Q: 3.3 — Geodesy: Great geometry relies on sphericity

Engineers of bridges, tunnels, and long highways take into account the curvature of the Earth to ensure accuracy in their projects. The Channel Tunnel between England and France, giant transcontinental pipeline projects, and undersea cable networks — all were built on a spherical model.

If the Earth were flat, these adjustments would be wrong and all the projects would fail. They do not fail.