You are steaming on course 168°T at a speed of 18 knots. At 1426 you sight a buoy bearing 144°T. At 1435 you sight the same buoy bearing 116°T. What is your distance off at the second bearing and predicted distance when abeam?
• Relative motion and bearings when passing a fixed object • The 3-bearing running fix / distance off by doubling the angle on the bow method • Using speed and time run to convert minutes into distance at 18 knots
• How much time passed between the first and second bearings, and what distance did you travel in that time at 18 knots? • How do changing bearings to a fixed object on the same course relate to your track line and your perpendicular distance off? • Which sighting (first, second, or abeam) lets you construct right triangles to find distance off using basic trigonometry or running-fix geometry?
• Convert 9 minutes at 18 knots into distance in nautical miles and keep that number handy • Sketch your course line and plot both bearings from your vessel’s positions to see the geometry clearly • Check which choice’s distances are consistent with the distance run and the change in bearing angles; eliminate any that make the triangle impossible or very distorted
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