The Influence of Satellite Elevation on Monitoring GNSS System Time Offset

Multi-system satellite navigation is an important development direction of Global Navigation Satellite Systems (GNSS) in the future. Because the system time of each satellite navigation system is independent, monitoring GNSS system time offset has become one of key issues solved in multi-system navigation. However, the monitoring accuracy of system time offset is affected by different elevations of satellites. First of all, the influence of satellite elevation on the signal propagation delay errors and monitoring results of system time offset is analyzed. On this basis, six kinds of weighting method based upon satellite elevation are proposed. Finally, with test data provided by a platform that monitors GNSS system time offset at National Time Service Center (NTSC), how various elevation weighting methods and cut-off elevation have an effect on monitoring results are verified. The results show that, for GPS and GLONASS, the monitoring accuracy is different adopting different elevation weighting methods, and the suitable cut-off elevation is 10 degrees.