While on a course of 216°pgc, a light bears 12° on the port bow at a distance of 11.2 miles. Which course should you steer to pass 2 miles abeam of the light leaving it to port?
• Relative bearings and converting a relative bearing on the bow into a true/pgc bearing of the object • Using a right triangle / off-track distance to find the course that gives a required closest point of approach (CPA) abeam distance • Understanding that "pass 2 miles abeam" means the perpendicular distance from your track line to the light is 2 miles
• First, sketch your present course line (216°pgc) and plot the light using the given relative bearing and distance. What is the pgc bearing of the light from the ship? • Once the light is plotted, think about the line you must steer so that the minimum distance from that line to the light is 2 miles, with the light on your port side. How do you relate this to a right triangle with hypotenuse equal to the distance at the moment you alter course? • Compare the small differences between the answer choices and your original course. Should the new course be to the left or right of 216°pgc to keep the light 2 miles on your port side?
• Confirm you correctly converted the 12° on the port bow into a true/pgc bearing of the light from the ship. • Verify that the distance you use as the hypotenuse in your right triangle is the distance at the point of course change (11.2 miles), not the 2‑mile CPA. • Check that the course you choose would make a line of position where the perpendicular distance from that line to the light is exactly 2 miles, with the light lying to port, not starboard.
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