Accurate Lengths Of IJN ships ?

[Pisces]

Originally Posted by LCQ_SH

I guess these techniques refer or should be related to 0° gyro angle attacks and the "four bearing" methods, right? I mean, for a u-boat that is easy to do without a radar as their hydrophone had a range for convoys around 30-50 NM which gives you enough time to determine course and speed.

Is that true that American hydrophone was so much less capable than German's by only being capable to pick up ships at 10K yards? the four bearing method and 0° gyro attacks by hydrophone listening are possible for a very slow moving ship. Late in the war subs had radar, but before radar, how was that possible?

4-bearing methods are totally unrelated. They might not even be historically accurate used in the game. At least, I haven't heard any of such in all the discussions here on subsim. Just because the game provides bearings in degrees doesn't mean the real hardware could pinpoint a target that well. We can use it because mathematics is ageless, and the user interface developers were kind to us.
The target being far or close does not help in determining a proper solution. For bearing-only methods to work well you need precisely defined bearing angle in reasonable time frames. You can do with less precise bearing if the time interval is increased. Or else it just tells you the target is going N-E-S-W-ish/in a wide arc/halfway omni-directional. The knowledge of sound propagation physics and technology level just was't so cooperative as in this digital/electronic age. Though I would guess it possible for them in that time to make a mechanical analog calculator for it. It's the input part that makes it unreliable.

I supposed the constant bearing method comes closest to '0-gyro angle' as that is how Dick O'kane's method is usually executed. But it doesn't have to. As long as the visual 'firing cue' bearing of the periscope is offset from the chosen torpedo track or gyro angle by the right amount of lead (generally speaking it only depends on target speed, AOB and torpedo speed), then it should hit despite the range of the target. (caveat any parallax correction due to the torpedo track curve and periscope offset from the torpedo tubes) If the target is further away, it also has farther to travel to the impact point. And so does the torpedo have the same time to get there! With the lead set up properly you only have to wait for the target to pass the periscope cue line. That is the concept of 'constant bearing'. The fact that 0-gyro angle makes setting this up more easily and avoids the torpedo-track-curve correction is the reason that this is the popularly choice of doing so.