Recently, a real-time accuracy of the differential Global Position System (GPS) receivers achieved a sub-metre level in code mode, and centimetre level in the Real Time Kinematics (RTK) mode. Thus GPS receivers became promising for low cost signalling concepts and other safety critical applications in the railway industry. This paper presents a verification methodology and experimental results of the US's GPS and Russia's Global Navigation Satellite System (GLONASS) based train position locator tests at Czech Railways. The verification methodology is derived from the current needs in signalling, and from the parameters of the satellite navigation systems. A key element in the investigation is a switch, on which reliable and continuous position determination of a routing train is most critical. Two-dimensional and one-dimensional routing detection models are analyed and esperimentally investigated on the switch-point. The trials were performed on Pardubice - Hradec kralove - Chocen line with the total track length of 100 km. Three mobile platforms were employed for the tests: 1) an electric locmotive operating passenger train for the long term locator verification, 2) a Diesel track motor-car for tests on a laboratory track in Pardubice stating, and 3) a remotely controlled ultra-light motor-driven track rover for the detailed locator tests. The data from/to the vehicles were transmitted along the entire trial track through the intelligent 150 MHz TDMA radio modem network with data rate up to 19.2 kb/sec. Finally, the safety-related requirements for future European navigation system GALILEO are specified and discussed.
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