First motivation for using of pseudolites (PL's) system was to extend the position locator based on the global navigation satellite system (GNSS) by the next navigation system for high critical applications as a movement of the train on the railyard and switches. A choice of PL's system was logic, because it minimizes requirements on the equipement used in the train. The same principle of measurement enables to use a hardware (antenna, receiver) common to the GNSS and also data processing can be common for both systems. This is necessary for the case, when there must be used a combination of satellite and pseudolite signal for one navigation channel, for example in the case of low visibility of only two satellites and two PL transmitters for example. In this case, only two satellites are insufficient for independent navigation channel and just as only two PL's and it must be used their combination. During a design of the PL's system configuration - number and dislocation of transmitters, the reference station and others - it was necessary to determine the usability of this system for required applications. For the certification of safety related applications based on the GNSS (GPS, GALILEO) can be used methods from the analogous system of PL's. This is system of local navigation based on same principle as the system of satellites - measurement of time delay. The local using is restricted from global using to the area with a radius order of 10 to 100 meters. Only one significant difference between the satellite and pseudolite system is fixed and absolutely accurate position of PL's transmitters. But, this fact simplifies the description of certification methods. The time variability and uncertainity of the satellite position must be necessary included to the final certification. Every measurement system is composed from several parts - hardware part (used sensors and process units), software part (software used for measured data process) and functional part (methods used for data process). And also every part can be more or less failured. These failures can be random or systematic. Typical examples of systematic failures are a drift of data or a noise. This paper will be intent on a description and certification of navigation systems and their application with regard of systematic failures of the functional part of measurements.
The using of pseudolite system in railway safety related applications
2008
7 Seiten, 5 Bilder, 1 Tabelle, 5 Quellen
Conference paper
Storage medium
English
Eisenbahnsignaltechnik , Erdefunkstelle , Funkempfänger , Funksender , Navigationssystem , Ortsbestimmung , Positionierung , Realzeitbetrieb , Risikoanalyse , Satellitennavigation , Sicherheitsanalyse , Systemarchitektur , systematischer Fehler , Systembeschreibung , Systemsicherheit , Zertifizierung
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