On 12 February your 0900 zone time DR position is LAT 16° 43.0' N, LONG 51° 42.0' W. Your vessel is on course 093° T at a speed of 18.5 knots. What is the zone time of local apparent noon (LAN)?
• Local Apparent Noon (LAN) occurs when the Sun crosses your local meridian (Sun on your longitude). • Relationship between longitude and time: 15° of longitude corresponds to 1 hour of time. • Difference between zone time meridian and your actual longitude, and how that affects the clock time of LAN.
• From your DR longitude at 0900, determine how many degrees of longitude you are east or west of the standard time meridian for your time zone. • Figure out how long it will take the Sun to move from its position at 0900 to your meridian, using 15° per hour as a guide. • Account for the ship’s east‑west movement between 0900 and LAN: does steaming on course 093° T at 18.5 knots move you significantly east or west, and does that make LAN earlier or later by the clock?
• Identify the correct zone description (ZD) and its standard meridian from the given longitude. • Convert the longitude difference (in minutes of arc) between your DR position and the zone meridian into time (minutes of time). • Make sure you use the ship’s speed and course to estimate how much the longitude will change by the time of LAN, and adjust your LAN time estimate accordingly.
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