Section 7. Installation
or, in the case of orthogonal sensors:
Resultant mean wind dire
ction, Θu:
Standard deviation of wind direction, σ (Θu), using Campbell Scientific
algorithm:
The algorithm for σ (Θu) is de
veloped by noting, as shown in the figure
Standard
Deviation of Direction
(p. 300),
that
where
Standard Deviation of Direction
Figure 78. 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,
Equating the two expressions for Cos (θ') and using the previous equation for s
i
;
Solving for (Θ
i
')
2
, one obtains;
300
Summary of Contents for CR1000
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Page 457: ...Section 8 Operation 8 8 1 3 Final Memory Tables Figure 119 Final Memory Tables 457 ...
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Page 461: ...Section 8 Operation 8 8 4 PCCard Memory Card Display Figure 123 PCCard CF Card Display 461 ...
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