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Old 04-21-2019, 05:35 AM   #1
jarlemag
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Default Time needed to locate convoy with hydrophones?

How much time do you consider is required to get a fix on a convoy's position and course using hydrophones only, in "average" and "best case" scenarios? Discuss!
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Old 04-21-2019, 07:14 AM   #2
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Depends on what accuracy you want to get from hydrophone only methods.

Since hydrophone induces a lot of bearing inaccuracies, you may want to adjust your listen intervals, and/or maneuver your boat to increase target bearing rate in order to reduce the impact of bearing inaccuracies.

I've been doing error analysis on bearing only methods recently with my TMA calculator, which is capable of calculate probability for positional/course error distributions, assuming a random bearing inaccuracy within a range of -0.5 to 0.5 deg. (http://www.subsim.com/radioroom/showthread.php?t=240508)

If you want a high level of accuracy for firing solutions, then you probably want the target positional error induced by bearing inaccuracies to be within 150 meters.

Consider a typical 4-bearing method scenario (constructed with a software called "Maneubo"): Let's say we have a medium-range medium-speed 6km/5kts target with an average bearing rate of 1 to 2 deg/min. And we choose a 10-minute time interval:



Code:
time t1 = 0 (sec)
ownship heading at t1 (deg): 0

target bearing at t1 (deg): 322.48

ownship straight direction from last position = 0 (deg)
ownship straight distance from last position = 0 (meter)
*******************************
time t2 (sec): 600

ownship heading at t2: 0

target bearing at t2 (deg): 338.23

ownship straight direction from last position (deg): 0

ownship straight distance from last position (meter): 0

*******************************
time t3 (sec): 1200

ownship heading at t3: 0

target bearing at t3 (deg): 355.6

ownship straight direction from last position (deg): 0

ownship straight distance from last position (meter): 0


target course: 78.12deg

probability of target course error within 5deg: 72.2727 %
probability of target course error within 10deg: 98.9091 %
probability of target course error within 20deg: 100 %

3 bearings when stationary can only get course solution.

*******************************
time t4 (sec): 1800

ownship heading at t4: 0

target bearing at t4 (deg): 32

ownship straight direction from last position (deg): 270

ownship straight distance from last position (meter): 2330


target course: 78.12deg, speed: 5.17377knots, distance: 6583.09

probability of target course error within 5deg: 70.1653 %
probability of target course error within 10deg: 98.9256 %
probability of target course error within 20deg: 100 %

probability of target positional error within 75m: 13.4711 %
probability of target positional error within 150m: 29.1736 %
probability of target positional error within 300m: 56.4463 %
Looks like we got a roughly 60% confidence of target positional error to be within 300m, when we consider a -/+ 0.5deg bearing inaccuracies. Looks marginally acceptable if we want a firing solution, but further increasing time intervals will improve the score.

If you only want a rough estimate of course and speed, you can decrease the time interval to 5 or 7 min maybe.

In this case when I'm about to take the 4th bearing, I moved to the opposite direction of
the target course because this will maximise bearing rate. You may want to avoid the following situation since the bearing rate is low and the solution is very error prone to bearing inaccuracies:


Last edited by ljqcn101; 04-21-2019 at 08:15 AM.
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Old 04-21-2019, 09:48 AM   #3
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Thanks for the very detailed post. A good start!

To further specify the question, the expectations for the "fix" I had in mind is one good enough to plan an intercept course.

The motivation for asking this question is the disagreement between people who say, "Find the convoy's position and course by hydrophones first, then plot an intercept course" and those who say "forget about determining course, just go flank speed on the surface in the direction of the convoy".

In my experience, visual contact can usually be made within 15 minutes of travelling flank speed on the surface on the initial contact bearing, with a dive to correct course halfway, (after about 5 km), while 15 minutes is also commonly cited as the "minimum time" for a triangulation by the 4 bearings method. Therefore, I'm currently leaning towards the first method (immediate flank speed run on the surface.)

Last edited by jarlemag; 04-21-2019 at 01:17 PM.
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Old 04-21-2019, 02:42 PM   #4
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Currently, with the closeness of the convoy at spawn you really do not need to go through the whole 3/4 bearing procedure to get to it. Just move towards the sound direction and trail it, with another hydrophone check if you feel unsure or excessive fog conditions apply. The current spawn condition is very forgiving in that.

But when you reach it, you are likely in an disadvantageous position and know nothing about where it is going. You shift the workload of gathering target movement to the visual contact phase. Doing the complicated method at a standoff can be considered as a time-investment into knowing roughly where he is going before you reach it. There is no rule that says which method you should follow. Some people like to keep things simple and do no-brainer actions to get a job done. Others simply like to use their wits and limited mount of information available to still get the end result. It's a choice.

But maybe in a future version of the game the developers introduce a more challenging situation where a convoy, or more likely an armed taskforce, moves much more rapidly (your surface speed now is 3 times faster than the average convoy speed) and from a further distance. (I hope!) Then it might prove more effective to use a systematic method of tracking the the contacts whereabouts, rather than to just dive-listen-sprint-repeat.

p.s. Has anybody even traced back the target course from a visual (verified) sighting to the moment of spawn?
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Old 04-22-2019, 01:51 AM   #5
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Would be nice if we had the tools in game to do this. I mean, atleast with SH4 you can somewhat attempt this sort of thing in game. Just another big question mark as to who this game is really geared at.
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Old 04-22-2019, 02:04 AM   #6
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Have you even played the game? Have you even tried the navigator station? In what way is it different or lacking to SH3/4/5? Aside from the ability to drag circles, it is equal if not better overall than in the Silent Hunter (4) games. Try using the odometer in the SH games for proper dead-reckoning. (it's there, but cumbersome) Try finding the precise timestamp on the clock of an event. Try writing text. Try drawing tangent circles to a line. You can do the exact same and more compared to those games. Stop talking BS.
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Old 04-22-2019, 02:26 AM   #7
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Quote:
Originally Posted by Pisces View Post
Have you even played the game? Have you even tried the navigator station? In what way is it different or lacking to SH3/4/5? Aside from the ability to drag circles, it is equal if not better overall than in the Silent Hunter (4) games. Try using the odometer in the SH games for proper dead-reckoning. (it's there, but cumbersome) Try finding the precise timestamp on the clock of an event. Try writing text. Try drawing tangent circles to a line. You can do the exact same and more compared to those games. Stop talking BS.
When you literally answer your own question, then tell me to stop talking BS........ "Yes it can't do what a decade old game can, but stop talking BS."
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Old 04-22-2019, 02:58 AM   #8
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Quote:
Originally Posted by Pisces View Post
Have you even played the game? Have you even tried the navigator station? In what way is it different or lacking to SH3/4/5? Aside from the ability to drag circles, it is equal if not better overall than in the Silent Hunter (4) games. Try using the odometer in the SH games for proper dead-reckoning. (it's there, but cumbersome) Try finding the precise timestamp on the clock of an event. Try writing text. Try drawing tangent circles to a line. You can do the exact same and more compared to those games. Stop talking BS.
It still desperately needs a parallel / sliding ruler.
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Old 04-22-2019, 03:07 AM   #9
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Originally Posted by Elphaba View Post
It still desperately needs a parallel / sliding ruler.
Oh don't do that. He doesn't like hearing that a ten year old game still does things this game can't.

He will instead demand you make your own game. I.E: The fanboi argument.
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Old 04-22-2019, 03:13 AM   #10
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Quote:
Originally Posted by Elphaba View Post
It still desperately needs a parallel / sliding ruler.
My thoughts exactly.

http://www.subsim.com/radioroom/showthread.php?t=240597
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Old 04-22-2019, 03:15 AM   #11
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Quote:
Originally Posted by Elphaba View Post
I don’t need you sticking up for me.

Pisces has proved themselves and their observations and fact based opinions over time; they’ve also been a great contributor to this community.

Most of us left the playground a long time ago; don’t drag me into your issues.
Oh sweetheart, I wasn't sticking up for you, I don't care enough about you to do that! And I don't care "who" someone is. If I don't agree with their opinion, I don't agree. Just because they threw money at Neal doesn't make them a special person, atleast, it shouldn't.
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Old 04-22-2019, 03:17 AM   #12
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Originally Posted by Slyguy3129 View Post
Oh sweetheart, I wasn't sticking up for you, I don't care enough about you to do that!
Try reading your recent posts - especially the one to me - and then read your ‘signature’ and realise just what a hypocritical nasty little troll you’re being.
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Old 04-22-2019, 03:24 AM   #13
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Originally Posted by Elphaba View Post
Try reading your recent posts - especially the one to me - and then read your ‘signature’ and realise just what a hypocritical nasty little troll you’re being.
Read my signature, then try grasping and comprehension. Then understand I haven't tried to silence anyone. Then Google "Hypocrisy" and get back with me! I'll wait.
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Old 04-22-2019, 04:02 AM   #14
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Quote:
Originally Posted by Slyguy3129 View Post
When you literally answer your own question, then tell me to stop talking BS........ "Yes it can't do what a decade old game can, but stop talking BS."
Correct, you can't drag circles. But tell us how that prevents you from drawing the lines to construct it. It doesn't. So that is why I said you should stop making unfounded accusations about the game and the quality of the game ascthe developers have provided thus far.

Can you do it accurately? Not really, depends on dexterity, eyesight, screen resolution and size, the ability to repeatedly align to the proper mark of the protractor. Are there ways around that? Yes, longer time intervals or more extreme movement to induce relative motion. Is it effective? The jury is still out on that. It was already out long before WP came out.

As you can read in the link I posted in a reply to Elphaba I was the first (I dare say) to mention this lack of the ability to draw paraĺlel lines. But if you read it carefilly enough then you might notice my attempt at providing constructive criticism and a relatively easy change (imho) with already present features. In stead of launching an attack with at how misserable the game is supposed to be. ( Like in a different thread you started)
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Old 04-22-2019, 04:15 AM   #15
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Quote:
Originally Posted by Pisces View Post
Correct, you can't drag circles. But tell us how that prevents you from drawing the lines to construct it. It doesn't. So that is why I said you should stop making unfounded accusations about the game and the quality of the game ascthe developers have provided thus far.

Can you do it accurately? Not really, depends on dexterity, eyesight, screen resolution and size, the ability to repeatedly align to the proper mark of the protractor. Are there ways around that? Yes, longer time intervals or more extreme movement to induce relative motion. Is it effective? The jury is still out on that. It was already out long before WP came out.

As you can read in the link I posted in a reply to Elphaba I was the first (I dare say) to mention this lack of the ability to draw paraĺlel lines. But if you read it carefilly enough then you might notice my attempt at providing constructive criticism and a relatively easy change (imho) with already present features. In stead of launching an attack with at how misserable the game is supposed to be. ( Like in a different thread you started)
Sorry, a game that can't do 1/3 the stuff a decade old game can do, is a game which has gone in the wrong direction. No matter how you try and spin it. When it's that far off, I don't see how "pointing it out nicely" will get anything fixed.

Don't reinvent the wheel, perfect it. Now all we have is a square that doesn't go anywhere.
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