How do weather services measure wind
Weather stations and airports around the world almost always include an anemometer. Because of ground friction, the wind speed varies with height, so instrumental deployment is set at a standard height of 10 metres in open rural areas. This may require some adjustment in urban or forested areas. In fact, measuring accurate wind speeds above tree canopies is particularly difficult. There is quite an art in correctly positioning the instrumentation.
Thousands of such anemometers and direction sensors are deployed on nearly every continent, and the results are part of the routine reporting. Such reporting may be every 24, 12, or 6 hours, or even shorter periods down to and including 'continuous'. Then comes the number crunching, in which the strength and direction is gridded and plotted on what appears to be a uniform distribution of points. In reality it is very far from a uniform distribution.  

With the introduction of increasing numbers of wind farms higher elevation wind measurements are becoming more important.