🔍 Key Concepts

• Relative motion between your vessel and the light when taking two bearings while on a constant course and speed • How to project the vessel’s track to the point of being abeam (bearing difference of 90° from your course) • Using the time and bearing change between two observations to find distance and time of closest point of approach (CPA) or abeam position

💭 Think About

• First sketch the vessel’s track as a straight line and plot the two observed bearings from the light; what geometric figure do these lines form? • How does the change in bearing over the measured time interval relate to the distance run and your distance from the light? • Once you know when you will be abeam of the light, how can you convert the time-to-go at 14 knots into distance off?

✅ Before You Answer

• Confirm your understanding of when a vessel is abeam of a light in terms of the relation between course and bearing • Carefully convert the time interval between the two bearings into hours before using the speed formula • After finding the time of being abeam, recompute the distance run from the last known position to check that the implied distance off is reasonable for the geometry you plotted