The helplessness we feel in view of natural disasters demonstrates very clearly that, at present, our knowledge of the Earth's complex system and our tools for the timely detection of potentially disastrous events are rather limited. The continuous global monitoring and detection of changes in the Earth system, occurring at local to global spatial scales and over timescales ranging from extremely short duration events (e.g. earthquakes, volcanic eruptions, land slides, or flooding) to long (decadal to geological) time scales (e.g. melting of ice sheets, sea-level change, glacial-isostatic adjustment, plate tectonics, or land degradation) is therefore of crucial importance. This implies really challenging extremes to be met with the detection and quantification of catastrophic events in (near) real-time on the one hand and barely detectable, but critical long-term trends (e.g. sea level rise) on the other hand. The Global Geodetic Observing System (GGOS) is geodesy's answer to this challenge.
The Global Geodetic Observing System (GGOS) was established by the International Association of Geodesy (IAG) in July 2003. In April 2004 the IAG, represented by GGOS, became a participating organization of the Group on Earth Observation (GEO) and in May 2006 GGOS was accepted as a member of the Integrated Global Observation Strategy Partnership (IGOS-P). GGOS is the contribution of geodesy to the Global Earth Observation System of Systems (GEOSS). It provides the metrological basis and the reference systems and frames, which are crucial for Earth observing systems. GGOS is built on the IAG Services (IGS, IVS, ILRS, IDS, IERS, IGFS, etc.) and the products they derive on an operational basis for Earth monitoring, making use of space- and ground-based geodetic techniques such as Very Long Baseline Interferometry (VLBI), Satellite and Lunar Laser Ranging (SLR/LLR), Global Navigation Satellite Systems (GNSS), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), altimetry, InSAR (Interferometric Synthetic Aperture Radar) and gravity satellite missions, gravimetry, etc. All these observation techniques are considered integral parts of GGOS, allowing the monitoring of the Earth's shape and deformation (including water surface), the Earth's orientation and rotation, and the Earth's gravity field and its temporal variations with an unprecedented accuracy. The observed quantities give direct evidence of many global processes that have a crucial impact on human society such as earthquakes, volcanism, floods, sea level change, climate change, ground water redistribution, mass balance of the polar ice sheets, etc.GGOS relies on the observing systems and analysis capabilities already in place in the IAG Services and envisions the continued development of innovative technologies, methods and models to improve our understanding of global change processes. GGOS provides a framework that ranges from the acquisition, transfer and processing of a tremendous amount of observational data to its consistent integration and assimilation into complex numerical models of the Earth system (including solid Earth, oceans, atmosphere, hydrosphere, cryosphere and the interactions thereof). This is being achieved by an international effort and a close, multidisciplinary cooperation with groups working in related fields such as geodynamics, geophysics, oceanography, hydrology, glaciology, meteorology, and climatology.
This presentation will introduce GGOS, its organization, and its essential contributions to an integrated Earth monitoring system, to early warning systems and to the understanding of global change and its impact on environment and society.