Magnetic Variation

Magnetic Variation (or declination) is the angular difference between true north (geographic) and magnetic north at a specific location. Variation changes with geographic position and also slowly shifts over time as Earth magnetic poles move.

Variation is expressed as East or West: at a location with 10°W variation, magnetic north is 10 degrees west of true north. Pilots must account for variation when converting between true and magnetic headings. Variation is shown on navigation charts using isogonic lines (lines of equal variation).