Selected aspects of implementing the requirements of WGS-84 standard in land navigation for precise determination of a railway vehicle route

The paper presents a model of a hybrid INS/GNSS system developed at AFIT, designed to determine the current trajectory of a railway vehicle during its travel at a speed of around 100 km/h(30m/s) and to precisely determine the trackage axis. The architecture of a hybrid system for determining the trackage axis in conditions of GNSS signal interference was presented. Particular attention was paid to modeling INS errors in the determination of a vehicle trajectory (determined “on-line” within the current correction process by the GNSS) and modeling INS errors in the determination of the vehicle travel trajectory (determined “off-line” within the periodic correction process by the GNSS). The analysis involved the impact of inaccuracy of the WGS-S4 standard determination of selected geodetic parameters used in inertial navigation (i.e., local values: gravitational acceleration, Earth radius and the Earth angular speed) on the course of navigational position determination errors by an INS operating in automatic mode (without correction).