On 28 July your 1937 zone time DR position...

Question 1 / 2066636eea28f7522a1c51adc8

Question 1 of 2066636eea28f7522a1c51adc8

On 28 July your 1937 zone time DR position is LAT 26°13.0' N, LONG 78°27.0' E. At that time, you observe Deneb bearing 048.7°pgc. The chronometer reads 02h 37m 42s, and the chronometer error is 00m 15s fast. The variation is 4°W. What is the gyro error?

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🔍 Key Concepts

• Gyro error vs. variation vs. deviation – know which one is being solved for • Relationship between pgc (per gyro compass), true bearing, and gyro error • Using chronometer time and GHA/Declination to get the true azimuth of a star (Deneb) at a given DR position

💭 Think About

• First, think about how to get the true azimuth of Deneb from the given DR position, date, and time. What sight-reduction or azimuth method would you use? • Once you have the true bearing of Deneb, compare it to the 048.7° per gyro compass. In what direction would the gyro have to be in error so that it reads 048.7° when the star is actually on the true azimuth you computed? • Carefully track the steps: true ↔ magnetic (using variation), and magnetic ↔ gyro (using gyro error). Which conversions do you really need here, and which can you ignore?

✅ Before You Answer

• Verify your chronometer correction and make sure you’re using the correct UTC (Greenwich time) for the sight, not zone time. • Confirm you are interpreting 048.7°pgc correctly as a bearing per gyro compass, not per magnetic compass. • Before choosing an answer, check that the sign of gyro error (E or W) is consistent with your comparison between true and gyro bearings: remember the rule for deciding whether the gyro is easterly or westerly in error.

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Question 1 of 20

2.4°W

2.8°E

3.6°W

3.6°E

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Question 1 / 2066636eea28f7522a1c51adc8

Question 1 of 2066636eea28f7522a1c51adc8

Back

Question 1 of 20

66636eea28f7522a1c51adc8

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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