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
While I started off in engineering I was the CIC Officer for 18 months.
I was initially paired with the Weapons Officer for bridge watches. He taught me all the tips and tricks. He also taught me to do maneuvering board approximations in my head. Damn useful for DivTacs and operating with a carrier.
One of the things that got me instant respect when I took over CIC was that I was better at maneuvering board than anyone except the Senior Chief.
WWG1WGA
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(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
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