On 31 January your 0920 zone time DR...

Question 1 of 2707066636eea28f7522a1c51ae0d

On 31 January your 0920 zone time DR position is LAT 24°16.0'S, LONG 151°33.0'E. Your vessel is on course 258°T at a speed of 18.5 knots. What is the zone time of local apparent noon (LAN)?

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Question 1 of 27070

On 31 January your 0920 zone time DR position is LAT 24°16.0'S, LONG 151°33.0'E. Your vessel is on course 258°T at a speed of 18.5 knots. What is the zone time of local apparent noon (LAN)?

🔍 Key Concepts

• How to find meridian passage (LAN) time from your DR longitude and course/speed • Relationship between Greenwich hour angle (GHA) of the Sun and your longitude at LAN • How to convert between UTC, zone time, and longitude (time zone approximation: 15° per hour)

💭 Think About

• First, if the Sun is on your meridian at LAN, what must be true about the Sun’s GHA and your longitude at that instant? • From 0920 until LAN, your ship is steaming on 258°T at 18.5 knots. Is this heading taking you toward a greater or smaller east longitude, and how does that affect the LAN time? • Once you estimate the UTC of LAN from the Nautical Almanac idea, how do you adjust using your approximate time zone (based on your longitude) to get zone time?

✅ Before You Answer

• Compute how far (in degrees of longitude) your DR position will shift between 0920 and any candidate LAN time, using course and speed; be careful to adjust speed to longitude change using the cosine of latitude if needed • Check that at your chosen LAN time, your corrected longitude at LAN roughly matches the Sun’s GHA relation for meridian passage at that date • Verify that the final answer is in zone time, not UTC, and that the time zone used matches your central meridian (closest multiple of 15°) for 151°E longitude