Isogonic lines

Isogonic Lines: Magnetic Variation Reflected on Aeronautical Charts

Isogonic lines are a set of lines drawn on aeronautical charts that help to connect points with the same magnetic variation. This is crucial for pilots who use aircraft compasses to navigate accurately and efficiently. Magnetic variation is the difference between true north (the direction towards the geographic North Pole) and magnetic north (the direction towards which a compass points).

Isogonic lines reflect the magnetic variation, which varies from place to place, because the Earth’s magnetic field is not homogeneous. The variation depends on factors such as the location and altitude of the aircraft, as well as the intensity and direction of the geomagnetic field. Therefore, isogonic lines must be periodically updated based on measurements taken by magnetic sensors and instruments.

Isogonic lines form a complex network of curves that resemble contour lines on a map. They are usually drawn at intervals of 5 or 10 degrees, and they converge at points called agonic lines where the magnetic variation is zero. Agonic lines are significant because they indicate the true north, which is essential for navigating over long distances.

In summary, isogonic lines are a cartographic feature that shows the magnetic variation on aeronautical charts. They help pilots to navigate accurately and safely by aligning their compass readings with the magnetic field. Isogonic lines are an essential tool for aeronautical navigation, and they require periodic updates to reflect changes in the geomagnetic field.