A reference satellite selection method based on maximal elevation angle during the observation period

In the research and precise applications of Global Navigation Satellite System(GNSS), it is often necessary to choose a reference satellite for differential combination calculation, such as Real Time Kinematic(RTK) positioning, Uncalibrated Phase Delays(UPD) solving based on between satellite difference etc. In a specific period, the more reasonable selection of the reference satellite is, the better achievements of the calculation results will be. In this paper, three reference satellites selection principles are used: 1) the observation period is long enough; 2) satellite elevation angle is high enough and 3) reference satellite is not changed in a specified period. Based on these principles, two common reference satellite selection algorithms are compared, including the algorithm of Maximal Elevation Angle in Whole Period and the algorithm of Longest Period Span with a restriction condition of maximal elevation angle during the specified period. After analyzing the changes of elevation angle of all the visible GNSS satellites of three observation stations in different latitude with time, it is found that there is a parabola relationship between elevation angles (over 30°) of satellite and epochs. This paper presents a fast reference satellite selection algorithm based on the maximum elevation angle at the epoch period center. The analysis results show that the new algorithm is more easily realized under the same conditions than the other two algorithms, and the selected reference satellite not only has enough available period, but also has better geometry structure.