Contact Intercept

[Maceaciadh]

Originally Posted by Pisces

Ok, lets say the initial AOB is 90 degrees port. (target goes from your right to left. And your fastest speed is 16 kts. ( so the initial distance to the track is 59 km in 2 hours)

After 2 hours the contact moved 22 kilometers along it's track.
This makes your distance to the new projected meeting point 63 km. (it's 22 degrees to the left)
But this will take longer: 2 hours 8 minutes.
And so, in that time the target moves 23.7 km.
This again moves the projected meeting point even further to the left (23.6 degrees)
And so your distance to this new meeting point grows slightly to 63.6 km
It would take you now a minute more to reach that.
And so on,
and so on. But let's consider this minute close enough for now

In other situations you might have to do more repeated calculations, as your distance to the projected meeting point creeps further away.

So, how do you consider repeatedly calculating the distance that the target moves in the same time it takes you to do it "the easiest and fastest"?

To each his own method, of course. But I think those words better apply to the graphical method as described. Where no calculation is needed.

this is by far the easiest and fastest method out there(i use it). perhaps you have misunderstood what he meant by it. you draw a line of the contacts course and if you want mark crosses every 16KM(ship at 8Kts) to help visualise it(just double the speed in knots gives you a slight overestimation in KMpH) then as stated set course to an appropriate point on that line. you move your waypoint along the line and the navigator gives you a time to that waypoint. adjust accordingly and you are there. no fuss, no hassle, no time wasted drawing stuff (unless you like that way). after all the targets heading is an estimation so why solve it properly something that is wrong?

a bit hard to explain without pictures but really there are 2 bits of math
1)doubling ships speed from Kt to KMpH
2)roughly guessing where your intercept is.

FYI after the target travels 102KM it has a possibility of being beyond hydrophone range from the bearing inaccuracy (20KM radius)

after a while you develop a seamans eye and can drag it almost perfectly to an intercept

PS if in heavy fog may be better to do that whole circle business to save diving and listening alot but you can still be wrong over long distances so be careful