Definition

Noun

  • Lines on a chart connecting points of equal magnetic variation on a compass.

Origin

19th century. From the Greek word isogon, meaning equal angle.

Comments

Edmund Halley published the first chart to incorporate isogonic lines in 1701.

References

Kemp, P. (1994). The Oxford Companion to Ships and the Sea. Oxford University Press.

Rogers, J.G. (1985). Origins of Sea Terms. Mystic Seaport.