At 1126 you take the following set of bearings: Chesapeake Light bears 143°T Cape Henry Light bears 254°T What was the current encountered since your 1042 fix?
• Set and drift of current as the difference between DR (dead reckoning) position and fix • Using cross-bearings of two lights to obtain a fix at a specific time • Calculating current speed: Drift (knots) = Distance (nm) / Time (hours)
• From your 1042 fix, advance your course and speed to 1126 to get your DR position. Where would you be with no current? • Plot the 1126 bearings of Chesapeake Light and Cape Henry Light to obtain your actual fix at 1126. In what direction does the vector from DR to fix point? • Measure the length of that DR-to-fix vector in nautical miles and compare it to the elapsed time between 1042 and 1126. What current speed does that give?
• Be sure your bearings are plotted as TRUE on the chart (convert from relative or magnetic if needed). • Double-check the elapsed time between 1042 and 1126 in hours (including decimals) before computing drift. • Confirm that your set is expressed as the direction toward which the current is flowing (in degrees true) and that your drift is in knots, rounded to the nearest tenth as in the choices.
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