🔍 Key Concepts

• Relationship between gyro error, variation, and true heading • How to interpolate deviation between two known compass headings • Difference between east and west errors and their signs in calculations

💭 Think About

• First convert the given magnetic compass heading and gyro information into a common reference (usually true). What sequence of corrections do you apply? • Locate the two table headings on either side of 104°. How would you estimate the deviation in between those values? • How does a 2° E gyro error affect the reading of the gyro compared to true? Does the gyro read higher or lower than true?

✅ Before You Answer

• Be clear on the sign convention: East errors are usually considered positive and West errors negative in many formulas—verify what you use and stay consistent. • Confirm which headings in the table are per ship’s compass (PSC) and which are per gyro compass (PGC) and how that relates to the 104° magnetic compass heading. • After interpolation, double‑check whether the final deviation should be labeled E or W based on whether the compass is pulled toward east or west of magnetic north.