Estimation of the GPS to Galileo time offset and its validation on a mass market receiver

The European GNSS, Galileo is currently in its In-Orbit Validation (IOV) phase where four satellites are available for computing the user position. Galileo El OS and GPS C/A represent a very effective constellation pair in a consumer grade receiver: the signals are conveyed on the same analog path and measurements can be combined in a single position, velocity and time (PVT) solution, provided that the Galileo to GPS Time Offset (GGTO) is available. Algorithms for GGTO estimation are presented in this paper, including a real-time implementation on a compact hardware receiver, based on the Teseo-II chipset. Experimental results are provided, showing the benefit in terms of accuracy and availability of the Galileo plus GPS multi-constellation solution respect to the GPS only case. Also analyzed are the effects on the GGTO estimate of different ionospheric models, namely: GPS Klobuchar and Galileo NeQuick. Both simulated scenarios and real, recorded Galileo IOV samples from a roof antenna are used in the validation of the proposed algorithms.