Impact of Unknown Digital Map Errors on Satellite-based Navigation in Railway

Satellite navigation is considered one of the key technologies for future train control and railway signalling. Since Global Navigation Satellite System (GNSS) does not provide a location solution directly on the track domain, the use of a precise railway track map is essential to be integrated with GNSS. However, most current localization solutions assume that the track map, which relates the geographical position of the track with its unique location in the railway network, is perfectly known without any error. In this paper, we investigate and discuss the impact that digital track map errors can have on track-constrained GNSS positioning. First, we derive the mathematical basis that accounts for the propagation of map errors to the position solution. Then, we present the impact on the detection capability of pseudo range faults if these map errors are not known or ignored. The analysis show the importance of accounting properly for these errors to guarantee certain requirement levels.