At 1930, your vessel is between York River Entrance Channel Lighted Buoys "1YR" and "2". From this position, you change course to 142°pgc at an engine speed of 8.0 knots. At 2001, you obtain the following information: Chesapeake Channel Tunnel North Light bearing- 131°pgc Thimble Shoal Light bearing - 248°pgc What were the set and drift between 1930 and 2001?
• Plotting lines of position (LOPs) from bearings to fixed aids to navigation to find an observed position • Determining course and distance made good (CMG and DMG) versus ordered course and engine speed through the water • Using the current triangle to find set (direction) and drift (speed) from the difference between DR and observed position
• After plotting your DR track from 1930 to 2001, where is your DR position compared to the fix obtained from the two bearings? Think about the direction from DR to fix. • How does the time interval (31 minutes) and the scale of the chart help you figure out the speed of the current affecting the vessel? • When you draw the current vector from the DR position to the fix, in which compass direction does it point, and how long (in nautical miles) is that line?
• Confirm you convert the 31‑minute run at 8.0 knots into nautical miles correctly before plotting the DR position. • Make sure you plot both bearings as reciprocal bearings on the chart (from the aids to your vessel), not as headings from the vessel. • Measure the distance and direction from DR position to the fix carefully; convert the distance over 31 minutes to knots before matching it to the answer choices.
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