Well, for starters, if you don't have a boat
speed sensor, the B&G does not have the data it needs to calculate true wind speed. It can only read its wind sensor, so you are always getting apparent wind. Now, it is certainly true that the GPS
can give you SOG, and that this is more useful than a paddlewheel that gives you speed through the water
, but, on at least older units, that's what they usually require. Your manual may well tell you the sensor that is needed.