More accurate models of the static mean geoid and its temporal variability are vital for:

— a precise marine geoid, needed for the quantitative determination, in combination with satellite altimetry, of absolute ocean currents, their transport of heat and other properties;

— a unified global height reference system for the study of topographic processes, including the evolution of ice sheets and land surface topography;

— new understanding of the physics of the Earth’s interior;

— estimates of the thickness of the polar ice sheets and their variations through a combination of bedrock topography derived from gravity measurements and ice sheet surface topography from altimetry;

— estimates of the mass/volume redistribution of fresh water in order to further understand the hydrological cycle;

— improved understanding of post-glacial rebound processes on a global scale.

Magnetic field measurements are also valuable in a range of applications, including navigation systems, resource exploration drilling, spacecraft attitude control systems, assessments of the impact of ‘space weather’ caused by cosmic particles and earthquake prediction studies.

The precision location capabilities of satellite laser ranging and other systems (such as DORIS and GPS), sometimes in combination with interferometric SAR (INSAR), are applied in support of studies of crustal deformation, tectonic movements and Earth’s spin rate.