Wind speed 3 May 1999 is often quoted as the highest-recorded surface wind speed, although another figure of has also been quoted for the same tornado. Yet another number used by the Center for Severe Weather Research for that measurement is . However, speeds measured by Doppler radar are not considered official records. An anemometer is one of the tools used to measure wind speed. A device consisting of a vertical pillar and three or four concave cups, the anemometer captures the horizontal movement of air particles (wind speed). Another tool used to measure wind velocity includes a GPS combined with pitot
Content (measure theory) by This is an outer measure, in other words it has the following properties: The function μ above is an outer measure on the family of all subsets. Therefore it becomes a measure when restricted to the measurable subsets for the outer measure, which are the subsets "E" such that μ("X") = μ("X"∩"E") + μ("X"\"E") for all subsets "X". If the space is locally compact then every open set is measurable for this measure. The measure μ does not necessarily coincide with the content λ on compact sets, However it does if λ is regular in the sense that for