Question 1 of 2921866636eea28f7522a1c51b65c

You swung ship and compared the magnetic compass against the gyro compass to find deviation. Gyro error is 2° E. The variation is 8° W. Find the deviation on a gyro heading of 166°.

PSC PGC 030.5° 020° 061.5° 050° 092.0° 080° 122.5° 110° 152.0° 140° 181.0° 170° 210.0° 200° 239.5° 230° 269.0° 260° 298.0° 290° 327.5° 320° 358.5° 350°

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Question 1 of 29218
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You swung ship and compared the magnetic compass against the gyro compass to find deviation. Gyro error is 2° E. The variation is 8° W. Find the deviation on a gyro heading of 166°.

PSC PGC 030.5° 020° 061.5° 050° 092.0° 080° 122.5° 110° 152.0° 140° 181.0° 170° 210.0° 200° 239.5° 230° 269.0° 260° 298.0° 290° 327.5° 320° 358.5° 350°

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🔍 Key Concepts

• Relationship between gyro heading, true heading, variation, and compass deviation (the classic T–G–M–C relationships) • Meaning of gyro error 2° E and how to correct a gyro reading to obtain true heading • Using nearby entries in a deviation table to estimate deviation at an in-between heading (interpolation)

💭 Think About

• From a given gyro heading and gyro error, what is the true heading? Think about the mnemonic for east/west gyro error (e.g., "gyro least, error east"). • Once you have true heading, how do you use variation 8° W to find the corresponding magnetic heading with no deviation? • Compare the computed magnetic heading with the PSC (standard magnetic compass) value near that gyro heading: does the compass read east or west of magnetic, and by about how much?

✅ Before You Answer

• Be clear on the sign of gyro error 2° E: decide whether you should add or subtract it from the gyro heading to get true. • Apply variation 8° W in the correct direction when converting between true and magnetic (remember how west variation affects magnetic vs true). • Use the PSC/PGC pairs around 166° gyro (on either side of 166°) to judge both the trend and approximate size of deviation; this will help you rule out answers that are too large or with the wrong east/west sign.