Train location data from passenger mobile phones

The location of trains within a railway system is derived in a number of ways and for multiple purposes.

One use of this data is for “train prediction” - in the UK, these are the dot-matrix displays on the platforms and concourse which show you the expected arrival/departure of your train. Or sometimes “Delayed” or “Cancelled”.

This data is usually derived from track circuit or axle counter block data - which tells the passenger information system the approximate location of the train. The system calculates the predicted arrival time from the current location and expected delay.

The resolution of this system is pretty low - signalling blocks can be very long.

However, given that your train is carrying many passengers with GPS enabled phones...

A system which collects GPS data from multiple passenger phones could interpolate train position to a higher resolution, allowing more accurate train arrival predictions.

GPS is not considered accurate enough (generally) for railway signalling (as it may have to distinguish between trains located on adjacent tracks) - but it may be that filtering across a large-enough set of data provides enough accuracy for railway signalling also.