Hidrophone atack

[bojan811]

I saw the video with the some lad.
He actualy hears the boats on his hidro and hunts them without rising his periscop.
I looked a video and tried to repeat his actons , but with no suces.

He was using some 4 berinline mesurments with the (180-A1):2=first angle...sound familliar?

If do please answer here so that I can make my questions.
Only the people who actualy was capable to repat that tutrial in practise with sucses.
I don`t wanna hit them without the use of atack p , just wanna find them in poor visibility and bad weather.

Sorry for the speling and the grama.

Thanks in advance.

[Mittelwaechter]

Hi Bojan,

feel free to ask your questions.

[abclkhan]

That is a nice tutorial, I dont know how did the author find those formulas, but I use it frequently.

[Mittelwaechter]

We all should have learned in school!

I'm short to my 'best before' date and I had to refresh my knowledge too.
I've asked an unbearded greenhorn for some update.

Ask your kids - they may help you!

[bojan811]

Originally Posted by Mittelwaechter

Hi Bojan,

feel free to ask your questions.

Ok. Here we go.
r=C1-M

r=? , C1=?, M=? I would like to know the mining of these elements.
This is for the beginig.
Thanks for reply

[Mittelwaechter]

Hi Bojan,

please read this and try to understand:

http://www.subsim.com/radioroom/show...t=u42Hydrohunt

r=radius

C1 is center of circle 1

M is the center of auxillary circle (wich divides 'assumed' travelled distance of contact between first and third bearing)

Read: r = C1 "to" M !!

[bojan811]

OMg!
Thanks, I`ll read and try to understand the princip.

Q:
Why is 8 min and not 9 like in the u49 video tutorial.Wich time to use 8 or 9 min?

Q2:How to determine the "S" when the space between beringline 1 and 2 is not the same length like the length (space) between 2nd and 3rd.So wich one to use?
Lets pretend that form 1st to 2nd is 1km and form 2nd to 3rd is 1,9 km wich value to use?

[Mittelwaechter]

Hi Bojan,

you may choose the amount of minutes by yourself. It's not fixed and can be adapted to the given situation. Just keep it constant for your setup.

Let's assume you are at periscope depth (= PD) and your hydrophone operator detects a contact, moving slow. It should be far out - due to the hydrophone range - and maybe it will take some time to get a different second bearing.
Ask for an update after 6 minutes and if there is no significant change in bearings add another 4 minutes - or 6 minutes.

Whenever you are satisfied with the angle A1 - keep this time index constant. The bigger the angle between the first two bearings the better.
(well up to a certain degree! )

If the bearing doesn't change the contact is moving towards you.
In this case wait and ask your operator for contact reports until the bearingangles start to grow. Now the contact is quite near and you may want to choose a rhythm of only 4 minutes to find the coursedirection.

____________


For your second question:
"s" has to be constant - as long as we assume the contact is moving with constant speed on a straight line.
The contact sails "s" knots in x minutes - from the first bearing point to the second one (x minutes) - to the third bearing point (again x minutes).
The distance has to be "s" on the courseline as long as you keep the time for updates constant.

The diameter of the auxillary circle (center M) represents these two distances "s" - in relation to the bearings you read and construct under the first and second "baseline" (P1 - M and M - P2).
You have to copy the resulting angle of the auxillary setup onto your first real bearingline to find the courseDIRECTION. The courseDIRECTION line is cut by the second bearing into two equal parts - between the first and third bearingline.
Now you can add one part ("s") to the courseDIRECTION and set the imaginary "fourth bearing".

Comprehensible explanations?

[bojan811]

Extremely!

I just have a sound contact I will try to apply this advices.
Weather is bad , visibilty is poor, precipitation is high in one word ideal for testing the knowlege.

Will report wright back.

Ok I asked for the 1st bering it was 350. After 6 min the bering was still 350 , after 4 more min it was 349 and afther whole 20 min(6+4+difference to 20) it was 348.So that my first angle will be 88 degrees right( not so good angle).Is this good so far or am I doing something wrong.

Yes, and I have to ask how big is the M diameter.Do I draw the M circle before I get the 2nd bering line or not? On the video i saw that he draw M ciircle and the triangles and just added the angle later on.

My 3rd bering after 20 min is 340.So my new A2 is 82 degrees(good angle if I may add).

So now I got the course angle of the target it`s 5 degrees.

And when I inserted the angle on the actual map I got the 2,7 in between 1-2 nd and 10,1 in between 2 and the 3rd.

I draw imaginary "fourth bearing" ploted the 5 degree angle and I got some nasty sh`t.
I don`t know what I do wrong. I will have to read this tread over and over , and practise.

Is it important when I caught a sound contact, what if he is of me in the middle distance?
How big the circe on the contact should be 20 km or less?

Last edit:

Omg I found a good exchange rate targets, just as the distance was wrong.Is aob angle in fact the angle of 5 degrees in my case or not?Because his angle on bow was 95 confirmed later on.

[Pisces]

Originally Posted by Mittelwaechter

We all should have learned in school!

I'm short to my 'best before' date and I had to refresh my knowledge too.
I've asked an unbearded greenhorn for some update.

Ask your kids - they may help you!

Pfff!! I want proof in problem 76 that angle OCD is infact 35 degrees! And I don't have kids...

As for the subject of this thread... I do not mean to detract of Mittelwaechter's technique (infact I applaud him for being the first here to descibe it, and I tried to keep his video online) but I made a tool with which you can check your results for accuracy/errors made. It works by just alligning the right bearing difference numbers (bearings 1-2 vs. bearings 1-3) on the wheel and reading the AOB from the 1st bearing. In essence the geometrical drawing by Mittelwaechter and the formula for my tool is the same (I didn't check it, but it must be as the situation is the same). My tool does not replace the whole tutorial (since it cannot calculate range and speed), but can be used instead of making this 2-triangle-drawing instead. I personally find the drawing technique to be too sensitive to any drawing inaccuracies made. The method is sensitive allready due to the fact that bearings are reported in degrees instead of finer resolutions. But you should make up your mind yourself on that.

http://www.subsim.com/radioroom/showthread.php?t=147719

[Mittelwaechter]

Hi Bojan,

let's sort it out as far as possible.

Your first and second bearing was identical and after 20 minutes they enclosed an angle of only two degrees.

=> as you realized the contact is coming towards you.

Wait until the difference of two bearings within a "short" time interval (maybe 6 minutes) changes for 'some' degrees. Make the last bearing the 'second one' and the one before the 'first bearing'. The new time constant is six minutes now and you can work with it.
Take the third bearing after six minutes and you have all the data for your auxillary drawing. The contact is quite close to your position, but it doesn't matter at all because you don't have to sail far to get in shooting distance.

The diameter of the initial auxillary circle (M) is irrelevant - all the following drawings, angles and circles are relative to your initial auxillary circle M.
You can zoom in and work with a radius of 250 meters or you zoom out and work with a radius of 150 km - it doesn't matter. Your map shows either only small markings or huge circles in "normal mode".

Draw your circle M before you start to hunt by hydrophone. (maybe somewhere in the Indian Ocean?)
Perpare the base angles too - as I did it in the tutorial.

Start to work on your auxillary drawing after the second bearing - well you have the first angle (A1) by then.

______________

Your first reading was 350°, your second reading 348°

=> A1 = 350° - 348° = 2° (too small to be good for SH3 map!)

The base angles at P1 - M are (180 -2A1) : 2 = 88°

Your third reading was 340°

=> A2 = 348° - 340° = 8°

The base angles at M - P2 are ... = 82°

Here is your auxillary drawing - starting with the green circle M,
adding the base angles in blue (88° and 82°),
the dotted golden circle lines C1 and C2 (they are too big for my Z.u.L program ),
the black U-Boot position
and the red AOB angle of 2°




Thinking about the wonky SH3 map tools you should be good with your 5° AOB.

The difference results (after 20 km!) in ~ +1000 meters real shooting distance. But you are quite perpendicular to the contacts course and the distance is irrelevant for this kind of attack.

You should definitivley hit the target with a "one degree fan shot" of two eels.
__________________

A medium range contact can be reported short after you dive to PD.
It is important as you can conclude the time index for the bearing reports has to be short - or the contact will pass you.

A 20 km hydrophone circle is good enough for all your work.
Depending on equipment, weather and skill of your operator the real range may differ.

Keep up the good work!

Edit: the later confirmed AOB was 95°? Not sure what you are talking about in this passage, but if the AOB was 95° at the time you wanted to open fire (did you do a visual check?) you did a good job mate!

[bojan811]

Originally Posted by Mittelwaechter

Hi Bojan,

let's sort it out as far as possible.

Your first and second bearing was identical and after 20 minutes they enclosed an angle of only two degrees.

=> as you realized the contact is coming towards you.

Wait until the difference of two bearings within a "short" time interval (maybe 6 minutes) changes for 'some' degrees. Make the last bearing the 'second one' and the one before the 'first bearing'. The new time constant is six minutes now and you can work with it.
Take the third bearing after six minutes and you have all the data for your auxillary drawing. The contact is quite close to your position, but it doesn't matter at all because you don't have to sail far to get in shooting distance.

The diameter of the initial auxillary circle (M) is irrelevant - all the following drawings, angles and circles are relative to your initial auxillary circle M.
You can zoom in and work with a radius of 250 meters or you zoom out and work with a radius of 150 km - it doesn't matter. Your map shows either only small markings or huge circles in "normal mode".

Draw your circle M before you start to hunt by hydrophone. (maybe somewhere in the Indian Ocean?)
Perpare the base angles too - as I did it in the tutorial.

Start to work on your auxillary drawing after the second bearing - well you have the first angle (A1) by then.

______________

Your first reading was 350°, your second reading 348°

=> A1 = 350° - 348° = 2° (too small to be good for SH3 map!)

The base angles at P1 - M are (180 -2A1) : 2 = 88°

Your third reading was 340°

=> A2 = 348° - 340° = 8°

The base angles at M - P2 are ... = 82°

Here is your auxillary drawing - starting with the green circle M,
adding the base angles in blue (88° and 82°),
the dotted golden circle lines C1 and C2 (they are too big for my Z.u.L program ),
the black U-Boot position
and the red AOB angle of 2°




Thinking about the wonky SH3 map tools you should be good with your 5° AOB.

The difference results (after 20 km!) in ~ +1000 meters real shooting distance. But you are quite perpendicular to the contacts course and the distance is irrelevant for this kind of attack.

You should definitivley hit the target with a "one degree fan shot" of two eels.
__________________

A medium range contact can be reported short after you dive to PD.
It is important as you can conclude the time index for the bearing reports has to be short - or the contact will pass you.

A 20 km hydrophone circle is good enough for all your work.
Depending on equipment, weather and skill of your operator the real range may differ.

Keep up the good work!

Edit: the later confirmed AOB was 95°? Not sure what you are talking about in this passage, but if the AOB was 95° at the time you wanted to open fire (did you do a visual check?) you did a good job mate!

First let me thank you for all your effort.


And yes the aob was 95 when I intended to shot at him.I confirmed that on the spot.But as i sad he was to far away from the spot where he supposed to be.But hey I find him in ****i weather and I nailed him.

I`ll try to work out whit this.

Thanks a a lot for everything.

[bojan811]

Q:How to calcualte the contacts speed.

Tutorial formula was some thing like this...
60min :9min (used time to mesure the beringlines)=6.66

then 6.66X traveled distance in between beringlines =X metars

and X metars : 1852= speed

Should I use the same calculation with the ecseption of 9 min because I used 6 for my calculation.


Ok its bad weather again and I practise.

Contact sound on 294 b , start the clock and put `st bering line, 2nd afther 9 min (298bering) so the P1 - M=86 and 3rd bering line was on 301 afther 9 min so the P2-M=87.

I draw the c1 and c2 and got the Uboat intersection but it was on the right (not the left) side.

So I mesured 2 angles one was 37 from right to left and the other was 135 i think form right to right.
So I used the 37 angle and draw a courseline , then I added the 4 br line, and ploted the real curse.
When I mesured I got the distance to the target about 11Km but the actual distance was less than 8 km. And target AOB was 26 degree, not 37 and not 135.

This picture is showing the actual position of the tareget and you can see the 37 degree course based on hidrophones reports

[Mittelwaechter]

Hi Bojan,

congratulations to your successful hydro hunting job!

To answer you question: yes!

For contact speed calculation you need two factors:
travelled distance and time used to travel that distance.
To find speed we have to divide distance by time (v = s / t).
I.e. we get 926 meters per 6 minutes = 154,333 meters/mins

But we are used to km/h - kilometers per hour.
That's 154,333 x 60 = 9260 meters/hour or 9,260 km/h

SH3 doesn't use km/h but knots.
Therefore we have to convert our calculated speed into knots.

1 knot is 1,852 km/h or 1852 meters/60 minutes.

9,260 km/h : 1.852 km/h = 5 (knots)



Good hunting, Herr Kaleun!

[Mittelwaechter]

Edit: I checked your screenshots.

How comes A2 is smaller than A1?
Have a look at your 2.3 circle to add "s" - does it match the criterias? Does the second bearing cut the courseDIRECTION into two equal parts between first and third bearing? It should be a hint something is wrong.

Assuming A1 and A2 are correct - you made a mistake at the auxillary drawing.




The AOB is 11° - not 37°.

The 'side' you choose for the auxillary drawing is not important. I mentioned it in the Konrad story but it is not necessary to care for.

For an incoming contact the AOB must be smaller than 90° (in SH3 smaller than 60° !!)

Is your U-Boot at full stop for the first three bearings? Do you stop for the crossbearing? Try to mark the point of the crossbearing.

Draw the 20 km bearings from the outside/the circleline onto your boat and move them like I did it in the tutorial. Remeber the bearing is a "cone" of 350 meters width on the hydrophonecircle. Try to center the bearingline to minimize error.

Try to work as exact as possible to counter the inaccuracy of the SH3 maptools.

Let's call it a day!

Regards

Mittelwaechter