Example 1
The DR latitude of a ship on course 090° is 49°30.0 N. The ship steams on this course until the longitude changes 3°30.0.
Required - The departure.
P = DLO x COS LAT
= 210 x COS 49.5°
= 210 x .649448048
= 136.4 mi
Example 2
The DR latitude of a ship on course 270° is 38°15.0 S. The ship steams on this course for a distance of 215.5 miles.
Required - The change in longitude.
DLO = p x sec L
= 215.5 mi ÷ cos 38.25°
= 274.4 ÷ 60
= 4°34.4
I use a TI-30X calculator for all the sailing problems. If anybody needs help in solving these problems let me know. There are numbers that I change around, I can give the exact buttons to push on the calculator to help you see this. The only reason I mention this is that I don't have a math background and a long time ago I had a old salt show me how to do the sailings. It makes things a lot simpler.
