Isogonic chart

isogonic chart
a chart that features a system of isogonic lines, each for a different value of the magnetic declination
isogonic line ...

isogonic chart Chart showing isogonic lines properly labeled with their magnetic declination. isogonic line Line joining points on the Earth's surface having equal magnetic declination as of a given date. isopleth map See: map, isopleth ...

See also: Area, Transit, Tide, Survey, Stadia