My method is much more crude, but effective especially when rain or fog makes it impossible to visually identify a target outside of 500 yards. I first estimate a course for the target (easier if you have radar installed) and maneuver so I am submerged approximately 600 yards perpendicular to its course. Being submerged allows the sonar operator to be effective. I know from experience that a MK14 at high speed will travel 700 yards in about 20 seconds, so I need to know the firing point that will intercept a target with a straight run fish dead ahead and 700 yards out. I estimate the speed of the target based on sonar reports and observation through the Attack Map to see how long it takes to travel 10 degrees on the Attack Map. I can then guestimate what angle the target should be at to make the connection with the fish. I use a combination of the sonar operator following the target to get bearing changes and the Attack Map. Also, even though the periscope is visually useless, if the estimated torpedo track on the Attack Map is not straight ahead (relative bearing zero) I adjust the periscope position until the track line is dead ahead. This ensures a straight shot, all other things being equal. So, if the target covers 20 degrees of arc in say, 20 seconds, I will fire when the target is 20 degrees from dead ahead. I tried working up a table for torpedo speed (electrics run much slower) and target speeds, but it got to be too much work. I could be more scientific about it, but gut feel and dead reckoning works pretty well.
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