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This spreadsheet includes the calculations described below and is also used to process wind data into the desired output logging interval. For example, if you want data at 15-minute intervals, set up the module to log at 1-minute intervals and then use the spreadsheet to process 15-minute data for average wind speed, maximum wind gust, and average wind direction.
Wind direction is logged as the number of degrees from north, on a scale of 0
to 359. For example, wind from the northeast is logged as 45°. Straight (linear)
averaging does not work for directions going from 359 to 0. For example, if you
apply a linear average of direction readings of 354 and 2 degrees, you get an
average of 178 degrees rather than the correct direction average of 358.
Follow these steps to calculate vector averaging in Excel:
- Calculate sines: SIN(RADIANS(angle)
- Calculate cosines: COS(RADIANS(angle)
- Calculate x and y components as averages over desired range of readings:
x = AVERAGE(sines)
y = AVERAGE(cosines) - Convert the x & y components to degrees:
MOD(DEGREES(ATAN2(y,x)),360)
ATAN2 is arctangent with two arguments
MOD is used to ensure angle is 0–359