New Hydrophone Interception Tutorial

[nefelodamon]

Hello all,

After playing a while, I got fascinated by the idea of intercepting and shooting at targets only with the use of Hydrophone.

So after a lot of reading, watching other tutorials and videos I present you my version of Hydrophone interception.

DL here: http://www.filefront.com/14186971/Hydrophone.Interception.Tutorial.by.Nefelodamon.pa rt01.rar
View here: http://nefelodamon.blip.tv/

As I state at the end of my video, I dont claim that I re-invented the wheel. On the contrary, I used information available around the internet and here, at subsim.
My tutorial was inspired by the excellent video of Mittelwaechter called ''Hydrohunt''. I used his method of "4th bearing" position calculation as he describes it on his videos.

I hope you will enjoy my tutorial and that more users will turn to manual targeting:arrgh!:

[Mittelwaechter]

Ooh! - That's a brilliant and easy technique to get the course direction of the contact.

Whoever is interested in hunting by hydrophone should watch this clip and learn the magic of the technique.

Well done Sir! :up:

[Pisces]

My sentiments exactly!!! :rock: :up: :yeah: :rock: :woot:

A minor suggestion if you need to copy over parallel lines (or the moved distance of the target between the bearings) is to use the arrow of the compass. When you move the circle elsewhere on the map the arrow points in the same direction. I find that easier than setting up a new protractor with the same angle value, as it also has the added chance of inaccurate angles.

[meduza]

Thanks for the tutorial! :yeah:

[makman94]

very nice video Nefelodamon ! bravo !

you don't need to draw the 20km radius circle at all ! only the four lines for the bearing and no matter how long they will be
i suggest to get the pato's image (the one that have circles till 4.650m radius--here: fixes+new 'one degree bearing' (http://www.subsim.com/radioroom/downloads.php?do=file&id=1095)) and directly place the bearing lines to the bearings that are given from sonarman (it will make your life ...easier)
also for the last report of sonarman (the one that will give you the 'hot' 'fifth' bearing line is no need to come to a dead stop .when you get the report from sonarman...pause the game and draw the line to the given bearing
also,once you get the direction of the target and you want to turn your boat to a 90degrees angle course ,simply add (or minus--depends from if you have the target from your left or right of you) 90 to targets course and set your boat to this direction
and something for last , when you use the tdc and want to set the 90 aob ,be sure that your periscope is pointed to 0 degrees.anytime you will use the tdc ,always be sure first that the peri is pointing to 0 degrees (all this in case that your course is setted to a 90 degrees angle with target's course)

you made a great video !

bye

[Pisces]

...

and something for last , when you use the tdc and want to set the 90 aob ,be sure that your periscope is pointed to 0 degrees.anytime you will use the tdc ,always be sure first that the peri is pointing to 0 degrees (all this in case that your course is setted to a 90 degrees angle with target's course)
...
Yes, I was just about to reply on this too. Look when he is going to set the tdc dials for the first time. He sets the AOB to 90. (adjusts range dial, but that is not important here) Then he sets the bearing dial to 000 (was set to 352 because of that course correction) Note how the AOB dial follows that movement. But then as he sets the tdc back to auto-mode the bearing dial flips back to the direction the (attack) periscope is looking (still 352), but the AOB dial doesn't follow. For this 90 degrees setup it doesn't matter much in accuracy. But for different AOB setups it could be alot worse.

[Contact]

Just finished watching it, awesome technique. I just don't like that it is no option to see what type of freighter is coming but thats it's not so important :) :up:

[Pisces]

Just finished watching it, awesome technique. I just don't like that it is no option to see what type of freighter is coming but thats it's not so important :) :up:Ofcourse you have the option, nefelodamon just didn't do it. Infact you should, torpedos onto neutral vessel leave bad stains.

[Contact]

Yes I will have to watch that video again another few times just get a better grip on it :)

Imagine a frustration if you have external cams off and you get a sound contact and you do all that hard work just to find out you was hunting a neutral :haha:

[bojan811]

Very good tutorial.
:yeah:

[nefelodamon]

Thank you all for your nice words :DL.

Actually I hope this will be only the first tutorial of more to come.
I want to perfect my technique with motion vectors (while in move) and also to demonstrate a convoy attack with that technique.

Now for the comments...

makman94
you don't need to draw the 20km radius circle at all ! only the four lines for the bearing and no matter how long they will be
i suggest to get the pato's image (the one that have circles till 4.650m radius--here: fixes+new 'one degree bearing' (http://www.subsim.com/radioroom/downloads.php?do=file&id=1095)) and directly place the bearing lines to the bearings that are given from sonarman (it will make your life ...easier
I like to draw the 20 km circle just to know the area of operations. I know it really does not adds to the technique but it helps me set a course to a good spot where I can have the 5th bearing ( a good spot relative to the 4th bearing line).

makman94
also for the last report of sonarman (the one that will give you the 'hot' 'fifth' bearing line is no need to come to a dead stop .when you get the report from sonarman...pause the game and draw the line to the given bearing
also,once you get the direction of the target and you want to turn your boat to a 90degrees angle course ,simply add (or minus--depends from if you have the target from your left or right of you) 90 to targets course and set your boat to this directionThat is up to any player to decide. Personally I dont like pausing the game at any time. Also the way to turn the boat at 90 degrees, I could find 10 ways to do that. Its always up to the player, and what comes handy that time.

makman94
and something for last , when you use the tdc and want to set the 90 aob ,be sure that your periscope is pointed to 0 degrees.anytime you will use the tdc ,always be sure first that the peri is pointing to 0 degrees (all this in case that your course is setted to a 90 degrees angle with target's course)You are absolutely right on that. I miss that point. Periscope should always point at 0 degrees when making changes :oops::oops::oops:
Ευχαριστω καρντάση... Τα χαιρετισματα μου απο την μακρινη Ιρλανδια :-)


Pisces
Yes, I was just about to reply on this too. Look when he is going to set the tdc dials for the first time. He sets the AOB to 90. (adjusts range dial, but that is not important here) Then he sets the bearing dial to 000 (was set to 352 because of that course correction) Note how the AOB dial follows that movement. But then as he sets the tdc back to auto-mode the bearing dial flips back to the direction the (attack) periscope is looking (still 352), but the AOB dial doesn't follow. For this 90 degrees setup it doesn't matter much in accuracy. But for different AOB setups it could be alot worse.The same as above. I should have been more careful with that. And it is true that the 90 degrees solution it self tolerates some error. But anyway, accuracy never hurts :-)

Contact

Imagine a frustration if you have external cams off and you get a sound contact and you do all that hard work just to find out you was hunting a neutral :haha:Or a fishing boat :damn:
Propeller sounds its a must. Too bad that cannot implement in game. I was reading that the way the sound files are called for each boat is hard coded into the game :-(

Again thank you for the comments. I hope more videos will come soon :-)

[tomfon]

That was an excellent tutorial nefelodamon! :yeah:
A clever way to intercept and sink a single ship. Really nice. Well done!:up:
I'm waiting impatiently the video you said you'll make to demonstrate an attack to a convoy. This will be even more interesting.:yep:

Χαιρετισμούς. :sunny:

[Pisces]

Nefelodamon:

I tipped the guys in the Sh4 forum about your tutorial. Keep an eye on that thread incase there are questions there aswell. Though I'll do my best aswel.

http://www.subsim.com/radioroom/showthread.php?t=154537

[nefelodamon]

Thank you Pisces. For sure I will keep an eye to that post for any queries might arise.

I started already working on the next tutorial. It will be about intercepting a target while your U-Boat moves.
It will be ideal for any targets that move away from your boat. Today on the train to work I had a nice idea on how to achieve that with only 4 bearings. It will involve a bit more plotting than the previous tutorial though ;-)

Again only with SH tools. I have the believe that SH provides everything necessary. No better WO than the ruler and protractor ;-)

This tutorial will include some vector work. I try to perfect the drawing technique as the scale confuse me a bit:06:

I hope by Monday will be ready :-)

Thanks again!

[nefelodamon]

You can also view the tutorial here: http://nefelodamon.blip.tv/

The quality of video is amazing and is full length. I cant understand why people insist on youtube!!!

Greetings!

[Huliganul18]

When you put de 4 baring lines and whait for sonar to tell you the bearing (angle) after you copy the angle of his course.... there must be the target ?

on my first try my target is a little more long range than that point

[Pisces]

When you put de 4 baring lines and whait for sonar to tell you the bearing (angle) after you copy the angle of his course.... there must be the target ?

on my first try my target is a little more long range than that pointI don't completely understand what step in the procedure you are asking about.

- You first ask 3 bearings,

- From that you make the drawing for the target course. (just the direction of it, because you cannot know where he is yet, so you draw it at any range)

-Extend the line of the target course into the future. You predict where he will be a time interval after the 3rd bearing. And draw a 4th (imaginary) bearingline through it from the listening position.

- Right after that you move away quickly from where you were listening. surfaced. Either parallel course to the target (if he has passed you allready), or perpendicular to the last real bearing line (3rd, if you are still infront of him).

- When the interval between the 3rd bearing line and 4th imaginary line is about to pass you dive to do a hydrophone check. From your new position you draw the real 4th bearingline.

-The target is at the intersection of the imaginary 4th and real 4th bearing line.

I hope that makes it clear for you. Could you make a small drawing or screenshot if it wasn't?

[Mopy]

Thanks for the tutorial. Nicely done :)

I'll be trying this in a few years (game time)

[JMV]

excellent tutorial nefelodamon ! Difficult to make it more simple.
Keep on the good work. Awaiting your next video with moving sub impatiently...

To Neal or Moderator :
How come Nefelodamon still has a " nub " avatar. Please give this guy a few notches up the ladder, with a decent title !

[JMV]

Made a reference post to this technique in the sticky for newbies.

[Huliganul18]

how can i install that big protactor ?

i search the forum but find nothing. please give me a link - tutorial of how can i instal that

thx

[PL_Cmd_Jacek]

Does anybody has a solution, how to to use this method during movement ? I played NYGM Tonnage Mod, and it is not possible to stop your uboot without sinking.

[Platapus]

Thank you for posting this technique.

I do have one request. While the video is excellent, it would be easier for me to understand if your technique where written down with screen shots. I keep getting lost right where you start drawing circles between bearing lines. :88)

[Pisces]

Platapus: Did you notice he placed text descriptions of what and why he did things? He used circles to determine where all points are that are equal distances (constant speed over equal time interval) away from the center. He starts of with a random line as a guess on the course (and range and speed) of the target. Then he uses the circle to prove it is wrong because the 3rd bearing doesn't intersect the same point as where the circle and random line intersect. Then he uses two protractor tools (118 degrees drawn between bearing 1 and the guessed course) to effectively make a line parallel to bearing 1 that does go through the circle and guessed courseline. Then he locates where the parallel bearingline and the real 3rd bearing line intersect. That point, and the center of the circle on bearing 2, define the direction or course of the target. (But not the range and speed!, because those 2 are proportionally related. You need a different point of view to 'fix' that.) Anyway, he first corrects the guessed course into this new course and extends the true course line back to bearing 1. And also expands the circle and direction of the radius arrow to match that. Then he cleans up the plot, erasing: the guessed course, the aiding protractor tools, and finally the circle. And also added marks on the established bearingline intersections. (I personally would have left the circle on the map, pointing the arrow in the direction of the target's course to avoid Bernard situations. As the points where the marks are are not confirmed by range, just points that define the course in relation to the bearings. It makes them look more real positions than they are. But that's just me.)

To predict where the sound comes from at the time of bearing 4 he re-creates the circle and moves it up to the mark on bearing 3 and extends the course line again to create the intersection of the predicted bearing 4. Again, the circle is used to keep 2 points equally far away from the center, and on the same line diametrically opposed. Then he plot's a predicted 4th bearingline through it from the listening location. In the mean time he ordered course and speed to sprint away from his listening location.

Is that enough to get you back on track?


PL_Cmd_Jacek: If you move just a knot or so in the direction of the sound when you are waiting to take the first 3 bearings, then it would have minimal effect on the result. The drift of the sound bearing is primarily due to speed vector-components perpendicular to the bearing. If you move slowly and roughly along the bearingline you generate a very small, probably insignificant, perpendicular speed vector-component yourself. Just keep a steady course so you do not mess up you bearing measurments. Ideally you would want to use true bearings. But the game only reports relative bearings, so they need to have some reference direction that doesn't turn as you go.

EDIT: this might help the both of you to solve your questions: http://www.filefront.com/13598315/bearingsonly-TMA.pdf This technique uses essentially the same drawing to determine the course (relative motion), except it 'guesses' with a course perpendicular to bearing 1. Determining speed and range is quite different though. Just keep in mind, if your sub is hardly moving at all, his speed and course creates pretty much all the relative motion there is.

[Canovaro]

Best Hydrokill I have ever seen! Very well done.
Great video too! I have a drawing on how to do it but a video is more practical.

Thank you for making it available.

:up:

[PL_Cmd_Jacek]

EDIT: this might help the both of you to solve your questions: http://www.filefront.com/13598315/bearingsonly-TMA.pdf This technique uses essentially the same drawing to determine the course (relative motion), except it 'guesses' with a course perpendicular to bearing 1. Determining speed and range is quite different though. Just keep in mind, if your sub is hardly moving at all, his speed and course creates pretty much all the relative motion there is.

Thank you for your promt response, this material looks very interesting. I have to try it.

I also has a question regarding your 3-bearingAOBfinder from your filefront page. I do not understand, what exactly means "angle on relative motion"

Edit: and also what mean: DRM, MRM and SRM (from the example)

[Dekessey]

Well done, very clear and helpful.

Thanks!

:salute:

[Pisces]

Thank you for your promt response, this material looks very interesting. I have to try it.

I also has a question regarding your 3-bearingAOBfinder from your filefront page. I do not understand, what exactly means "angle on relative motion"

Edit: and also what mean: DRM, MRM and SRM (from the example)Good question. I knew someone would eventually want to challenge me on that. To understand what I mean with "angle on relative motion" those other 3 abbreviations need to be understood. It is very wel explained in "The Radar Navigation and Maneuvering Board Manual", :ping: specifically chapter 3. Here is the link to the full pack of pdf files:

http://www.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/RNM/pub1310.zip

The file I uploaded to my filefront page (the link I gave in my previous post) are 2 pages from chapter 6, which has excercises and problems you can try to solve.

But I'll try to summ it up here.

DRM = "direction of relative movement". (refferenced to north)
SRM = "speed of relative movement", knots
MRM = "miles of relative movement", or basically just the distance the target moved in a relative plot.

If both you and your target are moving at the same speed and the same course, then you two do not move relative to one another. He wil keep being at the same range from you and at the same bearing. The speed vectors are identical. Same length and same direction. There is no space between the heads of the vectors (when you draw them from the same origin).

If the both of you had for example a course due north, but he is faster and behind you, then he would come closing up on you. Both speed vectors are still pointing in the same direction (north), but his vector is longer.The space between these arrowheads is the relative motion vector. In this case the relative motion is also pointing north. The relative motion vector starts at your speed's arrowhead, and ends at his speed's arrowhead. (vectors can be drawn anywhere in a drawing, as long as their length and direction is the same. so don't take their placement too literal)

In this case the speed of relative motion is easy to compute. Because the vectors are aligned and in the same direction it's the difference in length. But if your course and speed is completely different from his course and speed you need to make a drawing of them and measure the space between it. The 2 vectors start at a common point, and the relative motion vector closes the triangle, starting at the arrow head of your speed vector. Also this space between the arrow heads has a direction, hence the 'direction of relative motion', which is measured as an angle to north.

'miles of relative motion' is really the distance between plots you make i.e with your periscope. Except!, on a maneuvering board you do not plot the target position from your current location as you move along the map. (like it is shown in most tutorials here) On a maneuvering board each plot of the target is done from the center of the circular board. This makes it very easy to see how the target moves relative around you. You are allways in the center. (well, not always, but I'll let the maneuvering board manul explain when not)

So what is that 'angle on relative motion'? Well it looks a bit like 'angle on the bow', but cannot rely on a visual picture of the bow orientation. Angle on the bow is the angle between the line of sight (or bearing) and the course(heading) of the target. If the viewer through the periscope or on the bridge isn't moving then target is the sole cause of the relative motion. And the 'direction of relative motion' is the same as his course, and the 'speed of relative motion' is his speed. If you can accurately guesstimate the angle, you can derive the target course based on the viewing angle and own course. But if the viewing ship is also moving, then the 'direction of relative motion', aswel as the 'speed of relative motion' changes from the motionless situation. Then there is no direct link anymore between the angle or view on the bow, and his relative motion. And my tool cannot be used anymore to provide AOB as it was explained in those steps. Well, it can, but that would be too complicated to explain now, if this is all new to you. I'm not even sure I was clear enough with this explanation.

I really should have named it 'angle on direction of relative movement'. Or 'angle on DRM'. That would have been a more propper term. But probably made even less sense. I don't know. I just think like a mad professor. :know:

[PL_Cmd_Jacek]

Thank you professor :know:. You gave me a lot of knowledge and now is time for me to think and utilize the new knowledge :damn:.

[Platapus]

Is that enough to get you back on track?


Yes it is as this is a graphical way of simulating the use of a 10-point divider. If some smart modder could come up with a way to code a 10-point divider (can't be that tough) (hint hint hint) this technique would be a breeze. :yeah:

What I do sometimes is plot the sound reports on paper and use my old and trusty (rusty) 10-point dividers. If you are either lucky to find one at a flea market or are willing to spend about $200.00 you can buy one.

However a in-game 10 point divider (or since it is just code, it can be a 5-point divider) would make hydrophone targeting easier.

I seem to remember some other modern subsim that had an in-game mulit-point divider that was used to get course from hydrophone/sonar readings... so it is possible to code it.

Whether it can be coded in to SH3/4/5, I can't answer.

In the mean time, since we are sans 10-point dividers we have to come up with simulating it graphically like was done in the tutorial. :yeah:

[Pisces]

I don't think this is a thing that modders can 'code'. Sofar I haven't seen a mod that adds a different maptool than those that are allready in there. Or be able to make a user-interface image resize/stretch in realtime ingame by using the mouse. Such (map helper) tools seem to be built-in. It could ofcourse be a nice addition to SH5 though. But that's better suggested to the developers than the modder community.

But I can manage with a circle as a 3-point divider. You could ofcourse use multiple circles for increasingly large time intervals if you really need to project such a long path. The ultimate DIY solution is taking a piece of rubber band and draw equally spaced marks on it, and then stretch it on your screen. But I personally don't like such fit-and-fumble techniques. Just a bit of clever geometry tricks and the answer is there. Love that.

[berobispo]

Hi!

impressive hydrophone hunt, nefeladamon!:up:

I still prefer the passive sonar only approach method proposed by joegrundman. I have rewritten it because I found some parts a little confusing.

The reason why I prefer it is basically you don't need to surface at all (if you are ahead enough of the target:03:) to get a good estimate of the target's position and course. Whereas your method involves surfaced flanking as a conditio sine qua non.

Please have a look at my rewrite, comments very much welcome!

http://www.filefront.com/14758805/Passive-Sonar-Approach-revisited.pdf/
I this folder you will also find joegrundman's original guide and the altered rear side of the 1943 SACF, altered to show meters.

http://www.filefront.com/user/berobispo
happy hunting:arrgh!:

[Pisces]

...Whereas your method involves surfaced flanking as a conditio sine qua non. ... Uhm, I left my latin dictionary on the steps of the coloseum. Can you translate?

[berobispo]

sorry, "conditio sine qua non" means "this is an absolut prerequisite"/"it definitely won't work until..."

literal translation:

"condition without none" I'll do something/Something will work

[Pisces]

I wouldn't say that flanking is an absolute prerequisite for it to work. But you do need to move away from where you were listening. And in such a direction that makes both 4th bearinglines(the predicted one from the old location and the real one from the new location) intersect as perpedicular as possible. It depends if you are allready behind the target whether you need to flank to catch up with him and move in front. But you also do not need to get ahead of him to make this work. You could also sprint away in a lagging position to make those 4th bearings intersect clearly. It just means that you'll have to catch up and overtake later for sure. But with a good fix on his course and speed.

I must admit I have only lightly read through your technique in that pdf. And I can't seem to download it right now from filefront to better take a look at it. But what I remember from it was that you essentially make a submerged interception. Adjusting your course until the sound direction doesn't drift any more. Well, it does certainly work if you are ahead of him far enough. Or to say that more accurately, he must have a small AOB to make up for your slow speed. Which you have no way to tell. Also you never know when you are supposed to be on top of him. As you don't what his range is, or what the closure rate is. On top of that, you are draining your batteries. I wouldn't like to go into a fight with my batteries allready partially drained. You'l never know what friends the target has nearby. Personally I find that your way has too many unknowns and guesswork as a conditio sine qua non. ;)

[berobispo]

I wouldn't say that flanking is an absolute prerequisite for it to work. But you do need to move away from where you were listening. And in such a direction that makes both 4th bearinglines(the predicted one from the old location and the real one from the new location) intersect as perpedicular as possible. It depends if you are allready behind the target whether you need to flank to catch up with him and move in front. But you also do not need to get ahead of him to make this work. You could also sprint away in a lagging position to make those 4th bearings intersect clearly. It just means that you'll have to catch up and overtake later for sure. But with a good fix on his course and speed.


-Yes, I agree. It will work when you are behind the target at the fourth bearing. But you must overtake him, which again means staying on the surface for quite some time.


I must admit I have only lightly read through your technique in that pdf. And I can't seem to download it right now from filefront to better take a look at it. But what I remember from it was that you essentially make a submerged interception. Adjusting your course until the sound direction doesn't drift any more. Well, it does certainly work if you are ahead of him far enough. Or to say that more accurately, he must have a small AOB to make up for your slow speed. Which you have no way to tell. Also you never know when you are supposed to be on top of him. As you don't what his range is, or what the closure rate is. On top of that, you are draining your batteries. I wouldn't like to go into a fight with my batteries allready partially drained. You'l never know what friends the target has nearby.

-you find out pretty fast (<5 min) if you are ahead enough (i. e. AOB is small enough), if target is still gaining, you might consider surfacing and flanking for a little while and check if the AOB is small enough then. This way, time on the surface is reduced to the mininum. When finding at the fourth bearing that you are behind him, you need to go a much longer way

-read part 2 of the guide to see out that it is completly feasible to get a satisfactory range estimate in another 15 min (max). This way, you can decide whether going in submerged or surfaced or if you should reload steam or electric torpedoes for the upcoming dawn/sunset...

Personally I find that your way has too many unknowns and guesswork as a conditio sine qua non. ;)
-on the contrary! keeping a constant bearing on the target lets you feel its pulse! You notice when he changes course, for example!

[Pisces]

-on the contrary! keeping a constant bearing on the target lets you feel its pulse! You notice when he changes course, for example!Ok, that is true. Any change in course would not be noticeable during the time it takes to take the bearings and move. And probably leaves you with the wrong solution as to his course and speed.

So I guess each method has it's pro's and cons. In the end it depends on which you can live with. And neither is garuanteed to work for sure.

But I'd love to re-read your document. But it isn't on filefront anymore. The link is dead.

[berobispo]

Yes, as you say, each method has its advantages:DL, btw, I have updated the link:

http://www.filefront.com/14758805/Passive-Sonar-Approach-revisited.pdf/

[Dissaray]

Damn, looks like I am going to have to take another page of notes, makes three now. All these smart people keep making these fancy vidios about how best to use all these toys and I think, "OOOOO I got to try that one out."

Befor I saw that I didn't think the hydrophone was much good to me, just a good tool for making a pre-scope check if there are any baddies about. Now I might actualy have to kill some thing with it. I also didn't know you could shoot from that deep, what is the maximum depth for shooting anyway?

[Wilcke]

Here is a great tool that use quite often! The developer has his own thread here on SubSim.

http://www.subsim.com/radioroom/downloads.php?do=file&id=648

[=FI=Ghost]

Excellent tutorial mate, I am looking forward to try it out in practice. I have a question tough.

When you start drawing the first 3 bearing lines, what is the minimum difference in bearing between first two observations in order to start drawing the lines? To clear things out, your second observation after 5 minutes showed less than 10 degrees difference in bearing, so you waited another five, and then another five. So I guess it has to be at least 10 degrees difference between first two observations? Am I right?

[KL-alfman]

I've worked with nefelodamon's method for some time now (thx again for the tutorial!).

still have problems with the drawing when the target's bearings change only slightly and the target is moving away. most of the time I then surface and try to get into a better (and nearer) position and start again with the readings.
I also do prefer a difference of more than 8° in the various readings, because it's easier to draw the lines and circles on the nav-map. if the target is closing to your position there's no problem to expand time for the different readings, imo.

[=FI=Ghost]

I've worked with nefelodamon's method for some time now (thx again for the tutorial!).

still have problems with the drawing when the target's bearings change only slightly and the target is moving away. most of the time I then surface and try to get into a better (and nearer) position and start again with the readings.
I also do prefer a difference of more than 8° in the various readings, because it's easier to draw the lines and circles on the nav-map. if the target is closing to your position there's no problem to expand time for the different readings, imo.


Thank you for your reply!

[comet61]

I usually wait a little longer to take the 3rd BL. Though I try my best to follow the guidelines on doing it this way, I usually wait until I have 7-9° interval between 1 and 2 BL's and 10° or more for the 3rd BL. That way seems to work pretty well. My guess is that I am 65% to 75% accurate on interception using Nefelodamon's tracking method. If the circle radius goes beyond the 3rd BL I have to wait longer to place the 3rd BL a little further along the circumference of the 20km circle. The only problematic situation is if the target is too close at the end of all the calculations once I have located my target along the 4th BL. It would seem that if your target is coming toward you at an angle at less than 10km from your position, your reaction time for proper set up and A0B is somewhat harried. Missed a few targets because of that. Especially if they're going 9kots or better.

Anyway...I really enjoy tracking this way now that I am using the Attack disk/speed calculator in the MaGui mod.

[KL-alfman]

but the time-intervals taken for the four bearing-lines have to be the same, otherwise this method won't work, I suppose .....

[comet61]

but the time-intervals taken for the four bearing-lines have to be the same, otherwise this method won't work, I suppose .....Perhaps. But I haven't seen that much of a deviation. I use the time between the 1BL and 2BL as a basis to set the 3rd & 4th BL. It may not be 100% what was shown in the video, but it still works for me. Usually I have a much higher margin of error if the target is coming toward me somewhat fast. I don't always do it this way. I usually try my very best to follow the guidelines set in the training video as much as possible. However, I believe there are times when time compensation is required. If 20minutes is required for 1bl to 2bl then I use 20 minute intervals for the 3rd and will do the same for the 4th. Once I have all 3 bearing lines drawn and the general direction line made I turn the sub to a close perpendicular course to the target not knowing exactly it's actual position.

Counting the beats of the screws does give me a general idea on speed. Once I have the plot along the 4th BL and have drawn a course of the target via the protractor tool and calculating speed (using the chart I have on the propeller counts) I can be within 3km-5km of the target which gives me plenty of time to calculate AoB and get lined up for a shot. Once I have the target in visual I can calculate distance and speed with a lot more accuracy. Like I said, I am usually 65-75% successful which to me is acceptable. I do miss. Especially if the target is fast moving or the seas are very rough. I have stopped attacking in very rough seas now, except maybe at night.

I like this method of tracking. It is fun. I practiced this method in a Type IIA in Aug of 39 in the North Sea several times to get myself honed in on the practice. It is paying off.

[KL-alfman]

I like this method of tracking. It is fun.


same for me!
and thx for the hint about calculating the speed by the target's screws. never done that before, but surely will. :up:

[Pisces]

The time between taking the bearings MUST be the same. The longer the time the better the AOB accuracy will be. With just a few degrees of initial bearing change the drawing becomes almost useless. The math behind it needs to 'measure' the accelleration of bearing change. You cannot see that with almost parallel bearings.

The crew calls out the bearing right on the exact degree. (Hmm, how unrealistic! :down: Try measuring by listening yourself. :damn:) So if you make sure your uboat doesn't turn during the whole process then you can get the first 2 bearings very accurately. From that follows a time period that you need to wait for the 3rd bearing. You do not need to get to the second, but to 10 seconds is close enough if the whole time-span between bearing 1 and 2 is more than 10 minutes. Unfortuneatly, the 3rd bearing-time doesn't neatly fall on an exact bearing when the time runs out, but somewhere in between. If the time runs out closer to the next bearing call out than it does to the one before you might need to draw the bearingline in the second half of the degree maybe even round up to the next. Especially very small or very large AOBs (0-10 or 170-180) take very long to change one degree.

Lets give some examples.

------------------------

Assume for a moment you hear a contact. You do not know it yet but at the first bearing the target has an AOB of 41 degrees (closing).

You wait until it has moved 5 degrees exactly (cheating with the crew's call outs). How much time this takes is entirely dependant on speed and range. But you can certainly draw this out on the map or a piece of paper (sharp pencil and protractor and compass works more accurate than the game map).

I promise that you will find the bearing has changed 11 degrees to bearing 3 after the second time interval, if drawn accurately. (How do I know? Check and make this! (http://www.subsim.com/radioroom/showthread.php?t=147719))

But now, lets say we didn't pay attention when listening to the sound, or didn't draw the 3rd bearing accurately. Instead we draw the 3rd bearing line 12 degrees further from the 1st bearing, not 11. That should have produced a drawing with an AOB at the 1st bearing of 26 degrees. That's 15 degrees wrong. (Not bad you might say, but you have to take into consideration you were cheating with the bearing call outs)

-----------------------

Ok, now same situation: AOB 20, but you waited longer and got 10 degrees between the first 2 bearings. Draw it out and you will find the 3rd bearing is (almost) 24 degrees away from the 1st. The bearing accelerated an additional 2 degrees (2 times as many degrees: 10=2x5, 11x2=22 24-22=2), enough to refine the bearing preciscion limit of 1 degree.

But again we forked up with the 3rd bearing. We measured and have drawn it to 25 degrees. Do Nefelodamon's drawing and see it comes up with an AOB of 36 instead. That's 5 degrees error in AOB. So, now with twice as many initial degrees (between bearing 1 and 2) we reduced the AOB error to one third.

=================================

Another situation: Assume AOB at 1st bearing is 85 degrees (almost at closest point, about to move away from you)

You wait for the first 5 degrees to get bearing 2. (Shouldn't take long. Guess what the AOB is at that point ;) )

Ok you wait another period like that, and at bearing 3 it should be 10 degrees further from the 1st. (For the math wizards, what sort of triangle does it remind you of?)

But instead, we draw the 3rd bearing at being 11 degrees, as Bernard had navigator duty at the time. This should produce a drawing that has an AOB at the 1st bearing of 41 degrees. ....YIKES!! That looks way out of whack! 44 degrees error from the real thing!

---------------------

Ok, we wait a longer period to improve that error. As we seriously need it this time. (even if we cheated with the call-outs)

10 degrees to the 2nd bearing. Unfortunately, that doesn't change the picture that much. An accurate drawing would put the 3rd bearing at 19.7 degrees from the 1st. That is too close to 20 (double the amount of bearing drift) to see the acceleration (actually, decceleration this time) of bearing change.

Instead we wait until the bearing has drifted 20 degrees for bearing 2. Ok that is better. This should put bearing 3 at 37 degrees from bearing 1. As a side note, did you notice the bearing change has slowed down. 37 degrees is less than the double of 20 (40). ...

But here we mess up again. We measured or drawn bearing 3 not at 37 but at 38. This produces a drawing that has an AOB of 79 degrees at bearing 1. Yeah!!! that's much more like the real thing. Only 6 degrees error from the real AOB of 85 degrees at bearing 1


---------------------------------------

In conclusion: If the target is still far away, starting out with a small AOB, the effect of bearing error isn't that much. If you cheat by taking the time between the exact bearing call-outs you (can) do as-good-as the rough course indications of mapcontacts. If you measure bearings by listening yourself you need to take into account bearing errors of atleast 1 degree. And therefore you need to allow more time between the bearings to let the bearing change acceleration show through.

You can't know before hand what it's AOB is when you first hear it. It could just as easily be as close as it will ever get to you. And from that follows an AOB close to 90 degrees. Due to the math and geometry behind it this creates excessive sensitivity to bearing errors, even if cheating with exact bearing call-outs. For these situations you must allow longer periods between bearings (more degrees) to let bearing acceleration/decceleration to show through. Use short periods initially to get a rough idea, but double up the bearing changes to refine the AOB.

Keep note of the exact times at which bearings are reported. This way you can re-use bearing 3 of a short period drawing, as bearing 2 for a 'twice-as-long-period' drawing.

Patience is a virtue and asset!

[KL-alfman]

thx for the additional explanations and examples!
I understand that the method of hydro-hunting a target is really very important in SH3 (or any sub-simulation). exercising will improve the skills in it (and I do a lot of exercises), next theme for me will be then: manual targetting. :hmmm:

[Pisces]

For those that need some papers in their hands to understand this technique. Worry no more!

http://www.subsim.com/radioroom/showthread.php?t=160817

[Paul Riley]

All this is just what I have been looking for.Nice to have that extra string in your bow.
Thanks to all involved.

[Stavros]

Thanks nefelodamon, very useful video :up:
(http://www.subsim.com/radioroom/member.php?u=234866)

[JMV]

Hello nefelodamon,

You said a long time ago :

"Actually I hope this will be only the first tutorial of more to come.
I want to perfect my technique with motion vectors"

Long time we didn't hear from you, very much enjoyed your tutorial, are you up with something any time soon ?

[aus3620]

I'm probably months behind this thread but thanks for the tutorial nefelodamon and comments by Pisces et al. Also jerm138 for the "paper" tutorial. It takes the game to a new level of interest and challenge.

[PappyCain]

Good thread. Wouldn't it be great if one could multi-player on the same boat and have various key stations (i.e. Hydrophone) held by different players working in unison ....

:salute:

[Pisces]

You can in DW, but not in SH3

[Freelanca]

I just have to say I love the video tutorial but one thing that i was wondering is it common that one can sit and wait for 1hr 30 mins without loosing contact or range to catch and shoot.

[Pisces]

It depends on how fast it moves, and how far away his track is from you. His slow speed makes the bearing move slowly. Him being far away makes the bearing move slowly aswel. However, the further out his track is, the bearing also cuts out a thinner pie/pizza-slice while it is in your hydrophone coverage. So he stays less time inside your hydrophone range.

Hopefully this explains it a bit better:

http://www.subsim.com/radioroom/showpost.php?p=1021427&postcount=27

[K-61]

Not to gainsay what is an excellent thread, but wasn't this sort of thing not practical in WW2 U-boats? I've read elsewhere that the hydrophones were good enough for getting the general bearing of contacts, but not precise enough to use this [very clever] technique. In other words, are we using a post-war technique by using this method?

Please don't take my comments as being derisory of this method. I salute anybody who is clever enough to do this sort of thing; I just don't wish to employ ahistorical methods as I simulate being a WW2 U-boat Kaleun.