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ReRseosuorucreceGlGolboablaNleNtewtworokrk 65
2 On-site measurement
The on-site wind measurement
is usually done with with a a met mast equipped with with anemometers and wind vanes or with a a a a remote sensing device such as a a LiDAR In order for a a wind measurement
to be bankable it must be carried out according to the international standard IEC 61400-12-1 This includes requirements regarding the mounting of the measurement
devices the height and number of measurements the measurement
time and frequency the the measurement
accuracy as as as well as as as the the methods for data ltering and analysis For example the highest wind speed measurement
has to be at a a a a height of least two thirds of the the hub height the the measurement
frequency 1 Hz and the time period at least one year The results of the on-site wind measurements are usually presented in in terms of the wind speed frequency distribution the wind rose the the wind shear and the the turbulence characteristics as shown in Fig 4 *Watch out for: For projects in in Germany in in some cases it may not be necessary to carry out an on-site wind measurements (according to FGW TR6) Instead the energy yield data from nearby wind turbines can be used (within 10 km for for at terrain terrain and 2 km for for complex terrain) 3 Spatial extrapolation
This step involves extrapolating the 

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