New Hydrophone Interception Tutorial

[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]

Originally Posted by 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

I 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.

[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.

[PL_Cmd_Jacek]

Originally Posted by Pisces

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!

[Pisces]

Originally Posted by PL_Cmd_Jacek

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", specifically chapter 3. Here is the link to the full pack of pdf files:

http://www.nga.mil/MSISiteContent/St...NM/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.

[PL_Cmd_Jacek]

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

[Platapus]

Originally Posted by Pisces

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.

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.