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Modern geodetic observations from a wide range of space and terrestrial technologies contribute to our knowledge of the solid Earth, atmosphere, ocean, cryosphere, and land water storage. These geodetic observations record the “fingerprints” of global change processes and thus are a crucial independent source of high accuracy information for many global change studies. Many of the geodetic techniques require a globally distributed ground infrastructure, and associated space segment elements. In the past decade and half a variety of technique-specific services have been established under the auspices of the International Association of Geodesy (IAG) to facilitate global coordination of geodetic activities and to ensure the generation of high accuracy and reliable geodetic products to support geoscientific research. The Global Geodetic Observing System (GGOS) is an important component of the IAG, and is intended to be an “umbrella” for the IAG Services, with a primary coordinating function to ensure the development of an adequate global geodetic infrastructure, and a suite of integrated multi-technique products, that will meet the needs of scientific users. Coordination means bringing together the different geodetic observing techniques, services and analysis methods so as to ensure that the same standards, conventions, models and parameters are used in the data analysis and modelling of “Earth system” processes. Integration implies the combination of geometric, gravimetric, and rotational observations in data analysis and data assimilation, and the joint estimation and/or modelling of all the necessary parameters representing the difference components of the Earth system. The geodetic observations collected during the last decades have facilitated major scientific discoveries related to geohazards, climate and the global water cycle. Geodesy has the potential to contribute even more to global change studies, particularly if coordination and integration of the geodetic activities are continued. |
