Isogonic lines

Isogonic lines are the lines drawn on a map connecting points of equal magnetic declination. Magnetic declination is the angle between magnetic north and true north at a given location on the Earth's surface.

Explanation:
Isogonic lines are used to represent the variation in magnetic declination across the Earth's surface. They help in understanding the magnetic field of the Earth and are important in navigation and surveying.

Definition:
Isogonic lines are the lines on a map that connect points with the same magnetic declination. They are also known as isogons or agonic lines.

Magnetic Declination:
Magnetic declination is the angle between magnetic north and true north, measured in degrees. The magnetic north pole and the geographic north pole are not aligned, and the difference between the two is the magnetic declination. This declination varies depending on the location on the Earth's surface.

Mapping Isogonic Lines:
Isogonic lines are drawn on maps to indicate areas with the same magnetic declination. These lines are drawn by connecting points with the same declination value. The lines are often curved and can be closely spaced in some regions, indicating rapid changes in declination.

Use in Navigation:
Isogonic lines are important for navigation, especially when using a compass. A compass needle aligns itself with the Earth's magnetic field and points towards magnetic north. However, since magnetic north is not the same as true north, it is necessary to correct for the declination. By knowing the isogonic lines and the associated declination values, navigators can determine the correction needed to align their compass readings with true north.

Conclusion:
Isogonic lines represent points of equal magnetic declination on a map. They help in understanding the Earth's magnetic field and are useful for navigation purposes. By connecting points with the same declination, isogonic lines provide a visual representation of the variation in magnetic declination across the Earth's surface.