[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.