At 1516 your position is LAT 41°11.3'N, LONG 71°48.6'W. You are on course 300° per standard magnetic compass at 9.4 knots. At 1600 your position is LAT 41°14.0'N, LONG 71°58.1'W. What were the set and drift?
• Set and drift definitions (set = direction current pushes you; drift = speed of that current) • Plotting an EP (estimated position) from course and speed, and comparing it to the fix • Using time difference to convert miles of offset into knots
• First, from 1516 to 1600, how many minutes have passed, and what fraction of an hour is that? • From your ordered course and speed, where should you be at 1600 (EP) if there were no current? Then, where are you actually (second fix)? • Draw the vector from the EP to the actual fix: which direction is that (set), and how far in miles over the elapsed time (drift)?
• Be sure you convert minutes of time to decimal hours correctly before computing distance run • Measure the distance from original fix to EP, and from EP to actual fix using the latitude scale on your chart • When you find the current’s direction, remember that set is expressed as the direction TOWARD which the current flows, in true degrees (°T)
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