In the past, low quality sensors were blamed for imprecision in railroad monitoring.Most hall sensors can detect the train only at a certain position but can't provide GPS accurate information. A more robust technique are software defined feedback sensors which are particle filters.[1]
[1] Heirich, Oliver. "Bayesian train localization with particle filter, loosely coupled GNSS, IMU, and a track map." Journal of Sensors 2016 (2016).