What is the significance of the isogonic chart?

The significance of the isogonic chart lies in its capability to illustrate magnetic declination, which is the angle between magnetic north (the direction a compass needle points) and true north (the direction along the Earth's surface towards the geographic North Pole). This chart displays lines, known as isogons, that connect points where the magnetic declination is the same. Understanding magnetic declination is essential for navigation, especially in surveying and mapping, as it allows surveyors to correct for the differences between true north and magnetic north in their measurements, ensuring higher accuracy in positioning and direction. This is crucial in various applications, including land surveying, navigation, and mapping, where precise orientation is necessary for the integrity of the work being performed.

In contrast, the other options do not relate to the primary use of isogonic charts. Rainfall levels are typically represented on climatological maps, geological formations would be done through geological maps, and elevation changes are depicted on topographic maps. Each of these areas has its own specific types of charts and mapping techniques, distinct from the magnetic information provided by isogonic charts.