Flat-Earth Thinking Removed

Since the eariy beginnings of photogram-metry, practitioners knew that the Earth was not flat, and that aircraft maintaining a specified and constant flying height actually followed the Earth's curvature. See Figure 1. However, they also knew that their "plotting tables" were flat. This posed the problem of how to reconcile the difference. Creating plotting tables with elaborate curved surfaces was not practical - especially since the curvature would need to change for each type of map projection they represented.