Why must a land navigator account for magnetic declination when using map and compass together?

• A. Magnetic declination is the difference between true north and magnetic north.
• B. It measures the distance to the magnetic pole.
• C. It is the rate of change of declination with latitude.
• D. It is the angular difference between grid north and magnetic north.

Answer: (A)

When you navigate with a map and a compass, the compass points toward magnetic north, while the map is usually oriented to true north. The angle between those two references is magnetic declination, and you must account for it so your compass readings line up with the map.

That’s why the correct idea is that magnetic declination is the difference between true north and magnetic north. In practice, you adjust your bearing by this declination: if declination is east, add it to a magnetic bearing to get the true bearing; if it’s west, subtract it. This adjustment lets you plot your course correctly on the map and ensures your direction aligns with the terrain you’re navigating. Declination varies by location and slowly changes over time, so checking an up-to-date value on the map or a trusted source is important.

The other statements describe related ideas but not what magnetic declination is: it’s not a distance to the magnetic pole, it’s not the rate of change with latitude, and the angular difference between grid north and magnetic north refers to grid variation, a separate concept.