Self‐assisted first‐fix method for GPS receiver with autonomous short‐term ephemeris prediction

Abstract

The time needed to get the first position is one of the key parameters to assess the performance of a global position system (GPS) receiver. Here, the authors present an autonomous satellite orbit prediction algorithm to provide usable ephemeris before the broadcast ephemeris is completely collected. Experimental results show that, with the ephemeris prediction algorithm, the TTFF of the receiver saves ∼74% in cold start mode. Furthermore, the accuracy of the presented algorithm is improved by using an empirical SRP model with parameters depending on the angle between the Sun and the satellite's orbital plane. Simulation results show that, for GPS PRN 5, when the SRP model with constant parameters is used to extrapolate the orbit for 5 days, only 43% of the position error is within 10 m, but this percentage can reach to 87% using the SRP model presented here. In addition, some single point positioning experiments with simulated satellite signals and real satellite signals are conducted to analyse the positioning results of the receiver with ephemeris prediction. The experimental results verify the effectiveness of the proposed algorithm.