[moftz]

How many people on the boat do you need that know celestial navigation? Sounds like something you could have someone go to school for to specialize in and then make sure you've got at least one on every boat rather than make everyone learn. We've got plenty of ways to defeat jamming, the newest block of GPS satellites have ways to increase signal power in certain areas and anti-radiation missiles can blow up a jammer. GPS only comes from space so it's pretty easy to find someone on the ground messing with it. We also have things like star trackers that are used on satellites to determine position without GPS that could easily be implemented on a boat if not already on there. These systems could be hardened against EMPs and only brought out in case of absolute emergency. I don't see the need of every navigator having their own sextant.

[goatinaboat]

How many people on the boat do you need that know celestial navigation?

Easy. The same number that know how to use a GPS. Your one guy may be the first casualty.

We've got plenty of ways to defeat jamming, the newest block of GPS satellites have ways to increase signal power in certain areas and anti-radiation missiles can blow up a jammer.

What do you do when your enemy dumps a load of sand in orbit?

[ls612]

GPS isn’t in low earth orbit it’s in a very high orbit so it shouldn’t be vulnerable to either asat missiles or space junk clogging up its orbit

[mjlee]

I don't think it was ever the case that everybody on board was taught astronav. It's very much a thing that's taught to the people who need to be able to calculate where the ship is.

That's about 4 or 5 people on a typical warship, and then you can add to that pool the number of people who did hold a job that required the skill but have since been promoted.