On 12 December your 1830 ZT DR position is...

Question 1 / 2066636eea28f7522a1c51aa4e

Question 1 of 2066636eea28f7522a1c51aa4e

On 12 December your 1830 ZT DR position is LAT 24°16.0' S, LONG 41°18.0' W. You are on course 235°T at a speed of 16.0 knots. You observed 3 celestial bodies. Determine the latitude and longitude of your 1930 running fix. Body Zone Time GHA Observed Declination Altitude Rigel 1845 329°19.7' 19°54.7'' S 8°13.4' Peacock 1910 107°58.4' 32°43.9'' S 56°47.8' Markab 1930 73°04.1' 39°53.1' N 15°06.5'

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🔍 Key Concepts

• Running fix using multiple celestial lines of position (LOPs) taken at different times • Advancing or retarding earlier LOPs to a common time using DR (dead reckoning) track, course, and speed • Effect of latitude and longitude shifts over 1 hour at 16 knots on final position compared to original DR

💭 Think About

• First, compute your DR position at 1930 ZT from the 1830 ZT DR using course 235°T and 16 knots. How far and in what direction have you moved in that 1 hour? • Next, think about whether the running fix from three bodies close in time to 1930 is likely to move you a little or a lot from that 1930 DR position. Would a huge change in latitude (several degrees) be reasonable over 1 hour? • Compare each choice’s latitude and longitude with your 1930 DR position. Which options show a small, realistic correction from DR and which show changes that are too large or inconsistent with your course and speed?

✅ Before You Answer

• Calculate distance run = speed × time (in nautical miles) between 1830 and 1930 and confirm that no answer choice implies a position shift larger than this along the track • Check that the change in latitude sign and magnitude between 1830 DR and each answer matches a vessel steering 235°T (southwesterly) for 1 hour at 16 knots • Verify that the change in longitude between DR and each answer is consistent with moving generally west-southwest in the Southern Hemisphere, considering that west longitudes increase as you move west

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Question 1 of 20

LAT 24°12.5'S, LONG 41°10.9'W

LAT 24°16.9'S, LONG 41°18.2'W

LAT 24°25.2'S, LONG 41°39.9'W

LAT 27°46.9'S, LONG 41°31.2'W

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Question 1 / 2066636eea28f7522a1c51aa4e

Question 1 of 2066636eea28f7522a1c51aa4e

Back

Question 1 of 20

66636eea28f7522a1c51aa4e

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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