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.
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?
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.
There were recent exercises in the Baltics where US forces were exposed to learnings from the Ukraine conflict. Very different than fighting ISIS.
Turns out GPS jammers, proper drones, etc. can wreak havoc. The IDF got smoked in Lebanon for the same reason, the game has changed. Well prepared state-level adversaries are not the same as militias in pickup trucks and SVBIEDs.
"The common thread running through the paper is the challenge posed by Russia’s jammers and other electronic warfare tools.
An enemy equipped with these “could effectively neutralize a GPS system from 50 miles away using one-fifth the power of a tactical radio,” the report estimates, so “we should assume that GPS will be either unavailable or unreliable for the duration of the conflict if the [brigade] faces a near-peer threat or sophisticated non-state actors.” "
Others can speak for the military, but among civilians, it seems almost nobody learns orienteering anymore.
I only have anecdata, but the last several times I've been on remote camping trips, I've taught folks the basics myself. And a relative's son, a Boy Scout, was told by his troop leader that the Orienteering merit badge was obsolete, don't worry about it.
They now have a skill gap of mid-seniority navigators who have no astro-nav experience and will struggle under GPS denial.