Course to intercept method revised

[Dantenoc]

here's a revision of Claren's easy course to intercept method previously posted, but now corrected. The purpouse of this method is to acurately estimate where to head to in order to intercept a radio contact.

Step one (the setup):

Your U-boat, located at point 1, receives a contact report of a ship located at point 2. Take notice of the contact's speed and heading. Slow means around 6 knots, medium means about 9 knots, and fast... well, I never bother with those.
Our hope is to intercept the ship at some point 3 were we'll both meet.

Step two:

Using the protractor tool, click on your ship, then on their ship, and then drag the second leg of the protractor tool off into the direction where the contact is heading. Take absolutely NO notice of the angle formed :P

Step three:

Using the ruler start measuring from the contact's position of into the direction where it's heading. Measure a distance representative of it's speed. In this example the contact was reported as slow, so I measure 6 kms to represent 6 knots.

Step four:

Using the compas, draw a circle centered at the end of the measurement you just did (labeled P3b in the image). The radius of this circle should be your intercept speed. In this example, I think I have a good angle of aproach, and don't feel like wasting too much fuel, so I leave the circle's radius at 12kms, representing the 12 knots to wich I'll speed up to to intercept the target. Take special notice of where the circle intercepts the leg of the protractor that goes from your ship to the contact (labeled P1b in the image).

Step five:

With another protractor tool, click at the center of the circle (P3b), then the point where the circle intercects the line that goes from your U-boat to the contact (P1b), and from there click in the direction of the contact. DO TAKE NOTICE OF THIS ANGLE... Lets call it Angle A

Step Six:
Here's the magic of trigonometry; the little triangle you have just made (points P1b, P2 and P3b) solves the problem of interpecting the target IF your shiped where positioned perfectly for a one hour interception course (it would have to start at P1b). Our situation isn't as ideal of course, but pitagoras says that what holds true for the little triangle holds true for the big one, the one that will be formed with your position (P1), the contact's position (P2) and the real intercept point (P3)... so:

Using yet another protractor tool, click on the vicinity of the contact (iif you can't click exactly on the contact because of all the overlaping protactors, then simply click somwhere along the line formed by your U-boat and the contact), then on your u-boat, and then drag the second leg of the protractor so that it PERFECTLY REPLICATES ANGLE A.

Your done Point Three, indicated by the thick black arrow in the image is where the target is going to be just at the moment of interception... SO START HEADING FOR IT, HER KALEUN!!!


To see another example of this method in action, go here:
http://www.subsim.com/phpBB/viewtopic.php?t=48026

[DMarkwick]

Ah-ha, nice method, thanks for sharing this tip

Incidentally, most of my problems intercepting reports is getting the initial reported angle right, if the reported heading is "ESE" it's pretty difficult to get an accurate idea of where they are actually heading, the one you estimate could be 10 or 20 degrees off.

[The Avon Lady]

Dantenoc, can you please explain to us math inhibited airbrains what exactly is wrong with Claren's method, when will it not work and why?

[don1reed]

Good job, Dantenoc.

@DMarkwick:
http://www.vrcurassow.com/2dvrc/maps/windrose.html

Rgrds,

[Hartmann]

Good work

I use the nomograph metod

i trace a line over his heading,and then i use the nomograph to estimate his speed.

after, is question of estimate how many kilometers runs in an hour of time,

finally i plot a course to the nearest point of his estimate heading keeping in mind the time that i need to reach this point, because the target is mooving too.

is useful do a hidrophone checks for detects the target

[Dantenoc]

Incidentally, most of my problems intercepting reports is getting the initial reported angle right, if the reported heading is "ESE" it's pretty difficult to get an accurate idea of where they are actually heading, the one you estimate could be 10 or 20 degrees off.

I know ... This a very unfortunate downside to modding the game with things like RUB... I vote to put the little tale on the ships back in, so that we can better judge the ships direction. In the movie Das Boot the radio report that they get (the one that they don't chase because it's too far away) states the ships heading in degrees (around 60 if I recall correctly), which is a whole lot better than a simple compass heading.

Dantenoc, can you please explain to us math inhibited airbrains what exactly is wrong with Claren's method, when will it not work and why?

As to why Claren's method doesn't really work... let me see if I can explain I suspect we're actually talking about the same method except that Claren had a momentary lapse of dislexia when he posted and switched two things around. Unfortunately, this being war... and even more so: MATHEMATICS IN WAR, well... make a tiny mistake and your dead

The tiny detail is this: Your ship's speed shouldn't be measured from your position to the contact's current position as previously described by Claren... there's no point in it, since your sub will NEVER be heading directly at the target (if it did, the target would be long gone by the time you got there). Rather, your speed should be measured on a line that paralels the course that you WILL actually take to intercept the target (very much like when you measure the contact's speed following it's heading)

Having said that, then why does Claren's method seem to work sometimes (and even very well in some cases!)?... well... because most well behaved triangles have inner angles that aren't that different from one another, so if you switched them by mistake you can get away with it sometimes (specially if the contact isn't that far away to begin with, since errors in angles are exagerated with long distances only). The method presented here will allways work.

I would like to give a big thumbs up to Claren nonetheless because he is one of few that took the time to post something TECHNICAL with images and all

[Shivaran]

Yup, nice work you two !

I was going to explain some maths but you obviously type way faster than I do

[Captain_AJ]

I have been using your old method . It seems that the convoy is about 8 hours ahead of me . I paused the game a few times and madr sure that I was doing your suggestions correctly . Still I was Off > I will use this new method and see if thereis a change .. Thanks for the good work !!

[Captain2]

By the way is it not PYTHAGARUS but great job

[Pisces]

Originally Posted by Captain2

By the way is it not PYTHAGARUS but great job

Actually, it is most commonly written as Pythagoras, I think.

[Sailor Steve]

I doubt he'll get the message. It's been four years since he last visited these boards.

[Rhodes]

Originally Posted by Sailor Steve

I doubt he'll get the message. It's been four years since he last visited these boards.

Who? Pythagoras?

[derrinurban]

Originally Posted by kimuraijn

I have been using your old method . It seems that the convoy is about 8 hours ahead of me . I paused the game a few times and madr sure that I was doing your suggestions correctly . Still I was Off > I will use this new method and see if thereis a change .. Thanks for the good work !!

If I remember correctly, when this method was originally posted on the server, one of the points/notes/important details of using this method (this is the one I have personally always used) was that this gives the ideal intercept course. In order to ensure that you have sufficient time to find the contact and set up for the intercept/shot/etc, you should increase you speed by a few knots. In the example, if you are plotting your intercept at a speed of 12 knots, actually set your sub speed to 14 knots. This will allow for any variations due to wind, waves and the like and put you in position before the contact arrives.

Hope that made sense.

[desertstriker]

scratches head
i like the mothod change direction to intercept with general location where you think intercept will be get close submerge (if done right sound contact should be there) change course accordingly as the ships sometimes change direction. a little simpler if you don't have the math talent but could be considered noobish but hey why fix it if it works