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Mile (US Survey)

The US survey mile is a unit of length used in land surveying in the United States. It is defined as exactly 5,280 survey feet, with one survey foot equal to 1200/3937 meters (approximately 0.3048006096 meters). This makes the US survey mile equal to about 1,609.3472 meters, slightly longer than the international (statute) mile, which is exactly 1,609.344 meters.

The US survey mile was established to maintain consistency with older land measurement systems based on the Mendenhall Order of 1893. It was commonly used in mapping, legal land descriptions, and public land surveys.

Although the difference between the survey and statute mile is very small (about 3.2 millimeters), it can be significant over large distances. As of 2023, the U.S. has officially retired the survey foot (and survey mile) for most applications, favoring the international foot and mile to standardize measurements.

Nautical Mile (International)

A nautical mile (international) is a unit of measurement used primarily in maritime and aviation contexts. It is defined as 1,852 meters or 1.852 kilometers, which is approximately 1.1508 statute miles. The nautical mile is based on the Earth's geometry, representing one minute of latitude along any meridian. This makes it particularly useful for navigation, as distances on charts and GPS systems often relate directly to degrees of latitude and longitude. The international nautical mile was officially adopted by the United States in 1954 and is now used worldwide for consistency in global navigation. It is closely linked with the knot, a unit of speed equal to one nautical mile per hour. The standardization of the nautical mile has greatly simplified communication and coordination in international travel, trade, and defense across oceans and airspace. Its use continues to be essential in global navigation systems today.