Loxodrome

The travel direction is a tangent to the curve, and the direction of the pole is represented by great circles running through the pole (longitudes). A ship or an airplane follows such a curve when the compass bearing is kept constant. As a result, navigation along a loxodrome is easy, but it is not the shortest path. The shortest distance between two points is represented by a great circle running through the two points. A loxodrome is a straight line on a Mercator projection map and a logarithmic spiral on a stereographic projection map.