For the understanding and the mathematical description of the processes inside and outside of the Earth our planet has to be considered as a complex system consisting of many components and the relationships and interactions between these components have to be taken into account.
The investigation and observation of many of such subsystems and the interrelations between them are integral parts of global geodesy. GGOS (Global Geodetic Observing System), the observing system of the International Association of Geodesy (IAG), is the main contribution of geodesy to Earth system research. GGOS provides measurements and models in the three areas which are named the pillars of geodesy: geokinematics, Earth rotation and gravity field. The synergetic fusion of those three fields builds the basis for the allocation of most stable and precise geodetic reference frames which are crucial for the assessment and interpretation of global geodynamic processes.
The components of system Earth, which are relevant to global geodesy and vice versa, are (see figure): the solid Earth, atmosphere, hydrosphere, cryosphere, biosphere, and antroposphere. Also the planets exert a big influence on the Earth. The gravitational interaction of the Earth, sun, moon, and planets cause the main part of the Earth's motion in space (precession and nutation). Gravitational forces of the celestial bodies acting on the Earth induce relative accelerations in system Earth relative to the center of mass, so called tidal accelerations. These are responsible for the oceanic and atmospheric tides and (because of the deformability of the Earth) the solid Earth tides.
The working group 'Interactions in System Earth' currently has two focus areas:
- Earth rotation
- Observation: GNSS, VLBI, ringlaser
- Geophysical excitation: Atmosphere & ocean tides
- Earth rotation: angular momentum and Earth-atmosphere interaction torques
- Station positions: atmospheric pressure loading
- Path delay: mapping functions, ray-tracing
- Ionosphere: delay correction maps
For additional information about the working group activities refer to the project section and the corresponding web pages.