General dead reckoning is hard. But dead reckoning for train travel should be massively easier. Train movement is constrained to tracks so you only need to res

General dead reckoning is hard. But dead reckoning for train travel should be massively easier. Train movement is constrained to tracks so you only need to resolve how far along track train has moved + possible junctions, which should already make the problem much simpler than e.g. airplane ins where you are resolving full 3d position. To make things even more easier, you only need to reckon between individual stops which prevents error accumulation over the whole trip. Lastly you have schedule information, so you know roughly where the train should be at any given moment.