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World's first GPS-free quantum navigation trial succeeds at sea
(interestingengineering.com)
This is a most excellent place for technology news and articles.
In the middle of the ocean? Wouldn't that require a sextant, night time, and a lot of expertise?
And an extremely accurate clock (depending on how accurate you want your location to be).
https://en.wikipedia.org/wiki/Marine_chronometer
Wait until you hear about inertial navigation!
All you really need is to see the Jovian eclipses.