Great-circle, or orthodromic, navigation finds the shortest distance between two points on a globe. Doing so requires spherical trigonometry and a substantial burden of angular calculation rather than a single fixed heading. Navigators developed charts and planning methods that made the mathematics usable before electronic systems could solve it automatically. By the 1920s and 1930s, an aircraft observer-navigator had to perform this work with tables and mechanical aids while in flight. These duties made the second crew member an operational specialist rather than dead weight in an early long-range aircraft.
Chapter · 29:19-33:43
Great-circle routes made mathematics an aircrew duty
The shortest route across a globe required spherical trigonometry, charts, and a trained observer-navigator before electronic calculators.