What is the purpose of the "Spheroid" in geodesy?

The purpose of the "Spheroid" in geodesy is primarily to model the shape of the Earth for various applications. A spheroid, which is often referred to as an ellipsoid in geodetic contexts, approximates the Earth’s shape more accurately than a sphere due to the Earth's equatorial bulge caused by its rotation.

In geodesy, understanding the Earth's shape is crucial for accurately positioning, navigation, surveying, and many other applications related to mapping the planet. The spheroid provides a mathematical model that can be used in conjunction with coordinates to create a reference framework for determining locations on the surface of the Earth.

Other options relate to different aspects of geodesy but do not fully capture the primary role of the spheroid. For instance, measuring ocean depths and creating digital maps can involve various methodologies and reference systems, while defining gravitational pull pertains to another area of physics. Thus, the function of the spheroid is fundamental to providing a reliable and practical model for the Earth's dimensions and surface, which is essential in geodetic work.