You are on a voyage from Corpus Christi, TX to Fort de France, Martinique. The distance from pilot to pilot is 2190 miles (2521 statute miles). The speed of advance is 15.0 knots. You estimate a layover in Charlotte Amalie, Virgin Islands, of 16.0 hours. If you take departure at 0654 (ZD +6), 27 November, what is your ETA (ZD +4) at Fort de France?
• Speed–time–distance relationship using nautical miles and knots • Converting zone description (ZD) time changes as you move eastward • Accounting for layover time separately from sea passage time
• First, ignore the layover and time-zone changes: how many hours does it take to travel 2190 miles at 15 knots? • After you find the sea time, add the 16-hour layover at Charlotte Amalie. What is your total elapsed time from departure to arrival? • Starting from 0654 (ZD +6), add the total elapsed time, then adjust the final result from ZD +6 to ZD +4. Are you moving to a time zone that is earlier or later?
• Be sure you are using nautical miles with knots (not statute miles) in your calculation. • Carefully convert fractional hours (if any) into hours and minutes—don’t round away important minutes. • When changing from ZD +6 to ZD +4, confirm whether you should add or subtract time when moving to a time zone closer to Greenwich (smaller ZD).
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