What increments are used on a deviation table?

• A. 5 degree increments
• B. 10 degree increments
• C. 15 degree increments
• D. 20 degree increments

Answer: (C)

A deviation table uses fixed heading steps of 15 degrees. This convention comes from how compass deviation is measured and recorded on ships: when the compass is swung, deviations are determined at standard headings spaced about 15 degrees apart, giving a practical balance between detail and simplicity. With the table, you look up the deviation for the nearest 15-degree heading and apply it to correct a magnetic heading toward the true heading. More frequent increments (like 5 or 10 degrees) would require many more measurements and a larger table, while larger gaps (like 20 degrees) would reduce accuracy for day-to-day navigation.