Speed Calculator!

[Cpt. Chaos]

Hi @ all.

Here at the forum I read the following:

"It's fairly easy to work out speed by hand (as long as you have calculator handy).

It does require a bit of trigonometry though (remember SOHCAHTOA?)....and it's most accurate if you are stationary or at least very slow while doing it (just like the training mission).

1) Having got range etc, lock the target in the scope (or for more "realism" you can do it without locking the target).

2) Note the bearing to the target as displayed at the top of the scope view and then start your clock (Let's say for example it was 320 degrees when you started the clock).

3) Wait 10 secs. (You can use any time you like, but 10 secs is as good as any).

4) As soon as the 10 secs is up check the new bearing of the target (it should have changed). Anyway, let's say the ending bearing was 325 degrees.

5) Ok take the difference in the two bearings 320 - 325 = 5 degrees brg change in 10 secs.

6) Using our stadimeter range, and our noted time and bearing change, a bit of trigonometry will give us the speed.

There is One important thing here - the stadimeter will give you a range in Yards - there are 3 feet to a yard! Personally I prefer to work in feet so I do a conversion from Yards to feet (just multiply the range from the Stadimeter by 3).

So let's say we have

Range - 1020yds
Brg Change - 5 degrees
Time - 10 secs

a) 1060 yds = 3060ft

b) Use -- Tan Brg Change x Range (in feet) = Distance travelled by target in feet

So using the numbers above :

Tan 5 x 3060 = 267.71ft

The target travelled 267.6ft in 10 secs. To determine speed in Knots we do :

c) 267.7 x 6 = 1606.3ft (we multiplied by 6 because we used 10 secs as our time period, there are '6 lots of 10' in a minute). The target is doing 1606.3ft per minute.

d) 1606.3 x 60 = 96377.5ft - This gives us the distance in feet the target travels in an hour.

e) Last step, convert 96377.5ft to Knots. Simply divide by 6076 (that's the number of feet in a Nautical Mile). So 96377.5 / 6076 = 15.86. Call it 16 Knots.


Important note on all of this, if you are not perpendicular to the track of the target, this system will not be accurate since the trigonometry in use is for right angle triangles. However, as long as you're more or less in the right place this should be accurate enough.

It looks like a lot of work, but you can get through the maths quickly enough and come out with an accurate result. If you're struggling for time, just pause the game when you've got the time and bearing change and you can take as long as you like going through the numbers.

For the training mission you should find this kind of data (depending on where/when in to the mission you take the data)

Range 1020 yds
Bearing change ~ 3 degrees in 10 secs

Doing the maths again ((Tan 3 x 3060) x 360)/6076 = 9.5 Kts

Scratch another enemy vessel"


Nice thing, really. But needs some time. To make things easier for us, I've implemented the whole calculation into an excel sheet. You just have to enter range, bearing change and measure time. And voila, there it gives you your targets speed!

I tested it and it seems to work quite exactly.

I just need the email adress of someone who could upload it here or at other sites. And I'll send it to him.

[Cpt. Chaos]

Well, even if nobody seems to be interested in (stupid guys!) I found a forum making me abled to upload the file.

http://www.aotd-flottille.de/wbb2/at...achmentid=2400

Gute Jagd!

[RedHammer]

Thanks alot Cap Sure is appreciated


S! to all

Your friend in the Pacific

RH

[SharpShin]

Thanks for this! I will give it a try.

[Liszt_]

I prefer many of the methods applied here:

http://www.paulwasserman.net/SHIII/#...%20Chart%20(DS)

It's for SH3 but the same logic applies.

[greyrider]

good work cpt, this is just another excellent way to determine speed,

i really like this, kinda like the hurry up offense in pro football, striike quickly to score.

i havent tried it out yet, sh4 runs crappy on my computer, i know the devs will fix it, im not worried about that.

i dont have sh3 on my computer anymore, and im not reloading it, but ill use your formula just as soon as sh4 is playable.

thanks for your work, this forum needs tactical thinkers like you, stay around ok?

[Cakewalk]

Sweet, just tried it and it works great

Good stuff, like you said the closer it is to 90 degrees the more accurate it is, excellent method though.

[NefariousKoel]

Yep, thanks. This is definitely useful for quick shots under 1750 yards. Just what we needed.