Hänsel, F.; Ganzelmeier, L.; Becker, U.; Schnieder, E.:
Mobile Testbed for the Accuracy and Availability Measurement of Satellite Navigation Systems.
Proceedings of International Symposium on Certification of Galileo System & Services Cergal, Braunschweig, ''4 2005. Cergal 2005 - International Symposium on Certification of Galileo System & Services .


Safe operation control in non-guided traffic requires high availability and reliability of vehicle localisation technology. Normally the requirements for vehicle localisation systems can only be met by complex multi-sensor systems comprising on-board and trackside components like odometers, gyroscopes, transponders, etc. In recent times, satellite-based localisation technology has been increasingly used in traffic applications, and GPS–based systems are already in operation. One of these systems' most promising advantages for traffic is the fact that they provide absolute location information without requiring any trackside equipment. However, satellite-based localisation requires the reception of signals from at least four distinct satellites (simultaneously). But on many tracks, this visibility prerequisite cannot be fulfilled because of shadowing effects from the natural environment, buildings etc. This results in a considerable loss of localisation availability. In the near future, the information about the vehicle's position will be used for new, advanced driver assistance systems. In some of these systems the information about the position will be safety relevant. For these applications, the localisation system must meet special requirements in terms of availability and accuracy. For the homologation of these systems it will be necessary to precisely quantify the availability and the accuracy of the positioning subsystem under conditions that meet those during normal operation. For these qualifications a special measurement vehicle has been built at the Institute for Traffic Safety and Automation Engineering of the Technical University of Braunschweig. This vehicle facilitates the evaluation of the satellite based positioning's accuracy and availability under dynamic aspects. On the other hand this vehicle provides a testbed for experiments with upcoming satellite positioning systems with regard to dynamic aspects. This paper gives an overview of the applied methodologies in order to analyse satellite navigation systems in general and particularly satellite-based vehicle localisation systems in detail. The structure of the mobile testbed in form of a measurement vehicle is presented in details. The built up equipment allows the qualification of single satellite receivers up to complete vehicle localisation technologies.