Telling Heading From Hydrophone Bearing

[Rykaird]

So I'm off the lovely Spanish coast in an absolute frog-drowning storm. Can't see a thing - near zero visibility. I'm submerged to conserve fuel, running due north, and I get a merchant contact, bearing 064, constant distance.

I get repeated contacts, and each bearing gets greater, as in increasing towards 90. Given I don't know his range - other than the rather non-helpful "long" - is there a way to even get an estimate so I can lay an intercept? In this weather I'm going to have to get right on top of him to ever see him.

Anyway, if there is a way, or I'm barking up the wrong sausage, let me know. Thanks!

[High Voltage]

I've read that some people make their marks on the contact line that extends from their sub at the point at which the line starts fading away. Inexact but it's a start.

I use a slightly different method:

Assuming the ship is reported as being at a "constant distance", I pick an arbitrary measurement with the ruler, say 6km for one that's reported long distance. I will make a couple of markings along the contact line at "6" from my sub, and at different intervals which will give me either the contact's course, or one that is parallel to it. By then using the nomograph on my map (download the mod) I have the distance travelled by the ship between two markings, as well as the time it has taken it to travel this distance, I therefore get a very rough estimate of the ship's speed.

Having his speed and rough course, i can plot a course that will give me a general intercept course.

Frequent hydrophone readings when i reach that spot will allow me to fine-tune my position.


Does any of what I've written make sense?

:doh: :doh:

[Mush Martin]

Somewhere here there is a manual sonar tutorial.

it may even take the shape of an academy session
inl game.

I cant recall but check the list of
tools and tips in the stickies

MM

[ReallyDedPoet]

Somewhere here there is a manual sonar tutorial.

try here:up:
http://www.subsim.com/radioroom/showthread.php?t=104858&highlight=hydrophone+tutorial

edit: Sorry dude, just noticed you were all over that thread.

[Corsair]

So I'm off the lovely Spanish coast in an absolute frog-drowning storm. Can't see a thing - near zero visibility. I'm submerged to conserve fuel, running due north, and I get a merchant contact, bearing 064, constant distance.

I get repeated contacts, and each bearing gets greater, as in increasing towards 90. Given I don't know his range - other than the rather non-helpful "long" - is there a way to even get an estimate so I can lay an intercept? In this weather I'm going to have to get right on top of him to ever see him.

Anyway, if there is a way, or I'm barking up the wrong sausage, let me know. Thanks!

Doesn't look good... As you travel slow, if it is a medium speed, you can forget it. Long range is anything above 3 Kms but could be a lot more. If you put your ears behind the hydrophone, you should get an idea from the sound if it's really far. Since you're travelling north and the contact is constant distance moving from 64 towards 90, it's probably heading something near south, which is your opposite direction.
As anyway you won't be able to make a proper attack in these visibility conditions, I wouldn't even bother trying to catch him.

[BigZed]

When your sonarman finds a contact hit "H" to go to the sonar and search within the bearing range that he called out. When you find the proper bearing of the ship click the "hydrophone" station button then click "sonar" then click "find range to target" or "range to target". As long as you keep the needle on the target bearing (in the top right corner it should say "merchant" or "warship" or "unknown") then after a few seconds you will get a reading of how far the ship is. Once you get that hit the checkmark in the pad at the upper right corner and that will send the info to your attack periscope.

Right now ive just started to learn how to manual target ships and fire torps manually so my "realism" settings are about 81% or 85% something like that. That is how i find my range to targets when submerged and dont have enough time to open the recognition manual.

[GreyBeard]

When your sonarman finds a contact hit "H" to go to the sonar and search within the bearing range that he called out. When you find the proper bearing of the ship click the "hydrophone" station button then click "sonar" then click "find range to target" or "range to target". As long as you keep the needle on the target bearing (in the top right corner it should say "merchant" or "warship" or "unknown") then after a few seconds you will get a reading of how far the ship is. Once you get that hit the checkmark in the pad at the upper right corner and that will send the info to your attack periscope.

Right now ive just started to learn how to manual target ships and fire torps manually so my "realism" settings are about 81% or 85% something like that. That is how i find my range to targets when submerged and dont have enough time to open the recognition manual.

I must be missing something here. What does opening the recognition manual have to do with the range to a particular target?

[immortal44]

I assume when he's surfaced he finds the range using notepad, which requires you to identify the ship in order to find the range.

[greyrider]

rykaird,

if your are in your sound room, with the bearing needle of the hydrophone laying on the target bearing, and your listening to his screws,
on the loudest bearing, look up on the sound operators note pad.
if you do not see "warship", "merchant", or "unknown" written on his notepad, then your target is somewhere between 7.5 km and 34 km.
the sound operator writes the sound cone of the targets screws on his notepad.
but he only writes his soundcone for ranges 7.5 km and less, beyond that its up to you to determine range by sound cone and amplitude.
the sound operator must be recording the inner sound cone, because the complete sound cone can be as much as twenty degree's, even at 8 km.



anything over 7.5 km, he writes nothing.
anything 7.5 km and closer, he begins to draw and record his soundcone of the target by writting it on the notepad.
he does this by writing the type of sound contact he has on his notepad on every bearing he hears the inner cone, which is the width of the soundcone,
which is determined by range.

example:
merchant bearing zero degree's, range 8 km, target is closing, target course is 180, speed unknown, u-boat at dead stop, course 000.


target range now 8 km, sound operators notepad blank

target range now 7.5 km SO notepad entry, "merchant" appears on bearing ooo: fringe bearings 359 and 001 blank, sound cone width is 1 degree.

target range now 7 km SO notepad entry, "merchant" appears on bearings 359 and 001: fringe bearings 358 and 002 blank, sound cone width is two degrees.

target range now 6.3 km SO notepad entry, "merchant" appears on bearings 358,359 and 001,002: fringe bearings 357 and 003 blank, sound cone width is four degrees.

target range now 4.1 km SO notepad entry, "merchant" appears on bearings 357,358,359 and 001,002,003: fringe bearings 356 and 004 blank, sound cone width is six degrees.

target range now 2.8 km SO notepad entry, "merchant" appears on bearings 356,357,358,359 and 001,002,003,004: fringe bearings 355 and 005 blank, sound cone width is eight degrees.

target range now 1.0 km SO notepad entry, "merchant" appears on bearings 355,356,357,358,359 and 001,002,003,004,005: fringe bearings 354 and 006 blank, sound cone width is ten degrees.

target range now 400 m SO notepad entry, "merchant" appears on bearings 354,355,356,357,358,359 and 001,002,003,004,005,006: fringe bearings 353 and 007 blank, sound cone width is 12 degrees.

for longer ranges i compare the amplitdue of the screws verse the background noise of the hydrophones, if it seems that the noise is louder than the screws, then i know the target is
at least over 15 km away.
if the screws sound louder than the background noise, then the target is closer than 15 km.
hope this helps, and good luck!

[Rykaird]

I read the manual for the hydrophone tutorial, but it seemed to address only determining speed of the target, not the bearing.

I think there must be a way to determine heading from repeated bearing measurements using:

1) the time gaps between the bearing changes (hypothetical example - to move from a bearing of 60 to 65 degrees took 2 minutes, but from 65 to 70 degrees took 1 minute - this would imply he's closing).

and

2) a rough estimate of his speed (e.g., slow = 5 knots, medium = 9 knots).

I'll noodle on it some more. It seems like a series of triangles. And as we know, the triangle is all powerful.

[greyrider]

i'm pretty sure your target is at a 90 degree right angle to you already, as long as it keeps saying constant distance

[Rykaird]

rykaird,

if your are in your sound room, with the bearing needle of the hydrophone laying on the target bearing, and your listening to his screws,
on the loudest bearing, look up on the sound operators note pad.
if you do not see "warship", "merchant", or "unknown" written on his notepad, then your target is somewhere between 7.5 km and 34 km.
the sound operator writes the sound cone of the targets screws on his notepad.
but he only writes his soundcone for ranges 7.5 km and less, beyond that its up to you to determine range by sound cone and amplitude.
the sound operator must be recording the inner sound cone, because the complete sound cone can be as much as twenty degree's, even at 8 km.



anything over 7.5 km, he writes nothing.
anything 7.5 km and closer, he begins to draw and record his soundcone of the target by writting it on the notepad.
he does this by writing the type of sound contact he has on his notepad on every bearing he hears the inner cone, which is the width of the soundcone,
which is determined by range.

example:
merchant bearing zero degree's, range 8 km, target is closing, target course is 180, speed unknown, u-boat at dead stop, course 000.


target range now 8 km, sound operators notepad blank

target range now 7.5 km SO notepad entry, "merchant" appears on bearing ooo: fringe bearings 359 and 001 blank, sound cone width is 1 degree.

target range now 7 km SO notepad entry, "merchant" appears on bearings 359 and 001: fringe bearings 358 and 002 blank, sound cone width is two degrees.

target range now 6.3 km SO notepad entry, "merchant" appears on bearings 358,359 and 001,002: fringe bearings 357 and 003 blank, sound cone width is four degrees.

target range now 4.1 km SO notepad entry, "merchant" appears on bearings 357,358,359 and 001,002,003: fringe bearings 356 and 004 blank, sound cone width is six degrees.

target range now 2.8 km SO notepad entry, "merchant" appears on bearings 356,357,358,359 and 001,002,003,004: fringe bearings 355 and 005 blank, sound cone width is eight degrees.

target range now 1.0 km SO notepad entry, "merchant" appears on bearings 355,356,357,358,359 and 001,002,003,004,005: fringe bearings 354 and 006 blank, sound cone width is ten degrees.

target range now 400 m SO notepad entry, "merchant" appears on bearings 354,355,356,357,358,359 and 001,002,003,004,005,006: fringe bearings 353 and 007 blank, sound cone width is 12 degrees.

for longer ranges i compare the amplitdue of the screws verse the background noise of the hydrophones, if it seems that the noise is louder than the screws, then i know the target is
at least over 15 km away.
if the screws sound louder than the background noise, then the target is closer than 15 km.
hope this helps, and good luck!

Thanks! The fact on the 7.5km range of the sound operator writing anything on his notepad is a huge help right there, as is the tip on the 15km.

I'm not sure what to do with the sound cone information - how does the cone width give me range exactly? Thanks for the help here - I think I'm getting closer to being able to hunt "blind."

[greyrider]

been so long since i posted, i forget how to quote, but you said

I'm not sure what to do with the sound cone information - how does the cone width give me range exactly? Thanks for the help here - I think I'm getting closer to being able to hunt "blind."
http://www.subsim.com/radioroom/smartdark/user_online.gif http://www.subsim.com/radioroom/smartdark/report.gif (http://www.subsim.com/radioroom/report.php?p=414435)

wow! i guess i dont have to remember.

anyway to answer, it comes in handy when your being attacked by more than one dd. now, by sweeping a dd's soundcone, youll be able to tell which one is your biggest threat, the bigger the soundcone, the closer the range

[High Voltage]

you guys are golden! I'm not sure where you got all of this info as my soundman Bernard usually just yells out "Wasserbomben" when I'm resting in my bunk, but I've printed out this info for further study.

PS Where DID you find out about the 7.5km rule?

[Rykaird]

anyway to answer, it comes in handy when your being attacked by more than one dd. now, by sweeping a dd's soundcone, youll be able to tell which one is your biggest threat, the bigger the soundcone, the closer the range

This works very well - I was able to tell that I was closing the gap on a distant merchant by counting the number of degrees in the cone and watching to see if they increased.

I still think there must be a way to get some guestimate of his course using the hydrophone, a stopwatch, and his approximate speed. But maybe not - it may require the range. I'll have to brush up on my side-angle-side geometry theorems.

[Dantenoc]

Read this:
http://www.subsim.com/radioroom/showthread.php?t=92743

to interpret the lines made on the example pictures, just remeber that they represent aproximate positions for the target at different points in time that where given to you as intervals (for example "medium range") and hence they're not points but lines that go from "here to there" according to the range estimate given. You can see that as the range to target closes the lines shift to smaller sizes. For example the last ones are only 1 km long, since "short" range means from 0km to 1km, whereas the previous ones where 2km long, because "medium" range means more than 1km but less than 3km (giving you a 2km interval). And of course, the big line that represent's the target's track is drawn and continualy updated so that it cuts through all of the "contact" lines (this assumes that the target is traveling in a straight line).

Anyway, just read it carefully and I'm sure you'll get it.

Also, observe how this technique is used auxiliarly in the 2nd part of the "Video Hunt":
http://www.subsim.com/radioroom/showthread.php?t=97682
And of course, there's allways this thread:
http://www.subsim.com/radioroom/showthread.php?t=88961

[xlbob]

I've read that some people make their marks on the contact line that extends from their sub at the point at which the line starts fading away. Inexact but it's a start. (snip)


That's how I did it. I play at 61% realism. Sailing to my assigned patrol area or when patroling the asigned grid, every now and then I will go to periscope depth every now and then (every two or three hours), keep the speed ahead full, and tell SO to do normal sweeping.

When I get contatc report, I got the map and zoom in to the max magnification. Once I get max zoom, I mark the end of the contatc line. I stay submerge and keep the speed and mark the contact line again, when the contact line moves., which indicate the ship is moving, I mark the end of the contact line again. After several marks, I usually end up with at least 5 marks, I draw a line connecting those marks. That line is the ship's path. To figure which direction it goes, I simply extended the line and determine where i plan to intercept it.

This method works every time for a single ship and convoys. If a convoy, simply make more marks on several contact lines. You'll be able to tell if the convoy consist of two columns or three columns, then you can position your boat inside the convoy.

When I say "every time" I mean every single time in my last 2 careers, with the last one lasted up to 6th mission :D

I also find out on several occasions, that when the map is zoomed in to the max magnification, the difference between the ship's position as indicated by the marking on contact line and the actual position of the ship seen through the periscope is about 100 m. The contact line shows the ship(s) to be 100 m farther then its actual position.

Bob

[Corsair]

I've read that some people make their marks on the contact line that extends from their sub at the point at which the line starts fading away. Inexact but it's a start. (snip)

That's how I did it. I play at 61% realism. Sailing to my assigned patrol area or when patroling the asigned grid, every now and then I will go to periscope depth every now and then (every two or three hours), keep the speed ahead full, and tell SO to do normal sweeping.


You will hear a lot more things with engines slow or full stop...;)

[xlbob]

You will hear a lot more things with engines slow or full stop...;)

Thanks Corsair, :up: I'll keep that in mind when I start a new career tonight :D

Funny thing is, this may sound stupid, I often feel that I have to be at my assigned grid as soon as possible, finish my patrol and get the hell back home as quickly as I can ... don't want to spend more time than necessary at sea, it's not really safe out there :D

Bob

[Corsair]

Most of the time it's not in the assigned grid that you find targets...;)

[11Bravo]

What realism setting gets the sonar man to write something on the notepad and draw lines on the map?

I have never seen this with any contact in 7 patrols so far. I use sonar to find most of the ships, but the only help I get is when the sonar guy says contact, merchant at long range on some bearing. I make the bearing my new course, drive 20 minutes and submerge for a new listen. Lather, rinse, repeat until the watch crew sees the ship. Then I use maneuver and manual targetting. The idea of getting some of this information from sonar is intriguing...I am useing 87% realism, with only external view and event view on...

[Abd_von_Mumit]

What realism setting gets the sonar man to write something on the notepad and draw lines on the map?

I have never seen this with any contact in 7 patrols so far. I use sonar to find most of the ships, but the only help I get is when the sonar guy says contact, merchant at long range on some bearing. I make the bearing my new course, drive 20 minutes and submerge for a new listen. Lather, rinse, repeat until the watch crew sees the ship. Then I use maneuver and manual targetting. The idea of getting some of this information from sonar is intriguing...I am useing 87% realism, with only external view and event view on...
"No map contact updates" should be off.

[Rykaird]

I've read that some people make their marks on the contact line that extends from their sub at the point at which the line starts fading away. Inexact but it's a start. (snip)


That's how I did it. I play at 61% realism. Sailing to my assigned patrol area or when patroling the asigned grid, every now and then I will go to periscope depth every now and then (every two or three hours), keep the speed ahead full, and tell SO to do normal sweeping.

When I get contatc report, I got the map and zoom in to the max magnification. Once I get max zoom, I mark the end of the contatc line. I stay submerge and keep the speed and mark the contact line again, when the contact line moves., which indicate the ship is moving, I mark the end of the contact line again. After several marks, I usually end up with at least 5 marks, I draw a line connecting those marks. That line is the ship's path. To figure which direction it goes, I simply extended the line and determine where i plan to intercept it.

This method works every time for a single ship and convoys. If a convoy, simply make more marks on several contact lines. You'll be able to tell if the convoy consist of two columns or three columns, then you can position your boat inside the convoy.

When I say "every time" I mean every single time in my last 2 careers, with the last one lasted up to 6th mission :D

I also find out on several occasions, that when the map is zoomed in to the max magnification, the difference between the ship's position as indicated by the marking on contact line and the actual position of the ship seen through the periscope is about 100 m. The contact line shows the ship(s) to be 100 m farther then its actual position.

Bob

Awesome. And here I was trying to use trig, the stopwatch, and a bunch of other stuff to solve it. :damn:

I thought the hydrophone information was bearing only - I didn't know that it provided a reasonably accurate estimate of distance as well. Going to max zoom is a great tip, and using this data to map convoy columns is also very useful.

Gentlemen, thanks very much to all of you for your assistance with this problem. I've learned an awful lot on this thread, and a tremendous amount of faulty guesswork on my part has just been eliminated from my patrols.

[xlbob]

What realism setting gets the sonar man to write something on the notepad and draw lines on the map? (snip)

11Bravo, it's not the SO who marks and draws the lines on the map, it's done manually by me. My realism setting was 61% and last night I started a new career with 67% realism.

I also use sonar to find ships. And when SO reported contact, long range or short range, clsoing or moving away, I stay submerged for a while longer, go the navigation map, zoom the map to maximum and start marking the end of the contact line. Then set my course to intercept the ship. It works every time.

[High Voltage]

What realism setting gets the sonar man to write something on the notepad and draw lines on the map?

I have never seen this with any contact in 7 patrols so far. I use sonar to find most of the ships, but the only help I get is when the sonar guy says contact, merchant at long range on some bearing. I make the bearing my new course, drive 20 minutes and submerge for a new listen. Lather, rinse, repeat until the watch crew sees the ship. Then I use maneuver and manual targetting. The idea of getting some of this information from sonar is intriguing...I am useing 87% realism, with only external view and event view on...

Hey Bravo, this is how i used to do it as well, but the problem with this method is that you end up chasing the contact as opposed to intercepting it. You're always heading to wear the ship "was", instead of where it's "going"...