Estimation Method Of Real-time Precise Satellite Clock Offsets Based On The Regional GPS Network

The development of precise point positioning (PPP) technique is changing the GNSS traditional mode of precise relative positioning. And the extensive use of GNSS precise positioning played an important role in the promotion. The main advantage of PPP is the real-time and dynamic application, and the PPP becomes one of the research hotspot in GPS Technology. The real-time PPP application is limited by the real-time clock offsets estimates within a delay of a few seconds and its accuracy of GPS satellite. Therefore, it is quite important and valuable to study the estimation method of satellite clock offsets, develop the calculation software and improve the accuracy and timeliness of satellite clock offsets based on regional GPS reference network.The basic theories and methods of satellite clock offset estimation are systematically investigated in the paper. The major corrections and related mathematic models in calculating precise satellite clock offsets are discussed in detail. And then based regional GPS observations network, three models of estimating satellite clock offsets are derived. According to the satellite clock offsets estimation model without ambiguity resolution, a program for the precise satellite clock offsets estimation is developed. Finally, Clock offsets of the complete GPS constellation are estimated based on the GPS data from the SOA coastal GNSS observation network and our Clock offsets estimations are compared to the final IGS(the International GNSS Service) clock corrections. The results show that their agreement is about 0.5 nanoseconds between our satellite clock offsets results and the final IGS clock corrections. The accuracy of these results are similar to the those from IGS data analysis center. In addition, based on the regional GNSS network, the use of the predicted Ultra Rapid products from IGS, the accuracy of real-time satellite clock offsets is about 0.5 nanoseconds. It is nearly the same as those with the IGS Final GPS orbits. This result will help the further research on the real-time calculation and application of the satellite clock offset.