Apparent wind in knots and degrees. Note that a number of additional factors come into play when converting the measurements from the masthead anemometer into the true wind if a high degree of accuracy is required, including the following: In the presence of a current, the true wind is considered to be that measured on the craft drifting with the water over the bottom, and wind with respect to the sea bed as the "ground" or "geographical wind". The apparent wind on board (a boat) is often quoted as a speed measured by a masthead transducer containing an anemometer and wind vane
Wind-powered vehicle exceed that of the wind, both directly "into the wind" and directly "downwind" by transferring power through a drive train between the rotor and the wheels. The wind-powered speed record is by a vehicle with a sail on it, "Greenbird", with a recorded top speed of . Other wind-powered conveyances include sailing vessels that travel on water, and balloons and sailplanes that travel in the air, all of which are beyond the scope of this article. Sail-powered vehicles travel over land or ice at apparent wind speeds that are higher than the true wind speed, close-hauled on most points of