Which of the following best describes magnetic deviation?

Magnetic deviation is best described as the difference between true north and the heading indicated by the magnetic compass due to interference from local magnetic fields. This interference can be caused by various factors, such as ferrous metal within the aircraft, electrical systems, or other nearby magnetic sources. Because of these influences, the compass may not reflect the true magnetic heading, which can lead to navigation errors.

Understanding magnetic deviation is essential for pilots, as they must account for these discrepancies to ensure their compass readings accurately represent their actual heading. Correctly interpreting this phenomenon helps maintain safe navigation, especially in environments where precision is critical.

The other responses do not accurately capture the essence of magnetic deviation. The angle between magnetic north and geographic north describes magnetic variation, while adjustments for deviations in compasses are essential but do not define what magnetic deviation is. Additionally, while aeronautical charts do contain various measurements, they do not standardly measure magnetic deviation.