I don't understand the reference to the paddlewheel rgnmstr. True wind
direction = wind direction (true north) if the boat was anchored at a
point on the water, e.g. not relative to the boats movement or water
current. To achieve this (with the boat in motion), you need the
apparent wind & speed, SOG (from the GPS) and ship heading (true north)
from your flux gate (COG from GPS introduces error) to get a close
approximation, and a little more accuracy can be had if you include
adjustments for angle of heel error, heading error (compensate for mast
& sail induced air flow), a yaw sensor on the mast, etc ... oh yea, and
you need an instrument package that uses this, some like Raymarine wont
use SOG from the GPS.