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04142019, 07:12 AM  #1 
Swabbie
Join Date: Jul 2016
Posts: 13
Downloads: 22
Uploads: 0

4Bearings Technique Tool
Hello Submariners,
I made a 4 bearings technique helper! Give your initial course, the time interval you will use and 3 bearings, It will give you the course of the target. Then give it your course and the distance travelled before the 4th bearing. Enter the 4th bearing and it will give you the solution. You can find it with more infos at : https://drive.google.com/drive/folde...NLFmWnrsztrf4I And here's a geogebra construction, I made, to test the correctness of the tool : https://www.geogebra.org/graphing/ab7wekqx Let me know what you think. 
04142019, 09:51 AM  #2 
Seaman
Join Date: Jan 2013
Location: Hong Kong
Posts: 37
Downloads: 65
Uploads: 2

Good to see more implementations.
I've also made one for more general TMA scenarios, without restrictions on time intervals, number of bearing inputs, or ownship movements. You can check the source code and formulas to see if it's useful to you. (http://www.subsim.com/radioroom/showthread.php?t=240508) If you're interested you can also check out the tool for Dangerous Waters, which performs line detection on any given image and draw TMA solutions on it, like this: (green line is the solution) 
04142019, 11:05 AM  #3 
Swabbie
Join Date: Jul 2016
Posts: 13
Downloads: 22
Uploads: 0

Hi,
I've seen your tool that's nice. I'm interested in the quad prog optimisation problem. Especially, in a first place, trying to find the solution going in straight line at constant speed. I'd like it to be really simple to use. Enter as few data as possible as gathered in the game and get the true course solution. I should add a bit more info to be able to redraw target true course in the game as easily as possible. Anyway, it's not perfect and it's hard to get good solutions in game. Hard to be precise with the hydrophone, but at least with the course and rough estimation on distance you can plan on where to go next to get a periscope solution at a good angle. I'll git my code and check the optimisation problem when I got the time (I shouldn't be doing this :P) I like the geogebra construction 'cause it's really accurate. You can move the angles to check your solution for distances and courses. 
04142019, 01:23 PM  #4 
Silent Hunter

@Thecoroner: You can't get a solution from 4 lines (or more) by going constant speed in a straight line. You either need to make a course change or a speed change at some point, or both.
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04142019, 03:40 PM  #5 
Nact Morder U77
Join Date: Jun 2005
Location: USA
Posts: 638
Downloads: 270
Uploads: 0

Awesome work
There are so many methods for hydro hunting,, I have discovered a few that are less time consuming and are somewhat accurate. the trick is to train your ear for pounding water propeller sounds and learning distance by the sound. I recommend trying a few that are easy to remember and easy to plot in the map& and less time consuming, and will not expose your boat .. these are the methods I use
Bstankos
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Captain AJ 
04152019, 03:49 AM  #6 
Swabbie
Join Date: Jul 2016
Posts: 13
Downloads: 22
Uploads: 0

Yeah, I know. But you can still get infos and estimations but the solution won't be unique unless you take a turn or else. As with 3 bearings at stop, you can get the course but not a unique solution.

04152019, 04:08 AM  #7 
Swabbie
Join Date: Jul 2016
Posts: 13
Downloads: 22
Uploads: 0

Yeah, you can quite quickly tell if the ship is going towards you or else. I guess only by playing with the gain you could get a range estimation (I can't ^^)
I bet the best can even roughly id the ship like that. (telling if it's a merchant or warship for example). But it's really hard to pick a point in a convoy and be sure to follow exactly that one to take bearings marks. I'll check your videos. I watched a lot by stoianm if i recall correctly like 10 years ago. I found some pdf explaining how to 4B running at constant speed (and taking turns) too. I'll try to add that in the tool some day. Thanks for feed back :) 
04152019, 04:19 AM  #8 
Seaman
Join Date: Jan 2013
Location: Hong Kong
Posts: 37
Downloads: 65
Uploads: 2

You can open up an audio recorder and watch the waveform. But that's cheating anyways.
I think there may also be a way to estimate the speed by counting propeller turn per minute and then multiply by a constant number (something like TPK in Dangerous Waters). But we got over 160 types of merchants and those sound signatures may all be different. 
04152019, 04:27 AM  #9 
Seaman
Join Date: Jan 2013
Location: Hong Kong
Posts: 37
Downloads: 65
Uploads: 2

That's good if you want to add constraints. You can check AdamMil's website to see his description: http://www.adammil.net/blog/v103_Per..._Analysis.html
Since I don't have problems like ghost solutions on the wrong side of the observer, and adding course/speed constrains is more of a DW thing, I just stick to BFGS algorithm for optimisation. 
04152019, 04:39 AM  #10  
Seaman
Join Date: Jan 2013
Location: Hong Kong
Posts: 37
Downloads: 65
Uploads: 2

Quote:
Code:
time t1 = 0 (sec) ownship heading at t1 (deg): 0 target bearing at t1 (deg): 90 ownship straight direction from last position = 0 (deg) ownship straight distance from last position = 0 (meter) ******************************* time t2 (sec): 120 ownship heading at t2: 0 target bearing at t2 (deg): 85 ownship straight direction from last position (deg): 0 ownship straight distance from last position (meter): 300 ******************************* time t3 (sec): 240 ownship heading at t3: 0 target bearing at t3 (deg): 80 ownship straight direction from last position (deg): 0 ownship straight distance from last position (meter): 300 target course: 358.88deg, speed: 6.26725knots, distance: 999.996m target course: 358.16deg, speed: 7.67643knots, distance: 2000m target course: 358.17deg, speed: 7.66992knots, distance: 1995.38m target course: 357.67deg, speed: 9.08642knots, distance: 2999.99m target course: 357.68deg, speed: 9.07374knots, distance: 2991m target course: 357.31deg, speed: 10.4969knots, distance: 3999.99m target course: 357.04deg, speed: 11.9077knots, distance: 4999.99m probability of target course error within 5deg: 13.6364 % probability of target course error within 10deg: 23.0909 % probability of target course error within 20deg: 49.2727 % probability of target positional error within 75m: 3.81818 % probability of target positional error within 150m: 13.6364 % probability of target positional error within 300m: 27.9091 % ******************************* time t4 (sec): 360 ownship heading at t4: 0 target bearing at t4 (deg): 75 ownship straight direction from last position (deg): 0 ownship straight distance from last position (meter): 300 target course: 358.34deg, speed: 6.26019knots, distance: 1000.58m target course: 358.37deg, speed: 6.23728knots, distance: 984.243m target course: 358.35deg, speed: 6.25775knots, distance: 998.846m target course: 358.36deg, speed: 6.24476knots, distance: 989.58m target course: 358.39deg, speed: 6.21228knots, distance: 966.41m target course: 357.3deg, speed: 7.66408knots, distance: 2001.17m target course: 357.32deg, speed: 7.63115knots, distance: 1977.72m target course: 357.31deg, speed: 7.64557knots, distance: 1987.99m target course: 356.57deg, speed: 9.06974knots, distance: 3001.76m target course: 356.59deg, speed: 9.02861knots, distance: 2972.5m target course: 356.58deg, speed: 9.0449knots, distance: 2984.09m target course: 356.04deg, speed: 10.4765knots, distance: 4002.35m target course: 356.06deg, speed: 10.4307knots, distance: 3969.78m target course: 356.05deg, speed: 10.4356knots, distance: 3973.29m target course: 355.64deg, speed: 11.8839knots, distance: 5002.94m target course: 355.65deg, speed: 11.83knots, distance: 4964.62m target course: 355.63deg, speed: 11.8987knots, distance: 5013.45m probability of target course error within 5deg: 24 % probability of target course error within 10deg: 48 % probability of target course error within 20deg: 81.3333 % probability of target positional error within 75m: 4 % probability of target positional error within 150m: 16 % probability of target positional error within 300m: 34.6667 %
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Automatic TMA calculator for Wolfpack Automatic TMA line detector and solver for DW/SC/688i Last edited by ljqcn101; 04152019 at 05:00 AM. 

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