On 24 March your 0800 zone time fix gives you a position of LAT 22°16.0'N, LONG 31°45.0'W. Your vessel is steaming a course of 285°T at a speed of 16.5 knots. An observation of the Sun's upper limb is made at 0938 zone time, and the observed altitude (Ho) is 46°32.2'. The chronometer reads 11h 41m 01s, and the chronometer error is 02m 50s fast. Local apparent noon occurs at 1214 zone time, and a meridian altitude of the Sun's lower limb is made. The observed altitude (Ho) for this sight is 68°55.8'. Determine the vessel's 1200 zone time position.
• Run a dead reckoning (DR) track from the 0800 fix to the time of the 0938 sight using course, speed, and elapsed time • Convert chronometer time to GMT using the given chronometer error, then find GHA and Dec for the Sun at the time of the 0938 sight and work a standard sun sight for longitude • Use the meridian passage (LAN) sight of the lower limb to determine latitude from meridian altitude, applying the correct dip, refraction, semi‑diameter, and declination corrections
• First, compute the DR position at the time of the 0938 sight from the 0800 fix. How far (nm) do you travel in 1h 38m on course 285°T at 16.5 knots, and what is that DR position? • From the chronometer reading and error, what is the correct UTC at 0938 zone time? Use that to derive a longitude line from the 0938 sight: is your longitude east or west of the assumed? • For LAN at 1214 zone time, use the observed meridian altitude and Sun’s declination to compute latitude. Is the Sun north or south of your position on that date, and is it north or south of the equator in late March? That tells you whether to add or subtract declination.
• Confirm your time conversions: zone time → UTC using the correct time zone based on your approximate longitude, then apply chronometer error properly (fast vs. slow) • Check that your course and distance run are correctly broken into latitude and departure components when updating DR positions • Verify your latitude from LAN logic: correct use of LHA = 0°, correct sign of declination, and whether to use Ho of the lower limb plus semi‑diameter to get apparent center altitude before applying the meridian altitude formula
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