Rapid Re-convergence in Real-time Precise Point Positioning with Ambiguity Resolution

J. Geng

Abstract:	Precise point positioning (PPP) has become a valuable tool in the scientific analysis of Global Positioning System (GPS) measurements. The recent progress in integer ambiguity resolution at a single station has exploited the potential of PPP to achieve higher positioning accuracy than that of PPP with real-valued ambiguities. Despite this advancement, real-time PPP is still suffering from the long convergence periods prior to the first fixed solution. Hence, uninterrupted satellite signal availability during the observation is normally required in order to avoid re-convergences, consequently limiting the practicability of real-time PPP especially for engineering applications. To overcome this limitation, the author has developed and assessed a novel method in which predicted ionospheric delays, derived from the previous fixed solution, are used to generate precise ionosphere-corrected and ambiguity-fixed wide-lane observations which contribute to tightly constraining the position parameters, and then significantly reducing the re-convergence periods in real-time PPP. In this paper, this method is assessed using 24-hour 1 Hz real-time observations from European base stations on Day 188 under quiet ionosphere condition, and on Day 285 under relatively active ionosphere condition in 2008. Among these stations, about 25 are used as base stations to determine the real-time satellite clocks and uncalibrated phase delays, and 29 on Day 188 and 48 on Day 285 are used as rover stations. Re-convergences at these rover stations are simulated through introducing total loss of signal lock at an interval of 3600 seconds. It is found that the accuracy of the predicted ionospheric delays is affected more critically by low elevation angles than by time latencies. More importantly, with this method the reconvergence periods are reduced on average from around 1000 seconds to roughly 25 seconds with a success rate of approximately 90% of all re-convergence cases, improving the availability of kinematic positions with fixed ambiguities from about 70% to more than 90%. Therefore, the proposed technique has the potential to make ‘stop-and-go’ PPP a practical and useful tool for the engineering applications, enhancing the competitiveness of real-time PPP compared with currently prevalent Network RTK (Real-time Kinematic) positioning.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	2437 - 2448
Cite this article:	Geng, J., "Rapid Re-convergence in Real-time Precise Point Positioning with Ambiguity Resolution," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 2437-2448.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In