Contact Intercept
 

Hello Sailors.

I'm having a problem with intercepting contacts. Spending a lot of time studying and trying it out, but I keep coming up short.

First, let me say I've done my studying. I'm reading the tutorials and practicing in game.

Right now, in particular, I'm using this tutorial. It seems to be all that I need for now, and this is the one I want to master. I'll add more tools to my bag later for certain, but right now my question is based on this method.

I'm using thread The Hunt: An illustrated example of how to sink a ship.

My problem comes up when it's time to draw the circle. Just for the sake of conversation, I'm using a scale factor of 10. If My target is going 9 knots, then my line showing his track is 90knots. Therefore, if my speed is 12, my compass circle is using a radius of 120.

The instructions i'm following for this part of the procedure is as follows...

So you draw a circle, centered at the end of the ruler measurement you did in step 3, with a radius of 160 mks... why 160 mks? because in step three you chose to represent each knot by 10 mks, remember? (If in step three you'de had measured 6 kms for the 6 knots you would now be drawing a circle radius of 16 kms for 16 knots, and so on). Let's look at your circle
http://static.flickr.com/36/93898889_aa6ce333c7_o.jpg
Take special notice of were the circle cuts the line formed from your u-boat to the contact.

This is where my problem comes in .... My circle never intersects the line formed from my u-boat to the contact. My circle is always waaaaay too big. It's the correct size according to the tutorial, which I understand it should be u-boat speed x 10. (10 is the multiplier I used when drawing the target ships course) However, even though it seems to be the correct numbers, it doesn't create any useful information. It's just a circle around the whole shebang.

I really want to be able to do this method. I won't be able to do it until I understand whatever it is that I'm overlooking.

Can anyone see my error? I can't.

Thanks in advance.

Six

Maybe that's because there isn't one. You're not doing anything wrong I think so far. The circle intersects the line between you and the contact in the vicinity of the gridnumber AM24. Give me a moment while I upload my modified image.

The colors are in reference to Kylania's image I showed in another thread.

The light green protractor leg pointing ahead of the contact is the way to go.

http://img11.imageshack.us/img11/303...ptsixcoins.png

Link to Kylania's image: http://www.kylania.com/sh3/Intercept_Plotting.png

Thanks again Pisces.

I'll keep practicing it. I'm not sure why my circle keeps being bigger than my entire plot... Maybe I should be extending lines out further...

In my picture, it's all in one area inside one sector... In your picture, and in her picture, its over an area of about 4 sectors.

I guess I need to scale down a bit with the plotting tools, or use more of the map and draw longer lines....

Maybe that's why I'm having a hard time. Perhaps my common sense hasn't quite kicked in yet.

I'll keep trying, and thanks for all your help.

Hmm, now I noticed this image was taken directly from the Hunt thread. :/\\!! Why don't you make a screen dump of your own map, and upload that? Then we can see what you are doing wrong. Instead of how Dantenoc did it.

Ok.... I have an example for you, Pisces. I wanted to show you what messes I'm making over here.

Here is a picture of MY plot.....

http://desmond.imageshack.us/Himg84/...ng&res=landing

Clearly I'm not paying attention to something that's important, but I just don't know what it is.

Clearly my circle is too big, but it does follow the instructions of the tutorial.

I'm thinking that there's some bonehead common sense procedure that every captain worth his weight in salt already knows. Except me.

Small Edit..... I DID scale my circle down until it cut through the line between myself and the contact... and when that happened, the circle ended up cutting through that line in 2 locations. And the distance of the circle was not any factor of 12. So.... that confused me even more.

Thanks again, in advance, for any help you can provide.


Six.

I think that your problem is your making circle radious with own speed by factor instead of use this value for circle diameter. in your example with own speed 12 knots he circle radious must be 60km that means 120km diameter.

Possibly, but In the tutorial photo, they did use a factor of 10 for 16 knots, and the radius was 160Km. (and in that example, the target line was also 60 kilometers).

Tricky.

Hi, you made the correct drawing. But in this case your speed turns out to be to big. If you draw a circle of 60 (6 kts) or 90 (9kts) you wil see is intersects. After that you know your angle and still can steam up with 12 kts but you will arrive very early. It is all about math. If you understand it ones it is a peace of cake.

In this case you could draw a cirkel from position 60 towards your sub position, divide by 10 and you have your intersection speed. Intersection point would be position 60. Of course make sure your speed is a little higher because maybe your target is running 7 kts.

If the circle intercepts in two places, use the point closest to your sub to determine your angle.

In another ocassion, if your cirkel from 120 (12kts) would fit inside this triangle, and 12kts was your max speed, You should forget about intercepting this target.

Greetings, Marcel

In other words use a smaller scale factor here. With x10 the circle gets too big, x5 might just be enough, but x3 would surely be ok.

Here's some pics, that hopefully clarify, unfortunately drawn in Google Sketchup as I don't have access to the game right now

http://i.imgur.com/IIqyw.jpg

http://i.imgur.com/YxHsK.jpg

http://i.imgur.com/Ee79N.jpg

http://i.imgur.com/SA4kK.jpg

I find the easiest and fastest way to intercept a contacts course is by doing the following:

1. Draw a line from the contact in the direction that it is heading.
2. Ask the navigator to plot a waypoint that intersects somewhere along the line (track) that you have drawn showing the contacts course.
3. See how long it will take your u-boat to reach that waypoint (intersection) and from this work out how far the contact would have travelled in this time. From this ajust your course (waypoint) accordingly.

Example: Contact is travelling east at 6 knots. At full speed my u-boat will take 2 hours to reach the contacts track. In this time the contact will have travelled just over 22 kilometres. From this decide if you need to move your waypoint along the contacts track closer to the original contacts position or further away to make the intercept.

Hope all that makes sense.

Nemo

I love these threads with all the charts and must try out these new skills one day but for now I am happy using the same method as Captain Nemo.

I also make use of the knots to kilometres travelled in n hours charts that are in the GWX super mod.

I like to arrive early and then man the hydrophone and listen for the thump thump of my approaching prey.

Everything Sublynx explained in hit maps is true and explaine well. You only should consider, do I won't to intercept during daylight? I noticed it is 10:02. If you arrive early and don't get your periscope up too many times, use torps from a short distance, it may work.

Good luck with your hunt, Marcel

Yes, I see what you are missing. Due to your multiplication by 10 the red circle encompasses the entire distance from you to the target. The easy solution would be not to enlarge by 10, but just draw 1 for 1. (like Sublynx did in the later message with multiple images: #9, but that was apparently 3 for 1 )

Alternatively, if you didn't want to redraw the whole thing. The propper course of action (no pun) would be to extend the line between the target and you beyond your actual location. This is allowed because the line between you and the contact is supposed to be a bearingline extending into infinity. It shouldn't really stop where you are. The length of it is of no concern for the intercept course. Just as long as that green protractor angle has the corner at where you are.

You are forgiven, for it wasn't really explained in the Hunt thread. See the following image:

http://img515.imageshack.us/img515/9...tsixcoins2.png

No no, definitely not diameter. The edge of the circle represents the collection of courses at the defined own speed. It has to be the radius that must correspond to the speed. The target speed being 12 or 120, while the contact speed is (assumed) 6 or 60, thus halve of it, is entirely coincidence.

Wow I didn't think about that solution to the problem at all. Very clever, and makes sense now that you point out the fact to us :)

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.

Thanks so very much, to all of you. This definitely clears it all up for me... And now I can practice instead of pulling my hair out of my head.

Six.

2 intersections is indeed possible if your chosen intercept speed is close to the minimum required. The minimum speed is when the red circle touches the (infinite) black bearing line between you and the target. Another way to draw it is to drag the corner of the yellow protractor along the black line until it is 90 degrees. You have to go faster than that, or you will never meet!

The closer intersection of the red circle and the black line is the slower way to close. The course that results is actually having you trying to get away from him along the bearing line. But his closing outways your moving away. Always use the furthest intersection.

That's why I suggest not to multiply with odd-lot numbers, 2,3,4,5,6,7... . Stick to 1, or 10. And extend that bearing line if needed. No brain-burning by multiplying is required.

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

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.

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.

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.

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. :)

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.