Variation refers to which condition?

• A. Compass error caused by the difference in the physical locations of the magnetic north pole and the geographic north pole.
• B. An error in heading due to wind drift.
• C. The angular difference between true north and magnetic north at a location.
• D. A local interference effect near power lines.

Answer: (D)

Variation is the angular difference between true north and magnetic north at a specific location. This is the amount you use to convert between true headings and magnetic headings on charts and in flight. It changes with where you are and over time as Earth's magnetic field evolves, so pilots consult updated variation values on aeronautical charts. The other ideas describe different things: wind drift is heading error from crosswinds, and local interference near power lines is about compass deviation caused by nearby magnetic fields, not the broad location-based difference between true and magnetic north. The notion of a difference in the locations of the magnetic and geographic poles explains why variation exists, but the navigation definition you use is the angular difference at your location.