Which term describes the angular difference between true north and magnetic north?

• A. Deviation
• B. Variation
• C. Magnetic dip
• D. Compass error

Answer: (B)

Variation is the angular difference between true north and magnetic north. True north points to the geographic North Pole, while magnetic north is the direction the compass points at the surface. Because Earth’s magnetic field isn’t aligned with the geographic poles, the compass heading differs from the true heading by a location-specific amount measured in degrees east or west, and this variation can change over time as the geomagnetic field evolves. This is the term used to convert between true headings and magnetic headings in flight planning and navigation. By contrast, deviation is the error caused by the aircraft’s own magnetic interference, magnetic dip (inclination) is how steeply the field points downward toward the Earth, and compass error is a general term for various compass reading errors.