At 0741 you are still steering a course of 206° true, with a speed of 18 knots. At this time you observe Cape Charles Lighted Bell Buoy "14" bearing 222°T and Hog Island Lighted Bell Buoy "12" bearing 015°T. What were the set and drift experienced since 0725?
• Set and drift as the difference between DR (dead reckoning) and EP (estimated position) • Plotting lines of position (LOPs) from two bearings to obtain an EP • Converting time difference and distance between DR and EP into a current vector
• From 0725 to 0741, what DR position do you reach on course 206°T at 18 knots? (First find distance run, then plot it.) • How do the two simultaneous bearings from Cape Charles Buoy "14" and Hog Island Buoy "12" give you an EP on the chart? • Once you have DR and EP, in what direction did the current push you, and how far, over that time interval?
• Be sure you compute the run correctly: speed × time in hours between 0725 and 0741 • Check that both LOPs from the buoys are plotted from the correct charted positions of the aids to navigation • When finding set and drift, confirm: set = direction of DR→EP vector (true), drift = distance DR→EP ÷ time (knots)
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