Great circle

A great circle is the intersection of a sphere with a plane through its center, and on the Earth it is the shortest path between two points. A great-circle track between two positions not on the same meridian or the equator crosses successive meridians at a continuously changing course, so it is sailed as a series of short rhumb-line legs between computed waypoints. The saving over the rhumb line grows with latitude and with east-west distance, which is why ocean passages in high latitudes are planned on the great circle subject to ice and weather limits.