1. Earth's gravity field

A point of mass on the Earth's surface, rotating with it, undergoes an acceleration known as gravity acceleration. This acceleration is the result of the Newtonian attractions of the Earth's masses (gravity), the centrifugal acceleration due to the Earth's rotation, and the Newtonian attraction of the other bodies in the solar system (in practice, these are essentially the Moon, not very massive but close, and the Sun, distant but very massive). The modulus of the acceleration of gravity at a given point and time, known as gravity, therefore depends on the distribution of masses in the Earth and in the immediate vicinity of the measurement point, its geographical position and its relative position to the Moon and Sun.

In the International System (SI), the unit of gravity is the meter per square second (m/s ² ). Spatial...