||It has been suggested that this article be merged with Board of Longitude. (Discuss) Proposed since May 2011.|
The Longitude Prize was a reward offered by the British government for a simple and practical method for the precise determination of a ship's longitude. The prize, established through an Act of Parliament (the Longitude Act) in 1714, was administered by the Board of Longitude.
The problem of longitude 
The measurement of longitude was a problem that came into sharp focus as people began making transoceanic voyages. Determining latitude was relatively easy in that it could be found from the altitude of the sun at noon with the aid of a table giving the sun's declination for the day. For longitude, early ocean navigators had to rely on dead reckoning. This was inaccurate on long voyages out of sight of land and these voyages sometimes ended in tragedy. Finding an adequate solution to determining longitude was of paramount importance.
For details on many of the efforts towards determining the longitude, see History of longitude.
Prizes offered 
The main longitude prizes were:
- £10,000 for a method that could determine longitude within 60 nautical miles (111 km)
- £15,000 for a method that could determine longitude within 40 nautical miles (74 km)
- £20,000 for a method that could determine longitude within 30 nautical miles (56 km).
In addition, the Board had the discretion to make awards to persons who were making significant contributions to the effort or to provide ongoing financial support to those who were working productively towards the solution. The Board could also make advances of up to £2,000 for experimental work deemed promising.
As a result of the disputes and changes in the rules (legislated or otherwise) for the prize, no one was deemed qualified for any of the official prizes. None of the major prizes were ever awarded.
Significant recipients 
|John Harrison||£14,315||Received in several payments. £5,315 was awarded during his work on his chronometers from 1737 to 1764 with the remaining £10,000 provided in 1765.|
|Tobias Mayer||£3,000||Contributions to the lunar distance method. His widow received the money due to Mayer's untimely death.|
|Thomas Mudge||£3,000||Construction of chronometers with improvements to Harrison's designs.|
|John Arnold||£3,000||Design and improvements to chronometers.|
|Thomas Earnshaw||£3,000||Design and improvements to chronometers.|
|Charles Mason||£1,317||Various contributions and improvements on Mayer’s lunar tables.|
|Jesse Ramsden||£615||Design and construction of a superior dividing engine (£300) and publishing the design (£315).|
|Larcum Kendall||£500||Construction of a copy of Harrison's H-4.|
|Leonhard Euler||£300||Contributions to the lunar distance method in aid of Mayer.|
|Nathaniel Davies||£300||Design of a Lunars telescope for Mayer|
Harrison also received £8,750 from Parliament in thanks for his work, bringing his total lifetime award to £23,065.
In culture 
Rupert T. Gould's 1923 "The Marine Chronometer" (ISBN 0907462057) is a thorough reference work on the Marine Chronometer. It covers the chronometer's history from the earliest attempts to measure longitude while including detailed discussions and illustrations of the various mechanisms and their inventors.
Dava Sobel's 1996 bestseller Longitude (ISBN 0-14-025879-5) recounts Harrison's story. A film adaptation of Longitude was released by Granada Productions and A&E in 2000, starring Michael Gambon as Harrison and Jeremy Irons as Rupert Gould.
See also 
- History of longitude
- Nevil Maskelyne
- Lunar distance
- Inducement prize contest
- John Harrison
- Larcum Kendall
- James Cook
- Powder of sympathy
- Philip III of Spain longitude prize
- Rømer's determination of the speed of light Longitude
- Latitude can also be determined from Polaris, the northern pole star. However, since Polaris is not precisely at the pole, it can only estimate the latitude unless the precise time is known or many measurements are made over time. While many measurements can be made on land, this makes it impractical for determining latitude at sea.
- Taylor, E.G.R., The Haven-finding Art: A History of Navigation from Odysseus to Captain Cook, Hollis & Carter, London 1971, ISBN 0-370-01347-6
- Sobel, Dava, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, Walker and Company, New York, 1995 ISBN 0-8027-1312-2
- Varzeliotis, A.N. Thomas, Time Under Sail, Alcyone Books, 1998, ISBN 0-921081-10-3