Evaluation Method of GNSS–based Positioning Functions for Safety Applications in Operational Conditions

Most of the positioning functions in railways today rely on track side sensors that are efficient, but offer mainly discrete positioning, lead to high maintenance costs and differ between countries. Railways demonstrate their interest for the localization technology based on GNSS. Use of the satellite technology for safety operations is a major possibility. The condition is to evaluate the positioning function in terms of the RAMS attributes, as required by railway standards. However, no current evaluation methods are able to consider the signal degradations of wireless communications caused by the railway environment. We propose, in this paper, a methodology based on an Operational Experience Feedback procedure for quantifying RAMS properties and their sensibility to the operational conditions. The applications will focus on the Tr@in–MD project devoted to dangerous good tracking. Scenarios, i.e. temporal sequences constituted of up and down states that succeed randomly, will help to provide the results. To obtain different scenarios of evolution, the Ergospace software will be used. Raw data associated to a wagon that runs on an itinerary in different typical railway environments, with different satellite configurations, will be collected and processed.