The Performance Study Of Broadcast Ephemeris Parameters And Fitting Method

Abstract:At present, the global navigation and positioning system already develops into every field of society deeply. Establishing and developing independent Beidou satellite navigation system is related to the development of the national defense security and economic construction of our country. The design of satellite broadcast ephemeris parameters and user algorithm is an important technology of navigation and positioning system,and its accuracy, reliability and efficiency will have direct influence on the performance of the navigation and positioning, so it is necessary to research the broadcast ephemeris parameters and fitting method of GPS and GLONASS. The work has some referential meaning on the ephemeris parameters design of our country global navigation and positioning system. When we calculate satellite coordinates in the use of GPS broadcast ephemeris parameters and user algorithm, we may meet the condition that satellite coordinates accuracy is greatly reduced because of the missing data. How to solve this problem is worthy of discussion. This paper does some research work on the above problems, and the following will briefly introduce the main content and the innovation points of the thesis:1. The development of four current main navigation and positioning systems is analysed. It shows that researching the broadcast ephemeris parameters and fitting method of GPS and GLONASS is necessary, which can provide the basis for the development of global navigation and positioning system in our country.2. As a current wide application and good method in processing missing data, EM algorithm is studied in detail, and apply to satellite orbit calculation by combining chebyshev fitting method when it has missing datas. The research shows that the EM algorithm can dig out the potential data of observation data, then make up for the deficiency that chebyshev polynomial must reduce the order because of the lack data, finally improve the precision of satellite orbit coordinates.3. GPS broadcast ephemeris parameters and fitting method is studied. According to the GPS16and GPS18parameters, concrete examples are given, which analyzes the effect on the performance of the ephemeris algorithm when changing some parameters. Then interpolating satellite orbit by using the GPS precise ephemeris validates the affection. Results prove that GPS18parameters can improve the accuracy of ephemeris fitting effectively by adding two perturbation parameters which can absorb the perturbation error of satellite orbit better.4. GLONASS broadcast ephemeris parameters and fitting method are studied, which is compared with the GPS broadcast ephemeris parameters and fitting method through the concrete example.Then interpolating satellite orbit by using the GPS precise ephemeris validates the merits of parameters and fitting method of two systems. The result indicates that GPS broadcast ephemeris parameter model has a higher accuracy, but GLONASS broadcast ephemeris parameters model has a quicker computation speed, which is suitable for determinating orbit which changes fast.