Intercept course?

Kip336 · 03-06-13, 12:37 PM

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 · 03-06-13, 12:41 PM

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 · 03-06-13, 04:07 PM

[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 · 03-06-13, 05:09 PM

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 · 03-06-13, 05:12 PM

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

Zander · 03-06-13, 06:14 PM

Quote:

Originally Posted by 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..

)

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 :

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 · 03-07-13, 01:54 PM

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 · 03-07-13, 02:19 PM

Quote:

Originally Posted by 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.

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 · 03-08-13, 04:39 AM

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

Kip336 · 03-08-13, 12:25 PM

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?

03-06-13, 12:37 PM	#1
Kip336 Torpedoman Join Date: Jun 2009 Posts: 119 Downloads: 19 Uploads: 0	Intercept course? 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 )

03-06-13, 04:07 PM	#3
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	[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. Last edited by Pisces; 03-06-13 at 04:56 PM. Reason: Make it simpler

03-06-13, 05:12 PM	#5
CapitanPiluso Forum Captain Join Date: Apr 2007 Location: Buenos Aires Posts: 273 Downloads: 22 Uploads: 0	For a complete intercept solution you could try Mobo http://www.subsim.com/radioroom/showthread.php?t=118990 __________________ (Yo no fui ) My DW pics :https://goo.gl/photos/5gBN7WFntLBSAsc17 My SSM2007 pics :https://goo.gl/photos/1Fa6GaEom28AZuc57

03-06-13, 12:41 PM	#2
Beardmoresam A-ganger Join Date: Oct 2011 Posts: 74 Downloads: 444 Uploads: 0	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.

03-06-13, 05:09 PM	#4
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	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.

03-07-13, 01:54 PM	#7
Beardmoresam A-ganger Join Date: Oct 2011 Posts: 74 Downloads: 444 Uploads: 0	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.

03-08-13, 04:39 AM	#9
Kip336 Torpedoman Join Date: Jun 2009 Posts: 119 Downloads: 19 Uploads: 0	I'll actually use the calculator option ... I tend to keep my iPhone close so I'm sure itll work.

03-08-13, 12:25 PM	#10
Kip336 Torpedoman Join Date: Jun 2009 Posts: 119 Downloads: 19 Uploads: 0	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?