The four bearings method

[Kuikueg]

Originally Posted by makman94

yes Kara ,i am sure ! in fact it is... proved ! yes ,'red line' is a geometrical locul and this geometrical locul is (as Kuikueg showed) a straight line. now, your fourth bearing is a straight line also and i am telling you that if you don't change course and speed during your time intervals these two lines will be the SAME line.
i will send you the prove of this at your pms.
if not...then it is a fault at your map drawings or caused becuased of inaccuracies of silent hunter.
send me the mission you played to give it a try and i will tell you my results

I don't know if you are not understanding each other but I'll try to clarify.
The need for changing course, either for the fourth bearing or for any other depends only on the circumstances. The fourth bearing won't be in general equal or parallel to the red line even though you don't change course. Actually, in my explanation of the method, you could draw a straight line in the diagrams representing submarine's course and the solution holds, because it does not depend even on the location of the submarine. But in certain circumstances, such as those in Makman's video, you may need to change course in order to obtain a non parallel bearing and increase accuracy of the solution. I insist: is circumstantial.

Something that catches my attention is that, if I understand well, Karamazov is not taking a fifth bearing to calculate course and speed of target. Four bearings is enough to know that, but it implies repeating the calculations backwards through the bearings and finding an initial red line through which to find the initial position of target via first bearing. Is that what you are doing, Karamazov? Are you maybe estimating true course by sight from those used in the construction? Are you doing anything else I can't think of?

Edit: sorry Karamazov, your picture made things really clear for me. You take a fifth bearing. Silly me. Thanks for your comments.