Operation
The design of a wind vane is such that the weight is evenly distributed on each side of the surface, but the surface area is unequally divided, so that the pointer can move freely on its axis. The side with the larger surface area is blown away from the wind direction, so that the smaller side, with the pointer, is pivoted to face the wind direction. Most wind vanes have directional markers beneath the arrow, aligned with the geographic directions.
Wind vanes, especially those with fanciful shapes, do not always show the real direction of a very gentle wind. This is because the figures do not achieve the necessary design balance: an unequal surface area but balanced in weight.
To obtain an accurate reading, the wind vane must be located well above the ground and away from buildings, trees, and other objects which interfere with the true wind direction. Changing wind direction can be meaningful when coordinated with other apparent sky conditions, enabling the user to make simple short range forecasts. From the street level the size of many weathercocks is deceptive.
Read more about this topic: Weather Vane
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