What are the sailings? They're the collective calculations needed to compute course and distance for a voyage. There are both plane and spherical sailings, and each has its own particular use. Plane sailings work on shorter voyages of several hundred miles or less as they don't account for the curvature of the earth and are less accurate on a larger scale. Spherical sailings do account for the curvature of the earth and are more accurate on the larger scale, though they don't involve simply geometry and plane trigonometry like the plane sailings do.

Plane Sailings

Parallel Sailings

Mercator Sailings

Mid-Latitude Sailings

Great Circle Sailings

Composite Sailings

P1 = Point of Departure	P2 = Longitude of Arrival
L1 = Latitude of Departure	λ1 = Longitude of Departure
L2 = Latitude of Arrival	λ2 = Longitude of Arrival
l = Difference of Latitude	DLo = Difference of Longitude
CN = True Course	C = Course Angle
p = Departure; difference in longitude (in nm)