But he uses 1.5 in both the examples of moving towards and away from the target. The constant in both, though is the U-boat speed of 2 knots and 1.5 is 75% of 2, so I'd conclude that you add or subtract 70-75% of your own speed.

I've been giving this some more thought and it's an intriguing method. However, I was thinking about if you were at a much smaller and more awkward AoB than the example, say at 30º. In this case the ship will take longer to cross the point of view and so the calculation isn't so straight forward. So I thought there must be some relationship between the time taken and the angle on bow. I came up with the following theory:-

- When timed at 90º AoB the ship will have moved it's entire length across the view finder in a set amount of time.
- When timed at any other angle, the ship will be perceived to move less distance across the view finder over a longer time.
- The perceived length (PL) of the ship is in direct relation to the AoB. The perceived length is sin(AoB) * actual length (AL). You can then divide this by the ships length to get the ratio of PL:AL, but seeing as sin(a) = opp/hyp, then simply taking the sin(AoB) gives the same result.
- If we multiply sin(AoB) by 100 we have the PL expressed as a percentage of the AL. So what, you ask? Well, the prefect time recorded at 90º should be the same percentage of the actual recorded time at your AoB. So, if you take the timing you recorded for the ship to traverse the centre line of the view finder and multiply it by the sin(AoB), you should get close to the amount of time it would have taken for the ship to cross at 90º AoB.

I could only test this with the figures given in the example above (I agreed with RAM that it looks about 75º, but the stopwatch looks more like 31.5 seconds to me). Eg:

A 78.5m tramp steamer traveling at 5 knots (2.56 m/s) will take 30.66 seconds to move it's own length.

If we take sin(75) * 31.5 = 30.42. Pretty close, huh? If we adjust slightly to 77º AoB we get 30.69.

I haven't been able to properly test this, and I'm sure that some proper mathematician will come along and tear it to pieces, or point out that it's already been proven before, but there you go. It was almost as much of an exercise for me to refresh a bit of trig.

There you have it...to my untrained brain, if you have an accurate AoB and you get a timing, you can quite quickly work out the speed of the ship, even from difficult angles.

Why not use the simple and reliable of going to the hydrophone. Yes, I'm talkng about turns per knot. I forget the TPK value that ships have in this game, but it's somewhere here on this forum. I think it was around 24 TPK.

The method goes like this:

Count how many times the shaft of the ship turns per minute. The cargo ships have 4 blades, so you would be counting every 4th chug you hear. It will sound something like CHUG...chug...chug...chug...CHUG...chug...chug. . .

Divide the turns per minute by the TPK value, and you have the speed of the target.

Please note that you don't have to listen for a whole minute. You can do just fine by approximating.

Multiply by 1.946? I thought Dimitrius said to ADD 1.946? I'm confused here....:-?

27 knots:o - what ship are you hunting mate - looks like a big British battleship :ping: :rock: i don`t know any merchant that has ability to travel that fast:D .

CaptainNemo12
You got thise right - just like _Seth_ sad
meters per second x 1.946 = knots
simple is that ;)

:rotfl::rotfl:Just an example people would remember, mate!

Well at lest he does not spam:yep:

I must appologize about my previous post. The method using turns per knot doesn't work for SH3, as the developers did not model it. :cry:

It works, thanks mate.

Just made a small excel sheet where you only have to type in shiplength and estimated AoB, and you get the time it would take the ship to cross your viewfinder with speeds ranging from 1-34 knots

I've protected all cells apart from the ones where you type in AoB and ship length, so the formulas are save from user error, but if someone wants to refine it, there's no password entered for the sheet protection.
Almost forgot to post the link

http://members.chello.at/reinhold.bisanz/Speedcalc.xls

Link doesn`t work.

Right-Click + Save as ;)

Hmmmm thanks but trying to open it crashes my Excel. What version of excel are you using??

Actually I'm using Open Office, so I guess that may well be the problem. I'll reupload it without protected cells, when I get home, I don't know if that's what causing it crashing tho. Common sense would tell me it can't be the formulas, I mean even if they'd be wrong for Excel, it should be possible to open the file, but maybe display errors in the cells with formulas.

when I've uploaded the new file I'll edit the post with the link.

This only works with the stock version of the game, the tables that have once been made to use this method won't work if you have different sound packs intstalled.