Hydrophone Hunting (tutorial)

[Alcibiades]

Hunting a target with the hydrophone. Using 100% realism (no map contacts)

I asked for help with this a few days back and since have been having a blast with it. Picking up the sound of a target's 'whoop whoop' of the propeller well beyond visual range - plotting their course, moving to PERFECT intercept location.... all while well beyond visual range. Then waiting while they slowly come into view right along their pre-plotted "path" and into the sights, 500m away. Fun!

Anyway, I made these two PDF files with 15 steps to illustrate how to track a ship with the hydrophones. I originally made them for myself, to help with understanding how it works - but figured I'd share them as they may be helpful for others. They are designed to be a simple step-by-step guide that can be easily printed.

They require a basic understanding of how to use the drawing tools for in-game plotting.

(edit) noticed some are missing S2. Be sure you download BOTH sheets. The first (S-1) has steps 1-8 and plots heading. The second (S-2) has steps 9-15 and shows how to get speed and distance.


SHEET 1
http://www.filefront.com/16063311/Hydrophone%20Tracking%20S1.pdf

and

SHEET 2
http://www.filefront.com/16063315/Hydrophone%20Tracking%20S2.pdf



Also, I sure as heck didn't invent this stuff - I just learned it a few days ago. Most helpful to me was the video by nefeldamon on the SHIII forum. I'd suggest checking it out also if you have the time. (the PDF files are based in concept around his example) http://www.subsim.com/radioroom/showthread.php?t=154461

And again big thanks to Kylania for pointing me to his video in the first place and also helping me find a site where I could upload the PDF files.

Hope this is helpful to anyone else who may want to try this.

[Capt_Sluggo]

Thank you, Alcibiades! This will be a lot of fun. Less dangerous than visual hunting, too.

[gutted]

Ahem:
http://www.subsim.com/radioroom/showthread.php?t=167103

^ Once you lean the basics... you can stop drawing all those nasty lines. Post #12, shows a step by step using it.

[Alcibiades]

Ahem:
http://www.subsim.com/radioroom/showthread.php?t=167103

^ Once you lean the basics... you can stop drawing all those nasty lines. Post #12, shows a step by step using it.


Yes, I agree that your program can take all the 'work' out of it. You did a heck of a job making that program. And it looks pretty nice :yeah: - but that is the part I find fun :shifty:. Maybe I'm weird and I just like drawing lines and circles :yep:. I could also just turn map contacts on and let the computer show me the ship and it's course :down:.

But I don't want to do that. I like to figure it out myself, and it really is NOT hard at all.

In fact it's pretty easy. Draw a few lines and circles, wait, repeat, and boom, you have their heading. move, repeat, and you have their distance and speed. No calculations... no work... just drawing some lines, angles, and circles. The PDF's I made are just that - a simple (and easy to follow) step-by-step explanation of how to make the lines and circles.


/shrug anyway, I just think it is a blast to figure out where the target is (well beyond visual range), move to their course, set up, and then sit and quietly wait while they chug along into the firing lane :rotfl2:


Now I patrol a bit, submerge, all stop, and wait... (TC++) that way I can pick up a contact as soon as they come into range - at max distance. Plot, intercept, and WHAM!!:dead::dead::dead: :rock::rock::rock:

Word of caution, it will work against a convoy, but unless you are tracking the EXACT same ship (each time you get the bearing), the course you plot will be off by a bit :nope:. Still plenty close enough to get well in front of them, but you'll then need your scope to finish the firing solution :up:.

Also, the longer you wait between bearings - the farther apart the bearing lines are (in degrees) - the more accurate you'll be. Just don't wait too long or they'll sail right on past and out of range!!! :haha::haha::har:

[Placoderm]

This is AWESOME! :yeah:


Thank you!!



:salute:

[Bothersome]

Hmm... OK you said in step 11.2 that I need to move my sub to a new position. But my sub won't go but 9 knots while submerged. How did you go faster than the target to overtake it even a little. And you calculated the target was moving 10 knots. Now what?

I think I'll stick with my approach.

Target detected at 0.00 (180 due south). Wait a couple of minutes and get bearing from sonar guy again. Notice it increased to 2. Turn sub to heading 270 speed set to full and wait 2 minutes. What is target bearing doing? I'm at 6 knots bearing holding steady at my 272. Steady as she goes for 5 minutes. New bearing, target at 270. Hold course and verify target is getting louder. If not, give up or run around it on surface. If it is getting closer, I'm already on intercept course (based on your example heading and speed). When target gets real close I use periscope to get set up for shot. If target was falling behind some then I slow and stop as bearing stops decreasing (I'm in front of it).

No fuss, no muss. And no lines and circles.

And, the main benefit. I don't have to race it. As I have put my sub in front of the target much earlier.

Granted, I won't be able to pull the trigger on the target WITHOUT using the scope. Your method might actually have a decent chance of finding bearing and speed and allow you to prepare a shot without ever seeing the target. Which I guess is needed in heavy rain and fog. But like I said, if I had to use your method in that example given, I'd never be able to overtake the target at step 11.2 to get set up for the shot.

[gutted]

Hmm... OK you said in step 11.2 that I need to move my sub to a new position. But my sub won't go but 9 knots while submerged. How did you go faster than the target to overtake it even a little. And you calculated the target was moving 10 knots. Now what?You surface and run at flank speed (battery recharging switched off if need be).

If you timed him with atleast 15-20 minute intervals.. you have plenty of time to move to a new location.

You dont HAVE to surface though, it just helps. The target WILL be along the predicted bearing.. all you need to do is be in a spot to "look across it" to see where.

[Alcibiades]

But like I said, if I had to use your method in that example given, I'd never be able to overtake the target at step 11.2 to get set up for the shot.

Remember that in 11.2, you are NOT overtaking the target. It is still somewhere along the third bearing line or well behind you (bearing 220ish in the PDF when the sub is moving to new position). But still, surface and run at flank speed. you can do 15 or more knots even in rough seas.

Keep in mind that when you take your third bearing and have the targets heading, it is still usually a LONG way off (12+ km). (unless it happens to be coming straight at you, but you'll know that by then as the bearing does not change). You can surface well out of sight and have plenty of time to flank speed (or not) and plot an intercept that will easily put you well ahead of them.

At 10 knots the ship will cover approx 9 km in 30 min. provided it is even coming slightly towards you - you can still plot an intercept course that is significantly shorter than his course... even if you were running at his speed.


And yes, I agree your method will work and usually get you close enough provided ok visibility. And thats great if its easier. It is the way I was using my hydrophones before. But once, I tried to track a ship in the dark rain with <250m visibility... Ugh! I tracked him forever! stopped and took 15+ hydrophone bearings... my map looked like a geometry exam that I once flunked. Kept crossing back and forth near him w/out seeing him. Chased his arse all night! Finally came directly from behind him (after his bearing didn't change any more :) ) and had to be RIGHT on top of him before I saw him. Finished him off with the deck guns and then promptly came to the forum (thanks Kylania) to ask how to plot a course with just hydrophone :haha::har:

But really, it's not that hard once you figure it out and then with a few lines and circles, you can get their course and speed... Then set up for a great shot - and still have time to get a cup of coffee while you wait for them to come into the shooting gallery :rotfl2:

Either way, everyone can track how they find best - as long as the merchant ship is sent to Davy Jones Locker, who can argue? :arrgh!::arrgh!::arrgh!:

[Bothersome]

I see your point. It's a solvable problem and you have provided an answer.

I'm just thinking out loud...

Why do I need to use only one tool in my boat to make this kill.

Imagining a situation...

1. Target is part of the mission.
2. It's heavy rain and fog. So can't use Scope.
3. Target is escorted so can't come to surface.
4. Escorts have radar so can't use radar for range.
5. If they get detection, target serpentines and that would make the shot very hard and have to avoid destroyers.

The problem is... How can I maneuver the boat without the escorts hearing me. Certainly not with any speed.

If I didn't have escorts to worry about, why not just give surface chase and use radar to get range and when close to 1000 yards or meters, climb into the deck gun and get a little practice in. You can't see it at 1000 in heavy rain and fog, but you can get the accurate bearing from sonar tracking and 1000 is close enough to get a lot of hits. Chase him till he sinks.

The question is: When is it the best time to need this method of passive acoustics only?

Edited: I posted the above before seeing your message Alcibiades (http://www.subsim.com/radioroom/member.php?u=260990)

[Alcibiades]

Imagining a situation...

1. Target is part of the mission.
2. It's heavy rain and fog. So can't use Scope.
3. Target is escorted so can't come to surface.
4. Escorts have radar so can't use radar for range.
5. If they get detection, target serpentines and that would make the shot very hard and have to avoid destroyers.

The problem is... How can I maneuver the boat without the escorts hearing me. Certainly not with any speed.

If I didn't have escorts to worry about, why not just give surface chase and use radar to get range and when close to 1000 yards or meters, climb into the deck gun and get a little practice in. You can't see it at 1000 in heavy rain and fog, but you can get the accurate bearing from sonar tracking and 1000 is close enough to get a lot of hits. Chase him till he sinks.

The question is: When is it the best time to need this method of passive acoustics only?

Edited: I posted the above before seeing your message Alcibiades (http://www.subsim.com/radioroom/member.php?u=260990)



Ha! Good Question!:haha::haha::har:

Sounds like an ugly situation for sure! I don't think hydrophone tracking would work there. Unless you could stay WAY away until you determined their course. Also, you have to get the bearing to the same ship in order for it to work. That would be tough in a big convoy and if you get the wrong ship, your course and speed estimate will be off. dunno, try to get in front and sit and wait?:hmmm:

I'd say it works best for: a single slow moving ship that does not change course or speed and is not moving 90 AOB or away from you. In fact that might be all it works for :rotfl2:

but at least in that case it is possible to get the contacts course information before even getting into visual range

[ERPP8]

You know Benno has a great skill called "Total revealing"

[gutted]

The question is: When is it the best time to need this method of passive acoustics only?

When the target is far away and is closing. You'll save time searching, and already be in an optimal firing position with a good idea of his course & speed.

Just listen to him.. if he sounds close, then just surface and head in his general direction at flank speed (if he's moving left or right, add alittle lead). Probably wont be long before you spot em. If he's far out.. then you're better off waiting and listening.. else you'll have to dive and listen multiple times.

[gutted]

You know Benno has a great skill called "Total revealing"

And you learn nothing from using it.....

[timmy41]

in step 4 you draw the 'NW line', but what if the contact is to the SE or NW? it will not work?

[Pisces]

in step 4 you draw the 'NW line', but what if the contact is to the SE or NW? it will not work?Why wouldn't it? The bearings show where the target is (and was). In step 4 Alcibiades has just drawn a line in a random direction (well, from bearing 1 over to and across bearing 3). Look at step 5 to 8. Using the circle and line parallel to bearing 1 he corrected the NW line to the correct course. It doesn't matter where he comes from or it's actual course being totally different. The circle and parallel line will show if it is a wrong guess, and what the right course is.

[Alcibiades]

Why wouldn't it? The bearings show where the target is (and was). In step 4 Alcibiades has just drawn a line in a random direction (well, from bearing 1 over to and across bearing 3). Look at step 5 to 8. Using the circle and line parallel to bearing 1 he corrected the NW line to the correct course. It doesn't matter where he comes from or it's actual course being totally different. The circle and parallel line will show if it is a wrong guess, and what the right course is.


Yes.

The line in step 4 is just a random line (guess) to allow use of geometry to get the real heading.


Also, since you were sitting still and not moving from when you took bearing 1 until when you took bearing 3 - then you know that the target is moving towards the west. And you guess he's coming towards you.

If the target is E or N of you when you first pick him up, follow the same procedure, but just "guess" his route and assume he is 'slanting' towards you.



additional note: you can also tell he is coming towards you based on how much larger the angle is between bearing line 2 and 3. The larger that angle, the sharper angle the target is heading towards you. if the big angle is between lines 1 and 2 (and a small angle between bearing lines 2 and 3) then hes moving away!


Hope the PDF's help!

word of caution again: be careful if trying to use it against a convoy!!! if you record a different ship each time you listen (likely), then your estimates will be off. usually close enough to plot a rough intercept course, but that's probably about all :-?

[timmy41]

aha, ok, so the line is just placed in the general direction.
There are a few tiny things that could use better clarification, simple tiny things like making the 'X's larger that signify the variable for kilometers. at step 14.4 I had to wonder for a second what the X was, until I zoomed in and saw the tiny x on the plot! The info is there, its just sometimes a bit hard to find, and maybe someone with bad eyes wouldnt even see it! Could either make the X's a bit larger, or explain on the bottom of step 14 that X is the distance the ship has traveled in the time interval one is using.
Overall, great guide! :yeah:

edit:
for convoys, one could simply manually listen for the median of the convoy and base off that knowing a medium convoy is about 5k wide and 3k forward, and so on. Yes?

[Pisces]

edit:
for convoys, one could simply manually listen for the median of the convoy and base off that knowing a medium convoy is about 5k wide and 3k forward, and so on. Yes?I guess so. But the sound level is probably not the same for small and larger ships. If it happens so that the convoy has rather silent ships mostly on one side then the peak sound-level of the whole convoy is slightly displaced to the louder ships. This would cause a slight deviation in the bearings. But listening to the sounds yourself is already quite crude. So you might not notice.

Basically, don't expect accurate readings from a convoy. But it is usually so big (wide) you'll run in to one of it's members anyway.

Advice: Do listen for the edges of the sound where it is faded out, and take the middle bearing! Trying to find the maximum sound-level is difficult to get accurately. It because of how our ears work. They can't detect small changes in a loud sound. But are better at detecting quiet sounds or no sound at all.

[Alcibiades]

aha, ok, so the line is just placed in the general direction.
There are a few tiny things that could use better clarification, simple tiny things like making the 'X's larger that signify the variable for kilometers. at step 14.4 I had to wonder for a second what the X was, until I zoomed in and saw the tiny x on the plot! The info is there, its just sometimes a bit hard to find, and maybe someone with bad eyes wouldnt even see it! Could either make the X's a bit larger, or explain on the bottom of step 14 that X is the distance the ship has traveled in the time interval one is using.
Overall, great guide! :yeah:




Thanks for the feedback. It is appreciated. When creating it - it's tough to tell what it will "read" like to someone else. Or what parts could be explained better. Thanks.


But be careful - hydrophone hunting can be addicting!!:D:D:D:D