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
Apparent wind of the true wind" minus the "velocity of the object". In sailing, "apparent wind" is the speed and direction of wind indicated by a wind instrument (anemometer) on a "moving" craft (on water, land or ice) in undisturbed air. It is composed of the "combined" speeds and directions of the craft and wind observed by a "stationary" wind instrument—the "true wind". A true wind coming from the bow increases the apparent wind induced by the speed of the craft, coming from the stern it decreases apparent wind, and coming from the side the apparent wind angle and speed change according