On 6 April your 0300 DR position is LAT 27° 42' S, LONG 128° 58' W. You are on course 097° T at a speed of 18 knots. You observed 3 celestial bodies. Determine the latitude and longitude of your 0600 running fix. ZONE OBSERVED BODY TIME GHA ALTITUDE (Ho) DECLINATION ------------------- -------- ------------- ------------ --------------- Fomalhaut 0530 203° 08.6' 25° 17.5' S 29° 43.4' Rigil Kent. 0536 194° 12.4' 35° 26.6' S 60° 45.3' Vega 0540 135° 43.2' 23° 06.8' N 38° 45.7'
• Running fix with multiple bodies: Advancing LOPs (Lines of Position) from each sight to a common time using course and speed made good • Assumed position and intercept method: Using GHA/dec and DR to compute Hc and Zn, then plotting intercepts toward/away the GP of each body • Time and DR advancement: Converting time differences between 0300 DR, sight times, and 0600 fix to distance run along the true course at 18 knots
• How do the times of the three sights (all near 0530–0540) relate to the 0600 running fix time, and how far does the vessel travel between each sight and 0600 at 18 knots? • When you plot the three LOPs advanced to 0600, does the final running fix fall generally ahead/astern and to port/starboard of your 0300 DR on course 097° T? • How will the mix of northern and southern declinations and the various observed altitudes (Ho) affect whether the intercepts for each star are toward or away from their geographic positions, and what does that do to your final latitude and longitude?
• Be sure you apply the correct run distance from the DR at each sight time to 0600 using ( \text{Distance} = \text{Speed} \times \text{Time} ) in nautical miles • Confirm that each LOP is properly advanced along the track 097° T (not perpendicular to it) when forming the running fix • After you get an approximate plotted fix, compare it logically to your 0300 DR position and total run in 3 hours (54 NM) to see which multiple-choice option is geographically reasonable in both latitude and longitude
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