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

[Pisces]

Originally Posted by Maceaciadh

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).

Ok, so this method is more guestimating than calculating. But still, it requires multiple checks (at hour marks) to see if you got there already.

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.

...

Because you want to get as close as possibl. Especially with fog and long range. Adding causes for error deliberately (like overestimating that 16 km equals 8 nautical mile) doesn't help with that. You want to be as exact as possible. Sure, the target course is uncertain. But that applies to both methods. Yours won't handle it any better than mine.

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

Then it's a good thing that the hydrophone actually works upto 33km. It's the crew that is either too deaf, or to lazy to report what you can hear yourself. So you have until 170 km.

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

Ok, that is true. Trial and error makes those braincells learn to do it intuitively. But you'll also get the hang of making that drawing after a while. You'll do it blindfolded. Ok, not litterally.

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

Yes, it all boils down to how sure you can be of the target speed and course. But also how well you can keep your own speed (and course). You always have to consider the possibilities that it's going to fail. That's why I try to reduce as much causes.

[Maceaciadh]

what hour checks are you on about? it takes me 20 seconds to set course to the intercept. i miss maybe 4 out of 5 times which is probably just changing of course.

also yea i read that on another thread (guessing you read it) i am going to start listening myself soon

[Pisces]

To add:

There is a fairly simple addition to the method to end up at a certain minimal distance away from the contact at the meeting point. You won't be able to figure out that easily with that alternate method.

But it would be considered more advanced. So if Sixcoins doesn't want to get overwhelmed he should cover his eyes now:

[Edit] This does require fairly reliable speed and course of the target. Most likely use is after first contact, and dodging around units in the dark.

1: You would replace the point of the contact location with a circle of minimum safe distance.

2: Then you would choose, "do I want to pass behind or in front of him?". In the image below you want to pass ahead of him.

3: draw the bearing line from the contact towards you along the edge of the minimum distance circle. Then continue from that.

[Maceaciadh]

still confused why you are putting some things forward there but if you like to draw stuff with your time who am i to argue lmao surely once you get within visual range you delete your first line and start taking more accurate visual measures or indeed hydrophone ones to find out speed and bearing.

also forgot to say on the last post but the 7% over error by just doubling makes for a good early arrival time. if you want to trail them like a convoy then just wait while they pass and take notes of all the good high tonnage ships within it. arriving early is always good even if you want to shadow.

[Pisces]

Originally Posted by Maceaciadh

still confused why you are putting some things forward there but if you like to draw stuff with your time who am i to argue lmao surely once you get within visual range you delete your first line and start taking more accurate visual measures or indeed hydrophone ones to find out speed and bearing.

Safety precautions. I want to set a course that gets me closer, but not too close. The dashed line is just shown to see how it compares with the 'straight' intercept way. It is not used.

also forgot to say on the last post but the 7% over error by just doubling makes for a good early arrival time. if you want to trail them like a convoy then just wait while they pass and take notes of all the good high tonnage ships within it. arriving early is always good even if you want to shadow.

That works too. But with your way your 'early time' is directly proportional to the distance at the start, or how long the intercept took. So for long distance targets you will arrive more early than closer ones. I don't see the need for that. With this added circle to the method you should pass it a fixed stand-off distance every time.