At 0600 zone time on 22 October, you depart Manila, LAT 14° 35.0' N, LONG 120° 58.0' E (ZD -8). You are bound for Los Angeles, LAT 33° 46.0' N, LONG 118° 11.0' W, and you estimate your speed of advance at 20.2 knots. The distance is 6,385.9 miles. What is your estimated zone time of arrival at Los Angeles?
• Time-Speed-Distance relationship for sea passage calculations • Converting zone time (ZD) to a common reference like GMT/UTC and back • Effect of crossing the International Date Line and changing longitude from East to West
• First, compute the elapsed time of the passage from the given distance and speed. What is the travel time in hours and days? • Convert the 0600 departure zone time (ZD -8) to GMT/UTC. After adding the elapsed time, what is the resulting GMT/UTC on arrival? • From the arrival longitude near Los Angeles, what is the correct ZD to apply, and how does that affect the local date and clock time?
• Be sure you use Distance ÷ Speed to get time, and keep the decimal hours straight when converting to hours and minutes. • Double-check the sign and value of the ZD at both Manila and Los Angeles; they are not the same and you change hemispheres (E to W longitudes). • Confirm whether you must account for calendar date changes due to crossing 180° longitude and long total travel time, not just the clock time.
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