Issues on Uncertainty to Train Positioning in Hybridized-GNSS Approaches

The adoption of the Global Navigation Satellite System in the context of autonomous railway traffic and train positioning is gaining a great interest, with recent proposals for its hybridization aimed at ensuring a continuous, reliable, and accurate positioning service. Among the proposed approaches, the integration with localization techniques available within the upcoming fifth generation communication networks is addressed. In this work, different hybridization solutions are reviewed under the perspective of the uncertainty of the attained results and performance. Open issues are identified, which should drive future research activities in this field.