Need help at calculating intercept stuff
 

Ahoi Ubootfahrer :ahoy:


i think i am going crazy. Not so long ago i spotted a small convoy of 3 ships. I was on same course and i got their speed. So i thought:"Hey would be good if i can pinpoint them, moving to an ideal position for waiting".

So i started drawing on paper and soon i realized that it is just too complicated for me :shifty:. Still i am not sure if this is right. Due to the fact that i am at work and i do not want to waste my precious time at home with doing paint and stuff, i drawed my thoughts here, hoping someone could help me. I guess its just a simple mathematical issue :hmmm:

http://dl.dropbox.com/u/25407293/pix...ausrechnen.jpg

So my question would be: how long i must advance or, how far i must go to reach the point X (or the length of a) so i can start going into position which would take 20nm (here sm, because in Germany we say Seemeilen).

Any ideas? :hmm2:

Except, the game uses kilometers for distances measured with the line tool if I'm not mistaken. (well SH3 and 4 do anyway with the German Uboats) So there is another curve ball. SM or nautical miles are 1852 m, or 1.852 km (english decimal notation, or 1,852 in european decimal notation.) Let's get this straight first, as it is a big difference. But to give an example I will consider the 20 nm case anyway.

Your drawing is not quite clear yet. In 4 hours you move 60 nautical miles on the parallel course, but the target moves only 40 nm. So the target will not be at "a", but 1/3rd of "a" (20nm) before it. When you have arrived at "a" I would turn 48 degrees to the right of the target course, while still keeping 15 knots speed. Then you would keep your position 20 nm forward of the target's beam (left/right line) as it moves along, but you would 'slide' to starboard towards it's track. You'll be approaching that line with about 11 knots (diagonally 15kts= 10 knots forward, 11.2 kts sideways ... Pythagoras rulez!!!) Your picture isn't clear in how far away you are from the target track NOW. This determines how long it will take before you reach the target track after the turn at "a". Your curved track of 20 (nm) is confusing the picture. I think both for you and for me.

If you are now 20nm to the side of the target then the diagonal leg after "a" takes 20nm/11.2kts=1 hour 47 min. But if it is 20 km (10.8 nm) then it takes 10.8nm/11.2kts= 58 min

(oh yeah, kts=knots)

When you arrived infront of the target near his track, it still takes him 2 hours before he passes in front of you.

Here's a drawing how I would do it: (although, being 20 nm ahead could be a bit over-cautious, what are critical detection ranges in SH5? )

http://members.home.nl/rico.v.jansen/running_ahead.jpg

Also have a look at stoianm's tutorials, it's a sticky thread...

http://www.subsim.com/radioroom/show...0&postcount=28

I cvan also recommend "Agru-Front-Lehrmaterialien-Gesamtausgabe", written by DonL1978.
This can be found here:

http://www.subsim.com/radioroom/showthread.php?t=167884

Various methods of intercepting a convoi can be found in Chapter 5

Thanks for the answers!

@Pisces thanks for the drawing. But i think its much easier :D
@flostt yes i know, but unfortunately the material does not have this special case like i described

So i drawed again. I think i got it. :stare:
Its easier than i thought :woot:

http://dl.dropbox.com/u/25407293/pix...usrechnen3.jpg

In the end you get there in time!

But, ... at 8:40 you are at the 'intercept' point on the surface, but the target is now 3.3 nautical mile away from you! Instead of the 10 nm advance you initially desired. Are you sure you won't be detected?

Doing the diagonal approach, you would keep this 10nm forward advance. I'm not sure if you need it, but you never said anything about the time of day or sighting conditions so I went for the safest solution. Unfortunately it does involve a bit of trigonometry, or drawing out the triangle on the map and measure the angle.

You are absolutely right. Have to try the triangle method too. I went for the safe method to stay out of their range.
In this case 3.3nm is to short. I'll check maybe i can create a simple formula :hmm2:

I think there is very little point working out a formula to keep you just out of visual range as you move to your intercept point. This is mainly because your victim's visual range is always going to be changing due to several factors (time of day, weather, sea state, your profile and height and more). For example, if a fog bank sweeps across their visual range will drop considerably and you will be able to take a short cut to an intercept point. Conversely, if your are heading to an intercept as dawn approaches, you are going to have to steer around their ever-increasing visual range.

If you just want the most efficient intercept course, just make sure your victim remains on the same visual/hydrophone bearing as you approach. This is good when you are aproaching from way outside their visual range.

You piqued my interest with your diagram, plotting an intercept course from an initial parallel course (just outside the victim's visual range), so I plotted it out myself (in 30 minute iterations). Guess what?... it turns out to be an ellipse (s'pose I should have seen that coming). Trouble is, an ellipse will be a bu**er to plot!
Still, all a bit academic, when visual ranges wobble all over the place!

I figured the following method would be even more complicated for Kretschmer the IV, so I decided to restrict myself to giving the 'simple' solution above. But using this following intercept/manouvering diagram you can really keep going around in neat circles around your target. Or just directly towards or away from it. But it involves frequent re-draws of it and course changes as the true target bearing changes. I guess with the propper mousecursor modifications this would be equally possible in SH5 as it is in SH3 and SH4.

http://www.subsim.com/radioroom/show...12&postcount=5

To get with your sub x miles in front of a target is just a special case of the "Intercept of moving target"-problem, where you are x miles behind a target, on a same course as the target and you try to intercept the target.
For calculation use then the usual formula for interception
http://img.xrmb2.net/?imgID=207664
from the "formularies for u-boat commanders"-handbook =>
http://img.xrmb2.net/images/695978.png

Well, my first and most important condition is: make it as simple as possible. Honestly, for me: i do not want to draw complicated figures just for one merchant. For a convoy i would do it :O:

Thats why i took 10 nm, to make 100% sure to stay out their visual range. 8000m would do it too i guess.

For groups with more then 2 ships, i attack at night anyway. In this case i use AGRUFRONT LEHRMATERIALIEN with Attack Disc to calculate circumstances for a night attack.