Earth radius
The French Geodesic Mission to the Equator (, also called the French Geodesic Mission to Peru and the Spanish-French Geodesic Mission) was an 18th-century expedition to what is now Ecuador carried out for the purpose of performing an arc measurement, measuring the length of a degree of latitude near the Equator, by which the Earth radius can be inferred. The mission was one of the first geodesic (or "geodetic") missions carried out under modern scientific principles, and the first major international scientific expedition.