Flat Earthers must learn Geology to be entirely convinced. Seriously, all equipment being used to measure ground movements or know the presence of metals underground take into consideration that the Earth is oblate spheroid.
Everyone can derive those equations (physics) being used and test those equations based from the output of those equipment.
However, it seems that they are just too hard to get them to read and understand.
Even the Greeks already knew and were able to measure that the Earth is at least not flat.