Analysis of Fitting Accuracy of Satellite Orbit Based on BDS Broadcast Ephemeris

In real-time positioning and navigation,in order to improve the efficiency of calculating the satellite position using the broadcast ephemeris of BDS,it is proposed to fit the satellite orbit to a polynomial. Firstly,using Chebyshev polynomial fitting method, the fitting period was fix to 1 h,the fitting interval was fixed at 5 min,and a checkpoint was selected every 30 s, different fitting orders was used,the Beidou satellite orbits of three different types of geostationary earth orbit,medium earth orbit and inclined geosynchronous orbit was fitted and analyzed. Then, the fitting order is fixed at 9, and the orbits of three types of satellites as a whole is fitted and analyzed using a fitting interval of 2 to 6 minutes..The example shows that as long as the appropriate fitting order is selected,the Beidou satellite orbit fitting accuracy of the three different types of orbits is high.The maximum fitting error is in the centimeter level,and the average error is in the millimeter level, which satisfies the precision requirements. When the fitting polynomial is fixed at the 9th order, the fitting accuracy of 2～6 min time interval can meet the precision requirement.The Chebyshev polynomial fitting method is suitable for the fitting of the satellite orbit of BDS broadcast ephemeris.