The invention of a marine clock (chronometer) which could be used to accurately measure longitude was arguably the most significant development in maritime navigation in the seventeenth and eighteenth centuries. Before their invention ships had great difficulty finding their way from one port to another. Fog, bad weather, and inaccurate charts made navigation, when no land was in sight, both dangerous and time consuming.
Latitude and longitude can be thought of in the same way as the index of a city street map with the latitude being north/south and the longitude being east/west co-ordinates. Once both are known a position can be accurately pinpointed.
While latitude could be found by observing the position of stars longitude proved far more difficult to find. In fact an accurate means of finding an east/west position baffled navigators until 1759 when the clocks made by the Englishman John Harrison were finally acknowledged as being accurate enough to keep time at sea. Continue reading “Chronometers – timekeeping, longitude & latitude”