Lateral Speed Method

[Efshapo]

Hi everyone,

This is my first post on this forum. I wanted to share something with you all.

In February, I discovered a new method to acquire data needed to shoot torpedoes. I only tested it on Wolfpack -that's why I post in this section- but it should work on any sub game, and even in real subs.

I searched a bit and so far, I haven't found this technique anywhere else. Maybe some of you could show me sources of what I think I merely rediscovered.

I will try to explain it in a few words:

Usually, one need at least AOB and target speed to shoot. Range is also needed if gyro angle is high.

Once the ship has been identified, range is quite easy to estimate. Speed can be trickier if you're measuring it from an AOB that is far away from 90°. And AOB must be the hardest one since you have to either plot target course, measure width/height ratio, or maneuver to a position where target features are visually aligned (kingpost at AOB 90°, some masts at AOB 45°, target track at AOB 0°...)

With my method, I only use range and lateral speed (perpendicular to the bearing). The point is that you can acquire these data from any AOB. Here is a step-by-step procedure:
- Measure range from target with your preferred method.
- Choose a vertical feature on the target (usually a mast) and measure the time it takes for this feature to cross a certain amount of horizontal graduations (centiradians) on the periscope at 6x magnification, I often use 8.
- Use the following formula to compute lateral speed : lateral_speed (kts) = 0.486 * range (hm) * nb_centirad / time (s)
- Enter 90° for AOB input in TDC (starboard or portside, depending on the direction of traveling of the target).
- Enter lateral speed as speed input in TDC.

Here is a video to illustrate (jump to 3'20s):


This previous method only works for one target. I refined it to work on a whole convoy:
- Choose one representative target among the convoy.
- Measure its lateral speed as seen above.
- Visually estimate its AOB.
- Use this formula to compute target speed estimation: speed = lateral_speed / sin(AOB)
- Enter estimated AOB in TDC.
- Enter estimated target speed as speed input in TDC.

There also is a simple trick to get a good estimation of AOB, using this same refined method:
- Choose one target among the convoy.
- Measure its lateral speed as seen above.
- Also measure its real speed with your preferred method.
- Use the following formula to compute AOB : AOB = asin(lateral_speed / real_speed)
- Enter this AOB input in TDC.
- Enter real target speed as speed input in TDC.

Here is a video to illustrate (jump to 3'30s):


In all these three procedures, the main data from which other are derived is lateral speed, which is actually the one that needs to be accurate for the TDC to yield a good gyro angle.

What do you guys think? Have you seen something similar used elsewhere?

-Efshapo