This was known as running down a westing if westbound, or easting if eastbound. In order to deal with not being able to calculate longitude, captains would sail to the known latitude of their destination, and follow the line of constant latitude home.

Once out of sight of land, longitude became impossible to calculate, which sometimes led to tragedies in stormy or foggy conditions. A stable surface to work from, known coordinates to refer to, a sheltered environment for the unstable chronometers of the day, and the ability to repeat determinations over time made for great accuracy.įor calculating longitude at sea however, early ocean navigators had to rely on dead reckoning, or if in sight of land, coastal navigation, which involves triangulating several bearings of the same land feature from different positions. In 1998, The Illustrated Longitude was published, supplementing the earlier text with 180 images of characters, events, instruments, maps and publications.ĭetermining longitude on land was fairly easy compared to the task at sea. The book was made into a television series entitled Longitude.

Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is a 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.

Longitude sobel