What does an ellipsoid represent?

An ellipsoid is a three-dimensional geometric figure that resembles a flattened sphere, which accurately represents the rounded shape of the Earth. The Earth's shape is not a perfect sphere due to its rotation, which causes it to bulge at the equator and flatten at the poles. By using an ellipsoid model, we can better account for these variations and achieve a more precise representation of the Earth's surface and gravitational field.

This model is particularly important in fields like geodesy and cartography, where understanding the Earth's shape is essential for creating accurate maps and navigating terrestrial positions. In contrast, the other options do not align with the definition or characteristics of an ellipsoid.