Chart Navigation & Plotting · Compass — Amplitude
You observe the sun on the celestial horizon bearing 110° per standard compass; the computed true amplitude gives a true bearing of 099°. With variation of 8°W, what is the compass deviation?
- A19°E
- B3°E
- C11°W
- D3°W✓ Correct
Explanation
Total compass error = true (099°) − compass (110°) = −11°. Because the compass reads higher than true, the error is westerly: 11°W. Compass error = variation + deviation, so deviation = 11°W − 8°W = 3°W.
Authority: Bowditch (Pub. No. 9), amplitude; compass error and deviation
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