This experiment is more logical and should be more accurate then looking over water, but they claim that the earth is CONCAVE!! Now its getting really crazy, now we have 3 different groups:

Convex earthers (the globemodel we learn in school and society)
Concave earther (Rectilineator experiment)
and Flat earther (People making observations of the supposely flat earth)

I give up on this discussion and will wait to make any conclusion till there is solid prove of any of the 3.