1 GNSS Receiver Autonomous Integrity Monitoring (RAIM) Performance Analysis STEVE HEWITSON AND JINLING WANG School of Surveying and Spatial Information Systems The University of New South Wales, Sydney, NSW, 2052, AUSTRALIA Ph: +61-2-9385 4185 Fax: +61-2-9313 7493 Email: s.hewitson@student.unsw.edu.au , jinling.wang@unsw.edu.au ABSTRACT The availability of GPS signals is a major concern for many existing and potential applications. Fortunately, with the development of Galileo by the European Commission (EC) and European Space Agency (ESA) and new funding for the restoration of the Russian GLONASS announced by the Russian Federation (Revnivykh et al., 2005) the future for satellite based positioning and navigation applications is extremely promising. With the complete co-operation of all these Global Navigation Satellite Systems (GNSS) greater levels of satellite visibility and therefore integrity can be expected. In this paper, a Receiver Autonomous Integrity Monitoring (RAIM) scheme along with Reliability and Separability measures are used to assess integrity performance levels of standalone GPS and integrated GPS/GLONASS, GPS/Galileo and GPS/GLONASS/Galileo systems where the clock offsets for each of the additional systems are estimated. It is shown herein, that a minimum of 3 satellites must be visible in an additional system in order to provide a full integrity contribution when the system’s clock offset is to be estimated within the adjustment. A comparison of the integrity results obtained via system clock offsets estimated in the adjustment versus the case where the offsets are known and the measurements are corrected prior to the adjustment is also made for a high elevation mask scenario. Global simulation results for combined GPS/GLONASS/Galileo show that, theoretically, for the time of simulation and for any point on the globe, an outlier of 20m can be detected with 80% probability at the 0.5% significance level and then separated from any other measurement with 90% probability. Corresponding values for the GPS only and combined GPS/GLONASS and GPS/Galileo systems respectively are approximately 435m, 110m and 28m respectively for the maximum MSBs and 312m, 50m and 26m respectively for the maximum MDBs. Temporal 24 hour simulations for the GPS/GLONASS/Galileo scenario delivered agreeable results with the global snapshots for a 15º elevation mask. For the case where system clock offsets are estimated within the adjustment, it was shown that only the reliability measure was available for 100% of the time, with horizontal external reliability values of no more than about 12m when a 30º masking angle was used. By assuming the clock offsets were determined and corrected for prior to the adjustment, the separability measure was markedly improved and was also available 100% of the time.