John Davis
Davis, John (1550?–1605), an English navigator and explorer. Davis invented the backstaff, an instrument that enabled a navigator on a ship at sea to determine the ship's position by measuring the altitude of celestial bodies. Davis introduced the device in 1590. It remained in use until the development of the sextant in the late 18th century.
Little is known of Davis' early life. He made his first exploratory voyage in 1585 in search of a northwest passage to Asia. He was killed by Japanese pirates during an expedition to the East Indies.