On 12 February your 0930 zone time DR position is LAT 25° 20.0' N, LONG 30° 40.0' W. Your vessel is on course 135° T at a speed of 11.2 knots. What is the zone time of local apparent noon (LAN)?
• Local Apparent Noon (LAN) occurs when the Sun is highest over your meridian (local longitude) • Difference between zone time meridian (ZTM) and your DR longitude • Converting longitude difference to time (4 minutes of time per degree of longitude)
• From your DR longitude, determine how far east or west you are from the standard meridian of your time zone at 0930 ZT. How many minutes of time does that represent? • Think about whether LAN will occur before or after 1200 zone time based on whether your vessel is east or west of the zone meridian and whether you are moving toward or away from it. • Between 0930 and about 1200, how far will you travel along your course at 11.2 knots? How much additional longitude will you gain or lose by LAN?
• First, find the zone description (ZD) and corresponding zone time meridian for your stated longitude. • Convert the total longitude difference (static difference at 0930 plus the change due to your motion) into minutes of time using 4 min per degree. • Make sure your final LAN time is reasonable relative to 1200 ZT (it should be close to, but not exactly, 1200).
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