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‘It’s the perfect place’: London Underground hosts tests for ‘quantum compass’ that could replace GPS
(www.theguardian.com)
this post was submitted on 19 Jun 2024
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the initial location doesn't need to be GPS, just a known anchor location. Which is trivial to implement in the case of trains, since stations don't move that drastically.
"Fixed" ground points move a surprising amount. The local ground can shift, and of course whole continents are constantly drifting.
surely these are things that should be considered, but they move in relation to what? And is this surprising amount of any significance for tens or hundreds of miles of rail?
In relation to all other points of interest, which are themselves all moving.
It's not really relevant for rail, no, but not because of inaccuracy and drift, but because the trains are on fixed paths already. Inertial navigation and dead reckoning are accurate enough to get from station to station, and each station can have local markers, even something as simple as a reflector at the end of the platform.
But they're not developing it just for rail. It would be incredibly valuable for submarines and mining, for example.
But wouldn't you scramble the precision with that? Stations can be quite big and anchoring to the station location means you already start with an offset to your location.
Depending on the accuracy over time, they could pinpoint a location while the user is sleeping and than use that as an anchor for the day.
But everything about that is speculative; let's see where this goes first.
you're thinking anywhere on the platform, I'm suggesting a known place near a station by which the train passes and its location - at that moment - is known.
All the system needs is a ground-truth location after a certain amount of time. GPS is just a cheap and convenient way to do it almost anywhere, but this location correction doesn't need to be satellite-based at all.
Yeah maybe that could work. I definitely agree that there's ways to get good anchor points. Maybe through cross-check with wireless networks even.