So it doesn't solve the issue inherent will all inertial navigation approaches (error accumulates very quickly because of the double integration), it just has less error?
Seems like an incremental improvement at best.
Seems like an incremental improvement at best.
Which means that if only one device knows where it is, you can calibrate, and if several know, you can even correct for mistakes.
If the system is precise enough, you only need to calibrate once in a while. Being at home/office, on the local wifi, once, could be enough.
Besides, nobody wants the GPS to go, but it's a nice alternative that can't be jammed by enemy forces and can be used for hiking, diving, etc.
I mean the exact position, down to a millimeter, when e.g. a photo sensor on a train passes past a LED mounted below the station platform. The LED's light is modulated so there can be no mistake, and its location is precisely known.
This is absolutely overkill for a train where you can just rely on a calibrated odometer to know your position.