What is a foot?
The foot is an imperial and US unit of length equal to 12 inches, or exactly 30.48 centimeters. It is a third of a yard and 1/5,280 of a mile.
The foot began as the length of a human foot, and so differed from place to place and from person to person. The modern international foot was fixed at exactly 0.3048 meters by agreement in 1959.
People's height is given in feet and inches in the US and UK, and aircraft altitude is given in feet nearly everywhere, metric countries included.
What is a US Nautical Mile?
A US nautical mile is a unit of measurement used primarily in navigation and marine activities. It is defined as exactly 1,852 meters or approximately 6,076.12 feet. The term "nautical mile" originated from the need for sailors to measure distances on the Earth's surface while taking into account the curvature of the Earth.
The US nautical mile is based on the international nautical mile, which was agreed at the First International Extraordinary Hydrographic Conference in Monaco in 1929. The length was set at 1,852 meters, close to one minute of latitude. The Earth is not a perfect sphere, so a minute of latitude varies slightly with latitude, but for practical purposes the US nautical mile is a fixed value.
Speed over water is measured in knots, one knot being one nautical mile per hour, so 10 knots is 18.52km/h. The US only adopted the 1,852 meter nautical mile in 1954 – it previously used a slightly longer one.