On 26 September your 0830 zone time DR position is LAT 23°04.0'N, LONG 129°16.0'E. Your vessel is on course 119°T at a speed of 20.0 knots. What is the zone time of local apparent noon (LAN)?
• Local Apparent Noon (LAN) occurs when the Sun is on your local meridian (hour angle ≈ 0°) • Relationship between longitude and time (15° of longitude = 1 hour of time) • How your run between 0830 and LAN (course and speed) changes your longitude and therefore the LAN time
• From your 0830 DR longitude, estimate the longitude where you will be at LAN, using your course and 20-knot speed over the time interval you are trying to find • Relate the change in longitude (east or west?) to how many minutes of time the LAN will be earlier or later than for your 0830 longitude • Compare your computed LAN time to the answer choices, checking which one is consistent with both the longitude-time relationship and your vessel’s eastward or westward movement
• Be clear whether sailing east makes LAN occur earlier or later in zone time, and why • Convert longitude difference to time using 15° = 1h, 1° = 4 min, 1' = 4 sec and apply the correct sign (add or subtract) • Check that the total run from 0830 to your candidate LAN time at 20.0 knots gives a position whose longitude matches the LAN condition for that time zone
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