Latitude was determined by measuring the sun's angle at noon with the aid of a table giving the sun's declination for that day.
Calculating LONGITUDE required an extensive knowledge of the moon's motion, and the moon was not visible every night, so this presented navigators with a major problem.
In 1714, the British Parliament established the Longitude Board and huge prizes were offered for a practical solution to find longitude at sea.
John Harrison—a humble British carpenter—invented an ingenious clock that could keep time accurately on a ship and therefore solve the longitude problem.
 John Harrison (1693-1776), inventor of the marine chronometer. |  John Harrison's final masterpiece, made around 1760, was a hand held marine chronometer. |
John Harrison—like all great inventors—had to battle years of apathy and ignorance before his invention was accepted by the Royal Navy....His invention would have GUARANTEED that BRITANNIA ruled the waves for centuries, yet he received absolutely no funding from the government.
For over 30 years, with only his son William as his helper, he worked to perfect his masterpiece—the marine chronometer....By that time, the Royal Society, and the top levels of the Royal Navy, were secretly controlled by Jesuits, so the last thing they wanted was an accurate way of guiding British ships at sea.
