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Selected the median value of Dir.10m + 230.1 - dir.3m. At FAR this is 3.0 1 +/- 5.4 3 degrees. See attached plot. The 2D sonic is aligned with the boom, so need to add the boom direction, 230.1, minus the offset of 3.1 degrees, or 227 degrees to the 2D wind direction data.
At FLR the 2D sonic was pointed nominally north, but must be off by 180 degrees. The median value of Dir.10m + 180 - dir.3m is 6.6 +/- 5 deg (10m speed > 2 m/s). Thus need to add 180 - 6.6 = 173.4 deg to 2D wind direction data. 