The angular difference between true north and magnetic north is called which term?

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

Answer: (A)

The main idea here is the horizontal separation between true north (geographic north) and where the Earth’s magnetic field points (magnetic north). That difference is called magnetic variation. It tells you how far off a true bearing is when you look at it on a magnetic compass, and whether you need to add or subtract degrees to convert between true and magnetic headings. It’s shown on charts as variation in degrees east or west and changes slowly over time with the geomagnetic field.

Magnetic deviation refers to errors caused by the aircraft’s own magnetism affecting the compass, not the global difference between true and magnetic north. Magnetic inclination (dip) is the tilt of the magnetic field downward from the horizontal, not the horizontal angular difference. Declination is a term you’ll sometimes see used interchangeably with variation, but in aviation practice the standard term on charts and for navigation is magnetic variation.