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.
What is a kilometer?
A kilometer is 1,000 meters, or about 0.621 miles. 'Kilo' is the Greek-derived prefix for a thousand. It is the unit for road distances nearly everywhere except the US and UK, which still use miles.
A kilometer is about 3,281 feet or 39,370 inches. At a walking pace of 5km/h it takes about 12 minutes to cover.
Going from kilometers to meters just means moving the decimal point three places. A mile has to be broken into 1,760 yards or 5,280 feet first, and neither of those is a round number of anything.