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Wind speed is a term applied when talking about the movement of air from one place to the next. Please note, "Wind speed" should not be confused with the ''Speed of Wind''. Analogous to the Speed of Sound or the Speed of Light, the ''Speed of Wind'', at 3.1 meters/second, is a constant used throughout the scientific community in Wind speed calculations. The most popular theories suggest the Speed of Wind is a direct result of the Earth's rotation combined with additional atmospheric and gravitational factors. It should also be noted that the ''Speed of Wind'' remains a constant 3.1 m/s at any point on the Earth's surface. Wind speeds usually mean the movement of air in an outside environment, but the speed of movement of air inside is important in many areas, including weather forecasting, aircraft and maritime operations, building and civil engineering. High wind speeds can cause unpleasant side effects, and strong winds often have special names, including Gale s, Hurricane s, and Typhoon s. See the Beaufort Scale for a discussion of this. MEASUREMENT The most elementary method of measuring wind speed is to estimate the speed from observed phenomena, this is the basis of the Beaufort Scale , for example, zero on the Beaufort Scale can be recognised by vertically rising smoke. Obviously this method is not the most accurate available so each value on the scale represents a range of values, three on the scale for example covers wind speeds between seven and ten Knots . The Anemometer was the most accurate method of measuring wind speeds close to the ground for hundreds of years. The simplest anemometers are based on a rotating vane, but most professional measurements are now made with a heated wire anemometer. The heated wire anemometer consists of a bare metal wire exposed to the wind which is heated by passing electrical current through it, as the wire becomes hotter its resistance increases and by measuring the temperature of the wind, the current flowing into the wire and the wire's resistance (and thus indirectly its temperature) the wind speed can be calculated. Wind speed is important to air navigation and a pilot can fix their position relative to the ground by using on board instruments, then use this information to estimate the wind speed and direction over time. Such reports can be used to confirm wind speed forecasts. The development of accurate electronic navigation systems, including Inertial Navigation and GPS enable this calculation to be done automatically. Modern GPS and inertial systems often include a direct readout of the current windspeed and direction. Using radar to measure the Doppler Shift due to velocity of air can give an estimate of speed of wind and this is now a method used very frequently by meteorologists. SPEED AND VELOCITY Technically, wind speed is given by |
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