🔍 Key Concepts

• Compass error and its two parts: variation (chart) + deviation (from ship’s compass) • Difference between a true bearing of a transit (from the chart) and a bearing per standard magnetic compass • How deviation depends on the ship’s heading rather than on the bearing observed

💭 Think About

• From the chart, determine the true bearing of the line joining Wolf Trap Light and New Point Comfort Spit Light "2". Compare that with the 048° per standard magnetic compass to find total compass error on that line. • Use your course of 203°psc and any known variation in the area to think about what the deviation on that heading should be. • Ask yourself: does this question let you judge the accuracy of the deviation table, or only the value of deviation/error on one specific heading or bearing?

✅ Before You Answer

• Be clear what psc stands for (per standard compass) and how it relates to per standard magnetic compass in the question wording. • Verify the local magnetic variation from the chart and its sign (east or west) before trying to isolate deviation. • Confirm whether deviation is tabulated by heading (ship’s course) or by the bearing of objects, and how that affects what you can or cannot conclude from a single observed transit.