There is a feedback loop between accuracy of clocks and accuracy of charts. Measuring longitude requires an accurate clock on a ship, which can keep a reference time to compare with local solar time.
The obvious challenges include motion of the ship and huge ranges of temperature encountered on global voyages.
Britain invented the best maritime clocks by encouraging open competition for a large prize.
You can see John Harrison's chronometers at the Royal Observatory in Greenwich - on the top of a small hill in a park in south-east London. It really is amazing how the original desktop clock monsters were shrunk down to a pocket watch that had better accuracy.
Greenwich was the prime meridian because Britain invented the best clocks.
Resolution 2, fixing the meridian at Greenwich, was passed 22–1 (San Domingo, now the Dominican Republic, voted against); France and Brazil abstained. The French did not adopt the Greenwich meridian as the beginning of the universal day until 1911. Even then it refused to use the name "Greenwich", instead using the term "Paris mean time, retarded by 9 minutes and 21 seconds". France finally replaced this phrase with "Coordinated Universal Time" (UTC) in 1978.
The obvious challenges include motion of the ship and huge ranges of temperature encountered on global voyages.
Britain invented the best maritime clocks by encouraging open competition for a large prize.
https://en.wikipedia.org/wiki/Longitude_rewards
See the book Longitude by Dava Sobel.
You can see John Harrison's chronometers at the Royal Observatory in Greenwich - on the top of a small hill in a park in south-east London. It really is amazing how the original desktop clock monsters were shrunk down to a pocket watch that had better accuracy.
Greenwich was the prime meridian because Britain invented the best clocks.