While on a course of 066° pgc, a light bears 18° on the port bow at a distance of 12.3 miles. What course should you steer to leave the light 4 miles abeam to port?
• Relative bearings vs. true (pgc) course • Right triangle formed by your track and the line of bearing to the light • Using basic trigonometry to keep a fixed abeam distance from an object
• Sketch the vessel’s initial position, the light, and the desired closest point of approach where the light will be 4 miles abeam to port. How does this form a right triangle? • What is the difference between the current distance (12.3 miles) and the desired abeam distance (4 miles), and how does that difference relate to the sides of the triangle? • How can you convert the relative bearing of the light (18° on the port bow) into a track angle that ensures the light will pass abeam at 4 miles to port?
• Be clear on the meaning of 18° on the port bow (relative bearing from the ship’s head). • Remember that abeam means 90° to your course at the closest point of approach. • Double-check which angle in your triangle corresponds to the change of course from 066° pgc before choosing the final course.
No comments yet
Be the first to share your thoughts!