On 7 March at 1838 ZT, in DR position LAT...

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Question 1 of 2066636eea28f7522a1c51ae45

On 7 March at 1838 ZT, in DR position LAT 34°26.9' N, LONG 58°16.2' W, you observe Polaris for latitude. The sextant altitude (hs) is 35°08.4'. The index error is 2.5' off the arc. The height of eye is 54 feet. What is the latitude at the time of the sight?

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Question 1 of 20

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🔍 Key Concepts

• Polaris (Pole Star) sight for latitude – understand the basic rule that Polaris’ observed altitude is approximately equal to your latitude, with small corrections. • How to apply index error (off the arc vs. on the arc) to the sextant altitude to get the observed altitude (ho). • How to compute dip (height of eye correction) and recognize if it is added or subtracted from the sextant reading.

💭 Think About

• Start by carefully correcting the sextant altitude (hs) for index error and dip to find the apparent/observed altitude. Ask yourself: does an index error that is 'off the arc' get added to or subtracted from hs? • Think about whether Polaris is north or south of the true pole and how that affects the relation between its corrected altitude and your latitude in the northern hemisphere. • Compare your final computed latitude to the dead-reckoning latitude (34°26.9' N). Does the Polaris result seem reasonably close, and are the answer choices spaced in a way that one clearly matches your corrected value?

✅ Before You Answer

• Make sure you apply the index correction with the correct sign based on 'off the arc'. • Confirm that the dip correction for a 54 ft height of eye is taken from the proper table/value and that it is subtracted from hs. • After applying all corrections, verify that your final latitude is north and within a few minutes of your DR latitude so that it is a realistic fix.

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