🔍 Key Concepts

• Compass error components: relationship between compass (C), magnetic (M), and true (T) bearings, including variation (V) and deviation (D) • How to use a charted range line (two lights in line) to know the correct true bearing of that line • Sign convention: how E/W variation and deviation affect the conversion between true, magnetic, and compass bearings

💭 Think About

• From the chart, determine the true bearing of the line between Stratford Shoal (Middle Ground) Light and Old Field Pt. Light. • Use the local magnetic variation from the chart to convert between true and magnetic, then compare the resulting magnetic bearing with the compass bearing 200° to isolate deviation. • Decide whether the compass is pointing too far east or too far west compared to magnetic; that tells you whether deviation is east or west and by how many degrees.

✅ Before You Answer

• Verify you are using the correct true bearing of the range (Stratford Shoal – Old Field Pt.) from the chart, not guessing. • Confirm the local variation value and whether it is E or W, and apply the correct sign convention when moving between T, M, and C. • After you compute deviation, double‑check: Does the sign (E or W) match the idea that "east is least, west is best" when comparing compass and magnetic?