Anemometer other forms of mechanical velocity anemometer is the "vane anemometer". It may be described as a windmill or a propeller anemometer. Unlike the Robinson anemometer, whose axis of rotation is vertical, the vane anemometer must have its axis parallel to the direction of the wind and therefore horizontal. Furthermore, since the wind varies in direction and the axis has to follow its changes, a wind vane or some other contrivance to fulfill the same purpose must be employed. A "vane anemometer" thus combines a propeller and a tail on the same axis to obtain accurate and precise wind speed and
Haar measure nontrivial but the modular function of formula_3 is trivial. The quotient of these cannot be extended to any character of formula_3, so the quotient space formula_114 (which can be thought of as 1-dimensional real projective space) does not have even a semi-invariant measure. Using the general theory of Lebesgue integration, one can then define an integral for all Borel measurable functions formula_84 on formula_3. This integral is called the Haar integral. If formula_11 is a left Haar measure, then for any Haar integrable function formula_84 on formula_3. This is immediate for indicator functions, being essentially the definition of left invariance.