> Mechanical clock accuracy used to be pretty important for navigation to determine longitude. Specifically: > One degree of latitude equals approximately 364

> Mechanical clock accuracy used to be pretty important for navigation to determine longitude. Specifically: > One degree of latitude equals approximately 364,000 feet (69 miles), one minute equals 6,068 feet (1.15 miles), and one-second equals 101 feet. One-degree of longitude equals 288,200 feet (54.6 miles), one minute equals 4,800 feet (0.91 mile), and one second equals 80 feet. * https://www.usgs.gov/faqs/how-much-distance-does-a-degree-minute-and-second-cover-your-maps https://www.usgs.gov/faqs/how-much-distance-does-a-degree-mi... > One minute of latitude covers about 1.8 kilometers (1.1 miles) and one second of latitude covers about 32 meters (105 feet). * https://education.nationalgeographic.org/resource/latitude/ https://education.nationalgeographic.org/resource/latitude/ When using a sextant: > Sextants measure the angle between the sea horizon and a celestial body. These angles are measured in degrees and minutes of arc (1/60th of a degee). Measuring this angle to an accuracy of 1 minute of arc (1') will result in a positional accuracy of 1 nautical mile. Accurate sextants can measure this angle to an accuracy of 0.2'. This means that theoretically one can determine their position to 1/5 of a mile [~320m]. Additionally, a good clock is required to accurately compute the GP of the celestial body. An error of 1 second in the clock will create a positional error of up to 1/4 of a mile [~400m]. * http://www.cse.yorku.ca/~amana/personal/navigation/ http://www.cse.yorku.ca/~amana/personal/navigation/ Airplanes also used to use sextants for trans-oceanic flights (when beyond radio beacon range). Part 63 of FAA regulations has a section on Flight Navigators: * https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D/part-63/subpart-C https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D... Doing a search for FAA-H-8083-18 will lead you to The FAA Flight Navigator Handbook.