noun
- Plural of isogony; lines on a map connecting points of equal magnetic declination (the angle between true north and magnetic north).
Usage: technical; geography; cartography
Examples
- Navigators use isogonies on nautical charts to account for the difference between true and magnetic north.
- The isogonies on this map show how magnetic declination varies across the region.
- Surveyors must consult isogonies when conducting fieldwork to ensure accurate directional measurements.