I'd just like to throw out a recommendation here for the book Longitude by Dava Sobel. It's about the invention of the marine chronometer by a self-taught carpenter. Fascinating read, and a real page turner too.
I’m reading and so far enjoying “A Brief History of Timekeeping” by Chad Orzel.
Not to discount Harrison’s achievements, but there are other interesting navigational approaches - using Tobias Mayer’s Lunar tables:
> Mayer is far less celebrated than Harrison, but his method was in many ways the more immediately successful of the two
Or, if society were to collapse and rebuild, Lewis Dartnell proposes a radio in “The Knowledge”, since a radio transmitter is probably simpler to build than an accurate chronometer.