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

• A. Magnetic variation
• B. Magnetic deviation
• C. Magnetic inclination
• D. Declination

Answer: (A)

The key idea is the difference between where true north points and where the Earth’s magnetic field points the compass. That angular difference at a given location is called magnetic variation. It’s the value you use to convert between true headings (geographic) and magnetic headings for navigation. In many texts this same difference is also described as magnetic declination, but in this context the term used is variation. Magnetic deviation, on the other hand, is the error caused by the aircraft’s own magnetic fields, and magnetic inclination refers to the tilt of the magnetic field lines with depth, not the horizontal difference between true and magnetic north.