Background models used in geodetic data processing

P. Gegout (1), F. Lyard (2), J.-M. Lemoine (3)
(1) DTP/GS (2) LEGOS (3) CNES/GS, Observatoire Midi-Pyrenees, 14, avenue Edouard Belin, 31400 Toulouse

The atmosphere, non-tidal oceans and hydrological variations fall into a class of models that can only be represented in empirical time-series; and are generally not used in a predictive sense in geodetic data processing. There are several notable common attributes of these series that affect their use in geodetic data processing. Their quality depends on location. They are outcomes of non-geodetic activities, so the attributes important for their use in geodesy are not always safeguarded (e.g. continuity, uniformity of standards, or long-term trends). This presentation surveys what we know of these issues as relevant to geodesy, and examines the contrast between the availability and the requirements for future gravity missions.