On 14 September your 1810 ZT DR position is LAT 27° 12.0' S, LONG 71° 10.0' E. You are on course 060° T at a speed of 15.0 knots. You observed 3 celestial bodies. Determine the latitude and longitude of your 1822 running fix. ZONE OBSERVED BODY TIME GHA ALTITUDE (Ho) DECLINATION ------------------- -------- ------------- ------------ --------------- Venus 1810 341° 30.4' 38° 48.9' S 12° 48.1' Altair 1816 255° 00.4' 41° 20.3' N 8° 49.3' Peacock 1822 247° 55.8' 48° 39.5' S 56° 47.8'
• Running fix using multiple celestial lines of position (LOPs) taken at different times • Converting time differences to distance run at a given speed along the given course (SOA 15.0 kn, course 060° T) • How advancing earlier LOPs along the DR track affects the final latitude and longitude compared with the original 1810 DR position
• First sketch your DR track from 1810 to 1822 on the plotting sheet. How far along course 060° T do you move in 12 minutes at 15 knots, and where does that put your DR at 1822? • Think about each body’s LOP: Venus at 1810, Altair at 1816, Peacock at 1822. Which LOP do you advance the most, and in what direction, before they all intersect at the running fix? • Compare the general direction of the shift from the 1810 DR to the final running fix. Should the fix end up slightly ahead/behind and to port/starboard of the DR track, given the azimuths (directions) to the bodies?
• Be sure you correctly convert minutes of time to hours (e.g., 6 min = 0.1 hr, 12 min = 0.2 hr) before computing distance run: ( \text{Distance} = \text{Speed} \times \text{Time} \). • Check that you advance each earlier LOP exactly along course 060° T by the proper distance, not along the LOP itself. • Before choosing an answer, compare all four choices to your 1810 DR: which option is closest to your plotted intersection and also lies near the DR track between 1810 and 1822?
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