying and Geo-Informatics in collaboration with Dr. Maorong Ge and Professor Harald Schuh at German Research Centre for Geosciences (GFZ) proposed a LEO enhanced global navigation satellite system (LeGNSS) comprising of low, medium and high orbital satellites. Specifically, they extended the GNSS system based on LEO constellation. They managed to provide efficient and accurate real-time precise point positioning services. The work is currently published in the research journal, Remote Sensing.

In brief, the research team first cross-examined the data collected from 14 BeiDou navigation satellite system, 24 global positioning system (GPS) satellites and 66 Iridium satellite constellations. Next, the data processing system entailed both server-end that functioned to estimate the orbit and clock for the satellites and user-end that functioned to investigate the signal-in-space ranging error and geometry dilution of precision. It was necessary to balance the precise orbit determination (POD) accuracy and complex calculations using two different approaches including low Earth orbit precise orbit determination comprising of ground tracking stations and GNSS precise orbit determination comprising of a LEO satellite subnet. Eventually, simulations were carried out to determine the influence of the low earth orbit on the clock and orbit quality and general performance of the LeGNSS.

The authors observed that both of the methods produced desired orbit and clock accuracy and particularly for LEO clocks. Consequently, LEO constellation significantly enhanced the positional geometries in isolated areas like polar regions achieving centimeter level, attributed to the precision positioning capacity of the LeGNSS.

In summary, the study successfully demonstrated the real-time precise point positioning application using the LeGNSS system by introducing various operations techniques. Therefore, this is expected to pave the way for enhancing the real-time precise point positioning performance of LeGNSS.

About the author

Bofeng Li obtained his BSc and PhD degrees from Tongji University, China, followed by three years of postdoctoral research at the GNSS Research Center, Curtin University, Australia. After that he was recruited back to Tongji University in 2013 through the Young 1000-Talent programme; he now holds a professorship there in geodesy and surveying engineering. He is a Head of GNSS group in Tongji University, focusing on the GNSS precise positioning and navigation-based location service.

His research interests include the new-mode precise orbit determination with a cluster of LEO satellites, real-time precise GNSS positioning, and multi-sensor fusion for indoor and outdoor navigation. He has published more than 100 papers, of which most on the leading journals. He has chaired the IAG 4.5.4 working group since 2012. He is a member of IAG-ICCT working group of multi-GNSS theory and algorithms and also a member of IAG 4.4.2 working group.

About the author

Haibo Ge received his B. Sc bachelor and Ph.D. degree at Tongji University, Shanghai, China. Currently, he works at German Research Centre for Geosciences (GFZ). His research interest is orbit determination and precise positioning.

About the author

Maorong Ge received his Ph.D. degree in Geodesy at the Wuhan University, China. He is now a senior scientist and head of the real-time GNSS group at the German Research Centre for Geosciences (GFZ). His research interests are GNSS algorithms and software development.

About the author

Liangwei Nie received his B.Sc bachelor and M.S. degree at Tongji University, Shanghai, China. He works on the orbit determination of combined multi-GNSS and low earth orbit satellites.

About the author

Harald Schuh is currently the Director of the Department 1 “Geodesy”, German Research Centre for Geosciences (GFZ). He is also the President of the International Association of Geodesy (IAG) since 2015. His research interests are space geodesy such as GNSS and Very Long Baseline Interferometry and its applications.

Reference

Ge, H., Li, B., Ge, M., Zang, N., Nie, L., Shen, Y., & Schuh, H. (2018). Initial Assessment of Precise Point Positioning with LEO Enhanced Global Navigation Satellite Systems (LeGNSS). Remote Sensing, 10(7), 984.

Go To Remote Sensing

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