Determining the shape

How did FET determine the shape of the earth? I mean FET says it is flat. That much is obvious, but why say it is a disc...could it not be a triangular or a square, a hexagon or something else? Why a disc?

The exact shape of the rim is unknown and, ultimately, quite irrelevant.  Calling the FE a disc is more of a convenience than anything else.  You know, sorta like calling the oblate spheroid earth "round".  However, there are also some FE'ers that believe that the flat earth is an infinite plane.

The exact shape of the rim is unknown and, ultimately, quite irrelevant.  Calling the FE a disc is more of a convenience than anything else.  You know, sorta like calling the oblate spheroid earth "round".  However, there are also some FE'ers that believe that the flat earth is an infinite plane.

I'm just stressing the RET has methods to determine the shape.