🔍 Key Concepts

• Compass deviation is the error caused by magnetic influences on your vessel, not by the earth's magnetic field itself • Relationship between compass heading, magnetic heading, and deviation (Magnetic = Compass + Deviation) in standard sign convention • How we assign east (+) and west (-) to deviation in common navigation formulas

💭 Think About

• Start with the standard formula that links compass heading, deviation, and magnetic heading. Rearrange it so deviation is on one side and compare magnetic vs compass values. • Ask yourself: if the magnetic heading number is larger than the compass heading number, must deviation be positive or negative in that formula? • Once you decide if deviation is positive or negative, match that sign to its traditional direction name (east or west).

✅ Before You Answer

• Write the formula explicitly: M = C + Dev (using the common sign convention) and plug in simple numbers where M > C to see what sign Dev needs. • Confirm which direction deviation is labeled as positive (east) and which is negative (west) in your study materials. • Double-check that you are not confusing variation (difference between true and magnetic) with deviation (difference between magnetic and compass).