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wiradikusuma | 1 month ago

Don't trains run on a fixed path, meaning we can use more traditional "positioning systems" like, umm, math? Or placing passive sensors or paint a big number on the wall?

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cameronh90|1 month ago

Maths isn't a sensor technology. Wheels slip, air pressure fluctuates, rotary counters misread, errors accumulate, so better raw data could get you a more precise estimate of your current position. Various position technologies are already in use (e.g. "balise") but they have their limits if you're after cm-level accuracy.

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.

avianlyric|1 month ago

> 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.

jojobas|1 month ago

An experimental cryogenic device doesn't sound very good in terms of reliability. A train could have a few free rubber-coated wheels dedicated for precise odometry, there could be cameras with optical flow/reference markers on the tunnel walls every so often, virtually anything seems to be better than sinking millions in quantum devices.

amelius|1 month ago

Maybe they used trains as an example because that's the only application for which the accelerometer technique is currently sufficiently accurate.

__alexs|1 month ago

The worlds longest linear encoder?