A Flexible Ephemeris Representation for Global Navigation Satellite Systems and Alternative Positioning, Navigation, and Timing Signal Sources Using B-Splines

Abstract

All global navigation satellite systems (GNSSs) include a broadcast ephemeris within their navigation data that allows users to compute satellite positions in real time. This information is essential to support stand-alone point positioning. While the accuracy and precision of the satellite positions have a direct impact on the quality of the user's position solution, the length of the ephemeris data affects both the time a receiver must stay locked onto the signals and the user's time-to-first-fix. Current GNSS broadcast ephemeris parameters are carefully selected to balance sufficient accuracy for position solutions and compactness for rapid reception by users. However, it is important to note that these specific parameters vary across different constellations. Each GNSS constellation has unique algorithms and physical constants specified in their respective interface control documents that are