Hi Bigreg, just noticed this while testing my Soundman orders that I'm currently Implementing.
(Something you possibly can fix - given your love for needles

)
First if we go the Hydrophone and rotate the needle to 0 degrees you'll notice the Bearing in the hydrophone notepad reads 180 degrees.
( A difference of 180 Degrees

).
Now using it in game:
Using the Nearest Sound Contact or Follow Nearest Sound contact commands in my officer orders. The soundman notified me a sound contact at 041 degrees. I rotate the needle to 041 degrees (No Sound there), I continue to rotate to approx 220 degrees (Guess what we got a sound here).
Also The note pad is reading 042 degrees at the point I'm getting the loudest sound return. (So the Notepad and the Soundmans report in the message log both are saying +/-040 degrees (Perfect).
But the needle is reading approx 220 degrees, so the needle is placed on the hydrophone 180 degrees of centre

.
Can this be fixed

, I don't think its something i caused during modding but its possible.
Can anyone else confirm there hydrophone reading off by 180 degrees.