Section 7. Installation
The EPA recommends hourly standard deviation of horizontal wind direction
(sigma theta) be computed from four fifteen-minute sub-intervals.
7.9.22.2.1 Measured Raw Data
•
S
i
: horizontal wind speed
•
Θ
i
: horizontal wind direction
•
Ue
i
: east-west component of wind
•
Un
i
: north-south component of wind
•
N: number of samples
7.9.22.2.2 Calculations
Input Sample Vectors
Figure 76. Input Sample Vectors
In figure
Input Sample Vectors
(p. 298),
the short, head-to-tail vectors are the input
sample vectors described by s
i
and Θ
i
, the sample speed and direction, or by Ue
i
and Un
i
, the east and north components of the sample vector. At the end of data-
storage interval T, the sum of the sample vectors is described by a vector of
magnitude U and direction Θu. If the input sample interval is t, the number of
samples in data-storage interval
T
is
N = T / t
. The mean vector magnitude is
Ū =
U / N
.
Scalar mean horizontal wind speed, S:
where in the case of orthogonal sensors:
Unit vector mean wind direction,
298
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 ...
Page 458: ...Section 8 Operation 8 8 2 Run Stop Program Figure 120 Run Stop Program 458 ...
Page 460: ...Section 8 Operation Figure 122 File Edit 460 ...
Page 461: ...Section 8 Operation 8 8 4 PCCard Memory Card Display Figure 123 PCCard CF Card Display 461 ...
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