Navigation on Railway Tracks by means of GPS/INS and Navigation Marks

摘要

The need for the navigation on railway tracks is from automatic track control to the exact localization of errors in track geometry. Common to all tasks is the demanded accuracy of ±0.5m. Until now there is, due to multiple path problems etc. no possibility to achieve this accuracy only by DGPS. Additional information is needed to proof and to improve GPS data. One classical approach is the combination of GPS and INS (Inertial Navigation Systems). But even very good INS have navigation errors of 1 nautical mile within 24 hours or ±1,2m per minute. So in long tunnels with a legth bigger than 3km we will risk to have errors of more than ±0.5m. To improve the accuracy we shall use Navigation Marks (NM). These are events in a track with precisely known location, like Inductive Safety Instruments (InduSI), switches or track crossings etc. Using data files containing all the information about the exact location of the NMs and a sensor to detect them precisely and reliably we have an update of the INS in the mean at every kilometer. Deutsche Bahn has developed optical sensors to detect InduSI, switches and crossings. A highly accurate INS like a MINICIN 4 or a SIGMA 40 with integrated GPS from Sagem allows the precise navigation, and in combination with a good odometer precise localization of a train, even at high speeds, within ±0.5m can be achieved. Such a system has the ability of autonomous navigation which is important when there is no GPS available. Together with the Sankt Petersburg Electrotechnical University (SPEU) Deutsche Bahn develops a system to determine the locations of the NMs. The task is to verify and to complete the existing data files. This system works with the optical sensors for detection of the NMs, a SIGMA 40 for Navigation and an integrated GPS in real-time or post processing where real-time DGPS is not possible. The system's configuration and operation as well as the working conditions are described in this report.