A ship steams 090° T for 200 n.m. in Lat 49° 10’ N. By how
much will her clocks have to the advanced?
Solution:
Step 1. We have to solve for the difference of longitude (dlo).
We can use the parallel sailing formula in getting Dlo.
Departure = Dlo × Cos Lat
Dlo = Dep ÷ Cos Lat
Dlo = 200 ÷ Cos 49° 10’
Dlo = 305.88 n.m.
÷ 60 (to convert it to degrees)
Dlo = 5.098°
Step 2. Convert degrees into time.
Since
the earth rotates 15 degrees of an arc per hour, so we have to divide the Dlo
by 15.
5.098 ÷
15 = 00 h 20 min 23.5 sec is the final answer
