🔍 Key Concepts

• Set and drift definitions and how they relate to DR (dead reckoning) and EP (estimated position) • Using lines of position (LOPs) from lighthouses to determine the actual track over ground • Converting the time interval (1910–1934) into hours to compute a current’s speed in knots

💭 Think About

• How would you plot your DR position at 1910 and your observed position at 1934 using the bearings to Little Gull Island Light and Race Rock Light? • Once you have the DR position and the observed (fix) position at 1934, how do you determine the direction from DR to fix, and what does that direction represent? • After finding the distance between the DR and the fix, how do you convert that distance over the 24‑minute interval into knots?

✅ Before You Answer

• Be sure the set is the direction toward which the current pushes you (from DR to fix), not the opposite. • Double‑check that your time interval from 1910 to 1934 is correctly converted into hours before computing drift (speed). • Verify your distance between DR and fix is in nautical miles, and then confirm that knots = nautical miles per hour.