I use true wind in combination with the GPS to navigate. Being on a
Swan 48 with B&G instruments that using the SOG from the GPS, all you
need to do is to convert between north and magnetic (if your navigating
by magnetic). On a boat with an ST60, I also have to compensate for
inaccuracies in the paddle wheel (I use a measured mile) and compensate
for current (i get a vague idea comparing paddle wheel with GPS SOG)
.... which is a lot of work, and then at that not possible 1/2 the time,
as half the boats I have sailed recently report zero (0) on the
Paddlewheel when the actual speed over water is under 3 knots (light
winds) (the owners tell me they use the GPS, and are not motivated to
maintain paddlewheels).

I figure on my own boat, I would like to get a real true wind, without
any hassel's. I was thinking that I could get the ST60 to use the SOG
from the GPS, but that isn't an option, and Raymarine isn't yet
motivated to make changes. The way they compute it, as stated in this
post, can be off my more than 60 degrees (as published "Establishing
more truth in true winds", 13 October 1997, Shawn R. Smith, Mark A.
Bourassa, and Ryan J. Sharp in )

Dan