Determining Angle on Bow - reliable mathematical approach found

[3catcircus]

Originally Posted by Davidorado

I reaaaally tried to wrap my head around this topic, but without these images it´s almost impossible.
Is anybody out there, who has these images stored or could draw something which could help me understand what is going on?


In the german book "Agru-Front Lehrmaterialien" from DonL1978 there was the same approach of calculating the AoB. But I wasn´t able to catch it either, due to the lack of explaining pictures.
At the end there was a table with AoB´s in the distance of 500-1000m with common ship lengths from 60-240m.

This might help in battle, but it´s not helpful for understanding.


Thank you in advance Kaleus

I wouldn't put much stock in this method. No one is going to thumb through a book of trig tables.

Easiest method beside eyeballing it is to plot. Range, bearing mark. Wait 3:15. Then range, bearing mark. You now have speed and course. With course, you can draw AoB.

U don't have to be all that accurate on range and bearing. The key is to get the speed. The two plotted points get you course. If you do it early enough, you can get at least 3 points. The more points you plot, the more your error goes down. As long as you aren't trying for a shot from over 5 km away, AoB within a few degrees is fine. The key is accurate speed.

[Davidorado]

Originally Posted by 3catcircus

I wouldn't put much stock in this method. No one is going to thumb through a book of trig tables.

Yeah, you are right. To me it´s more about the theory and "how it COULD be done". I was just curious because I read about it and wanted to test it.


Anyway, I found the solution to my problems:
1. In the "Agru-Front Lehrmaterialien" the formula contained a "tan^-1". The photo math app I used interpreted it as 1/x, which would be normally correct, but in this case it´s just a sign for arctan. But even with Excel I couldn´t solve this. Which leads me to number
2. Excel uses Radian. I wasn´t aware of this and never came it across in school. So I had to convert it.


I built a simple Excel calculator around these formulas and I now have 2 approaches of solving this.

1. The approach with Length, Distance and the apparent length
2. Own Course, own speed and two measurements of the enemy bearing+distance. Usually you would wait 5-15min between these.
Benefit of this approach is, you get target speed and and course too!



You just enter the data and Excel calculates the AoB magically. Of course you would still use your brain.

So if anybody needs this Excel sheet, I probably could upload it somewhere.

[Mister_M]

Originally Posted by Davidorado

So if anybody needs this Excel sheet, I probably could upload it somewhere.

Yes, please!

[Davidorado]

Okay, I managed to translate it as good as I could.
The coloumns A-AG are just general conversion tables I use on my patrols. I group these together with the little "-" sign above the coloumns.
AH-AU is where the AoB part lives in. Lines 1-30 is a conversion table of the calculator you find in AI42-AJ46 (origin is from DonL1978´s AgruFront-Lehrmaterialien) in case you don´t like calculating.
Generally: Every cell, where you have to enter data, is coloured gold. All of the others aren´t intended to get touched.

AI33-AS40 is the first AoB calc approach using the mast height, ship length and apparent ship length/height. The screenshots should guide you what is actually needed. The worksheet is protected, but you can click "unprotect sheet" (no password).

The second calc AI42-AJ46 is using the distance and the ship length in meter and now you need the difference of the bearing from bow to aft of the ship. DonL1978´s screenshots should assist you.
You measure the bearing to the bow of the enemy ship, the bearing to the aft, subtract it from the first bearing, divide it by to and enter it in the bearingdifference field.

The third uses a different method where you have to enter your speed, your course, the bearing and distance to target once, take the stopwatch, wait 5-15 min and take bearing and target distance a second time. You get the enemy course, speed and the AoB.

I used all three of these a few times but got mixed results. Please test it and say if I made any mistakes or you have something to criticize.


https://www.mediafire.com/file/w3oxe...-eng.xlsx/file