Satellite geodesy is the measurement of the form and dimensions of the Earth, the location of objects on its surface and the figure of the Earth's gravity field by means of satellite techniques. In other words, geodesy by means of satellites. It belongs to the broader field of space geodesy, which also includes such techniques as geodetic very long baseline interferometery VLBI and lunar laser ranging.
Traditional astronomical geodesy, which includes astronomical positioning, is not commonly considered a part of satellite geodesy. Also surveying by GPS has become so commonplace that it is less and less considered part of satellite geodesy.
Satellite geodetic measurement techniques
Geodetic use of global positioning satellite systems (GPS, GLONASS, Galileo)
Geodesy is primarily concerned with positioning and the gravity field and geometrical aspects of their temporal variations, although it can also include the study of the Earth's magnetic field.
Before the satellitegeodesy era, the coordinate systems associated with geodetic datums attempted to be geocentric, but their origins differed from the geocentre by hundreds of metres, due to regional deviations in the direction of the plumbline (vertical).
Faculty of Geodesy and Geoinformatics, University of Zagreb, Zagreb, Croatia
The latter is the study of the gravitational field of the earth and its relationship to the solid structure of the planet.
Satellite orbits and their perturbations were directly related to the geoid, while the positions of the tracking stations and geodetic nets were tied to the reference ellipsoid, and a major objective was to improve the quantitative definitions of both geoid and ellipsoid.
From comparison of distances measured by ground surveys and those determined by satellite techniques, the APL workers concluded that, with a modest number of satellite passes and four or more observing stations, relative positions of ground stations separated by continental distances could be obtained with a confidence level of about 10 meters.
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