Integrating Global Navigation Satellite System (GNSS) into railway application has a great potential because of its various advantages, such as lower cost, less trackside equipment, higher positioning accuracy, easier maintenance and so on. Railway system is a safety-critical system that requires high reliability, safety and real-time performance, so GNSS technology must be tested, verified and validated in railway system before putting into practical applications. However, due to the unavoidable restrictions and inconvenience of the railway field conditions, these tests cannot be accomplished on site. On this basis, this paper has developed a GNSS-based train trajectory simulation system which can provide GNSS data simulation of multi-train trajectory in multiple scenarios in order to support the tests and research of GNSS-based railway application, especially GNSS-based train localisation system and GNSS-based train control system.
The GNSS-based train trajectory simulation system is based on the railway timetable (also called schedule), rolling stock information and digital track map. The paper firstly researches on the timetable that stores information of each train at each specified station, including arrival time, departure rime, track to be occupied, and connections to other trains. With the timetable simulation, the train’s trajectory can be generated using the information provided by the digital track map. The output trajectory data is mainly GGA sentence which is compliant with the National Marine Electronics Association (NMEA) 0183 standard. The paper also calculates the satellite visibility based on satellite ephemeris to simulate the number of visible satellites during the trajectory with changing time and space. All the information and data, such as timetable, speed/distance curve, distance/time curve, station track occupation state, can be visualized and updated in graphics and diagrams for better view. In addition, the train motion behavior of acceleration, cruising, coasting and braking can also be modelled in the system, as well as the driver’s behavior.
The GNSS-based train trajectory simulation system has been realized using C# programming language in Microsoft Visual Studio 2010. And the field data of Shanxi coal railway transportation company railroad is used in the system. The simulation system is tested and the experimental results show that the developed simulation system can perform the expected functions, and provided data source for GNSS-based train localisation system. In addition, this simulation system has a good performance in compatibility and scalability.
