Integrity monitoring of train positioning with GNSS

This paper discusses the integrity monitoring of train positioning with GNSS. It is shown that the number of samples needed to approximate the probability distribution of errors caused by interference with a sufficiently small risk is astronomically large. As an alternative, a geometrical upper bound for these errors is proposed. This bound is calculated from an observed clock bias in each epoch regardless of the interference. Experiments with a commercial rubidium oscillator show promising results in terms of the accuracy of the clock bias observation as well as the realistic upper bounding of positioning errors.