Abstract
The main challenge of precise point positioning (PPP) applications is the long convergence time of typically a half hour, or even more, to achieve centimeter accuracy. Even when the multi-constellation is involved and ambiguity resolution is implemented, it still requires about ten minutes. It is becoming a hot spot to incorporate the low Earth orbit (LEO) satellite constellation for enhancing the Global Navigation Satellite System (GNSS), named here as LEO-enhanced GNSS (LeGNSS). In this system, the LEO satellites cannot only receive GNSS signals, but also serve as GNSS satellites by transmitting similar navigation signals to the ground users, but with higher signal strength and much faster geometric change due to their low altitude. As a result, the convergence time of PPP is expected to be shortened to a few minutes, or even seconds. Simulation software is developed to simulate GNSS and LEO observations for ground stations taking into account tropospheric delay, satellite clock errors, observation noises, as well as other error sources. Then the number of visible satellites, the geometry dilution of precision (GDOP), and the convergence time of the kinematic mode of PPP are evaluated on a global scale compared to those of GNSS systems. The simulation results show that LeGNSS can decrease the PPP convergence to 5 min. If there are more LEO satellites included in the LeGNSS, it is expected that the initialization of PPP can be further shortened.
Highlights
The long convergence time of precise point positioning [1] is a troublesome factor limiting its wider adoption, especially in real-time applications [2]
We investigated the benefits of LEO-enhanced GNSS (LeGNSS) compared with the current GPS, BeiDou Navigation Satellite System (BDS), and Iridium constellation itself
The conclusions are summarized as follows: (1) The low Earth orbit (LEO) constellation can improve the availability of the current Global Navigation Satellite System (GNSS) system, especially in the polar areas, since LEO are usually polar satellites
Summary
The long convergence time of precise point positioning [1] is a troublesome factor limiting its wider adoption, especially in real-time applications [2]. The European Galileo satellite navigation constellation has announced the start of initial service [18], which will consist of thirty satellites in three orbital planes With this progress, multi-GNSS PPP has attracted increasing interest in the GNSS community, and many types of research have been conducted to show the performance of multi-GNSS [19,20,21,22]. Though the convergence time can be improved compared to single-system PPP, it still takes several tens of minutes for multi-GNSS PPP initialization since the satellite geometry change with respect to a ground station is slow, taking satellites hours to pass overhead. LEO satellites move faster relative to ground stations, passing them in minutes instead of hours for MEO satellites This brings great geometry changes and, results in a shorter convergence time for precise positioning.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
