The irregular English suggests the writer of the piece operates under ESL.
As HTB notes, the spherical structure of the Earth and Moon was understood by Aristotle's time, and before the middle of the 3rd c BC, Eratosthenes, devised and conducted an experiment to calculate the circumference of the Earth (25,000 miles, a bit higher than the actual figure).
Ok, they knew the earth was round so if they could find the equator they could do latitude, but how’d they do longitude?