An imaginary line around the earth passing through both the north pole and the north magnetic pole, at any point on which a compass needle points to true north.‘Navigators on these so-called agonic lines do not need to make the usual correction to their compasses.’
- ‘Extended lines that mark the constant magnetic declination away from the agonic line are called isogonic lines.’
- ‘When using a compass east of the agonic line, the needle points in a direction that is west of true north.’
- ‘The agonic line goes through Wisconsin near my home but I still have a 1.5 degree east error.’
- ‘West of the agonic line, the needle points east of true north, and has an easterly or positive declination.’
Mid 19th century from Greek agōnios, agōnos (from a- ‘without’ + gonia ‘angle’) + -ic.
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