On 17 December your 0600 ZT fix gives you a position of LAT 27°16.7'N, LONG 138°39.2'W. Your vessel is on course 137°T, and your speed is 14.8 knots. Local apparent noon (LAN) occurs at 1207 ZT, at which time a meridian altitude of the Sun's lower limb is observed. The observed altitude (Ho) for this sight is 40°22.1'. What is the calculated latitude at LAN?
Official USCG Answer & Rule Citation
Correct Answer: Option D — 26°15.4'N
Advance the 0600 fix to the time of LAN (1207) using the vessel's course and speed. Determine the Sun's declination at LAN. Apply the meridian altitude formula (Lat = 90 - Ho + Dec) to the corrected Ho to find the latitude at transit, 26°15.4'N, following standard celestial navigation and dead reckoning.
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