TDC

[snakedocpl]

Interesting approach.

Originally Posted by TorpX

Actually, you don't necessarily need the target Aob.

Below, is a geometric solution for timing by wire that doesn't make use of any "stabilized line", or special equipment. In this solution, you do need to know the Aob, and of course, target bearing, and sub speed.
The 'line' moves with the sub, but the angle doesn't change.
The underlined term in the formula accounts for the movement of the line and the space along the target track marked by 'n'.

This one is similar to the German Ausdampfverfahren method.

Originally Posted by TorpX

However, if you had a mechanism to move or "stabilize" the line, there are other possibilities. Below is a diagram illustrating what a solution might look like with the line being moved. This simplifies the calculation of target speed in that the underlined term in the first formula is eliminated.

Note that for the mechanism to know how fast the line is to be moved, the range has to be known.

The initial rate of change of angle a =
(Vu*k sin a) / (2*pi*Range) * (360*60)
I computed an example for a sub moving at 3 kn., timing a target at 2,000 yds., at 45°.
(3*0.563*sin 45) / (2*pi*2000) * (360 * 60) = 2.05° per minute
The problem with the above is that the rate of change of the angle is not constant, so it would have to be dynamically calculated by the TDC, or some mechanism. Of course, the calculation is no more complicated than the other quantities the TDC calculates, so it is certainly possible.
Without some kind of mechanism to calculate the above, I don't really see any point in the technology.
I suspect the reason the feature was not carried over, was that it was rendered unnecessary by RADAR. With a RADAR plot, the target speed could be accurately determined without identification, or knowing the ship's length.

This in turn is similar to the German Auswanderungsverfahren method.

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Regards
Maciek