On 1 July your 0515 zone time fix gives you a position of LAT 23°24.0'S, LONG 151°42.0'W. Your vessel is on course 240°T, and your speed is 10.0 knots. Local apparent noon (LAN) occurs at 1215 zone time, at which time a meridian altitude of the Sun's lower limb is observed. The observed altitude (Ho) for this sight is 42°55.0'. What is the latitude at 1200 ZT?
• Run time and run distance between 0515 and 1200 zone time at 10 knots • Relationship between distance run north/south and change in latitude (1' of latitude = 1 nautical mile) • How a meridian altitude (LAN sight) gives you latitude, and how to compare that to your DR latitude at the time of the sight
• First, compute how many hours are between 0515 and 1200, then find how far the vessel travels along the 240°T course by 1200, and especially how many miles of that are in the north-south direction • Work out the DR latitude at the time of LAN using your starting latitude and the north-south component of the run, before using the Sun sight • Think about whether, between 1200 and 1215, your ship is moving toward the Equator or toward the pole, and how that motion would make the LAN-derived latitude differ from the 1200 DR latitude
• Be sure your time interval is correct: 0515 to 1200 is how many hours and minutes? • Confirm you used the course angle from north-south to get the right north-south component of the distance (use sine or cosine correctly) • Check whether the final latitude at 1200 ZT should be numerically larger or smaller than the starting 23°24.0'S, based on your north-south travel direction
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