Your vessel departs Yokohama from position LAT 35°27.0'N, LONG 139°39.0'E (ZD -9), at 1330 ZT on 23 July, bound for Seattle at position LAT 47°36.0'N, LONG 122°22.0'W (ZD +8). The distance by great circle is 4,245 miles, and you estimate that you will average 13.6 knots. What is your estimated ZT of arrival?
• Time zone (ZD) differences between departure and destination and how they affect local time vs. GMT/UTC • Using speed–time–distance: ( \text{Time (hours)} = \frac{\text{Distance (NM)}}{\text{Speed (knots)}} ) to find steaming time • Converting between Zone Time (ZT) and Greenwich Mean Time (GMT/UTC) when crossing the International Date Line
• First, work out how many hours the voyage will take using the given great-circle distance and average speed. Keep your units consistent. • Convert the departure local time (ZT at Yokohama with ZD -9) to GMT/UTC, then add the steaming time to get an arrival time in GMT/UTC. • Once you have arrival GMT/UTC, convert it to the destination zone time (ZT at Seattle with ZD +8), and then carefully adjust the date considering that you’re crossing from east longitude to west longitude across the Pacific.
• Be sure you are using the correct time zone signs (ZD -9 and ZD +8) and not reversing them when going between ZT and GMT/UTC. • Verify whether the International Date Line crossing causes you to gain or lose a calendar day when going from Japan to the U.S. West Coast. • Double-check that your final answer’s time of day and calendar date both match the total steaming time you calculated from departure.
No comments yet
Be the first to share your thoughts!