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Know your Nautical terminology
nautical mile
A nautical mile is a unit of measurement used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as one minute (1/60 of a degree) of latitude along any line of longitude. Today the international nautical mile is defined as exactly 1852 metres (about 1.15 miles).
Both the United States and the United Kingdom used an average arcminute, specifically, a minute of arc of a great circle of a sphere having the same surface area as the Clarke 1866 ellipsoid. The authalic (equal area) radius of the Clarke 1866 ellipsoid is 6,370,997.2 metres (20,902,222 ft). The resulting arcminute is 1853.2480 metres (6080.210 ft). The United States chose five significant digits for its nautical mile, 6080.2 feet, whereas the United Kingdom chose four significant digits for its Admiralty mile, 6080 feet.
knot
A unit of speed equivalent to 1 nautical mile (1.8520 km; 1.1508 mi) per hour. Originally the speed of a moving vessel was measured by paying out a line from the stern; the line was tied into a knot every 47 feet 3 inches (14.40 m), and the number of knots paid out in 30 seconds gave the speed through the water in nautical miles per hour. Sometimes "knots" is mistakenly stated as "knots per hour", but the latter is a measure of acceleration (i.e. "nautical miles per hour per hour") rather than of speed.
Both vessel speed and wind speed are commonly reported in knots.
Next time, by special request of xone, I will cover ship's bells.
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Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)
Converting Nautical time/distance/speed to metric totally screws up its usefulness.
A nautical mile is 2000 yards.
Distance covered in 3 minutes (in yards) / 100 = speed in knots.
In the CIC (Combat Information Center) of a ship, this 3-minute rule is used hundreds (or thousands) of times a day, to convert between time, distance, and speed, for plotting both true and relative motion, for ships, planes, subs, and wind.
If the distance traveled in 3 minutes is 2000 yards, your speed is 20 knots.
If the distance traveled in 3 minutes is 1342 yards, your speed is 13.42 knots.
The 3 and 6 Minute Rules
The 3 and 6 minute rules are used to quickly solve for distance in Nautical Navigation. The principles are then applied to other navigation principles including Rapid Radar Plotting and other tools. Basically these rules are used to quickly determining distance traveled in 3 and 6 minutes.
We also used a circular Nautical Slide rule to speed up conversions. Our maneuvering boards had a nomogram scale on the right side, with three scales for time, distance, speed, to be used with dividers or straight-edge, for the odd-ball time increments. Sometimes you just can't wait 3 minutes, like not usually.
The premise with these rules is that a Nautical Mile (NM) = 2000 yards (yds)
Additionally, 1 knot (kt) = 1 NM / hr = 2000 yds/hr (this is the equivalent to MPH)
3 Minute Rule:
Speed (kts) * 100 = Distance (yds) traveled in 3 minutes Example: if traveling 20 knots, the distance you've traveled in 3 minutes is as follows:
20kts *100 = 2000yds for 15 knots, 15kts * 100 = 1500yds MOVE THE DECIMAL TO THE RIGHT TWO PLACES – ANSWER IS IN YARDS
6 Minute Rule:
Speed (kts) / 10 = Distance (NM) traveled in 6 minutes Example: if traveling 20 knots, the distance you've traveled in 6 minutes is as follows:
20kts / 10 = 2NM for 15 knots: 15kts / 10 = 1.5NM
MOVE THE DECIMAL TO THE LEFT ONE PLACE – ANSWER IS IN MILES
Read more:
http://wiki.answers.com/Q/The_3_and_6_minute_rule#ixzz1OYT4x2Eq