On 9 September your 2043 ZT position is LAT 24°18'N, LONG 66°46'W. You observe Polaris bearing 001°pgc. At the time of the observation the helmsman noted that he was heading 031°pgc and 040°psc. The variation is 11°W. What is the deviation for that heading?
• Polaris gives you a true bearing close to true north in the Northern Hemisphere • Relationship between true, variation, deviation, magnetic, and compass headings ("True–Variation–Magnetic–Deviation–Compass") • How to use the observed bearing of Polaris and the ship’s compass heading to back out the deviation
• What is the true bearing of Polaris from your position at this date and time, and how close is that to true north (000°T)? • Once you know the true bearing, how do you step through the sequence True → Magnetic → Compass using the given variation to find what the compass should read with no deviation? • Compare the compass value you computed (no deviation) with the actual psc heading. Is the compass reading too far east or west, and by how many degrees?
• Confirm the correct use of the TVMDC relationship and the sign convention for west variation • Carefully distinguish among pgc (gyro), psc (standard/magnetic compass), and true bearings/headings • Verify whether the difference between the computed compass heading and the observed psc makes the deviation labeled E or W based on whether the compass is "ahead" or "behind" magnetic
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