You are running coastwise at 14 knots. You sight a lighthouse abeam at 0912. At 0939 the lighthouse is 4 points abaft the beam. What is your distance off at the second bearing?
⢠SpeedâTimeâDistance relationship to find how far you travel between bearings ⢠Meaning of "abeam" and "4 points abaft the beam" on the 32âpoint compass system ⢠The fourâpoint bearing method for finding distance off a fixed object
⢠First convert the time between the two bearings into hours, then use your speed to find how many miles you traveled in that interval. What distance do you get? ⢠On the 32âpoint compass, how many degrees is a "point"? So how many degrees is 4 points? Where is the lighthouse located relative to your beam at the second bearing? ⢠In the fourâpoint bearing problem, the distance run between the beam bearing and the bearing that is 4 points abaft the beam has a specific relationship to your distance off. What is that ratio?
⢠Be sure your time difference is in hours before multiplying by speed in knots ⢠Confirm that 1 point = 11.25° and therefore 4 points = 45° ⢠After finding the distance run between bearings, apply the correct geometric ratio (from the right triangle) to compute the distance off at the second bearing, then compare that result with the answer choices.
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