The Geoid and Earth Eotation

The physical principle is quite simple: the gravitational geoid is a function of the mass distribution of the Earth according to Newton’s gravitational law, so any mass redistribution produces changes in the geoid. Similarly, a mass redistribution will change the Earth’s inertia tensor and the Earth rotation vector will change accordingly as required by the conservation of angular momentum. The resultant mass redistribution changes the geoid and gives rise to mass-term excitation for Earth rotation. Tidal deformation in the solid Earth is simple (at least conceptually), being proportional to the tidal potential through the appropriate Love numbers. Global geoid and its variations are derived primarily based on observations of orbital behavior of near-Earth satellites. These observations consist of accurate tracking of satellites from ground stations, such as laser ranging and Doppler tracking. A good knowledge of the dynamics of all the non-gravitational forces acting on the satellites is also essential.