Track constrained RTK for railway applications1

At the start of missions trains compliant with the European ERTMS/ETCS standard have to run in Staff Responsible Mode (SRM) until the track where the train is lying on is identified by the Control Center (i.e., the Radio Block Center). Since SRM implies very low average speeds, this procedure produces a waste of time, and then money, every time a service starts. Thus, rail infrastructure managers are starting to ask for GNSS based solutions, able to determine which is the track occupied by the train in a very short time. Thus, in this paper we investigate PVT solutions based on multiconstellation receivers and dedicated augmentation networks that allow to determine the unknown track at the start of mission with the required safety Integrity level (SIL- 4). Particularly we focus our attention on RTK solutions that benefit of the constraint represented by the track for the train location, in order to speed up convergence. Considering that the saved money strictly depends on the time needed to solve phase ambiguities, a double frequency solution has been considered. In this contribution a detailed description of the overall processing and achievable performance is given. Assessment of the performance is provided by means of Monte Carlo simulations making use of observations recorded in the framework of the European Union Horizon 2020 Galileo-2014-1 ERSAT EAV Project.