In navigation, what is the primary use of declination?

Declination is a critical component in navigation, specifically regarding the relationship between magnetic north and true north. It refers to the angle difference between these two directions at a specific location on the Earth's surface. Understanding declination is essential for navigators because magnetic compasses point to magnetic north, which can differ from the geographic true north depending on where one is on the planet. By accounting for this angular difference, navigators can correct their compass readings to obtain true headings, allowing for accurate navigation.

The other options focus on aspects of navigation but do not specifically relate to the function of declination. Calculating distances typically involves other navigational methods, determining routes considers various factors including terrain and navigational aids rather than just declination, and elevation changes are more concerned with topographical features than with the angular measurement of magnetic versus true north.