quote:
Seems to me the craft or trade of Land Surveying served us well before complicating the process with "the science of Geodesy".

Which system of surveying provides evidence of curvature? (or do they?)

Cynics (like myself) would say the over-complex Geodesy was adopted as a surveyor tool to provide plausibility for "curvature".

Ok, I'll take a very brief stab at this and you'll need to Google for in depth explanations.

Aristotle was the first to try calculating the Earth's circumference, but it was another Greek Philosopher, Eratosthenes, who in 240 B.C. used angular observations of the Sun to calculate a circumference of approximately 25,000 miles. The generally accepted value today is 24,901 miles.

Later methods mainly involved triangulation and elevation survey techniques over large areas. The Brits were especially keen to know the Earth's shape in support of their Empire's Naval operations and navigation. For an interesting layman's read, look up the book "Longitude."

John Hopkins scientists in the 1950's noticed the Russian's Sputnik Satellite emitted a repeatable Doppler Signature, which lead to the then Defense Mapping Agency establishing a world wide Doppler Sat network to model the Earth's shape in support of the Navy's sat based Nav System, called Transit.

Modern methods include VLBI Astronomical observations, Gravimetric observations and of course the GPS system.

The resultant shape (geoid) is expressed in ECEF or an Earth Centered Earth Fixed coordinate system, referenced to the center of the earth. Simplified, it looks like this.

You'll recall the recent buzz over the "Northern Lights" being visible far south, and some asking why they saw only red, while others saw green. Like this.

To say that the Earth is flat gives you the burden of proving it expressed in scientific, physics terms. It's not sufficient to say "seems to me" or "I believe" or "I think."

Good luck.