On 11 November your 0730 zone time position...

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Question 1 of 2066636eea28f7522a1c51aa24

On 11 November your 0730 zone time position was LAT 19° 58.0' N, LONG 143° 54.0' W. Your vessel was steaming on course 084° T at a speed of 15.0 knots. An observation of the Sun's lower limb was made at 0931 ZT. The chronometer read 07h 29m 22s and was slow 02m 22s. The observed altitude (Ho) was 44° 17.6'. LAN occurred at 1125 zone time (ZD +10). The observed altitude (Ho) was 52° 17.4'. What was the longitude of your 1200 zone time running fix?

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🔍 Key Concepts

• Running fix using morning sight and LAN (Local Apparent Noon) on the Sun • Converting zone time (ZT) to Greenwich Mean Time (GMT/UTC) using the zone description (ZD +10) and chronometer correction • How a change in observed altitude (Ho) of the Sun relates to a change in assumed longitude near LAN

💭 Think About

• First, find the vessel’s DR (dead reckoning) position at the time of the morning sight and at LAN based on course and speed. How far (and in what direction) did you move between these times? • Convert both sight times from zone time to GMT using ZD +10 and the chronometer data. What GHA and declination would you be using for each Sun sight, and how would that affect your intercept and line of position? • For the LAN sight, think about how you determine longitude from the exact time of LAN and your zone time. How does that LAN-based longitude combine with your earlier LOP from the morning sight to give a running fix at 1200 ZT?

✅ Before You Answer

• Be sure you are applying the chronometer correction (slow 02m 22s) with the correct sign when converting to GMT. • Double-check your DR track and distances run between 0730, 0931 ZT, LAN at 1125 ZT, and 1200 ZT; a small time mistake can shift longitude by several miles. • Confirm that you are using the LAN observation to determine meridian passage time and longitude, and then advancing the appropriate line of position (LOP) to 1200 ZT before reading off the final longitude.

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