Meteorology · Instruments — Anemometer Correction
A ship's anemometer measures the wind relative to the moving vessel. To report the true wind you must:
- AVectorially combine the measured (apparent) wind with the vessel's own course and speed✓ Correct
- BSimply double the reading
- CSubtract the barometric pressure
- DUse the reading directly with no correction
Explanation
What the anemometer senses is the apparent (relative) wind. The true wind is found by vector subtraction of the ship's velocity from the apparent wind — graphically with a maneuvering board or by computation — before logging or reporting it.
Authority: Bowditch (Pub. No. 9), wind observation; WMO
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