Safety – Relevant Accuracy Enhancement and Signal Verification of GNSS Signals for Rail Applications
René Rütters, Prof Dirk Abel, Martin Baier, Björn Schäfer
Presently, satellite-based positioning services are virtually unutilised in train control. Crucial issues in train control include accuracy and integrity, as well as availability. A new approach to integrity and augmentation can help improve conditions in each of these areas. This solution makes use of the European Train Control System (ETCS) balises that are mounted standard on new European railway lines. A balise is an electronic beacon which represents a defined point on the track. In the moment a train passes a balise, its exact position is known. This core information is used in the new system. Once the train passes a balise, its position is saved in geo-coordinates and compared with the position determined via GNSS. This information corrects the train’s position by compensating for GNSS positioning errors partly caused by signal disturbances in the atmosphere. By generating a model of the atmosphere, the accuracy of GNSS positioning can temporarily be enhanced for a large regional environment. Additionally, a plausibility check is performed. The solution thus documents the integrity of satellite signals. Systematic manipulation of GNSS with an interfering transmitter can be detected as well.
The solution’s innovation lies in its combination of ETCS components and a GNSS receiver. Presently, research in this field focuses on the use of GNSS receivers as additional sensors without using information from the onboard ETCS unit. In contrast, this new integrity and augmentation system uses information from the existing ETCS infrastructure to improve the accuracy and integrity of GNSS positioning data.
The new integrity and augmentation system targets railway infrastructure providers.
Among other uses, balises are currently applied in resetting drift errors in vehicle data obtained with odometry. The new system can help to reduce drift errors: an integrity check facilitates the achievement of high security standards in train control. Thus, the number of balises on a line can be reduced and railway infrastructure providers can reduce the effort and costs in constructing, maintaining and operating their railways.
RWTH Aachen University
Institute of Automatic Control
phone: +49 (0) 24 18 02 74 83