Abstract
Global Navigation Satellite System (GNSS) ultra-rapid orbit is critical for geoscience and real-time engineering applications. To improve the computational efficiency and the accuracy of predicted orbit, a parallel approach for multi-GNSS ultra-rapid orbit determination is proposed based on Message Passing Interface (MPI)/Open Multi Processing (OpenMP). This approach, compared with earlier efficient methods, can improve the efficiency of multi-GNSS ultra-rapid orbit solution without changing the original observation data and retaining the continuity and consistency of the original parameters to be estimated. To obtain high efficiency, three steps are involved in the approach. First and foremost, the normal equation construction is optimized in parallel based on MPI. Second, equivalent reduction of the estimated parameters is optimized using OpenMP parallel method. Third, multithreading is used for parallel orbit extrapolation. Thus, GNSS ultra-rapid orbit determination is comprehensively optimized in parallel, and the computation efficiency is greatly improved. Based on the data from MGEX and IGS stations, experiments are carried out to analyze the performance of the proposed approach in computational efficiency, accuracy and stability. The results show that the approach greatly improves the efficiency of satellite orbit determination. It can realize 1-h update frequency for the multi-GNSS ultra-rapid orbit determination using 88 stations with four-system observations. The accuracy of the GPS, GLONASS, Galileo and BDS ultra-rapid orbit with 1-h update frequency using the parallel approach is approximately 33.4%,31.4%,40.1% and 32.8% higher than that of the original orbit, respectively. The root mean squares (RMS) of GPS, GLONASS, Galileo and BDS predicted orbit are about 3.2 cm, 5.1 cm, 5.6 cm and 11.8 cm. Moreover, the orbit provided by the proposed method has a better stability. The precision loss of all parallel optimization can be negligible and the original correlation between the parameters is fully preserved.
Highlights
Global Navigation Satellite System (GNSS) ultra-rapid orbit is the basis of geodetic research and real-time applications, such as real-time atmosphere monitoring [1,2], realtime PPP [3,4,5], real-time satellite clock estimation [6], and real-time orbit determination of LEO satellite [7]
The parallel approach properly makes use of parallel computing to improve the efficiency of multiGNSS orbit determination
The construction of normal equations, parameter elimination and orbit extrapolation in the GNSS precise orbit determination (POD) algorithm are optimized based on Message Passing Interface (MPI)/Open Multi Processing (OpenMP)
Summary
Global Navigation Satellite System (GNSS) ultra-rapid orbit is the basis of geodetic research and real-time applications, such as real-time atmosphere monitoring [1,2], realtime PPP [3,4,5], real-time satellite clock estimation [6], and real-time orbit determination of LEO satellite [7]. With the development of Galileo and implementation of BDS global service plan, the number of satellites in the constellation has increased dramatically to more than 130 [8]. On the other hand, the increase in the number of satellite constellations and stations makes the processing model more complicated and results in larger computational burden [9], which decrease the computational efficiency of Remote Sens. 2021, 13, 3464 multi-GNSS ultra-rapid orbit determination [10]. Further research on the rapid determination of multi-GNSS predicted orbits is critical for its high-precision applications
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