Part 50 of IEC 61400 specifies methods and requirements for the application of instruments to measure wind speed (and related parameters, e.g. wind direction and turbulence intensity). Such measurements are required as an input to some of the evaluation and testing procedures for wind energy and wind turbine technology (e.g. resource evaluation and turbine testing) described by other standards in the IEC 61400 series. Part 50-2 is applicable specifically to the use of ground mounted remote sensing wind measurement instruments, i.e devices which measure the wind at some location generally above and distant from the location at which the instrument is mounted (e.g. sodars, vertical profiling lidars). This document specifically excludes other types of RSD such as forward facing or scanning lidars.