isogone
/ˈaɪsəˌɡoʊn/
noun
- A line on a map connecting points of equal magnetic declination; same as an isogonal line.
- Understanding the isogone helped the surveyor calibrate his equipment.
- Cartographers drew isogones to show magnetic variation across the continent.
- The pilot checked the isogone before flying over the polar region.
Synonyms