This open access volume contains selected papers of the 2021 Scientific Assembly of the International Association of Geodesy – IAG2021. The Assembly was hosted by the Chinese Society for Geodesy, Photogrammetry and Cartography (CSGPC) in Beijing, China from June 28 to July 2, 2021. It was a hybrid conference with in-person and online attendants. In total, the Assembly was attended by 146 in-person participants and 1,123 online participants. The theme of the Assembly was Geodesy for a Sustainable Earth. 613 contributions (255 oral presentations and 358 poster presentations) covered all topics of the broad spectrum considered by the IAG: geodetic reference frames, Earth gravity field modelling, Earth rotation and geodynamics, positioning and applications, the Global Geodetic Observing System (GGOS), geodesy for climate research, marine geodesy, and novel sensors and quantum technology for geodesy. All published papers were peer-reviewed, and we warmly recognize the contributions and support of the Associate Editors and Reviewers.

This book series is composed of peer-reviewed proceedings of selected symposia organized by the International Association of Geodesy. It deals primarily with topics related to Geodesy Earth Sciences : terrestrial reference frame, Earth gravity field, Geodynamics and Earth rotation, Positioning and engineering applications.

These proceedings include the written version of 130 papers presented at the International Association of Geodesy IAG2009 "Geodesy for Planet Earth" Scientific Assembly. It was held 31 August to 4 September 2009 in Buenos Aires, Argentina. The theme "Geodesy for Planet Earth" was selected to follow the International Year of Planet Earth 2007-2009 goals of utilizing the knowledge of the world’s geoscientists to improve society for current and future generations. The International Year started in January 2007 and ran thru 2009 which coincided with the IAG2009 Scientific Assembly, one of the largest and most significant meetings of the Geodesy community held every 4 years. The IAG2009 Scientific Assembly was organized into eight Sessions. Four of the Sessions of IAG2009 were based on the IAG Structure (i.e. one per Commission) and covered Reference Frames, Gravity Field, Earth Rotation and Geodynamics, and Positioning and Applications. Since IAG2009 was taking place in the great Argentine city of Buenos Aires, a Session was devoted to the Geodesy of Latin America. A Session dedicated to the IAG’s Global Geodetic Observing System (GGOS), the primary observing system focused on the multidisciplinary research being done in Geodesy that contributes to important societal issues such as monitoring global climate change and the environment. A Session on the IAG Services was also part of the Assembly detailing the important role they play in providing geodetic data, products, and analysis to the scientific community. A final Session devoted to the organizations ION, FIG, and ISPRS and their significant work in navigation and earth observation that complements the IAG.

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.

This series of reference books describes sciences of different elds in and around geodesy with independent chapters. Each chapter covers an individual eld and describes the history, theory, objective, technology, development, highlights of research and applications. In addition, problems as well as future directions are discussed. The subjects of this reference book include Absolute and Relative Gravimetry, Adaptively Robust Kalman Filters with Applications in Navigation, Airborne Gravity Field Determination, Analytic Orbit Theory, Deformation and Tectonics, Earth Rotation, Equivalence of GPS Algorithms and its Inference, Marine Geodesy, Satellite Laser Ranging, Superconducting Gravimetry and Synthetic Aperture Radar Interferometry. These are individual subjects in and around geodesy and are for the rst time combined in a unique book which may be used for teaching or for learning basic principles of many subjects related to geodesy. The material is suitable to provide a general overview of geodetic sciences for high-level geodetic researchers, educators as well as engineers and students. Some of the chapters are written to ll literature blanks of the related areas. Most chapters are written by well-known scientists throughout the world in the related areas. The chapters are ordered by their titles. Summaries of the individual chapters and introductions of their authors and co-authors are as follows. Chapter 1 “Absolute and Relative Gravimetry” provides an overview of the gravimetric methods to determine most accurately the gravity acceleration at given locations.

Geodesy (the measurement of the size and shape of the earth), fascinating since the time of Erathosenes, became a basic science for the space program. Irene Fischer was a leader in the construction of the World Geodetic System (has an Earth reference ellipsoid named in her honor) when it was still being done by surveyors, piecing together terrestrial, gravitational and astronomical data. By the 1970s, satellite geodesy and marine geodesy were just coming into their own. Using her career, Fischer revels in explaining how the science unfolded, and how misunderstandings occur across scientific fields, e.g., why the "standard ocean" and the geoid do not easily translate across the fields of oceanography and geodesy. Her account should appeal to those writing the history of women in science. Government science, too, is less well studied than academic science even though some fields, such as geodesy, were always government led. Fischer provides food for thought, as well, to those who claim to study the management of science in bureaucratic settings different from those of industry or academia. Peppered among these themes are Fischer's solutions to historical mysteries such as why Columbus' used a figure for the size of the earth's circumference that was so much smaller than Erastothenes' or Posidonius' (with the added benefit of making it easier to persuade his patrons).