Which statement best describes true course and magnetic course?

Which statement best describes true course and magnetic course?

• A. True course is measured relative to true north.
• B. True course is measured relative to true north; magnetic course is adjusted for magnetic variation to account for magnetic north.
• C. True course and magnetic course are the same.
• D. Magnetic north is the sole reference used for navigation.

Answer: (B)

The distinction between true course and magnetic course is fundamental to navigation. True course is the direction you intend to travel relative to true north, a geographic reference. Magnetic course is that same direction but expressed in terms of a magnetic compass, so it must be adjusted for magnetic variation—the angular difference between true north and magnetic north. Variation is what causes the magnetic course to differ from the true course. Because the Earth’s magnetic north is not exactly aligned with its geographic north, charts show the local variation. To go from true to magnetic, you adjust by the variation: if variation is toward the east, you subtract it from the true course; if it’s toward the west, you add it. For example, a true course of 80° with a variation of 10° East becomes a magnetic course of 70°. If the variation were 10° West, the magnetic course would be 90°. The correct statement captures this relationship: true course is measured relative to true north, and magnetic course is adjusted for magnetic variation to account for magnetic north. The other choices either omit the magnetic variation, claim the two courses are always the same, or suggest magnetic north is the only reference used.

The distinction between true course and magnetic course is fundamental to navigation. True course is the direction you intend to travel relative to true north, a geographic reference. Magnetic course is that same direction but expressed in terms of a magnetic compass, so it must be adjusted for magnetic variation—the angular difference between true north and magnetic north.

Variation is what causes the magnetic course to differ from the true course. Because the Earth’s magnetic north is not exactly aligned with its geographic north, charts show the local variation. To go from true to magnetic, you adjust by the variation: if variation is toward the east, you subtract it from the true course; if it’s toward the west, you add it. For example, a true course of 80° with a variation of 10° East becomes a magnetic course of 70°. If the variation were 10° West, the magnetic course would be 90°.

The correct statement captures this relationship: true course is measured relative to true north, and magnetic course is adjusted for magnetic variation to account for magnetic north. The other choices either omit the magnetic variation, claim the two courses are always the same, or suggest magnetic north is the only reference used.