I presume you believe MANY have done just that. Surely their proof would be widely available and incontrovertible? Where is it?
Nowhere.
There is a science totally ignored by flat-earthers, and that is geodesy, Earth measurement on a large scale.
The period from Eratosthenes to Jean Picard can be called the spherical era of geodesy.
This science began with Eratosthenes (l. c. 276-195 BC), a Greek astronomer, geographer, mathematician, and poet best known for being the first to calculate the circuмference of the earth.
Jean Picard ( 1620-1682) was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand. He is principally notable for his accurate measure of the size of the Earth, based on a careful survey of one degree of latitude along the Paris Meridian.
As I said before, Domenico Cassini measured the Earth as egg shaped to falsify Newton's evolved bulging heliocentric Earth.