Last updated: December 30, 2019
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Navigation for Lewis and Clark

Photo courtesy of Norman Anderson, Lewis and Clark Honor Guard
They also used books and tables which provided information about locations of the sun, moon, and planets for use in determining the geographic locations after sighting the celestial objects.
The chronometer, possibly similar to this one, was the only form of accurately telling the time upon which many other calculations were based.
Learn more:
William Clark: A Master Cartographer