2007-03-10 00:10:16 · 6 answers · asked by Anonymous in Cars & Transportation ➔ Boats & Boating
Only hayharbr has the right answer. The other two are just nonsensical.
Knots (nautical miles per hour), mph (miles per hour), and kph (kilometers per hour) are all indicators of speed, using a different length definition. There's no specific reason to favor one over the other, it's just that tradition keeps us using knots for boats. MPH is used in many cases for boat racing in the US; not sure if they use KPH in Europe.
2007-03-10 07:43:09 · answer #1 · answered by Flyboy 6 · 0⤊ 4⤋
A nautical mile is based on the circumference of the planet Earth. If you were to cut the Earth in half at the equator, you could pick up one of the halves and look at the equator as a circle. You could divide that circle into 360 degrees. You could then divide a degree into 60 minutes. A minute of arc on the planet Earth is 1 nautical mile. This unit of measurement is used by all nations for air and sea travel.
A knot is a unit of measure for speed. If you are traveling at a speed of 1 nautical mile per hour, you are said to be traveling at a speed of 1 knot.
A kilometer is also defined using the planet Earth as a standard of distance. If you were to take the Earth and cut it in half along a line passing from the North Pole through Paris, and then measure the distance of the curve running from the North Pole to the equator on that circle, and then divide that distance by 10,000, you would have the traditional unit for the kilometer as defined in 1791 by the French Academy of Sciences.
A nautical mile is 1,852 meters, or 1.852 kilometers. In the English measurement system, a nautical mile is 1.1508 miles, or 6,076 feet.
To travel around the Earth at the equator, you would have to travel (360 * 60) 21,600 nautical miles, 24,857 miles or 40,003 kilometers.
So travel in the air or on the sea must be measured in knots, or "nautical miles per hour".
2007-03-10 09:50:55 · answer #2 · answered by mark t 7 · 3⤊ 0⤋
A nautical mile is one minute of arc on a great circle. It is not a measure of distance, but of an angle. A knot is how long it takes to transverse a minute of arc per hour. Sixty nautical miles is one degree of a great circle. Sailors navigate using spherical geometry. Coastal and celestrial navigation require angular measurements. Statute distances are useless on a sphere.
2007-03-11 01:05:29 · answer #3 · answered by Richard B 4 · 2⤊ 1⤋
It may just be a nautical tradition, using nautical miles per hour (knots) instead of km/hr or for that matter (statute) miles per hour. It also presents a standard rate that makes comparing speeds easier.
2007-03-10 08:23:55 · answer #4 · answered by hayharbr 7 · 1⤊ 3⤋
google search nautical mile and you can read up on it. The international community agreed on that measurement for both ships and aircraft.
2007-03-13 22:09:07 · answer #5 · answered by pilot 5 · 0⤊ 0⤋
Because water is moving...so the speed of the ship is relative to the movement of the water. If the ship is going with the current...its ground speed is much faster though the ship isn't actually moving faster relative to the water. Just the opposite going into the current.
2007-03-10 08:18:21 · answer #6 · answered by Captain Jack 6 · 2⤊ 4⤋