A vessel at LAT 28°20'N, LONG 16°00'W is to proceed to LAT 21°00'N, LONG 18°00'W. What is the course and distance by mid-latitude sailing?

Correct Answer: Option A — 194.0°T, 453.0 miles

Mid-latitude sailing uses the mean latitude to account for the convergence of meridians. ΔLat = 440' S, Departure = Δλ × cos(Lm) = 120' × cos(24.66°) = 109.1'. Tan(Course) = Dep / ΔLat = 109.1 / 440 = 0.248. Course = 194.0°T, Distance = ΔLat / cos(Course) = 453.0 miles.