An Approach to Inertial Navigation System-Aided Global Navigation Satellite System Carrier-Phase Positioning

Abstract

Current systems of the carrier-phase-based positioning require the use of differential methods, employing simultaneous measurements on a base station. The main problem, which hinders the absolute phase measurements, is insufficient mutual synchronisation of the satellite and receiver clocks. This insufficient synchronisation results in unknown parameters which are difficult to determine using the stand-alone equipment: the integer cycles number N, the phase at the transmitter's antenna j_s and the initial phase of the receiver's reference generator j_r^int. The new method proposed in this paper allows estimation of the two latter parameters with the aid of information from an inertial system. The main idea of the proposed principle is that INS and carrier-phase measurements have different error structures. The paper shows that a residual between the INS and carrier-phase measurements under certain conditions has a periodic nature, and the corresponding error source - bias on a satellite antenna - can be tracked and eliminated. The second error is the phase bias in the internal receiver generator, which can be estimated by Kalman filter. The method proposed to resolve the integer ambiguity needs a dual-frequency reception. Although this approach theoretically allows an absolute positioning, it is still desirable to use any type of a wide-area differential correction, because certain influences of the error sources cannot be sufficiently eliminated to take advantage of the carrier-phase measurements over the code measurements. The system was simulated using the Matlab/Simulink software package.