Shadowing convoy with hydrophones

kapuhy · 03-09-11, 02:09 AM

I have detected a convoy through hydrophones, heading roughly towards me. The problem is, weather is so bad that I barely see my own WO's face, so my usual method of observing the convoy through periscope from long range to learn its speed, heading and formation is useless. If I just blindly rush towards the noise, most probable result is smashing into some ships hull or meeting a destroyer at 200 meters range. Also, I can't take multiple bearings on any specific ship to calculate their heading from that, because the noises blend into each other (my sonarman is not affected by this, but he can only report on nearest target which is usually the maneuvering destroyer).

Do you have any methods to reliably calculate speed / heading of the convoy and setup the attack in such a situation or do I have to wait for the skies to clear while staying "somewhere near the convoy" (which might take weeks with my luck)?

desirableroasted · 03-09-11, 03:32 AM

As you note, the conditions prevent you from attacking the convoy safely. Even if you do manage to hit something, you are quite liable to lose it again in the murk & be unable to finish it off.

To track the convoy, I would put down markers at the extreme tip of each sonar contact. Wait five minutes and do the same. That should give you a rough indication of path and speed -- at least enough so that you can set a parallel course and wait for the weather to clear.

But you want to take new ranges every hour or so, in case the convoy decides to change path.

kapuhy · 03-09-11, 05:15 AM

Quote:

Originally Posted by desirableroasted

I would put down markers at the extreme tip of each sonar contact. Wait five minutes and do the same.

That would be hard with no contacts displaying on the map though. I can still draw the line manually, but this gives me nothing regarding distance to target.

I'm more afraid of bumping into an escort than losing contact entirely - the convoy makes a really strong noise and moves rather slow, so I can regularly dive and get close if the noise starts to fade, but I'd rather find a parallel course somehow to shadow the convoy from safe distance.

Edit: Oh, and additional question - this convoy is coming out of the Channel and into Atlantic or towards Gibraltar, either way it is still in Luftwaffe's range. If the weather clears and I send contact report, what are my chances of getting air support in stock 1.4b SH3? (like, "One in million, baby!" or "They mostly come within an hour. Mostly."?)

Pisces · 03-09-11, 06:36 AM

It's quite impossible to get any reliable course from 3 bearings taken of a convoy, since you can't get a clear indication of individual sounds. So forget that. Heading straight for them in the direction of the sound is also quite risky because if you come from somewhere head-on of them then you have a high relative motion. And subsequently hardly have any time to slow down before you get into their engage range.

As a solution I suggest to go in a direction that is a certain amount of degrees lagging to the bearing drift of the 'last' convoy sound. This allways get's you behind it. As it moves forward the bearings slip in left or right direction. Steer about 20 degrees behind it, and keep adjusting course. (not a fixed important value, just a rule of thumb) Sooner or later you are behind them and creeping up their tail if your speed isn't too high. (upper limit of the reported speed-range should be good) Then your relative speed is alot less (the difference of both your speeds) and you get more time to react as they are getting visual. If the bearing seems to change more rapidly then be carefull, then you are quite close. From then on just follow them until better weather comes along. But keep in mind that weather can change on a dime, so this instant you have fog, and the next you're spotted. So it's better to keep them between long and medium range by adjusting your speed up and down over the hours. It's going to be an arduous, long and nerve-wrecking task.

kapuhy · 03-09-11, 07:47 AM

Quote:

Originally Posted by Pisces

an arduous, long and nerve-wrecking task.

- a.k.a. commanding a WW2 submarine.

Thanks for the advice, I'll try that.

Gerald · 03-09-11, 10:15 AM

Shadowing convoy with hydro-phones, what was your title, so of course it is time consuming but not impossible, but everything should be done in real-time

desirableroasted · 03-09-11, 10:35 AM

Quote:

Originally Posted by kapuhy

That would be hard with no contacts displaying on the map though. I can still draw the line manually, but this gives me nothing regarding distance to target.

Apologies, I thought you were playing with contact lines automatically drawn. If not, then Pisces suggestion is about the only way to play it.

Gargamel · 03-09-11, 01:10 PM

http://www.subsim.com/radioroom/down...o=file&id=1711

Try this.

While I have not done this in practice, as I usually have music or a movie playing also, and the room is generally too noise to use the hydrophones myself (I know, I'm leaving a lot on the table by not doing this, but it's just not practical, so my SO is one of my first guys to get promo'd and qual'd), in theory this should work.

Again, this is a theory that I have not tried, but should work.

Find an extreme edge of the convoy in your phones. Merchant, not warship. I really wish there was a "closest merchant contact" for this. But if you can find either the Far leading corner, or the near trailing corner, that should suffice. The Near leading corner and Far trailing corners would be buried in the rest of the convoy, so the FLC and NTC are the only contacts you can trust. These would be the first merchants you encounter as you swing the phones onto each side of the convoy. These two corners should allow to you obtain a firm 'point contact' on the convoy, and should be re-obtainable. Depending on the aspect angle of the convoy to you, you'll have to use your best judgment/guess as to which one to choose.

Enter it's bearing into the calculator I linked above. As described above by DR, wait some time, 5-10 minutes per should do. Then find that contact again, and enter it's bearing into the calculator again. Rinse, Repeat.

After 3 entries, it should give you a pretty accurate heading of the convoy.

If you want to get really fancy, you could do this for both corners, just scribble down the bearings as you do it, and plot them both when you have a full set. This should help eliminate any error you might find, and will allow you to plot the travel paths on the map, allowing you to sprint ahead and hunker down along their path. I try to get just inside the first or second column depending on how big it is, so the lead escort will miss me.

03-10-11, 08:14 AM

Keep the "closest sound contact" at 000.
Whatever direction your facing when the hydrophone operator anounces "contact lost at 000" is there general diection of travel.
Unless the weather changes the best thing to do, following that, is Nothing.

03-09-11, 02:09 AM	#1
kapuhy Grey Wolf Join Date: Oct 2010 Location: Poland Posts: 874 Downloads: 72 Uploads: 3	Shadowing convoy with hydrophones I have detected a convoy through hydrophones, heading roughly towards me. The problem is, weather is so bad that I barely see my own WO's face, so my usual method of observing the convoy through periscope from long range to learn its speed, heading and formation is useless. If I just blindly rush towards the noise, most probable result is smashing into some ships hull or meeting a destroyer at 200 meters range. Also, I can't take multiple bearings on any specific ship to calculate their heading from that, because the noises blend into each other (my sonarman is not affected by this, but he can only report on nearest target which is usually the maneuvering destroyer). Do you have any methods to reliably calculate speed / heading of the convoy and setup the attack in such a situation or do I have to wait for the skies to clear while staying "somewhere near the convoy" (which might take weeks with my luck)?

03-09-11, 03:32 AM	#2
desirableroasted Grey Wolf Join Date: Feb 2006 Location: In the mountains, now. On the edge of the sea before. Posts: 933 Downloads: 47 Uploads: 0	As you note, the conditions prevent you from attacking the convoy safely. Even if you do manage to hit something, you are quite liable to lose it again in the murk & be unable to finish it off. To track the convoy, I would put down markers at the extreme tip of each sonar contact. Wait five minutes and do the same. That should give you a rough indication of path and speed -- at least enough so that you can set a parallel course and wait for the weather to clear. But you want to take new ranges every hour or so, in case the convoy decides to change path. __________________ "Well, now, that's true... the IXC is a bit of a chick magnet..but you really can't beat the VIIB for off-road fun."

03-09-11, 06:36 AM	#4
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	It's quite impossible to get any reliable course from 3 bearings taken of a convoy, since you can't get a clear indication of individual sounds. So forget that. Heading straight for them in the direction of the sound is also quite risky because if you come from somewhere head-on of them then you have a high relative motion. And subsequently hardly have any time to slow down before you get into their engage range. As a solution I suggest to go in a direction that is a certain amount of degrees lagging to the bearing drift of the 'last' convoy sound. This allways get's you behind it. As it moves forward the bearings slip in left or right direction. Steer about 20 degrees behind it, and keep adjusting course. (not a fixed important value, just a rule of thumb) Sooner or later you are behind them and creeping up their tail if your speed isn't too high. (upper limit of the reported speed-range should be good) Then your relative speed is alot less (the difference of both your speeds) and you get more time to react as they are getting visual. If the bearing seems to change more rapidly then be carefull, then you are quite close. From then on just follow them until better weather comes along. But keep in mind that weather can change on a dime, so this instant you have fog, and the next you're spotted. So it's better to keep them between long and medium range by adjusting your speed up and down over the hours. It's going to be an arduous, long and nerve-wrecking task. __________________ My site downloads: https://ricojansen.nl/downloads

03-09-11, 10:15 AM	#6
Gerald SUBSIM Newsman Join Date: May 2008 Location: Close to sea Posts: 24,254 Downloads: 553 Uploads: 0	Shadowing convoy with hydro-phones, what was your title, so of course it is time consuming but not impossible, but everything should be done in real-time __________________ Nothing in life is to be feard,it is only to be understood. Marie Curie

03-09-11, 01:10 PM	#8
Gargamel Lucky Sailor Join Date: Oct 2010 Location: Rome Posts: 4,273 Downloads: 81 Uploads: 0	http://www.subsim.com/radioroom/down...o=file&id=1711 Try this. While I have not done this in practice, as I usually have music or a movie playing also, and the room is generally too noise to use the hydrophones myself (I know, I'm leaving a lot on the table by not doing this, but it's just not practical, so my SO is one of my first guys to get promo'd and qual'd), in theory this should work. Again, this is a theory that I have not tried, but should work. Find an extreme edge of the convoy in your phones. Merchant, not warship. I really wish there was a "closest merchant contact" for this. But if you can find either the Far leading corner, or the near trailing corner, that should suffice. The Near leading corner and Far trailing corners would be buried in the rest of the convoy, so the FLC and NTC are the only contacts you can trust. These would be the first merchants you encounter as you swing the phones onto each side of the convoy. These two corners should allow to you obtain a firm 'point contact' on the convoy, and should be re-obtainable. Depending on the aspect angle of the convoy to you, you'll have to use your best judgment/guess as to which one to choose. Enter it's bearing into the calculator I linked above. As described above by DR, wait some time, 5-10 minutes per should do. Then find that contact again, and enter it's bearing into the calculator again. Rinse, Repeat. After 3 entries, it should give you a pretty accurate heading of the convoy. If you want to get really fancy, you could do this for both corners, just scribble down the bearings as you do it, and plot them both when you have a full set. This should help eliminate any error you might find, and will allow you to plot the travel paths on the map, allowing you to sprint ahead and hunker down along their path. I try to get just inside the first or second column depending on how big it is, so the lead escort will miss me. __________________ Luck is a residue of Design.

03-10-11, 08:14 AM	#9
Snestorm Stowaway Posts: n/a Downloads: Uploads:	Keep the "closest sound contact" at 000. Whatever direction your facing when the hydrophone operator anounces "contact lost at 000" is there general diection of travel. Unless the weather changes the best thing to do, following that, is Nothing.