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Originally Posted by Arclight
Speed can be determined by placing a mark on your target and starting the stopwatch. Let it run for 3 minutes and place another mark on your target. Measure the distance traveled in yards and divide by 100; 700 yards = 7kts, 1100 yards = 11 kts, etc.
Can't for the life of me remember the exact formula, forgot after installing RFB. I'm sure someone will barge in here to clarify and fill in the details.  |
1 nautical mile is about 2000 yards long (give or take 1%). So 1
naut'/hour is the same as 2000 yards/hour. Then in 3 minutes (which is 1/20th of an hour) it would have moved 100 yards. So, i.e. in the same 3 minute time a 7 knot target has moved 700 yards. If you need to work with (kilo)meters and knots it's about 3m15s instead of 3 minutes.
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You can determine speed from the scope, but this is beyond me. The marks are 4deg for the large ones and 1 deg for the small ones in low magnification, 1deg / 0.25deg in high magnification. Personally I only use them to determine a good angle to use with the offset dial for a nice spread.
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You can use the scope to get speed but not with those marks. They are really to be used for measuring sizes I think, although not of much use ingame. (Hitman has a cool tutorial somewhere to get AOB with it) The trick to get speed is to make an
imaginary motionless 'line' or perhaps better 'wall' through the sea with your vertical periscope line. You take the time a ship needs to move through this 'wall' from bow to stern (
on it's own speed) and based on it's real length (ID required) you convert that into a speed (yds/sec -> naut's/hour). The requirement is only that you must keep that imaginary wall from moving sideways. If your periscope is looking sideways, and you are moving forward/backward this 'wall' also move sideways because of that, and so you distort the measurement. You must turn your sub
towards or
away from the ship to avoid this, or be at standstill. (and so the ship will be seen at 0 or 180 degrees too) For best accuracy do both. It doesn't really matter how the ship is oriented (AOB) as the speed will be the same no matter what. It is just difficult to time the moment of bow and stern passage when the AOB is near 0 and 180 degrees (ship-parts are hidden from view and only a few pixels appart). Around an AOB of 90 degrees is better but definately not a requirement.