An improved ephemeris algorithm of BeiDou GEO satellite for user

The orbital inclination of 5° coordinate rotation is required in the GEO ephemeris algorithm for users. Aimed at this step, an improved method that the BeiDou GEO satellite position is calculated directly by using the classical broadcast ephemeris algorithm for user was presented, and meanwhile the corresponding broadcast ephemeris fitting algorithm based on the second class of non-singularity orbit elements was given. In this method, the classical orbit elements were replaced by the second class of non-singular orbit elements, which solves the problem that the coefficient matrix is non-positive in the process of the classical broadcast ephemeris fitting algorithm because of the small inclination angle. This avoids the orbital inclination of 5° coordinate rotation process, decreases the calculating steps time and enhances the GEO ephemeris algorithmic efficiency. The simulation results show that the accuracy of the improved method is as much as the original algorithm in the satellite orbit fitting process and is reduced slightly in the satellite orbit extrapolation process. But it can still meet the requirement of navigation and position for users. Finally, the validity of the improved algorithm is verified by using orbital data of the actual BeDou GEO broadcast ephemeris.