Dead Reckoning
This is method of navigation that doesn’t rely on external waypoints or input. If starting from a known position, with known speed and direction at all times, you can theoretically look at a map and figure out where you are.
It’s like a pirate map that says something like, “Walk 40 paces north from the oak tree, then turn left and walk 10 more paces.” The only known point is the starting point. You can tell where you are from speed, distance, and direction you have traveled.
Of course, you have to be exact about those things. If your calculations are mistaken, you’ll end up in the wrong spot and everything from that point forward will be wrong. So, you need to account for things like drifting and wind and anything else because inaccuracies on any step will cascade to every step that follows.
Why I Looked It Up
I was watching the new Mission Impossible movie, which is subtitled “Dead Reckoning.”
In the beginning of the movie, the log from a submarine says they’ve been traveling using dead reckoning, presumably as a way to avoid detection by checking with any external waypoint.
Note that the phrase was not mentioned again for the entire movie. It just sounds cool, I guess, so they figured out way to shoehorn it in.
However, it’s worth noting that the plot of the movie sort of fits. It’s about an AI “entity” that has taken over networks, so they can’t depend on anything digital anymore. To be sure of anything, they have to witness it, which sort of (…?) has something to do with the meaning of dead reckoning.