A system for testing and improving the accuracy of global navigation satellite systems (GNSS) in train tracking applications is being developed by researchers in Germany.
René Rütters and Thomas Engelhardt from the Institute of Automatic Control at Aachen University are working on a method to examine the integrity of satellite signals for potential use in the European Train Control System (ETCS).
In ETCS the speed of a train is compared with the maximum speed of the track. The train is automatically slowed down if the latter speed is exceeded.
To judge the speed, it relies on a combination of the use of on-board systems, such as wheel pulse generators and speed radars, as well as on-the-track devices, including electronic beacons that provide their position.
Rütters said: ‘The lack of GNSS in this application is partly due to the poor accuracy of the signals, which have a range of around 10m. What we hope to do is improve that accuracy to 2m by integrating on-the-track measurement devices with GNNS signals.’
The team at Aachen hopes to be able to correct errors in the GNSS-positioning information by calculating the range between the train’s antenna and each satellite as it passes an electronic beacon on the track.
If the difference between the positioning information is greater than the accepted level, a warning will be triggered to alert the train operators of an inconsistency.
Engelhardt said: ‘This is still at a very early stage, but we hope to have a prototype system that will demonstrate the concept within the next two years.’