A different description of the 4 bearing method

[SH4 fan]

I tried to follow the videos and the descriptions for the four bearing methods but I had a very hard time following them. I decided I needed to work it out from the reference materials and offer my own explanation. The image is a standard 8.5 inches by 11 inches for those who want to print it. https://i.imgur.com/pPahU8v.png

I also suggest copying and pasting the following text into Word or other word processor. since it contains color formatted text which is hard to read on grey background. I'm still working out how to do it from a moving sub.....that is a much harder problem to me and any help is appreciated.


1. Bearings b1, b2, and b3 are taken across equal time intervals (T) from S0.
2. Select an arbitrary point P along b2.
3. Construct line R which crosses b1, b2, and, b3 with an extra margin after b3.
4. Point A is where line R crosses b1. Points P and A will serve as reference markers for constructing HC1 and HC2 later in step 8.
5. Point B is equidistant from P as A but on the opposite side. Note: If B is outside b3 the target is moving away from S0, and the opposite is true.
6. At Point B construct lines b1' and b2' which are parallel to b1 and b2 respectively.
7. Points C and D are where b1' and b2' cross b2 and b3 respectively.
8. If Point B is outside b3, hypothetical Courses HC1 and HC2 are constructed by connecting A to D and P to C. If Point B is between b2 and b3 connect A to C and P to D.
9. Point E is constructed in the same way as Point B but along either HC1 or HC2 whichever is more convenient.
10. Bearing b4 is constructed by extending a line connecting S0 through Point E. When the next time interval of T occurs, the target will be on b4.
11. Range and Speed information can be obtained by moving S0 to S1 and obtaining Bearing b5.
12. Point F is where b5 and b4 intersect.
13. Target Course C1 is a line through point F.
14. From here speed is derived by measuring the distance along C1 between and between any 2 bearings.