Re-Asessing Real Navigation...

[Pisces]

Originally Posted by vanjast

...

I've done some measurments on a test mission going NWSE at 2 and 7 knots over 6 hours, in smooth and 'rough'ish' seas, and found I'm getting the same distance traveled on each speed setting.

@ 7 knots for 6 hours = 75.6km (75.6/6 = 12.6 -> 12.6/7 = 1.8)
@ 2 knot for 6 hours = 21.5km => 1.79

How did you set speed? By aligning the indicator on the speed dial to a specific mark? Or by using a special throttle setting (fraction of top MaxSpeed) in: SH3folder\data\Submarine\(subtype)\(subtypename).c fg
[EngineProperties]

The graphical scale on the dial might not be completely linear, and account for the suggestion that 1 SH3 nautical mile is close to 1.8km.

Personally, the 1.852 km/nm value has always seemed accurate to me. I'm sure I would have noticed the 2.8% difference at some point along the years.

[vanjast]

Speed controlled on the indicator dial.

I set the position as accurately as possible and wait for the number indicator to hit '7'. I suppose to do it scientifically I should average out a number of tries... but this is good enough
I tried 7 and 1 knot speeds and the SH3 Nautical Mile in both, came to 1.8Km.

[Karl Heinrich]

I've been doing the same research for my printable SH3 charts and came to the same conclusions - just as we know the "circumference" of SH3 World is 3125km larger than RL.

Shameless chart plug: http://www.subsim.com/radioroom/showthread.php?t=213987

The world is definitely equiretangular - programmed from the 120km long lat, which makes life easier for navigation in some ways. Also allows for easy RL comparisons with my coord method (which is less relevant with your Real Nav chart in-game of course)

Another shameless plug: http://www.subsim.com/radioroom/showthread.php?t=209834

Sea state does affect your speed, just watch the dial. If it moves between 6 and 7 kts I've found 6.5 kts is remarkably accurate for dead reckoning. However I suspect the level of time compression affects this. In still trying to break it to try and find out exactly how much it affects your speed more precisely.

[vanjast]

Originally Posted by Karl Heinrich

Sea state does affect your speed, just watch the dial. If it moves between 6 and 7 kts I've found 6.5 kts is remarkably accurate for dead reckoning. However I suspect the level of time compression affects this. In still trying to break it to try and find out exactly how much it affects your speed more precisely.

What I found (so far) is that the speed dial is representive of your horizontal speed (similar to Ground Speed in aircraft), instead of the 'Indicated/True' speed through the current sea conditions.

Say your indicated Log speed is 7 knots:
1) On a dead flat sea the horizontal speed would also be 7 knots.
2) As the sea conditions get worse, your ship has a vertical speed/movement component, which effectively reduces your horizontal speed, even though your indicated speed is still 7 knots.

SH3 seem to bypass this 2) reality and calculates your horizontal 1) speed for you, no matter which sea conditions. The wobbly Log in high seas.

It'll be nice to have this, wind resistance, currents, tides and seasonal conditions effecting navigation.