Quote:
Originally Posted by Bloomstomb
when I try to time the speed it tells me there is not enough data.
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Hi Bloomstomb, I have always found that trying to find the speed of a target by multiple range/bearing measurements over time to be problematic and unreliable. The quickest way to measure the targets speed is :-
Identify the target and read its length from the recognition manual either in yards
(Ly) or meters
(Lm). Whilst your boat is
stationary (very important), use the stopwatch to time how long the target takes for its stern to pass the point where the bow is at the start of your timer. This gives you the
(Ts) time in seconds it took for the target to travel its total length. Once you have that number a small calculation is required, so there is one for yards and one for meters :
In yards :
(178/Ts)*Ly = Yards travelled in 2 minutes 58 seconds
(Yt)
Yt/100 = Target speed in knots.
In meters :
(195/Ts)*Lm = Meters travelled in 3 minutes 15 seconds
(Mt)
Mt/100 = Target speed in knots.
you don't have to be looking at the target to do the calculations so one
careful measurement is all that's required. There is probably a dozen ways to re-write the calculations, this just keeps it clearer for me. In fleet boats, I needed to use a calculator but in the German boats the AOBF dial in the attack scope will do the math for you -
Line up the targets speed in knots (outer edge of middle ring)
with the targets length in meters (outer ring)
and read under the red marker (inner edge of middle ring)
= target speed in knots. It is quicker than any calculator and it is on the screen. Hope that helps.