Map-Based Solution Separation RAIM for Train Localisation

GNSS-based train localisation for safe applications has the potential to become a game changer for creating more effective, safer and more efficient train control systems. Although GNSS-based solutions have successfully been employed in positive train control systems in the United States, they still do not fulfil the necessary safety standards to be used for absolute safe train positioning applications within train control systems in Europe. This is due to a different legislative environment but also technical issues such as a higher density of traffic. In order to use GNSS-based positioning with the European Train Control System (ETCS), a Safety Integrity Level (SIL) of 4 has to be demonstrated which includes a tolerable hazard rate of 1 × 10?9/h. One solution to achieve this could be Receiver Autonomous Integrity Monitoring (RAIM) as it has been employed in aviation for a long time. However, the limited number of visible satellites for ground-based applications makes it often hard to reach the necessary number of redundant satellite measurements to employ these methods. Therefore we propose in this paper the usage of railway map data within the RAIM algorithm to reduce the number of parameters to be estimated and increase the number of redundant satellite measurements.