Intercept course?

[Kip336]

Yesterday I had a really good generated ASUW game in a 688i. Instead of directly pounding the enemy vessel like I usually do, I decided to do things the other way, and just track the vessel for a while.

As he was off on my bow, I wanted to get a nice intercept course. Other then guessing though, I didn't have any means to calculate the proper course.
Does anyone know how to calculate a intercept course? In SH3 you atleast had some good drawing tools to use to calculate it, but not in DW..


I ended up going onto a lagging course, slipping in behind him and then caught up to him by going just a knot or two faster.(He had no TA...)


(Also, even though you're just YARDS behind a big surface ship, you dont hear the ship outside of the sonar station :( )

[Beardmoresam]

I think you need to do a relative motion-plot-thing, although I'm no expert.
Basically I mark up my speed and heading + his speed and heading and see where it leaves us in x amount of time. I can then speed up or change course to make it more suited to my needs.

[Pisces]

[EDITED for simplicty]
I take the TARGET COURSE.
I subtract the TARGET BEARING from it. (don't care if the result is negative or beyond 360)
I take the sine function of it with a scientific calculator. (make sure it is in degree mode, not radians or gradians)
I multiply the result by the target speed.
I divide by my chosen intercept speed.

If the result is less than -1, or bigger than 1, then forget about chasing it, or speed up and redo the calculation. Bigger than 1 (or less than -1) means he's outrunning you. Exactly (-) 1 means the best you can do is move perpendicular to the bearing, and let him close the distance to you.

Take the inv(erse) sin, or arcsin, or asin, or sin -1 (!superscript) of the result.

[EDITED] Add the arcsin result to the TARGET BEARING. If the asin result is negative, then adding a negative is the same as subtracting from the TARGET BEARING while ignoring the sign.

Head that way, unless it keeps him in your sonar deaf-zones. Then you have to turn a bit to keep an ear on him, and make do with a bit less efficient intercept.

[Pisces]

In (Casio fx-82SX) button code:

Press mode button
Press 4
(Casio fx-82SX enters degrees mode)
Press AC a couple of time to clear accumulator memory.

Enter Target Course,
Press - (subtract)
Enter Target Bearing,
Press =,
Press Sin,
Press x (Multiply),
Enter Target Speed,
Press ./. (Divide)
Enter Ownship Speed
Press =,
Observe if between -1 and 1. If not, speed up and redo calculations.

Press Shift button,
Press Sin (Sin after Shift= arcsin)
Press +
Enter Target Bearing,
Press =

Set course to that!

If he is moving away then you obviously need to be faster than him.

[CapitanPiluso]

For a complete intercept solution you could try Mobo http://www.subsim.com/radioroom/showthread.php?t=118990

[Zander]

Yesterday I had a really good generated ASUW game in a 688i. Instead of directly pounding the enemy vessel like I usually do, I decided to do things the other way, and just track the vessel for a while.

As he was off on my bow, I wanted to get a nice intercept course. Other then guessing though, I didn't have any means to calculate the proper course.
Does anyone know how to calculate a intercept course? In SH3 you atleast had some good drawing tools to use to calculate it, but not in DW..

:( )

Are you saying that TMA doesn't give you a course, allowing you to plot an intercept point further out? TMA does give you course among other things, like speed, range....
Take a look at this you tube tutorial video, and note that at about 1:36min mark, he has speed, bearing, range and course down to a 1150 yards of the actual position along with its course..
I trust your question was in relation to tracking a target such that you can derive its course? If so the sonar and TMA does everything that you need to acomplish that. Here is the you tube link : http://www.youtube.com/watch?v=fh3E5dWYPJA

Look at his solution at about 1:33...

With speed and course you can easily calculate a possible intercept position, from his "present" position using the nav map tools.

[Beardmoresam]

Pisces, i'm not great at math but I'm guessing range cancels out in your equation by the fact that the further you are from target, the further you both have to travel to intercept??

I'm used to plotting it by vector analysis on paper as I hate trig lol.

[Pisces]

Pisces, i'm not great at math but I'm guessing range cancels out in your equation by the fact that the further you are from target, the further you both have to travel to intercept??

I'm used to plotting it by vector analysis on paper as I hate trig lol.Correct.

A picture makes more sense than a thousand words, so I agree with the paper method. But it does take some time, and clutter on the desk.

[Kip336]

I'll actually use the calculator option ... I tend to keep my iPhone close so I'm sure itll work.

[Kip336]

Arright.
I did some testing on my iPhone at work, and it seems to give out a pretty ok calculation. However, when I was doing it on a paper plot, target range was part of the plot. How is that not important in this calculation? For small distances, it barely matters. But when Im trying to get in a position to engage a russian fleet steaming at 20 knots, 50nm away, the distance between us should matter no?

[Beardmoresam]

With the method that Pisces described, nope. There are some very good visual animations for describing the effect on the SH4 forum. Just look up the Dick O'Kane method.

[Pisces]

It's all about the angles inside a triangle. The speeds arranged into a triangle must be of the same shape as the triangle made up of target course, intercept course and target bearing. The size of the triangle, or the exact lengths of the sides in terms of real distance doesn't matter for getting there at the same time as he does. Because the time it takes is the same for all lengths of the triangle sides, it can be taken out of the equation. You reduce the problem into an 1 hour situation.

From that you can calculate the missing pieces of information inside the triangle. You have to make use of a math rule known as the law of sines: the ratio of side length to the sine of opposing angle, is the same for all side/corner combinations.

a/sin(alpha)=b/sin(beta)=c/sin(gamma)

If alpha is AOB (the corner occupied by the target), then a is own speed.
If b is target speed, then beta is lead-angle (deflection; the corner occupied by you)
C would then be the closing speed along the target bearing.
And gamma would be the angle of the intercept point corner. (track angle???)

You only have to know 3 (AOB, own speed, targetspeed) out of 4 to calculate the missing lead-angle b.

The angle of the intercept point corner/ trackangle is not really of interest in practical use, but it is required if you want to calculate the time it takes to get to the intercept point. Since the closing speed determines the time needed for the range to be reduced to zero. So, since the sum of all angles inside a triangle is 180, you can figure out the gamma angle. Plugging that into the: a/sin(alpha)=c/sin(gamma) equation you can now calculate c (closing speed). And ultimately the time it takes to the intercept point from range.

[jadervason]

Necropost, I know...


but my "Dirty" method of intercept is simple: start by matching course with the target. turn (toward the bearing rate) so that bearing rate of the target is reduced to zero. apart from certain exceptions, you are now on an intercept course :)

With practice you will be able to make educated guesses as to how much to turn with trial and error. I usually do it in 10 degree chunks but you can just set the rudder and ease back when you get close also

[rentacow]

I use this: http://www.luizmonteiro.com/RA.aspx

Very handy tools on that website! :Kaleun_Salute:

[p7p8]

Intercept course in DW is not really needed for playing.

1) your sensors have different "dead zones" so you can't track your target like in SH. more important is maneuvering for good TMA solutions

2) almost all subs can go very fast underwater so math methods for interception target moving with 10 knots when you can drive with 20-35 knots is pointless

3) your weapons can do this automaticly

4) your weapon can be wire-guided

5) your weapon have own radar,sonar active/passive, IR detector etc.

6) going straight for long time with constant speed is not too good for you, because you are easy target for opponents

My advise:
Don't play DW like SH.

[FPSchazly]

Intercept course in DW is not really needed for playing.

1) your sensors have different "dead zones" so you can't track your target like in SH. more important is maneuvering for good TMA solutions

2) almost all subs can go very fast underwater so math methods for interception target moving with 10 knots when you can drive with 20-35 knots is pointless

3) your weapons can do this automaticly

4) your weapon can be wire-guided

5) your weapon have own radar,sonar active/passive, IR detector etc.

6) going straight for long time with constant speed is not too good for you, because you are easy target for opponents

My advise:
Don't play DW like SH.

I think there are two different concepts being discussed here: 1) intercepting a target's track (i.e., actually reaching it to be able to observe or engage it and not just watching it sail by because your intercept track wasn't correct) and 2) engaging enemies.

I am (quite) sure that what is being discussed in this thread is whether or not it is even mathematically possible to reach a track and, if so, wishing to determine the best way to get to that track. By best I mean the optimal combination of speed and course. I don't think anyone here is talking about setting up straight-running torpedo solutions.

[Mike Abberton]

You can estimate an intercept course with just range circles, assuming you know target course and speed. No calculators or outside references needed.

Time to Intercept Method:

1. Pick a desired time to intercept and draw a range circle around the target at a distance of Target Speed x Intercept Time. Draw an X on that circle where the target course intercepts it (cursor bearing from center of circle is displayed while you're drawing the circle). If you want a specific range other than zero at intercept, offset the X from the target course line at the desired distance (on your side of the course line obviously).

2. Draw a range circle from your sub that intersects the X, note the cursor bearing while it is on the X. That is your intercept course.

3. Intercept speed is the new circle radius divided by the Intercept time.

Speed to Intercept Method

Simplest method for this is to try different iterations of the Time to Intercept method, using shorter or longer intercept times, until you like the Intercept Speed calculated in Step 3. Once you do it a few times, you'll get a feel for where to start the iterations to speed up the process.

Admittedly, neither of these methods is likely to give the "exact" intercept course/speed for a given situation, but as others have said, with modern seeking weapons, you don't really need to be exact.

Mike

[p7p8]

I think there are two different concepts being discussed here(...)
I know but first question is:

why you need method for interception?

In my opinion mainly for attack target. in that case, my points about weapon are also important.

I think "interception" isn't good word because in some cases better attack possition is far away from target (for example with SUBROCS). I think "attack possitons" is much better term than "interception".

[FPSchazly]

That's understandable, semantics can be annoying. I'm just repeating what I've come to learn in my experience: getting close to a target, whether that means tracking it or attacking it, is known as "intercepting the track". Either way, "moving into attack position" or "intercepting the track" is a separate concept from a "firing solution".

[p7p8]

In my experience when player asks for "methods of interceptions" he want to do something familiar to "interception" in SH or Air simulation games.
Problem is in fact, that modern submarines are completly differend than submarines from WWII (or planes). In many cases tracking from long ranges forces manevouring for building TMA data. Main sonar array (good for interception) is TB 16. Main problem for this sonar is blind cone in bow direction. So you can't just go straight to your target. It is not only problem because it is also good oportunity for building TMA situation.
Because of the above, simply methods for "interception course" are pointless.

Other reason lays in abilitties of your and enemy weapons. Modern ASW or ASuW weapon give you very speciffic way to attack. You should take advanteges of your weapon. Ploting course of interception is good for close attack. But in many games, I've launched my rockets or torpedoes even from possitions behind island (to linked or earlier ploted target). This means "old-fashioned" interception is not always good for attack.

[FPSchazly]

I'm talking on a more basic level, a very basic level. An intercept course as in your target is 500 miles away going 16 knots in a given direction. What do you need to do to reach this target to be able to attack or even track it? Intercept math is still very much necessary.

Also, if you are intercepting a track that is moving perpendicular to you, you will not be heading directly toward it to get it, you will be heading to the point where your two boats will be at a future time. How do you determine this point? You use trigonometry to set an intercept course. Remember, very very basic. Don't think about stand-off weapons versus heavyweight torpedoes or helicopters in the vicinity. We're taking away all those complex layers away to get to the root of the problem. Only then can you start adding those complexities back in.

(Due to the nature of my work, I can't think about a problem without tearing away complexities and I assume that's how everyone else thinks, as well. Apologies for any confusion)

[jadervason]

You can estimate an intercept course with just range circles, assuming you know target course and speed. No calculators or outside references needed.

Time to Intercept Method:

1. Pick a desired time to intercept and draw a range circle around the target at a distance of Target Speed x Intercept Time. Draw an X on that circle where the target course intercepts it (cursor bearing from center of circle is displayed while you're drawing the circle). If you want a specific range other than zero at intercept, offset the X from the target course line at the desired distance (on your side of the course line obviously).

2. Draw a range circle from your sub that intersects the X, note the cursor bearing while it is on the X. That is your intercept course.

3. Intercept speed is the new circle radius divided by the Intercept time.

Speed to Intercept Method

Simplest method for this is to try different iterations of the Time to Intercept method, using shorter or longer intercept times, until you like the Intercept Speed calculated in Step 3. Once you do it a few times, you'll get a feel for where to start the iterations to speed up the process.

Admittedly, neither of these methods is likely to give the "exact" intercept course/speed for a given situation, but as others have said, with modern seeking weapons, you don't really need to be exact.

Mike

This is a good method. I hope to try it out. I do also still like my "bearing rate method" as it allows you to just go to a certain speed and "guide yourself in." However my method and I suppose yours to an extent require an accurate target track.


I know but first question is:

why you need method for interception?

In my opinion mainly for attack target. in that case, my points about weapon are also important.

I think "interception" isn't good word because in some cases better attack possition is far away from target (for example with SUBROCS). I think "attack possitons" is much better term than "interception".

Your premise is that contacts exist solely to be attacked. In the game this is mostly true. However sometimes you simply wish to get close to a target to identify with periscope. "You shouldn't kill a man without knowing for sure you ought to." In reality there may be other reasons as well, a submarine may rendezvous with a surface vessel without first giving an exact position, as to maintain the sub's discretion.

I agree that 1) an intercept course is not necessary with modern weapons and 2) an intercept course does not necessarily provide a good attack position for the aforementioned modern weapons.

Even still, suppose I am attacking a fast target with a TEST-71 torpedo. Autocrew and fire control does not seem to do a good job launching torpedoes on an intercept course and the TEST-71 has limited ability to catch a 30 knot target from behind. To be absolutely sure of killing my target I may wish to draw to within close distance ("no escape range") before shooting.

[p7p8]

I know that all of this is for very, very basic model of situation. But this situations won't happend in 99% of scenarios.

Do you use "interception course" for P-3 Orion ASW operations? Do you know what I mean?

BTW: "tearing away complexities" is not always good method for solving every problem. Sometimes you have specific context that changing the same situation completly.

[p7p8]

sometimes you simply wish to get close to a target to identify with periscope. "You shouldn't kill a man without knowing for sure you ought to." In reality there may be other reasons as well, a submarine may rendezvous with a surface vessel without first giving an exact position, as to maintain the sub's discretion.
I think this is reasonable only for civilian units. Fast warship can detect you from "good periscope range". Other complication is, you can raise periscope up to 10 kts. So you can't visual track fast target.

Even still, suppose I am attacking a fast target with a TEST-71 torpedo. Autocrew and fire control does not seem to do a good job launching torpedoes on an intercept course and the TEST-71 has limited ability to catch a 30 knot target from behind
Even when you attack from bow, your target can turn back.

To be absolutely sure of killing my target I may wish to draw to within close distance
TEST-71 have range only 8.1 nmi with max speed. That means, you should be 4-5 nmi before attack fast warship. Do you realy need "interception course" for this kind of attack? I think not.

[jadervason]

I use this: http://www.luizmonteiro.com/RA.aspx

Very handy tools on that website! :Kaleun_Salute:
Thanks for providing that link!

I think this is reasonable only for civilian units. Fast warship can detect you from "good periscope range". Other complication is, you can raise periscope up to 10 kts. So you can't visual track fast target.


Even when you attack from bow, your target can turn back.


TEST-71 have range only 8.1 nmi with max speed. That means, you should be 4-5 nmi before attack fast warship. Do you realy need "interception course" for this kind of attack? I think not.

Suppose my orders are to kill anything in a certain area. Suppose I detect a 25 knot warship in that area and determine with good confidence he is 20 miles away. Suppose I have a 35 knot submarine armed with TEST-71 torpedoes.

The gain rate of a 40 knot TEST-71 torpedo on a 25 knot warship is 15 knots. The run time of a TEST-71 torpedo is 12.2 minutes. 15 knots is 506 yards per minute, with 12.2 minutes available run time and a 15 knot advantage, the no-escape range of a 25 knot ship against a TEST-71 torpedo is about 6150 yards or 3nm. I can hit him from further if he does not evade but I want to be sure.

Target speed was 25 knots. Target bearing was 90. Target course was 180. Target distance was 20nm. Ownship best speed is 35 knots. Using the tool linked to above we achieve this intercept solution.

https://i.gyazo.com/01efc6d0aec8fada8d0e627d1b19fe8b.gif

Calculated intercept angle is course 136 at 35 knots for 49 minutes. 49 minutes is a long time! You could easily waste a lot of time with a poor intercept angle. I would probably run course 139 or 140 so that I would eventually be in position ahead of him, that way I could listen once in a while and verify my intercept. Then I can use my very small 3nm torpedo range to good effect. I hope this illuminates why some of us are so interested in the question "how to intercept."

[p7p8]

http://i.imgur.com/okSHSbk.jpg

[p7p8]

http://i.imgur.com/zRzxNaD.jpg

This is only example, but almost all attacks looks very similar

0) Only bearing and bearing rate

1) waiting for TMA data, identification
2) waiting for more TMA data, identification, you have course with medium error
3) you have range, course with medium error
4) you have speed with medium error and range/course with small error
5) you have speed without error (DEMON) and all data with small error
6) preparation for attack, you have all data

Like I said before, methods for ploting "course of interception" are crap in real situations.

[Karlbannsonr]

I've read this guide 12 times. I've watched people plot a course across multiple videos. I've played the game UBOAT for 7 hours. I can't intercept anything. I can't hit any targets. I literally can't even SEE a ship anywhere. Can't get my money back bc I played it too long. Seriously just cannot understand any of this.

[Aktungbby]

I'm too dumb to do anything rightKarlbannsonr!:Kaleun_Salute:...remain dumb, only try doing it left! :yeah: