🔍 Key Concepts

• Relationship between gyro error, variation, and true heading • How to get true heading from gyro compass when gyro error is known • Using the PSC–PGC table to determine magnetic compass deviation

💭 Think About

• Start by finding the true heading that corresponds to the given gyro heading, using the known gyro error. How does a 2° W gyro error affect the indicated gyro reading? • Once you know the true heading, combine it with the 8° W variation to find the correct magnetic (compass) heading you should expect without deviation. What is the relation: True–Variation–Deviation–Compass? • Compare the expected magnetic heading for that true heading with the actual PSC listed in the table for the matching PGC (gyro) to see if the compass is east or west of where it should be, and by how much.

✅ Before You Answer

• Be clear on the sign convention: a west gyro error means the gyro reads high or low compared to true? Confirm this before doing any calculations. • Make sure you’re matching the correct pair in the table: for a PSC of 210°, what is the corresponding PGC in the table, and what true heading does that represent once gyro error is applied? • Check whether the compass is east or west of the magnetic heading you’d expect from True and Variation. That will tell you whether deviation is E or W, and its size.