A Method for Monitoring the Availability of Required Navigation Performance for Locomotive Satellite Navigation Equipment

this paper proposes a method for monitoring the availability of required navigation performance of locomotive satellite navigation equipment operating along a rigidly defined trajectory. The study is motivated by the necessity to detect, in real time, violations of required navigation performance when the navigation solution degrades. The method is founded on analysis of the positioning error ellipse parameters and on comparing its size and orientation with permissible safety bound aries, while accounting for the specific characteristics of train operation on railway line sections and within stations. The proposed indicator is generated from current a posteriori estimates of positioning error, in contrast to conventional techniques that depend on a priori estimates. The approach is implemented by referencing the instantaneous coordinates to an interpolated trajectory derived from a digital track map. Numerical simulations of representative navigation-degradation scenarios to gether with experimental data obtained from a moving platform have confirmed the method’s effectiveness. It has been demonstrated that the size and orientation of the error ellipse vary in response to anomalous disturbances, permitting rapid detection of breaches of required navigation performance and identification of the direction of maximum positioning error. The method is intended for automated train control applications and onboard high-precision positioning systems in railway transport.