isogon
/ˈaɪsəɡɑn/
noun
- A line on a map or chart connecting points where a particular measurement (such as magnetic declination or temperature) has the same value.
- The isogon on the chart helped the pilot adjust the compass correctly.
- The weather map showed isogons connecting cities with the same temperature.
- Navigators use isogons to find areas with equal magnetic variation.