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