On 15 November your 0913 zone time fix gives you a position of LAT 22°30.0'N, LONG 68°28.0'W. Your vessel is on course 164°T, and your speed is 13.5 knots. Local apparent noon (LAN) occurs at 1118 zone time at which time meridian altitude of the Sun's lower limb is observed. The observed altitude (Ho) for this sight is 49°46.0'. What is the calculated latitude at LAN?
• LAN (Local Apparent Noon) and meridian passage of the Sun • Running a DR (Dead Reckoning) position from a known fix to a later time • Latitude by meridian altitude: relation between Ho, Dec, and Lat for the Sun on the observer’s meridian
• From 0913 to 1118, how much time has elapsed, and what DR latitude will you reach on course 164°T at 13.5 knots? • At LAN, is the Sun due south or due north of your position on 15 November in this latitude, and how does that affect whether you add or subtract declination from co-altitude? • How do you convert the observed altitude (Ho) to co-altitude, and how is co-altitude combined with the Sun’s declination to find latitude on a meridian passage?:
• Be sure you use the DR latitude at 1118, not the 0913 fix, when comparing to the calculated latitude • Confirm the Sun’s declination sign and approximate value on 15 November (north or south?) before deciding if you add or subtract • Double-check unit handling: convert minutes of time to decimal hours and then to nautical miles using speed in knots
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