This designates the shortest distance between two points on a sphere, and thus for navigators or aviators, the shortest route on the surface of the earth. On a conformal projection map such as Mercator’s, an orthodrome is not represented by a straight line but a curved line. In effect, this projection preserves angles but not distances. On a map using a Mercator projection, a straight line corresponding to a route that cuts all meridians at a constant angle is called a rhumb line or a loxodrome.

See also: Conformal (Projection), Equivalent (Projection), Projection (System of)
[French: Orthodromie]