Read legend at those tables carefully.
Tangent values are from left top, contangent values are from bottom right to top left (in opaque way).

Thanks...
me and mathematic...no good feeling

You're welcome, try it and you'll not be regret it ;)

BTW. you could be pretty comfortable to use 0.7 here, dont be very hard for yourself in this calculations as you cant get even those hydrophone bearing so precised..
And dont even push yourself to measure it in too perfect time, just feel free to have 2. bearing after 9:30 and third after 11 it doesnt matter so much.... (just dont mess it by 30% or so...)

In the end you always have to get more precise information optically from periscope anyway.
This is rather for decide good approach strategy and to know which bearing to have roughly before fire to not to have to turn ubote later..

Thanks for the videos!

I see in the video you can move an earlier made line by clicking it. I can't do this? Do I need to press a button or something?

Thanks !:Kaleun_Cheers:

A bit confused...
 

Hey palmic, I been trying to understand your methods, I been reading this one and trying to understand it, and I get stuck on one point, I am hoping you can help me with it.

So I will recap and show you how far I get.

First we have our course of 255 and our 3 bearings,

b1 = 71
b2 = 80
b3 = 87

each timed at 10 minutes in this case, while we are stationary.

Next we use your cheatsheet to find the cotangents,

cotan for b1 to b2 is 9 so we get = 6.3138 from your sheet,
and
cotan for b1 to b3 is 16 so we get 3.4874

so far so good.

next we have the formula

and this is where I cannot find out what the DRM is, direction of relative motion, is that not the angle beween our course and the target course? If so, how do we find the target course?

How do we find this?



----------------------------------------------------------------------------------------------------------------------



EDIT: I just read the conversation between you and hauangua, seems like he ran into the same confussion,

So what I understand is that, once you do the formula,
Cot(DRM -B1) = 2* Cot13 -Cot12 = 0.661

Then we Search in the cheatsheet for the closest value?
So in the Cheatsheet the closest value in this case is = 0.6644?

So 0.661 becomes 0.6644 which is = 56?

Am I understanding this correctly?

Cheat ?
 

HI Palmic

I overlooked your Tables they are very good , Odd description "Cheatsheet" its definitely not a cheat its just good Maths was this method Actually used by the Kriegsmarine ? Would be interested to know.

THX Best Regards Simon

WOLVES OF STEEL MEGAMOD

Hi Xall!
Sorry for my delay, i noticed right now.

Yes you have it right. Your targets DRM is 56.
Now you just have to subtract, or add it to first ABSOLUTE bearing.
Since your course in that time was 255 and the first bearing was 71, absolute bearing was 255+71=326.
Since bearings went up, you have to add, you would subtract otherwise.
So course of your target is 326+56=382=22!

For educative details about DRM please read the document from my initial post.

Just one more thing, you are unnecessarily too exact, round just to 1 decimal, your bearings from hydrophone and timing is the same unexact anyway and youll be surprised how exactly youll calculate even with one dec, its just way more quicker..

Happy hunting!

Hi Cyborg322, its like cheatsheat in school because it keeps my shortcuts for getting the sollution :)

I would bet they've used this, but they used just very rounded way how to getting these informations and they did just easier math in head i think..
They just remembered cotangents of most common angles rounded to 1 decimal point, thats enough even here to get good enough solution. I use it like this.

I am sorry to resurrect this old thread, but I would really like some help here with the target course determination.

Let me use my example, encountered in the game - "stationary" 4-bearings method, readings taken at the same time interval of 10 minutes:

Co = 287° (my u-boot course)
b1 = 48°
b2 = 59°
b3 = 70°

So, if I start calculation using the easiest formula:
1) Cot(DRM - B1) = 2*Cot (22) - Cot(11)
2) Cot(DRM - B1) = 2*2,4751 - 5,1446
3) Cot(DRM - B1) = 4,9502 - 5,1446
4) Cot(DRM - B1) = -0,1944 (this is negative, so I take absolute value, determine angle of 79 from the tables provided and put it further as (90-79+90 = 101) according to your instructions)
5) DRM - B1 = 101 degrees
6) DRM = 149 degrees (correct? or do I use here the true bearing of b1t = 335° (= Co + b1 = 287+48) already, which gives different DRM = 436 (-360?) = 76 degrees?)

How do I get from here to the target course?
Ct = Co + DRM according to your instructions, but no matter if I use 149 or 76, (resulting in either Ct = 287+149 (-360) = 76° (??) or Ct = 287 + 76 (-360) = 3°

For the Poseidon´s beard, I am unable to get to that correct target course of cca 91°, which I get with graphic resolution.

Thank you very much for any help.

Btw: Spiess line formula comes out to 80,24°, which is pretty close to expected 81° (and later verified 82° from graphic solution).

Real navigation target motion analysis cheatsheet
 

Hi McDonnel,
Your target course is 76.

Funny thing is how i shortened the calculation in your example:
Since angles between your 3 bearings (b1,b2,b3) are both the same (11), you can just pick the middle bearing, recalculate it to absolute bearing by adding your course (Co) and add 90 degrees, which is 436 (-360 = 76) :Kaleun_Wink:
If your angles are the same, course is logically perpendicular.

Don't forget that if the target would be moving to the left, you would be subtracting.

Very interesting thanks

Hey Palmic, I went to revisit this method, but the links to your cheat sheets are down, would you be so kind and upload them again? : )

Graphical solutions in the days before computers
 

I fell in love with the idea of the Submarine Attack Course Finder (Is-Was) 40 some years ago after reading and watching the movie Run Silent Run Deep. As you can see I come from the pre-computer generation which is also the generations around WW I and WW II, the Silent Hunter 3 and 4 game timeframe. I spent 23 years in the Navy and am a submariner, dolphins and all. I remember when the Squadron Admin Dept. got so excited about the new typing machine they had gotten that stored what you typed electronically and you could edit without using an eraser and correction fluid.


In ROTC I had to take a course in Navigation in which we learned the use of the paper and ruler maneuvering board, yes the one with all the circles. The maneuvering board was a great advance because you could graphically solve trig problems and not have to use trig tables and logarithms. The next step forward in the targeting solution problem was the Is-Was which then became the TDC.


Even in the Silent Hunter 4 game the TDC is much more powerful than I have seen it used on the various youtube videos and "Let's Play" videos. What I have usually seen is that people use the TDC as if they are aiming a gun.



Take a look at the Sublant and Subpac doctrine manuals and the OP-1442 & OP-1442A Torpedo Data Computer Mark 4 Ordnance Pamphlets which describe in detail how to use all the power of the TDC.

Hi Xall!
sorry for huge delay, here you go, please download all the files (link at top right) as I cannot guarantee how long it will be available.
Merry Christmas :salute:

https://drive.google.com/drive/folde...tu?usp=sharing