On 17 April your vessel is enroute from the Panama Canal to Kobe, Japan. Your 0400 zone time DR position is LAT 26°12.0'N, LONG 126°12.0'W. Your vessel is on course 285°T at a speed of 18 knots. What will be the zone time of sunrise at your vessel?
• Zone time vs. GMT (UTC) – how to convert between local time and Greenwich time based on longitude and zone description • Sunrise from Nautical Almanac – using the date and DR latitude/longitude to find sunrise at Greenwich and then applying corrections • Motion of the observer – advancing the DR position to the time of the event and checking if this affects the sunrise time
• First, estimate the correct time zone (zone description) for longitude 126°12.0'W and convert your 0400 zone time to GMT (UTC). What is the corresponding UTC time? • From the Nautical Almanac for 17 April at the DR latitude, what is the approximate UTC of sunrise, and how do you adjust it for your exact longitude? • After you get a first approximation of sunrise time in UTC, convert it back to your zone time and compare with the answer choices. Does the result make sense given how far east or west you are from the central meridian of your time zone?
• Be sure you are using the correct zone description sign (East vs. West longitudes) when converting between zone time and GMT (UTC). • Confirm that you are using the correct DR position for the event time – do you need to advance from 0400 using course and speed to the approximate sunrise time? • Double‑check whether you must apply any longitude correction to the Almanac sunrise time (which is usually tabulated for a standard meridian) before choosing your final zone time.
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