In this appallingly stupid time we are living in, with America's current aversion to facts and science, it is fascinating how the Ancient Greeks calculated the circumference of the Earth so accurately. May we return to a time when curiosity overcame ignorance and science overcame superstition.
Ancient Greeks proved Earth was round using sticks and shadows. Eratosthenes calculated its circumference to within 2% accuracy over 2,000 years ago. No satellites needed.