On 30 July your 1030 ZT DR position is LAT...

Question 1 / 2066636eea28f7522a1c51ae07

Question 1 of 2066636eea28f7522a1c51ae07

On 30 July your 1030 ZT DR position is LAT 17°46'N, LONG 139°30'W. You are on course 129°T, speed 24 knots. Determine your 1200 position using the following observations of the Sun. Zone Time GHA Declination Ho 1220 138°25.0' N 18°22.3' 88°43.3' 1226 139°55.0' N 18°22.2' 88°24.0'

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66636eea28f7522a1c51ae07

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🔍 Key Concepts

• Run a DR (dead reckoning) position from 1030 to the time of each sight using course and speed given • How to do a LAN (Local Apparent Noon) Sun latitude line: when the Sun is on/near your meridian, latitude ≈ 90° − Ho ± declination (with correct N/S sign logic) • Using two close‑in‑time meridian‑passage sights to refine longitude by time of meridian passage

💭 Think About

• First, compute the DR positions at the two sight times from the 1030 DR; how far have you traveled in latitude and longitude by 1220 and 1226? • For each sight, compare Ho with what you would expect at meridian passage to determine your latitude; how does the small time difference from true LAN affect this? • Use the difference in GHA between the two sights and the times to refine your longitude, considering how your east‑going course affects the DR longitude versus the observed longitude.

✅ Before You Answer

• Be sure to convert time interval to hours and minutes accurately when computing DR (e.g., 1h 50m, 1h 56m) • Check the sign conventions for latitude from a Sun meridian sight in the same hemisphere (Sun and observer both North) • After you get an approximate lat/long, compare with the four choices: which are most consistent with your east‑southeast track (129°T) and 24‑knot speed from the original DR?

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Question 1 of 20

LAT 17°24.0'N, LONG 138°59.8'W

LAT 17°21.6'N, LONG 138°56.2'W

LAT 17°18.7'N, LONG 139°07.6'W

LAT 17°15.1'N, LONG 139°00.0'W

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Question 1 / 2066636eea28f7522a1c51ae07

Question 1 of 2066636eea28f7522a1c51ae07

Back

Question 1 of 20

66636eea28f7522a1c51ae07

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

👋 Hi! I'm Genie, your AI study assistant. How can I help you with this question?

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