Link to facts, at the other wiki
In brief, figuring out how far north or south you are is easy, so long as you can see the sky. On the other hand, it used to be extraordinarily difficult to figure out how far east or west you were, especially when you were at sea. I've seen this referenced in fiction a few times. I'm not sure if it shows up often enough to be worth a page here, but it really ought
to. So maybe it does.
- The Baroque Cycle has a bunch of navigation without a solution to the problem. They need to keep their charts organized by longitude.
- The Island of the Day Before by Umberto Eco contains a number of different attempts to solve the longitude problem, including one that uses Sympathetic Magic (the theory is that a wounded dog is taken on the ship; the sympathetic magic is performed on the dog every night at midnight in Paris; by watching the dog's reaction and noting the local time, you can figure out your longitude much as with the "clock" method).
- I think I have a vague memory of some Aubrey-Maturin book where Jack loses/breaks his chronometer and is handicapped in a subsequent chase by having to navigate by dead reckoning. Am I making this up or not?