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?

Question

On 11 November your 0730 zone time position was LAT 19&deg;58.0'N, LONG 143&deg;54.0'W. Your vessel was steaming on course 084&deg;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&deg;17.6'. LAN occurred at 1125 zone time (ZD +10). The observed altitude (Ho) was 52&deg;17.4'. What was the longitude of your 1200 zone time running fix?

Accepted Answer

Option C: 142&deg;40.2'W. Calculate the longitude at LAN using the Sun's GHA at the time of transit. Advance the 0730 ZT position to the 1200 ZT time of the running fix using the vessel's course and speed. The intersection of the meridian line and the DR track yields 142°40.2'W.