Abstract
Real-time multi-GNSS precise point positioning (PPP) requires the support of high-rate satellite clock corrections. Due to the large number of ambiguity parameters, it is difficult to update clocks at high frequency in real-time for a large reference network. With the increasing number of satellites of multi-GNSS constellations and the number of stations, real-time high-rate clock estimation becomes a big challenge. In this contribution, we propose a decentralized clock estimation (DECE) strategy, in which both undifferenced (UD) and epoch-differenced (ED) mode are implemented but run separately in different computers, and their output clocks are combined in another process to generate a unique product. While redundant UD and/or ED processing lines can be run in offsite computers to improve the robustness, processing lines for different networks can also be included to improve the clock quality. The new strategy is realized based on the Position and Navigation Data Analyst (PANDA) software package and is experimentally validated with about 110 real-time stations for clock estimation by comparison of the estimated clocks and the PPP performance applying estimated clocks. The results of the real-time PPP experiment using 12 global stations show that with the greatly improved computational efficiency, 3.14 cm in horizontal and 5.51 cm in vertical can be achieved using the estimated DECE clock.
Highlights
As one of the most popular positioning technologies, precise point positioning (PPP) [1,2] has been widely used thanks to its high accuracy, proficiency, stability, and flexibility [3,4,5]
With the progress in high-speed internet communication and the achievements in the global navigation satellite systems (GNSS) data stream protocol and format design, i.e., Radio Technical Commission for Maritime (RTCM) and Networked Transport of RTCM via Internet Protocol (NTRIP) [11], great efforts are underway towards the global real-time GNSS precise positioning service, where the real-time high precision satellite orbit and clock product is fundamental [12]
Since the initial information in normal equation is mostly provided by pseudorange observation and Global Positioning System (GPS) time is usually chosen as the time reference, an additional Inter-System Bias (ISB) parameter can be introduced for R, E, and C to compensate its offset from GPS
Summary
As one of the most popular positioning technologies, precise point positioning (PPP) [1,2] has been widely used thanks to its high accuracy, proficiency, stability, and flexibility [3,4,5]. The result shows that the approach can achieve a comparable accuracy to that of the UD approach, whereas the computation time is reduced to one tenth This strategy was implemented into real-time multi-GNSS clock estimation and evaluated [18,19,20]. Along with the development of modern processors and servers, the parallel computing on a distributed framework is receiving increasing interest in scientific computation community In this contribution, we develop an alternative processing strategy for multi-GNSS real-time high-rate clock estimation, in which a number of UD and ED processing lines can be involved and their output clocks are combined to generate a unique clock product. As UD and ED observations are the basic observations used in most of the current clock estimation as well as in this study, the corresponding observation equations for multi-GNSS clock estimation will be introduced and discussed followed by the process for clock combination
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