Magnetic variation (declination)
Radio & navigation
Magnetic variation is the angle between true north and magnetic north at a location. It is different from compass deviation, which is caused by magnetic influences within the aircraft.
- German term
- Missweisung (magnetische Deklination)
Aeronautical charts show local variation and its change over time. To convert a true direction to magnetic, subtract easterly variation and add westerly variation: a true heading of 090° with 3° east variation is 087° magnetic. Compass deviation is a separate correction from the aircraft’s compass correction card; wind correction is separate too.
In practice
Check whether your chart, planning tool and navigation display use true or magnetic directions. Apply variation once, not twice, and use up-to-date chart information.
Related terms
Official sources
Content reviewed: 2026-11
For general information only. Always use official sources, your aircraft's flight manual and current national rules for flight decisions.