Four bearings...

[Pisces]

Originally Posted by Shkval

So I have 0.0000000007715 % chance to hit him with single torpedo ? Well guys you really know how to cheer up somebody... is there a cure for sonar guy? Some mod? More precise drawing tools?

@ETsd4... how did you get this 0.75 precision, and I was thinking about some "AOB+Bearing= Range" magic formula/drawing in my question...

Nope, sorry. A stationary listening or viewing point will never provide range information from bearings only. It doesn't matter how many bearing lines you provide, or how accurate they are. It just isn't there in the math formula. Range can only be found with a (4th) bearing from a different point of view.

Lately I constantly have some error in projected course of a target I don't know how much but it's not bigger than 7-8 degrees (I think...) when a target approaches on it's course sonar guy doesn't reads out "constant distance" as it should... but "closing" until about 35-40 degrees on my scope, then suddenly he changes to "moving away" . This happens no matter what way of tracking I use... moving... stationary... is this result of cumulative "round up" bearing errors? I'm off-course on the 90 degrees approach to projected course of a target.

7 or 8 degrees deviation in projected course is reasonably good or normal. At least good enough to know the general direction it is going, and to parallel course or chase after it. The accuracy of the projected course depends on the length of the time-periods, and the divergence of the bearing-differences. The bearings are reported in steps of 1 degree, so the divergence in the differences needs to be larger than that. More time allows the bearing-differences to encompass more degrees. For example, compare:

bearing set "a":
B1a=0,
B2a=6,
B3a=13
Bdiff 1-2=6
Bdiff 2-3=7


to

bearing set "b":

B1b=0,
B2b=11,
B3b=25,
Bdiff 1-2 = 11,
Bdiff 2-3 = 14.

Each set ("a" and "b") has the same AOB at bearing 1, namely 49 degrees.

In set "a" the bearing drift accelerated 1 degree during the second interval. This is just as large as the bearing inaccuracy. So useless to rely on.

In set "b" the bearing drift accelerated 3 degrees during the second interval (about twice as long as intervals at "a"). This is clearly bigger than the 1 degree measurement accuracy. And so results in a more accurate AOB.

Patience pays in accuracy. But there comes a time when the target is lost. So don't stay there once you know where the target is going to. Go at the same course to get the different point of view for the 4th bearing. With minimal risk of collision/detection.