GPS is a pretty cool case. It's not the first navigation system out there, not even close. But the designers did something pretty forward-thinking and a bit risky: they made a big chart of all the different ways to implement GPS. A system where the ground based receivers has to talk back to the satellite. A system where every user needs their own atomic clock. A system where every user needs to communicate with a satellite. A system where every user needs to communicate with a separate ground station. Systems whose accuracy decreased at higher velocities. etc. The final solution was one that required more satellites, but allowed users to determine their own 4D position without needing any outside resources. The only downside was that it required portable atomic clocks, which didn't exist yet.

Not sure if that's black swan territory or not, but IMO it was a great piece of forward-thinking that made GPS useful beyond just the original military applications.

No. You're correct. GPS is the culmination of 50 years of work in radionavigation, and it wasn't the first satellite navigation system either.

As so often, the refinement of the technique makes it so widely available and effective that, without being revolutionary in principle, it becomes revolutionary in effect.

Telecommunications is like that. A century ago a telex from Australia to England could make it from desk to desk in under an hour. The Internet is not revolutionary in that sense. And yet it is revolutionary anyway.

> I can imagine something like GPS was envisioned well before the first satellites were even launched into orbit.

I don’t know about that. Maybe it was. What I do know is that we have documented speculation about satelite based navigation the days right after the launch of Sputnik.

American scientist figured out the orbit of Sputnik independently from the Russians by measuring the dopler shift of the radio transmission with their radios. Then knowing where their radio is located they used an iterative optimisation process to identify the orbital parameters of the satelite. Immediately there they were talking about how if the orbit of the satelite were known they could use the same process backwards to fix their location. That was 21 years before the launch of the first GPS satelite.

Now, that is not exactly how GPS signals work, and with good reasons. But it is the first documented seed of the idea of satelite based navigation that I am aware of.

Source: https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/...