agonic linea·gon·ic line
an imaginary line on the earth's surface along which true north and magnetic north are identical: at any point along this line, the declination of a compass needle equals zero
An imaginary line on the earth's surface connecting points where the magnetic declination is zero.
Origin of agonic lineGreek ag&omacron;nos, having no angle (a-, without; see a–1 + g&omacron;nia, angle; see diagonal) + –ic.
(plural agonic lines)
- (cartography, navigation) A line on a chart or map joining points of zero magnetic declination.