This paper presents the results of a research project that investigated the potential benefits of a combined Galileo/GPS navigation system. The research addressed in detail the two key required navigation performance (RNP) parameters of accuracy and integrity. The project was supported by Alcatel Space and was a contribution to the Galileo definition studies (supported by the European Community under the GALA project). The results show significant improvements in both accuracy and integrity (achievable through RAIM) when a combined constellation is used rather than Galileo alone.
