Seems kind of hard to imagine that any accelerometer can be so precise you can use dead reckoning to the centimeter over a long time scale. Especially given how strong acceleration due to gravity is.
But fiberoptic gyro navigation is already a thing, and has been for decades. It's not super cheap, but it's cheap enough for an industrial application like this one. So I'm not sure what problem is being solved here.
* What would the Central Limit Theorem give us if a significant number of wheels on loco's and carriages were instrumented and ID logged over the years.
* What drift patterns and correction factors can be observed and fine tuned by passing {many} wheel streams through station to station and line end to line end "known distance" corrections.
For half a century or so aircraft height was largely done with air pressure alone.
To this day GPS accuracy is "improved" by logging the "drift" of fixed point stations giving us filter coefficients to correct for atmospheric wobble, acute angle uncertainty, as yet uncorrected time drift, etc.
It still is. Flight levels (20000 feet and above in the US) are defined by air pressure without reference to current atmospheric conditions (i.e. the actual altitude of FL200 can vary based on atmospheric conditions). Below 19000 feet, altimeters are calibrated to local conditions which are given to the pilots by air traffic control.
See: https://en.wikipedia.org/wiki/Altimeter that list five types (including trad. air pressure type)
Also trains have quite a large number of axles, I'm sure you could reduce error by counting all of them.
A curious advantage of instrumenting all axles for wheel turn counting is calibration against actual known distances (end to end, etc) over time reveals slow wheel degradation that can trigger carriage maintainance.
Not all operators do this, it's been done at various times for heavy rail mining operators with loooong trains and heavy daily usage.
The spit up of grease, leaves, metal particulate from rail and wheel grind, etc gets pretty thick.
The vision challenge is to cheaply and effectively keep a clean lens.
There's a similar challenge in monitoring production conveyor belts in mineral processing - vibration, tempreture, rocks kick about, dust make for a savage environment.
https://www.universalsignalling.com/news/latest#h.12nuchpah7...
I would wager that actually this is probably just a way of funnelling money into research around quantum rather than genuinely trying to solve this specific problem. This specific problem sounds like it could be solved for a lot less money using conventional accelerometers in combination with some other local location data (optical sensors for example, you're in a very controlled environment).
You’re absolutely correct, from the government’s perspective the interest in the technology is for high accuracy inertial navigation systems for defence purposes, not for the London Tube. If you look at the other companies involved in this project, there’s a number of defence contractors involved.
This project isn’t really new, and historically the pitch has always been: We want to develop GPS grade navigation that doesn’t depend on satellites, and is smaller and better existing inertial navigation units. Oh look the London Underground is the perfect test bed for our technology!
It’s underground, so no GPS or many external signals. It’s already well mapped so we have something to compare against. Tube trains are loud, hot and vibrant a lot, which makes it a challenging environment for inertial systems. Plus it’s cheap and very easy to roll a box on an existing train, drive a few km under the city, and then compare your results to GPS from when you go underground, to when you surface again.
https://www.theguardian.com/science/article/2024/jun/15/lond...
The idea of using it map the underground I think is a bit of a red herring. Makes a good story, and TfL will probably be grateful for the data. But it’s not the kinda thing anyone thinks is worth developing quantum accelerometers for.
So this is a much more precise inertial guidance system replacement? If true, I'd expect UK MoD to be involved to the point of making technology a military secret, but clearly it didn't happen.
Seems like an engineered solution to rely on "quantum".
Agree in principle though, is this extreme precision really needed?
Considering the tracks are linear, I would estimate the additional time needed to locate a fault within two meters as compared to two centimeters at "negligible".
On the alternative assumption that the faults are too small for humans to detect and we just need to replace the affected track... I would also estimate the additional time needed to replace two meters of track, as compared to two centimeters, at "negligible". It doesn't actually take less time to cut out a specific 1cm strip (containing no visible indications!) from a piece of cloth as to cut out a 1m strip that includes the 1cm strip somewhere.
My general thought as someone who doesn't know how rail maintenance is done is that rails should not crack in normal operation. If there is a crack that implies either the rail is end of life anyway and you replace it, or there is likely a manufacturing problem and you want to replace all the rail from that branch. Either way rail is manufactures in long sections (20 meters is my guess, but that is slightly educated guess that I won't stand by), so you would only need within a few meters to find the track section in question.
However I don't know how track maintenance is done. It is entirely possible that they grind/cut out the crack and then fill in (either cast in place, fill with weld, or just replace a a few cm) and in that case you would need to know within a few mm (though maybe inspection could find it if you are within a few cm).
Again, I am not a rail expert here. This is a place where I want to know and thus would like an expert to say. (though likely no experts are reading this...)
That said, I'm not buying that quantum INS is required for this over more established techniques like visual-inertial odometry. However, the UK seems to have a whole bunch of active quantum INS research projects, so I wonder if the tube stuff is just a weak public cover for the military/civil emergency applications that make the technology actually interesting.
The project is quite explicitly a defence project. IanVisits is just a transport blog, so the article focus on the transport aspect of this project. But reporting else where makes it quite clear this a defence project.
https://www.theguardian.com/science/article/2024/jun/15/lond...
The only reasons for the Tube being involved is as a test bed for the technology. It’s cheaper to put this box on a train and test it, than it is to put it on a boat or a submarine. It’s also handy that the researchers involved are based in London, so the commute to their test bed is nice and short.
https://www.railengineer.co.uk/controlling-the-elizabeth-lin...
> The signalling is essentially hands off and is timetable driven. The latter includes GoA3 reversing moves at Paddington and Abbey Wood which are fully automatic as are all entries into and out of a depot. The line uses axle counters for secondary train positioning information other than where neutral sections for the overhead power exist, where track circuits are deployed, these being seen as less vulnerable to any spark interference from the overhead catenaries.
Which then leads me to think the whole thing is a smoke screen, not sure why
> The project is being carried out in collaboration with Transport for London, QinetiQ, PA Consulting, Imperial College London and University of Sussex.
QinetiQ is a UK weapons developer, probably the UKs largest. So the defence angle isn’t really being hidden.
Older articles on this project from elsewhere outline the defence angle even more explicitly:
https://www.theguardian.com/science/article/2024/jun/15/lond...
But IanVisits is a transport focused blog, so the article has a transport focus, rather than a defence focus.
As to why any of this is happening on the underground, that’s pretty simple. Tube trains are a good real world test bed for this technology. Shove your quantum box on an existing train, drive it through the existing tunnels a few times as part of a normal tube service. Compare the run result and validate how accurate your technology is.
It’s a lot cheaper than putting it on a boat or a submarine. Not to mention Imperial College London is based in… London. They’re literally a five minute walk from a tube station.
being tested on trains makes complete sense
We won't know until someone looks at you. Until then you are on every station possible in the underground sorted of smeared out into a probability wave.
[1] https://www.nextbigfuture.com/2025/10/darpa-developing-quant...
Anyone here could solve this overnight with todays tech.
I want underground mini buses, optimizing their stops to the passengers' inside. Most of we passengers go to hub stations.
Tubes are like a 100-year old tech without remarkable changes.
27 (soon to be 30) trains per hour on the Jubilee line for instance, hundreds of people can get on and off each one.
I don't get it. Suppose this scenario:
- Instead of big formations, replace each wagon with an electric minibus. - Instead of stopping in all stations, each minibus stops in, lets say 3 or 4. - Each passenger checks into the bus dinamically assigned to their stop. - Minibuses can surpass each other.
You have less dwell time, each ride is reduced to one third of the time.
Instead of 10 formations of 6 wagons you have 60 buses.
You have same capacity and one third of traveling time per ride.
"Instead of relying on conventional sensors, these devices use clouds of atoms cooled to near absolute zero. At those temperatures, atoms start to behave strangely — acting as both particles and waves. As the atoms “fall” through a sensor, their wave patterns shift in response to acceleration. Using what’s effectively an ultra-precise optical ruler, the system can read these changes with extraordinary accuracy, without needing satellites at all."
It’s precisely the application of quantum physics that enables current prototypes of these IMUs to achieve 1-2 orders of magnitude less position error accumulation vs. state-of-the-art gyroscopes. Think 0.1m/min vs. 10m/min.
Obviously the tube isn’t the holy grail of applications, it’s just a test bed to improve the technology. Think about why GPS is useful. Imagine that, but entirely self contained.
beardyw•1d ago