On 15 November your 1030 ZT DR position is LAT 17°25'S, LONG 42°12'W. You are on course 059°T, speed 22 knots. Determine your 1200 position using the following observations of the Sun.
• Dead reckoning (DR) run between 1030 and 1200 at 22 knots on course 059°T • How a Sun line near noon often adjusts your DR more across track than along track • Relationship between your DR track direction and the expected change in latitude and longitude
• First, compute how many nautical miles you travel between 1030 and 1200 and in what true direction, then estimate how much that should change your latitude and longitude from the 1030 DR • Compare each answer’s latitude and longitude with your expected DR 1200 position: which ones are clearly too far from the DR track? • Think about where the Sun is in November at this latitude: would the Sun line correction more likely move your noon position mostly north-south, mostly east-west, or a mix of both?
• Be sure you correctly compute the distance run: speed in knots × time in hours • Check the sign of the longitude change: on a course of 059°T in the South Atlantic, does your longitude increase (go more W) or decrease (go more E)? • Verify which option lies closest to your DR 1200 position, then consider a small realistic shift from the DR due to the sight reduction (not a huge jump)
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