[Leandros]

Originally Posted by Alcibiades

The 3:15 rule is just a quick way of getting the target speed without a calculator.


SPEED = Distance / Time
You can of course, take any length of time if you want. For example, suppose that you timed at target for 20 minutes. And during those 20 minutes, the target moved 8km. Then you have distance and time so you can figure out speed.

Then the targets speed is 8km in .333333 of an hour OR 24km/hr.

To convert to knots, divide by 1.852. 24/1.852 = 12.95 = 13 knots.




to illustrate the 3:15 rule. Suppose a ship moved 500 meters in 3:15.

Then it's speed in km/hr = .5km/.05416666hr (3min 15sec = .05416666 hours) = 9.23 km/hr.

And 9.23/1.852 = 5 knots

That's fine. How do you then find the advance angle to fire when you know the speed. A formula for that? Provided you are at a right angle to the target.