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Longitude calculations can be simplified using a clock is set to the local time of a starting point whose longitude is known, transporting it to a new location, and using it for astronomical observations. The longitude of the new location can be determined by comparing the difference of local mean time and the time of the transported clock.
Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is a 1995 best-selling book by Dava Sobel about John Harrison, an 18th-century clockmaker who created the first clock (chronometer) sufficiently accurate to be used to determine longitude at sea—an important development in navigation.
John Harrison (3 April [O.S. 24 March] 1693 – 24 March 1776) was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of how to calculate longitude while at sea.
Dava Sobel (born June 15, 1947) is an American writer of popular expositions of scientific topics. Her books include Longitude, about English clockmaker John Harrison; Galileo's Daughter, about Galileo's daughter Maria Celeste; and The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars about the Harvard Computers.
The Greek Marinus of Tyre (CE 70–130) was the first to assign a latitude and longitude to every place on his maps. From the late 9th century CE, the Arabian Kamal was used in equatorial regions, to measure the height of Polaris above the horizon. This instrument could only be used in latitudes where Polaris is close to the horizon.
Longitude is given as an angular measurement with 0° at the Prime Meridian, ranging from −180° westward to +180° eastward. The Greek letter λ (lambda) [38] [39] is used to denote the location of a place on Earth east or west of the Prime Meridian. Each degree of longitude is sub-divided into 60 minutes, each of which is divided into 60 ...
Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time
The French Bureau of Longitude established a commission in the year 1897 to extend the metric system to the measurement of time. They planned to abolish the antiquated division of the day into hours, minutes, and seconds, and replace it by a division into tenths, thousandths, and hundred-thousandths of a day.