Lu, D.; Grasso Toro, F.; Schnieder, E:
RAMS Evaluation of GNSS for Railway Localisation.
ICIRT 2013 - IEEE International Conference on Intelligent Rail Transportation, Beijing, China, August 2013.
Global Navigation Satellite Systems (GNSS) are ready for various railway applications, especially the safetyrelated applications such as train detection and train localisation for the purpose of train control. Every safety-related application for railway should comply with a wide range of railway standards. In order to integrate GNSS into train localisation, a stand-alone satellite-based localisation unit should be developed. Then the demonstration of GNSS quality of service (QoS) should be implemented in consistent with EN50126 (Reliability, Availability, Maintainability and Safety, RAMS) standard. The RAMS standard seeks to evaluate massively the dependability (RAM) and safety aspects during the lifecycle before they are put into operation. However currently there is no RAMS evaluation method for GNSS-based localisation for railways available. In this paper, we propose a procedure and a model for evaluating GNSS in terms of railway RAMS, using the GNSS data derived from a large number of test runs along a railway line in the High Tatra mountains in Slovakia. We start by evaluating the accuracy, availability and then reliability as a whole to represent the QoS along this line. Since the localisation unit depends heavily on GNSS itself (especially satellites, signal in space and receivers), we investigate typical environment scenarios along this line in detail, for example open area, forest, etc. We evaluate quantitatively each scenario according to reliability and availability aspects, and on this basis we analyse the safety risks when GNSS is unreliable but available.