🔍 Key Concepts

• Compass deviation: the error caused by magnetic influences on board the vessel (ship’s own magnetism) • Difference between variation (Earth’s magnetic field vs true north) and deviation (ship’s magnetic field vs magnetic north) • How deviation cards are made: deviation listed for each heading

💭 Think About

• Ask yourself: Which of these choices would change how the ship’s own magnetism interacts with the compass? • Think about when you look at or use a deviation table on a vessel: what column do you look up first? • Which factors mainly affect the Earth’s magnetic field, and which affect only the ship’s magnetic field relative to the compass?

✅ Before You Answer

• Be clear on the definition of deviation vs variation before picking an answer • Recall what information is printed on a typical compass deviation card • Eliminate any options that relate mainly to position on Earth rather than the ship’s magnetic heading