Installing A Wind Speed Sensor

The goal of installing a wind speed meter (anemometer) is to position it in a location where the wind flows freely and is not influenced by nearby objects. The World Meteorological Organization has set the international standard height for wind measurement devices at 10 meters (33 feet) above ground, with no obstructions at or above this level. Attaining this height can not only be difficult but expensive as well. For most home weather stations installations, striking a compromise is likely the best alternative.

So what are your alternatives? Part of the answer to that is how accurate you want your measurements to be? Wind observations taken at 7 meters (23 feet) are accurate enough for the National Weather Service to accept. For a rooftop installation, the minimum height to avoid anomalous winds caused by the roof itself is 3 meters (10 feet) above the most exposed part. Accuracy of the wind speed indicator is not just a matter of height. Local obstructions like nearby mature trees, houses and buildings all have the potential of impacting anemometer readings. Unfortunately this is the reality of taking wind measurements and the choice of how to deal with it is ultimately yours.

Other requirements for the proper installation of an anemometer include mounting the mast absolutely vertical and orienting the wind direction indicator to true north for accurate wind direction readings. The mast can easily be leveled using a carpenter's bubble level, but orientation to true north is a bit more problematic. The best way to locate magnetic north is by using a magnetic compass and correct to true north by the magnetic declination for your area. Visit the National Geophysical Data Center (NGDC) page that will calculate it for your location. Do not use a GPS to make the determination, the magnetic compass is a more accurate tool to determine true north. If you need to brush up on magnetic declination, visit Wikipedia.