Originally Posted by old-sailer
Lets not get off track, this has nothing to do with my question.
GPS data has nothing to do with true to apparent wind. You need (1) the wind speed, (2) the wind direction relative to the craft, (3) the speed of the craft. The ST40 knows the direction of the wind and the speed of the wind and that's all that is required for true wind. It then needs the craft speed. Then it calculates baed on the formula.
Yeah, you're right -- apologies humbly rendered...