🔍 Key Concepts

• Permanent magnetism of the ship’s hull and how it was acquired • How magnetic latitude (moving toward or away from the magnetic equator) affects vertical and horizontal components of the Earth’s magnetic field • Difference between permanent and induced magnetism in a steel vessel

💭 Think About

• Think about what happens to the Earth’s magnetic field lines as you move from higher magnetic latitudes toward the magnetic equator. Do they become more vertical or more horizontal? • Ask yourself: permanent magnetism in the ship is fixed in the ship’s structure—so what actually changes with latitude: the ship’s magnetism, or the Earth’s field acting on it? • Consider whether a deviation card made in higher latitudes would still be valid near the magnetic equator. Would the deviation values get larger, smaller, or stay about the same?

✅ Before You Answer

• Be clear on the definition of permanent magnetism vs induced magnetism and which one changes with latitude. • Verify how the vertical component of the Earth’s magnetic field changes as you approach the magnetic equator and how that affects the heeling and quadrantal errors. • Check whether textbooks say that deviation due to permanent magnetism is largely independent of latitude or is strongly affected by changes in magnetic latitude.