For determining navigation routes, which tool is primarily used to correct magnetic declination on a map?

The declination diagram is the correct tool for correcting magnetic declination on a map because it provides the necessary information to account for the difference between true north and magnetic north. Magnetic declination varies by location and can change over time, so navigation requires accurate adjustments to ensure that the compass readings align properly with true north.

On a map, the declination diagram shows the angle of declination specific to that map area and allows navigators to make precise corrections to their headings when using a compass. This adjustment is crucial for effective navigation, especially in environments where accurate positioning is essential, such as wilderness areas or during search and rescue operations.

While other tools like GPS can provide coordinates and direct navigation without needing to account for declination, they do not directly address the need to adjust compass readings based on local magnetic variations. Topographic maps and compasses are valuable navigation tools as well, but they do not provide the specific declination correction needed for accurate navigation like a declination diagram does.