On 22 November your vessel is enroute from Accra, Ghana to Montevideo, Uruguay. You are on course 240°T and making a speed of 15.0 knots. Your 1129 DR position is LAT 28°25.0'S, LONG 42°40.0'W. You observed 3 celestial bodies. Determine the latitude and longitude of your 1137 running fix.
• Convert speed and time into distance run between 1129 and 1137 • Resolve motion on a given true course into changes in latitude (north/south) and longitude (east/west) • Recognize how a running fix will shift from the DR position over a short time interval
• From 1129 to 1137, how many minutes elapse, and how many nautical miles does the ship travel at 15.0 knots? • On a course of 240°T, are you moving more toward the south or the north, and more toward the east or the west? What does that do to the signs of the changes in latitude and longitude? • Looking at the answer choices, which ones show a position that is consistent in both direction and reasonable distance from the 1129 DR position for that short run?
• Make sure the distance run in 8 minutes at 15.0 knots is small (on the order of a few miles, not tens of miles). • Check that the chosen answer’s latitude change matches the expected north/south movement on course 240°T. • Check that the chosen answer’s longitude change matches the expected east/west movement on course 240°T and is of a realistic size for about 2 NM of motion at this latitude.
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