I hear the term "Class 1," but I am not exactly sure what this classification means. What impact does this classification have on the data?

According to the IEC-61400-12-1 standard, a classification index of 1.7A (A for flat terrain; B for complex terrain) equates to a standard uncertainty of 0.1 m/s (1%) at 10 m/s wind speed. Standard uncertainty is an estimate of the uncertainty of the anemometer subject to three influence parameters: off-axis response, friction, and aerodynamic rotor response due to turbulence. It should be noted that IEC-61400-12-1 has a requirement only for type A terrain and a suggestion of 2.5 class index for type B terrain.

Following the methods outlined in the Accuwind Study, the classification indices of the Class 1 Anemometer is determined to be 1.01A for flat terrain, which equates to a 0.06 m/s data uncertainty at 10 m/s.