You are on a voyage from New York, NY, to San Francisco, CA. The distance from pilot to pilot is 5132 miles. The speed of advance is 13.5 knots. You estimate 32 hours for bunkering at Colon, and 14 hours for the Panama Canal transit. If you take departure at 0600 hours (ZD +4), 16 May, what is your ETA (ZD +7) at San Francisco?
• Speed = Distance / Time relationship and solving for time of voyage using speed of advance (SOA) in knots and distance in nautical miles • Converting total steaming time from hours into days and hours, then adding bunkering and canal delays • Time zone changes and date changes when going from ZD +4 at departure to ZD +7 at arrival, including crossing several midnights
• First, ignore time zones and just find how many total hours (or days and hours) the voyage will take, including bunkering and canal time. What is your total elapsed time from departure to arrival? • Starting from 0600 on 16 May (ZD +4), add your total elapsed time to find the UTC time and date of arrival. Then, how do you convert that UTC to local time at ZD +7? • When you convert between ZD +4 and ZD +7, are you adding or subtracting time from UTC? How does that affect the calendar date in San Francisco?
• Be sure your distance (nm) and speed (knots) are in the same units before finding steaming time: ( \text{Time (hours)} = \frac{\text{Distance (nm)}}{\text{Speed (kn)}} ) • Carefully add bunkering hours + canal hours + steaming hours before doing any time-zone conversions • After you get an arrival date/time in one zone (or UTC), double-check the direction of time zone change (from ZD +4 to ZD +7) so that you don’t move the clock the wrong way and end up a full day off.
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