The earth is flat because a curve has never been measured.
A curve has been calculated but never measured regardless of the ability to actually see the curve (Neil degrasse tyson says an observer has to be 100miles + up in sky) measuring a curve would be entirely possible, if it existed and even after many years of flatearth chitter chatter not 1 single proof of curve has been provided by the WGS84 model crowd.
'FE Core' did however measure a level earth across Lake Isjell.

Lake Isjell is the largest lake in the Netherlands, created by a dam in 1932 that closed off the Zuiderzee from the North Sea. The lake is now a freshwater inland bay and a vital freshwater source, fed by the River IJssel. It is a popular spot for sailing, cycling, and visiting charming historical fishing town