At 0815: Montauk Pt. Light House is bearing 167°T Shagwong Pt. has a radar range of 4.5 miles Cerberus Shoal "9" Buoy is bearing 284°T If the engine is making turns for 10 knots, what was the set and drift of the current since 0748?
• Set and drift (set is the direction the current pushes you toward; drift is the speed of that current) • Difference between dead reckoning (DR) position and fix to find current • Use of speed made good and time run to find distance traveled
• From 0748 to 0815, how many minutes have passed, and how many nautical miles would you expect to travel at 10 knots with no current? • On the chart, what is your DR position at 0815 based only on course and speed, and how does that compare to your observed/fixed position from the bearings and range? • When you draw the current vector from DR position to fix, what is its true direction (set) and how long is it relative to the time interval (drift)?
• Be sure you measure the time interval correctly in minutes and convert to hours when needed • Measure the current vector from DR to fix, not from fix to DR, when determining set • Compute drift as distance of that current vector divided by time in hours; compare to the answer choices to see which matches your calculated speed and direction quadrant
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