Integrity monitoring and risk evaluation for BDS-based train positioning using track map database

Train positioning is a fundamental function which is required by many location-based railway applications. The rapid development of satellite navigation technology enables a better cost-effectiveness for the safety-critical railway train control systems. When using BDS (BeiDou Navigation Satellite System) in train control, it has to be ensured the positioning module takes full consideration of the potential safety risk, and the integrity monitoring is of great necessity to fulfill the safety requirement. In this paper, we expand the coverage of the integrity monitoring to the integration of the track map database, where map-matching is investigated to generate the error bound estimation using the match residual, and a global approach for determining Horizontal Protection Level (HPL) is proposed by integrating the local solutions. Based on that, some issues are discussed to evaluate the integrity risk and the availability of integrity monitoring. Results from simulation demonstrate the potential of the proposed method in practical applications, and illustrate the effect of integrity monitoring to the practical train operation scenarios.