On 10 August your 0430 ZT position is LAT 29° 56.7' S, LONG 139° 11.0' E. Your course is 321° T, speed 18.2 knots. You observed 3 celestial bodies. Determine the latitude and longitude of your 0500 running fix. OBSERVED STAR TIME GHA DECLINATION ALTITUDE -------------------- ------- --------------- --------------- ----------- Fomalhaut 0452 272° 03.3' S 29° 43.1' 46° 05.3' Canopus 0459 162° 05.5' S 52° 41.0' 41° 48.9' Achernar 0510 236° 28.2' S 57° 19.6' 60° 26.5'
• Running fix using three celestial LOPs at different times • Advancing/retarding LOPs along the DR track using course and speed • Using approximate DR position at 0500 to see which multiple‑choice options are reasonable
• First, from your 0430 DR position, what is your approximate DR position at 0500 using course 321° T and speed 18.2 knots? Is that north or south, east or west of your starting point? • How far (in nautical miles) do you travel between 0430 and the times of each sight (0452, 0459, 0510)? How will those distances affect where you advance or retard each LOP to 0500? • Once you have an approximate DR position for 0500, which of the four answers lies closest to that DR point in both latitude and longitude before you even plot the exact LOP crossings?
• Convert the time differences (in minutes) between 0430 and 0500 to hours before multiplying by 18.2 knots • Check that your north/south change in latitude matches the general direction of course 321° T from a southern latitude (are you moving toward or away from the equator?) • Make sure your change in longitude direction (east or west) is consistent with course 321° T and the fact that 1′ of longitude is less than 1 NM at about 30° S latitude
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