The Global Geodetic Observing System (GGOS) has been established by the Int- national Association of Geodesy (IAG) in order to integrate the three fundamental areas of geodesy, so as to monitor geodetic parameters and their temporal varia- ?9 tions, in a global reference frame with a target relative accuracy of 10 or b- ter. These areas, often called ‘pillars’, deal with the determination and evolution of (a) the Earth’s geometry (topography, bathymetry, ice surface, sea level), (b) the Earth’s rotation and orientation (polar motion, rotation rate, nutation, etc. ), and (c) the Earth’s gravity eld (gravity, geoid). Therefore, Earth Observation on a global scale is at the heart of GGOS’s activities, which contributes to Global Change - search through the monitoring, as well as the modeling, of dynamic Earth processes such as, for example, mass and angular momentum exchanges, mass transport and ocean circulation, and changes in sea, land and ice surfaces. To achieve such an - bitious goal, GGOS relies on an integrated network of current and future terrestrial, airborne and satellite systems and technologies. These include: various positioning, navigation, remote sensing and dedicated gravity and altimetry satellite missions; global ground networks of VLBI, SLR, DORIS, GNSS and absolute and relative gravity stations; and airborne gravity, mapping and remote sensing systems.

The Global Geodetic Observing System (GGOS) has been established by the Int- national Association of Geodesy (IAG) in order to integrate the three fundamental areas of geodesy, so as to monitor geodetic parameters and their temporal varia- ?9 tions, in a global reference frame with a target relative accuracy of 10 or b- ter. These areas, often called ‘pillars’, deal with the determination and evolution of (a) the Earth’s geometry (topography, bathymetry, ice surface, sea level), (b) the Earth’s rotation and orientation (polar motion, rotation rate, nutation, etc. ), and (c) the Earth’s gravity eld (gravity, geoid). Therefore, Earth Observation on a global scale is at the heart of GGOS’s activities, which contributes to Global Change - search through the monitoring, as well as the modeling, of dynamic Earth processes such as, for example, mass and angular momentum exchanges, mass transport and ocean circulation, and changes in sea, land and ice surfaces. To achieve such an - bitious goal, GGOS relies on an integrated network of current and future terrestrial, airborne and satellite systems and technologies. These include: various positioning, navigation, remote sensing and dedicated gravity and altimetry satellite missions; global ground networks of VLBI, SLR, DORIS, GNSS and absolute and relative gravity stations; and airborne gravity, mapping and remote sensing systems.

Geodesy is the science of accurately measuring and understanding three fundamental properties of Earth: its geometric shape, its orientation in space, and its gravity field, as well as the changes of these properties with time. Over the past half century, the United States, in cooperation with international partners, has led the development of geodetic techniques and instrumentation. Geodetic observing systems provide a significant benefit to society in a wide array of military, research, civil, and commercial areas, including sea level change monitoring, autonomous navigation, tighter low flying routes for strategic aircraft, precision agriculture, civil surveying, earthquake monitoring, forest structural mapping and biomass estimation, and improved floodplain mapping. Recognizing the growing reliance of a wide range of scientific and societal endeavors on infrastructure for precise geodesy, and recognizing geodetic infrastructure as a shared national resource, this book provides an independent assessment of the benefits provided by geodetic observations and networks, as well as a plan for the future development and support of the infrastructure needed to meet the demand for increasingly greater precision. Precise Geodetic Infrastructure makes a series of focused recommendations for upgrading and improving specific elements of the infrastructure, for enhancing the role of the United States in international geodetic services, for evaluating the requirements for a geodetic workforce for the coming decades, and for providing national coordination and advocacy for the various agencies and organizations that contribute to the geodetic infrastructure.

The international symposium Towards an Integrated Global Geodetic Observing System was an initiative of section II Advanced Space Technology of the International Association of Geodesy (lAG). Ittook place in the building ofthe Bavarian Academy of Sciences in Munich from October 5 -9, 1998. About 130 scientists from 24 countries participated in the symposium. It was organized jointly by the Deutsches Geodatisches F orschungsinstitut and the Institut fUr Astronomische und Physikalische Geodasie/Technische Universitat MUnchen. The objective of the symposium was an analysis of the state-of-art of geodetic space techniques and an outlook into the possibility of the establishment of a global integrated observing system. In view of the fact that most geodetic space techniques have reached or approach the one part per billion relative precision level the question arises what their j oint and coordinated operation could offer to the study of system Earth. For this purpose the symposium was divided into four themes, i. e. reference system and datum integration, strength and weakness of space techniques, upcoming gravity field satellite missions, and implications for Earth sciences. Each of these themes was addressed by invited lectures of prominent scientists with sufficient time left for discussion. The oral sessions were complemented by poster sessions. A panel discussion at the closing session completed the program.

These Proceedings include the written version of papers presented at the IAG International Symposium on "Gravity, Geoid and Earth Observation 2008". The Symposium was held in Chania, Crete, Greece, 23-27 June 2008 and organized by the Laboratory of Geodesy and Geomatics Engineering, Technical University of Crete, Greece. The meeting was arranged by the International Association of Geodesy and in particular by the IAG Commission 2: Gravity Field. The symposium aimed at bringing together geodesists and geophysicists working in the general areas of gravity, geoid, geodynamics and Earth observation. Besides covering the traditional research areas, special attention was paid to the use of geodetic methods for: Earth observation, environmental monitoring, Global Geodetic Observing System (GGOS), Earth Gravity Models (e.g., EGM08), geodynamics studies, dedicated gravity satellite missions (i.e., GOCE), airborne gravity surveys, Geodesy and geodynamics in polar regions, and the integration of geodetic and geophysical information.

This invaluable volume set of Advances in Geosciences continues the excellent tradition of the Asia-Oceania scientific community in providing the most up-to-date research results on a wide range of geosciences and environmental science. The information is vital to the understanding of the effects of climate change, extreme weathers on the most populated regions and fastest moving economies in the world. Besides, these volumes also highlight original papers from many prestigious research institutions which are doing cutting edge study in atmospheric physics, hydrological science and water resource, ocean science and coastal study, planetary exploration and solar system science, seismology, tsunamis, upper atmospheric physics and space science.

This book gives a systematic overview of the fundamental theories, frameworks and methods for measurement and evaluation applying to geodesy, though the contribution of geodetic spatial techniques for positioning and for establishing the gravitational field receives particular emphasis. These methods have led to a change in the setting up of geodetic basic networks that is also of importance in practical terms; for interdisciplinary geodynamics research geodesy can likewise make major contributions with their assistance. The current status of geodesy is illustrated by numerous examples from survey, evaluation and analysis; an extensive literature list makes further study all the easier. The book conveys an extensive overview of the profound changes that geodesy has undergone in the past twenty years.