Fast Computation Method of Real-Time Precise Satellite Clock Errors for Combined BDS/GPS
BeiDou Navigation Satellite System (BDS) had been officially operating since the end of 2012. It can provide service of navigation, timing, and positioning in the Asia-Pacific region. In recent years the precise positioning on BDS had been widely studied
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Abstract BeiDou Navigation Satellite System (BDS) had been officially operating since the end of 2012. It can provide service of navigation, timing, and positioning in the Asia-Pacific region. In recent years the precise positioning on BDS had been widely studied and the accuracy of BDS Precise Point Positioning (PPP) can reach centimeters. Due to the satellite clock error corrections are fixed in PPP model, the accuracy and stability of real-time satellite clock errors would directly impact the positioning accuracy of real-time PPP (RT-PPP) and are the key points of RT-PPP. In this contribution, the method of fast computation of real-time precise satellite clock errors for combined BDS/GPS was investigated. First, the estimation model of real-time satellite clock based on epoch-differenced observations was studied. Then, the extended Kalman filter (EKF) was used to estimate the satellite clock errors based on real observations which collected from multi-GNSS experiment (MGEX) stations. The accuracy of BDS/GPS real-time clock errors was also analyzed which compared with the final precise clock products. Finally, the performance of BDS/GPS RT-PPP with the real-time BDS/GPS satellite clock errors was investigated. The results showed that the real-time BDS/GPS clock corrections were comparable with the final precise clock corrections and can satisfy the accuracy requirement of RT-PPP.
Keywords Satellite clock errors Real-time BDS/GPS Precise point positioning
1 Introduction Precise satellite orbit and clock products are the key elements to perform Precise Point Positioning [1] (PPP). In PPP observation equations, the satellite orbits and clock are usually held fixed as known value. The errors of orbit and clock will Z. Pan (&) H. Chai K. Yang B. Feng D. Li Y. Zhou F. Ming Institute of Surveying and Mapping, Information Engineering University, Zhengzhou 450001, China e-mail: [email protected] © Springer Science+Business Media Singapore 2016 J. Sun et al. (eds.), China Satellite Navigation Conference (CSNC) 2016 Proceedings: Volume III, Lecture Notes in Electrical Engineering 390, DOI 10.1007/978-981-10-0940-2_9
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contaminate the PPP result [2] directly. For real-time PPP (RT-PPP), the latency of real-time satellite ephemeris must be taken into consideration. Although the accuracy of the predicted part of IGS ultra-rapid orbits (about 5 cm) can meet the requirement of PPP, the accuracy of the predicted satellite clock errors, however, is about 3 ns which equals to 0.9 m in range will introduce large error in PPP solutions. The reason for the low accuracy of predicted satellite clock is that the high frequency of atomic clock on satellite is sensitive to the clock noise which originates from a variety of effects and environment variations, so the accuracy of satellite clock errors will decrease quickly with time goes by and hard to predict [3]. Among the solutions to overcome the accuracy limitation of predicted satellite clock errors, the method of using a network of reference
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