### Great-Circle Sailing

The following form calculates the location of the destination (L1) given a location of departure (L0), a travelled Distance (D) and Bearing (Z0) for the great-circle track to be sailed. Since great-circle sailing implies a track of non-constant course, the Bearing Z0 is the initial course at the departure.
The picture on the left below will show the situation and explain the abbreviations and terms used.

 Location (L0) Distance and Bearing Latitude N/S  dd-mm.m Distance (D) Nm Longitude E/W ddd-mm.m Bearing (Z0) ° Destination (L1) Latitude ° Longitude ° D: Great-Circle Distance from L0 to L1 Z0, Z1: Azimuth angles under which the great-circle track intersects with the local Meridian in L0 and L1. The Agles Z0 and Z1 are measured clockwise from the northern branch of the local Meridian (true North) in L0 and L1 respectively and towards the (shortest) great-cirlce segment connecting L0 and L1. This way the resulting Azimuth angles represent true bearings. These true bearings are the initial courses to be sailed to travel from L0 to L1 (B0) or reverse (B1). The great-circle track gives the shortest path between L0 and L1, but the course to be sailed is not constant. The Destination problem can also be solved for a loxodrome track (track of constant course).