On September 9 your 2130 zone time (ZD +5) DR position is LAT 45°08'N, LONG 82°38'W. At that time, you observe Polaris bearing 000.5°pgc. The chronometer time of the observation is 02h 26m 09s, and the chronometer is 1m 43s slow. The variation is 8.7°W. What is the gyro error?
• Polaris as a latitude check and its relationship to true north • Converting chronometer time to GMT using chronometer error and zone description (ZD) • Relating true bearing vs. gyro bearing to determine gyro error (east or west)
• How do you get the correct GMT of the observation from the given chronometer time, chronometer error, and ZD +5? • Once you have the latitude and the approximate azimuth of Polaris (very close to true north), how does that help you find the true bearing to compare with the 000.5°pgc observed? • When the compass (or gyro) reads a bearing that is different from the true bearing, what rule tells you whether the error is easterly or westerly?
• Be sure you have applied the chronometer error (slow vs fast) in the correct direction when finding GMT. • Confirm you have converted from gyro bearing to magnetic and then to true, or directly compared gyro to true, in a consistent sequence. • Double-check your final step: when the instrument reads higher or lower than the true bearing, is that an east or west error according to the standard sign convention?
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