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
Vertical wind tunnel are operated year-round even in cold climates. Various propellers and fan types can be used as the mechanism to move air through a vertical wind tunnel. Motors can either be diesel-powered or electric-powered, and typically provide a vertical column of air between 6 and 16 feet wide. A control unit allows for air speed adjustment by a controller in constant view of the flyers. Wind speed can be adjusted at many vertical wind tunnels, usually between 130 and 300 km/h (80 and 185 mph, or 35 and 80 m/s), to accommodate the abilities of an individual and to compensate for