On 20 November your 0612 zone time (ZT) position was LAT 25°38.0'N, LONG 166°54.0'W. Your vessel was steaming on course 126°T at a speed of 20.0 knots. An observation of the Sun's lower limb was made at 0854 ZT. The chronometer read 07h 51m 14s and was slow 02m 52s. The observed altitude (Ho) was 27°58.3'. LAN occurred at 1147 ZT. The observed altitude (Ho) was 45°35.0'. What was the longitude of your 1147 ZT running fix?

Question

On 20 November your 0612 zone time (ZT) position was LAT 25&deg;38.0'N, LONG 166&deg;54.0'W. Your vessel was steaming on course 126&deg;T at a speed of 20.0 knots. An observation of the Sun's lower limb was made at 0854 ZT. The chronometer read 07h 51m 14s and was slow 02m 52s. The observed altitude (Ho) was 27&deg;58.3'. LAN occurred at 1147 ZT. The observed altitude (Ho) was 45&deg;35.0'. What was the longitude of your 1147 ZT running fix?

Accepted Answer

Option D: 165&deg;12.5'W. A running fix at LAN requires advancing the morning sun line to the time of the meridian passage. Using the vessel's motion between 0854 ZT and 1147 ZT, the longitude is adjusted based on the intercept and course made good, resulting in 165°12.5'W.