What shape represents the true physical shape of the Earth, influenced by its gravitation and rotation?

The geoid represents the true physical shape of the Earth as it reflects the Earth's mean sea level and accounts for variations in gravitational forces caused by factors such as the distribution of mass within the Earth. It essentially represents an equipotential surface, meaning that if you were to take a level surface that would align with the force of gravity, it would conform to the shape of the geoid. This shape is considered more accurate than a simple sphere or an oblate ellipsoid, as it better captures the irregularities of the Earth's surface resulting from its rotation and gravitational variations.

While the oblate ellipsoid is also a commonly used model in geodesy, it is a mathematical approximation that simplifies the true shape of the Earth by assuming uniform density and gravitation. The reference ellipsoid is similarly a simplified geometric representation and does not consider local gravitational effects, making the geoid a more accurate representation of the Earth's shape in practical applications.