noun
- Lines on a map connecting points of equal magnetic declination (the angle between true north and magnetic north).
Usage: technical; cartography; navigation; plural form; singular is isogonic
Examples
- Navigators use isogonics on nautical charts to account for the difference between true and magnetic north.
- The isogonics on this map show how magnetic declination varies across the region.
- Pilots must understand isogonics to correctly interpret compass readings during flight.
- The isogonics shift over time as Earth's magnetic field changes.
- Modern GPS systems have reduced the practical importance of isogonics for navigation.