At 0550, engineering repairs are complete and speed is increased to 9.6 knots. At 0630, Falkner Island Light bears 023°pgc and Horton Point Light bears 097°pgc. From your 0630 fix you steer to make good a course of 086°T while turning for 9.6 knots. At 0700, Falkner Island Light bears 336.0°pgc and Horton Point Light bears 105.5°pgc. The radar range to the south tip of Falkner Island is 5.7 miles. Which statement is TRUE?
• Use the time-speed-distance relation: Speed = Distance / Time to compare intended vs actual performance. • Plot or visualize the fixes at 0630 and 0700 using the bearings to Falkner Island Light and Horton Point Light to find the track made good. • Determine the set and drift of current by comparing the course and speed through the water (what you steered/turned for) with the course and speed made good (what actually happened).
• How can the two pairs of bearings (at 0630 and 0700) be used to find your positions and therefore the distance and true course between them? • Once you know the distance run in 30 minutes, what simple calculation gives you the speed made good, and how does that compare with 9.6 knots? • After finding course and speed made good, what vector must be added to your intended course and speed through the water to arrive at the actual track over the ground?
• Be sure you convert elapsed time from minutes to hours correctly when using the speed formula. • Confirm that you are using true courses when describing course made good and current set, and knots for all speeds including current drift. • Before choosing an answer, check whether the computed speed made good, course made good, and current set and drift are all consistent with each other; at most one option should fully match your calculations.
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