US Nautical Miles
Abbreviation/Symbol:
US nmi
US NM
Unit of:
Worldwide use:
The US nautical mile was 1,853.248 meters, or about 6,080.2 feet, until the United States adopted the international nautical mile of 1,852 meters in 1954.
The old US figure was 1.248 meters longer per mile, which comes to about 125 meters over 100 miles. It only matters when working from sources older than 1954.
Definition:
The US nautical mile is defined as exactly 1,852 meters or 1.15078 statute miles. The term "nautical mile" originated from the need for sailors to have a consistent and standardized unit of measurement for distances at sea.
The US nautical mile is the international nautical mile, agreed at a hydrographic conference in Monaco in 1929 and adopted by the United States in 1954. It began as one minute of latitude but is now fixed at 1,852m, so it no longer varies with the Earth's shape.
The US nautical mile is used on US marine charts, in navigation systems and in maritime regulations. It is the same 1,852m as everywhere else, and speeds are given in knots.
Origin:
The nautical mile began as one minute of latitude, which is why it suits navigation: distance can be read straight off the latitude scale on a chart. A minute of latitude is not quite the same length everywhere, so the US used a fixed value of 6,080.2 feet (1,853.25 meters) until it adopted the international mile.
The US adopted the international nautical mile of 1,852m (6,076 feet) in 1954. The body responsible was the US Coast and Geodetic Survey, now the National Geodetic Survey.
Common references:
1 US Nautical Mile is 1,852 meters
Usage context:
The US nautical mile was 6,080.20 feet (1,853.248 meters) until 1954, when the US adopted the international nautical mile of 1,852 meters. It is used for sea and air navigation.
To measure a distance on a nautical chart, set your dividers against the latitude scale at the side – one minute of latitude is one nautical mile, so there are no sums. Use that scale only: a minute of longitude shrinks towards the poles, so the scale along the top and bottom is no good for distance.
Aviation also relies on nautical miles for flight planning and navigation. Pilots use nautical miles to measure the distance between airports, waypoints, and other navigational aids. This helps them determine fuel consumption, flight duration, and establish flight paths. Nautical miles are especially important in aviation due to the vast distances covered during long-haul flights and the need for precise navigation.