alt Hacker NewsIIUC, GPS picks one satellite and 3 more to establish time differences between the first one and the other 3. There's only one point in universe where the set of differences would match what was observed, given the broadcast orbital data of satellites, and that gives the location of the receiver. It's like you are provided radii and center coordinates of 3 circles on a paper that intersect at 1 point and you are to math that point.
So GPS-like systems need precise orbital data and coherent clock from each satellites, or otherwise the receiver cannot figure out those radii.
Presumably you can have each sats reflect a clock from the same master ground station but that's not how GPS is implemented currently.
Coherency is a state. My question is if that state can be achieved by just tuning the individual clocks/locations based on GPS as a master. And, there's other tricks, with all the inter-satellite communication [1].
And, there's a contextual difference here between civilian GPS and military GPS. Much of the precision in the existing GPS satellites is to support the military use of GPS, with intentionally error injected into the civilian side.
And, by the nature of the hostile environment the military operates, military craft don't have as strong of a reliance on something that's ephemeral, like a GPS signal on a battlefield.
[1] https://arxiv.org/pdf/2501.05302