29 Part 50 of IEC 61400 specifies methods and requirements for the application of instruments to 30 measure wind speed (and related parameters, e.g. turbulence intensity). Such measurements 31 are required as an input to some of the evaluation and testing procedures for wind energy and 32 wind turbine technology (e.g. resource evaluation and turbine performance testing) described 33 by other standards in the IEC 61400 series. Part 50-1 is applicable specifically to the use of 34 wind measurement instruments mounted on meteorological masts, turbine nacelles or turbine 35 spinners which measure the wind at the location at which the instruments are mounted. This 36 document excludes remote sensing devices which measure the wind at some location distant 37 from the location at which the instrument is mounted (e.g. vertical profile or forward facing 38 lidars).