To minimize the anthropogenic impact on the System Earth and to preserve a living environment and resources for future generations, a better understanding of global change phenomena is required.
This is only possible if our studies, models, predictions, and political decisions are based on comprehensive observations of the System Earth. Observations of the System Earth are not only necessary for the scientific understanding of the Earth. They are fundamental for many social areas ranging from disaster prevention and mitigation, the provision of resources such as energy, water and food, gaining and understanding climate change, the protection of the biosphere, the environment and human health, to the building and management of a prosperous society worldwide.
This ‘system of systems’, through its GEOSS Platform (former GCI), proactively links together existing and planned observing systems around the world and support the need for the development of new systems where gaps currently exist. It will promote common technical standards so that data from the thousands of different instruments can be combined into coherent data sets.
By contributing to GEO and GEOSS, GGOS provides geodetic data which, when combined with other Earth observations, can be translated into support for political decision-making. The main objective is to provide open, timely, and reliable Earth observation data to facilitate the development of policies that address societal challenges. Thus, GEOSS is essential to implement the Sustainable Development Goals (SDGs) of the United Nations (UN), the Sendai Framework for Disaster Risk Reduction, and the UN Framework Convention on Climate Change.
How Geodesy can Contribute?
Geodesy is the science of determining and representing the shape of the Earth, its gravity field and its rotation as a function of time. A core element to reach this goal are stable and consistent geodetic reference frames, which provide the fundamental layer for the determination of time-dependent coordinates of points or objects, and for describing the motion of the Earth in space. Traditionally, geodetic reference frames have been used for surveying, mapping, and space-based positioning and navigation. With modern instrumentation and analytical techniques, Geodesy is now capable of detecting time variations ranging from large and secular scales to very small and transient deformations with increasing spatial and temporal resolution, high accuracy, and decreasing latency.
Sea Level & Atmospheric Observation
Modern satellite altimetry missions (such as Topex/Poseidon, Jason 1, 2 and 3; Envisat, Sentinel 3A and 3B, etc.) combined with precise satellite orbit determination and precise geoid models provided by Geodesy make the monitoring of the sea surface variations with high spatial and temporal resolutions possible. Similar satellites (like Cryosat-2) are dedicated to detect variations in the continental and marine ice cover.
Novel applications – especially regarding unseen benefits – are being identified on a regular basis thanks to the open geodetic data and analysis products provided by IAG technical services and GGOS.
Geodetic Earth observations based on space-based techniques are complemented and extended by terrestrial methods (in-situ observations) to measure and improve the modelling of short wavelength signals not detected by satellites; for instance, surface gravity data (terrestrial, airborne and marine gravity data) are essential to determine gravity field signals with resolutions less than 100 km. In the same way, tide gauge records are essential to improve the monitoring of the sea level in coastal areas, where the satellite altimetry techniques are not as accurate as in the open oceans.
Changes in the Earth’s size, shape, gravity field and orientation are inherently related to the Earth’s dynamics and to mass and energy transport throughout the System Earth. As the System Earth is a unique entity, any change within the System influences any geodetic observation. Consequently, to reach its primary goal of determining the time-dependent geometry, gravity field and rotation of the Earth, Geodesy is essential to the detection and appropriate handling of the signals emitted by the System Earth. Geodesy measures these signals with different sensors, in different domains, and in different time and space resolutions – providing a unique framework for monitoring and understanding the System Earth as whole, including its solid, fluid, and gaseous components.
Global Geodetic Observing System
The Global Geodetic Observing System (GGOS) is the contribution of Geodesy to Earth observations. GGOS aims to provide consistent and openly available observations of the spatial and temporal changes of the shape and gravity field of the Earth, as well as the temporal variations of the Earth’s rotation. This means delivering a global picture of the surface kinematics of our planet, including the ocean, ice cover, continental water, and land surfaces, and delivering estimates of mass anomalies, mass transport, and mass exchange in the System Earth. Surface kinematics and mass transport together are the key to global mass balance determination, and are an important contribution to understanding the energy budget of our planet.