On 17 January your 0730 zone time fix gives you a position of LAT 22°26.0'S, LONG 152°17.0'E. Your vessel is steaming on a course of 116°T at a speed of 17 knots. An observation of the Sun's lower limb is made at 1015 zone time. The chronometer reads 00h 13m 23s, and the chronometer error is 01m 49s slow. The observed altitude (Ho) is 66°02.1'. LAN occurs at 1152 zone time and a meridian altitude of the Sun's lower limb is made. The observed altitude (Ho) is 87°54.2'. Determine the vessel's 1200 zone time position.

Question

On 17 January your 0730 zone time fix gives you a position of LAT 22&deg;26.0'S, LONG 152&deg;17.0'E. Your vessel is steaming on a course of 116&deg;T at a speed of 17 knots. An observation of the Sun's lower limb is made at 1015 zone time. The chronometer reads 00h 13m 23s, and the chronometer error is 01m 49s slow. The observed altitude (Ho) is 66&deg;02.1'. LAN occurs at 1152 zone time and a meridian altitude of the Sun's lower limb is made. The observed altitude (Ho) is 87&deg;54.2'. Determine the vessel's 1200 zone time position.

Accepted Answer

Option A: LAT 22&deg;53.8'S, LONG 153&deg;25.6'E. Advance the 1015 ZT sun line to 1200 using the course and speed vector. Calculate the latitude at 1152 ZT using the meridian altitude formula (Lat = 90° - Ho + Dec). The intersection of the advanced line and the meridian latitude yields the 1200 position.