> Wouldn't dead reckoning with the accelerometer and gyroscope in addition to their machine learning improve this significantly? The thing that should help the

> Wouldn't dead reckoning with the accelerometer and gyroscope in addition to their machine learning improve this significantly? The thing that should help the most would probably be the hall sensor/magnetometer/compass. That should output decent dead reckoning. Doing this just with the gyroscope will work very well for short movements, but it will be close to useless on long, gentle curves. Unfortunately, those MEMS gyroscopes drift quite a lot over tens of seconds. Not a problem if you can do sensor fusion with the magnetometer (reckoning) and the accelerometer (where is "down"), but the latter can't be used on a fast train, acceleration/deceleration of the vehicle and forces in curves make finding gravity challenging. No idea how well a compass works inside a subway tunnel. But maybe I'm wrong, I just have experience trying an "artificial horizon" app on an aircraft - and here, the accelerometer is completely useless for "down". A single maneuver with some Gs and the horizon has no idea what the pitch angle is. Noisy magnetic environment, GPS off? It also doesn't know where it's going.