AMTStandards.orgAviation maintenance

Agonic line

A line drawn on an aeronautical chart along which there is no angular difference between the magnetic and geographic north poles.

Aviation Maintenance Technician Handbook — Airframe, p. G-1

Also defined in 2 more sources

An isogonic line along which there is no magnetic variation.

Helicopter Flying Handbook, p. G-1

An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation.

Pilot's Handbook of Aeronautical Knowledge, p. G-2