Well, I know the answer. Google confirms it.
In cartography, a map projection is a way to flatten a globe's surface into a plane in order to make a map. This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane.
I wanted to see a mapping of a flat earth's surface onto a planar map.
Or a measurement of that surface which could in turn be used to build a map.
It's problematic to have an idea that is thousands of years old but has no semblance of a model, a map or measurements.
I know of a scientific theory which unifies all observations from reality into a congruent model of that reality.