Researched
Marine Chronometer
Harrison's H4 (tested 1761-62) keeps time at sea within seconds, so ships can finally find their longitude.
Open in the interactive tree →Sailors could find latitude from the Sun but not longitude, which needs the exact time at a reference port. Britain's Longitude Act of 1714 offered a prize, and John Harrison's fourth sea clock, tested on a voyage to Jamaica in 1761-62, lost only a few seconds. Copies went with Captain Cook, and reliable longitude made sea charts, trade routes and exploration safer.
Prerequisites
- Mechanical Clock~1300
- Caravel & Circumnavigation~1450
- Sextant1731Longitude comes from comparing sextant sights with chronometer time
Unlocks
- Satellite navigation (GPS)1995GPS fixes position from precise time signals, the chronometer's longitude principle
Sources
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