What term describes the difference between magnetic north and true north?

Magnetic variation, also known as magnetic declination, refers to the angular difference between magnetic north, which is determined by the magnetic field of the Earth, and true north, which is the direction along the Earth's surface toward the geographic North Pole. This variation is critical for pilots to understand because it affects navigation. When using a magnetic compass, a pilot must account for this difference to avoid navigation errors, as maps and charts usually depict true north.

While magnetic declination and magnetic variation are closely related, the correct terminology focuses on the concept of variation as it applies to the difference over geographic locations. This helps pilots accurately convert compass directions to true headings necessary for precise navigation. The values for magnetic variation can change over time and across different geographic locations, which is why they are typically included on aeronautical charts.