On 30 July your 1030 ZT DR position is LAT 19° 02' N, LONG 138° 12' W. You are on course 309° T, speed 24 knots. Determine your 1200 position using the following observations of the Sun. Zone Time GHA Declination Ho 1220 138°25.0' N 18°22.3' 88°43.3' 1226 139°55.0' N 18°22.2' 88°24.0'
• Dead reckoning (DR) track from 1030 to the two sight times and to 1200 • How to use two Sun sights near local apparent noon (LAN) to refine latitude and longitude • Transferring a line of position (LOP) (or LAN fix) to a desired time along the DR track
• First, work out where your DR position would be at 1200 based on your course and speed. How far do you travel in 1 hour 30 minutes at 24 knots? • At each sight time, you have GHA and declination. How do you combine these with your assumed longitude to get Local Hour Angle (LHA) and then compute an intercept and azimuth? • Once you get a position from the Sun sights near noon, how do you "run" that position along your course and speed to find where you were at 1200?
• Make sure your time intervals (1030 → 1200, 1030 → 1220, 1030 → 1226) are correct and in hours and minutes before converting to distance at 24 knots. • Check your sign conventions: for west longitude, verify whether you use LHA = GHA − LONG or LHA = GHA + LONG, and keep everything between 0° and 360°. • After obtaining a position from the sights, be sure you transfer it correctly along course 309° T: verify distance run = speed × time and apply the correct course to change both latitude and longitude.
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