What must be determined at each observing location to convert wind direction from magnetic to true?

• A. True North Variation
• B. Local Magnetic Variation
• C. Wind Correction Factor
• D. Magnetic Declination Variation

Answer: (B)

To convert wind direction from magnetic to true you must know the local magnetic variation at the observing location. Magnetic variation is the angle between magnetic north and true north, and it varies by location and over time. With that local variation, you adjust the magnetic wind direction to get the true direction: if the variation is east, add it; if west, subtract it. For example, a magnetic wind direction of 270 degrees with a local variation of 10 degrees east becomes 280 degrees true. If the variation is 12 degrees west, the true direction would be 270 minus 12, or 258 degrees. This local variation is the specific factor you need at that location to translate magnetic references to true references.