Your 0830 DR position is LAT 27°33'S, LONG 79°17'E. Your vessel is on a course of 066°T, at a speed of 19.5 knots. Determine the time of LAN on 10 December.
• Local Apparent Noon (LAN) occurs when the Sun is highest on your local meridian, not necessarily at 1200 zone time • The relationship between longitude and time: 15° of longitude equals 1 hour of time • How to convert between Greenwich Hour Angle (GHA), longitude, and time to find when the Sun is on your meridian
• What must be true about the Sun’s hour angle relative to your longitude at the exact moment of LAN? • Starting from 0000 GMT on 10 December, how do you figure out when the Sun’s GHA will line up with your DR longitude? • How many minutes of time correspond to a 1° change in GHA, and how does that help you refine the LAN time to the nearest minute?
• Be clear about the sign of your longitude (East vs West) and how that affects when the Sun crosses your meridian • Verify whether you are using GMT (UTC) or zone time when you compare your result with the answer choices • Check that your computed time is reasonable for your longitude (East longitudes should see LAN earlier than Greenwich on the same date)
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