Your vessel is on a course of 358°T at 19 knots. At 0316 a light bears 024.5°T, and at 0334 the light bears 043°T. At what time and at what distance off will your vessel be when abeam of the light?
• Use the basic speed–distance–time formula: Speed = Distance / Time to find how far you travel between 0316 and 0334 at 19 knots • Understand that "abeam of the light" means the light is 90° from your ship’s heading (on the beam) • Think about how two bearings to a fixed object and the distance run between them can be used like a running fix to find the closest point of approach (CPA) and its time
• What is your vessel’s true course, and therefore what true bearing will the light have when it is exactly abeam on your starboard side? • How many miles do you travel between 0316 and 0334 at 19 knots, and how can you use that run together with the two observed bearings to construct (or imagine) a running fix triangle? • Once you determine the geometry of the triangle between the light and your track, how can you find both the distance off at abeam and the additional time needed from 0334 until that abeam point?
• Be sure you compute the distance run between 0316 and 0334 correctly using the speed–distance–time formula, with time converted to hours • Confirm you are using true bearings (not relative) and that "abeam" corresponds to a bearing 90° from your course line • Before choosing an answer, check that both your time after 0334 and the distance off at abeam are consistent with the geometry you constructed or visualized
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