ZIGZAG

[Vantskruv]

Thanks @derstosstrupp.
And thanks @Pisces for your thorough answer!


I have made some measurements, and indeed the little differences between the approximated bearing 4 and real bearing 4, makes it really hard to get the correct position of the convoy (in my example one degree of measured difference would change the targets course by about 10 degrees, and reduce their distance from ownship to the half!).



Though, I have been thinking about changing the course after measuring the bearing 3, as you told! But I ignored it as I thought changing the speed would be enough, and being afraid that calculations/measurements would have more errors because it is harder to approximate your position after a course and speed change, as I did the measurements on 30m depth without surfacing (playing safe).



I will reconsider, and try to implement course changes, and see if that, even though ownship position maybe a little more off, I may get a more precise result than only changing speed (hence, it is better to strive for the bigger difference between approximate bearing 4 and real bearing 4, while sacrificing approximation of ownship position?). I just need to figure out the turn radius of different speeds of the ship, both submerged and surfaced, and also if the speed will change while turning. Maybe it is not too hard to approximate/calculate your position after a turn after all, and that would beneficial.



Also, a theory of mine, I guess the 4-bearing method is more used at longer ranges, and I guess you may get better results if at long range, than close range. I am not sure what I am basing that of, it is just a hunch.

[Vantskruv]

@pisces
The red sentence in my explanation is written wrong, thanks.
And you understood it correctly:
Checking if the crosspoint of ARBG4 and CRS is at the point O+V1*3 on CRS.


I made this for myself just to understand what is going on.

[Pisces]

Originally Posted by Vantskruv

Thanks @derstosstrupp.
And thanks @Pisces for your thorough answer!


I have made some measurements, and indeed the little differences between the approximated bearing 4 and real bearing 4, makes it really hard to get the correct position of the convoy (in my example one degree of measured difference would change the targets course by about 10 degrees, and reduce their distance from ownship to the half!).

Yes, and not only course, but also the position shifts rapidly along those lines.

Though, I have been thinking about changing the course after measuring the bearing 3, as you told! But I ignored it as I thought changing the speed would be enough, and being afraid that calculations/measurements would have more errors because it is harder to approximate your position after a course and speed change, as I did the measurements on 30m depth without surfacing (playing safe).

I will reconsider, and try to implement course changes, and see if that, even though ownship position maybe a little more off, I may get a more precise result than only changing speed (hence, it is better to strive for the bigger difference between approximate bearing 4 and real bearing 4, while sacrificing approximation of ownship position?). I just need to figure out the turn radius of different speeds of the ship, both submerged and surfaced, and also if the speed will change while turning. Maybe it is not too hard to approximate/calculate your position after a turn after all, and that would beneficial.

I wouldn't worry so much about your exact position when taking the bearings. Especially in the beginning. When learning this try it in the tutorial mode, where the ship does not turn, and you get the correct solution to prove you results. (first move away some 20 km to make this a bit more representative) Use the nav-bot to provide you with positions even when underwater (though not continuous, but incrementally). It is more useful to learn when to speed up or make a course change and in what direction to get the geometry to work out well. And definitely try to go to the surface. You speed is 3 times larger than max submerged. And about twice the common merchant speed. The further your bearings are apart, the less your position errors matter.

Also, a theory of mine, I guess the 4-bearing method is more used at longer ranges, and I guess you may get better results if at long range, than close range. I am not sure what I am basing that of, it is just a hunch.

Well, at long range you have little else than your hydrophone and plenty time and room to manoeuvre to do so. At visual range you can also do it, and more precisely so with the periscope. But then you can also make direct use of the AOB and distance observation. So there are other methods that get quicker results. Even if the bearings change more quickly at shorter range. But it is also more likely to get suppressed submerged to avoid detection.

[gurudennis]

Empirically speaking, Hard convoys appear to zigzag on average by 15 degrees every 15 minutes, but the deviation from this average can be quite high, especially for the exact timing of zigzags.

Since a typical 4-bearing takes around 15 minutes, its utility is rather limited when facing a Hard convoy. You are much better off using Eyeball Mk1 as well as any and all techniques that do not require a prolonged period of observation.

Another practical implication is that you are well advised to time your attack to occur right after a course change (but not before the convoy settles on it properly) to minimize the chances of a whiff due to a random zigzag after torpedoes are in the water.

[ljqcn101]

Regarding measuring accuracy, it is said according to some historical TMA documents that it's better doing a lead-lag maneuver than a lag-lead, which means you can run parallel with the target at the beginning (usually observing a relatively low bearing rate), and then increase the bearing rate later by turning and lagging the target. The goal is to maximise the difference between the approximated 4th bearing and the real 4th bearing.

But it may not place you to a suitable position for attacking.

Speaking of the plotting, I personally likes to go creative using the draw-from-midpoint tool in Wolfpack, like this: https://www.subsim.com/radioroom/showthread.php?t=240883.