Campbell CR800 Series, Operator'S Manual, Page: 206 / 598

Section 7. Installation
206
or, in the case of orthogonal sensors:
Resultant mean wind direction, Θu:
Standard deviation of wind direction, σ (Θu), using Campbell Scientific
algorithm:
The algorithm for σ (Θu) is developed by noting, as shown in the figure Standard
Deviation of Direction
(p. 206),
that
where
FIGURE 48: Standard Deviation of Direction
FIGURE 49: Standard Deviation of
Direction
The Taylor Series for the Cosine function, truncated after 2 terms is:
For deviations less than 40 degrees, the error in this approximation is less than
1%. At deviations of 60 degrees, the error is 10%.
The speed sample can be expressed as the deviation about the mean speed,