Geodesy and Geoinformation: What's that?
For the description of the Earth and her changes the Physical Geodesy is providing the foundations. To determine the size and the figure of the Earth various and very different methods are applied: e.g. laser range measurements to satellites and reflectors on the Moon, observation with large antennas (radio telescopes) to invisible extra-galactic radio sources, and altimetry with radar scanning ot the sea surface from satellite. Accelerometers in satellites and aircrafts sense the Earth gravity field. With global navigation systems, levelling and gravity measurements terrestrial coordinate changes are monitored. The system Earth is regarded iwth its various implications:
- Change of Earth rotation axis and length of day
- Changes in the Earth gravity field and consequences on heights, sea and satellite orbits
- Changes of the Earth surface due to plate tectonics and other impacts
- Sea level change and variation of Earth and ocean tides
- Ocean currents
- Changes in heights and coordinates of reference points
By the establishment of global reference systems and Earth observations small changes caused by climate change and other natural and andropogenic influences on the Earth and resulting mass changes in and on the Earth can be monitored.