This is much like the question you asked regarding the procedure you supplied that you thought measured the curvature of water when it didn't.

What eratosthenes (his slave, actually), apocryphally, measured was the angle/length of shadows. Obviously.

What he calculated was the circumference of the world IF it was spherical, sunlight rays are always parallel, and a few other unvalidated assumptions.

If the world is not spherical and/or any of the other underlying assumptions were wrong then what he calculated was just nonsense.

This is much like the question you asked regarding the procedure you supplied that you thought measured the curvature of water when it didn't.

What eratosthenes (his slave, actually), apocryphally, measured was the angle/length of shadows. Obviously.

What he calculated was the circumference of the world IF it was spherical, sunlight rays are always parallel, and a few other unvalidated assumptions.

If the world is not spherical and/or any of the other underlying assumptions were wrong then he calculated was just nonsense.

This is much like the question you asked regarding the procedure you supplied that you thought measured the curvature of water when it didn't.

What eratosthenes, apocryphally (and his slave, actually), measured was the angle/length of shadows. Obviously.

What he calculated was the circumference of the world IF it was spherical, sunlight rays are always parallel, and a few other unvalidated assumptions.

If the world is not spherical and/or any of the other underlying assumptions were wrong then he calculated was just nonsense.