In this work, we present an on-board solution for train position tracking that can be used in cases of GPS failures and that does not suffer from the error accumulation problem of Dead Reckoning (DR). It is based on Received Signal Strength (RSS) measured in radio communication systems by several mobile stations having antennas placed on top of different carriages of the train. As the RSS is affected by the slow fading or shadowing, both the position and the shadowing are jointly tracked. We estimate the shadowing atlas consisting of the shadowing maps along the railway of the different base stations. The proposed solution applies Bayesian filtering for efficiently processing the observations.