On 27 March your 0730 zone time position is LAT 28°16'N, LONG 56°37'W. Your vessel is on course 158°T at a speed of 15.0 knots. An observation of the Sun's lower limb is made at 0915 zone time. The chronometer reads 01h 14m 11s, and the chronometer error is 00m 53s slow. The observed altitude (Ho) is 45°10.7'. LAN occurs at 1150 zone time, and a meridian altitude of the Sun's lower limb is made. The observed altitude (Ho) is 65°32.8'. Determine the vessel's 1200 zone time position.
• Meridian altitude (LAN) sight to get latitude from the Sun’s lower limb • Using time and course/speed between sights to advance a line of position (running fix) • Converting chronometer time, chronometer error, and zone time to correct UTC for longitude work
• From the LAN (meridian altitude) sight: how do you get latitude directly from the Sun’s true observed meridian altitude, applying index error, dip, refraction, semi‑diameter, and declination? Think about which way (N or S) you adjust. • Between 0730 and 1200, what distance do you steam on course 158°T at 15.0 knots, and how does that change latitude and longitude starting from the 0730 DR position? • For the 0915 sight, after correcting the chronometer reading for its error, what is the correct UTC, and how does the difference between this time and LAN time affect the longitude you derive?
• Be sure you use LAN time (1150 ZT) to find the ship’s latitude from the meridian altitude, not from the morning sight. • Check your run from 0730 to 1200 carefully: distance = speed × time, and split the run into north‑south (ΔLat) and east‑west (departure/ΔLon) using the course. • Verify that your final answer’s latitude matches the LAN meridian altitude result, and its longitude matches the longitude line from the 0915 sight advanced (or retarded) properly to 1200.
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