🔍 Key Concepts

• Relative motion of bearing lines as your vessel moves on a straight course • The relationship between change in true bearing and the distance run to calculate closest point of approach (CPA) or distance abeam • Using basic trigonometry or the 4-bearing/2-bearing running fix idea to find distance off when a mark is abeam

💭 Think About

• Draw your vessel’s track and plot the two bearings from the same position line. How does the bearing change as you move along your course? • Think about the angle between your course (096°T) and each bearing to the light. How can that angle help you relate distance run to distance off? • Once you find the distance run between the two bearings, how can you use the angles to that light to form a right triangle and solve for the distance abeam?

✅ Before You Answer

• Compute the time run between the two observations and convert it to hours before finding distance run at 17 knots • Check the angle on the bow for each bearing (difference between course and bearing) and be sure you’re using the correct angle inside the triangle • Verify that the final distance off abeam is less than the distance run between the two bearings, and that your selected answer is consistent with the geometry of the situation