GPS Geodesy

GPS Geodesy
Name	GPS Geodesy
Field	Geodesy
Established	1970s–1990s

GPS Geodesy GPS Geodesy is the application of the Global Positioning System in the science of measuring Earth's size, shape, gravity field, and rotation. It combines satellite constellations, reference frames, and observation networks to determine positions, velocities, and deformations for scientific, engineering, and navigational purposes.

Introduction

GPS Geodesy grew from collaborations among agencies such as National Aeronautics and Space Administration, United States Department of Defense, National Oceanic and Atmospheric Administration, National Geodetic Survey, European Space Agency, Japan Aerospace Exploration Agency, Russian Federal Space Agency, Indian Space Research Organisation, China National Space Administration, and academic centers like Massachusetts Institute of Technology, Stanford University, University of Cambridge, ETH Zurich, Universität Bern that implemented satellite ranging, reference frames, and time transfer. It integrates concepts from classical figures and institutions including Johannes Kepler, Isaac Newton, Leonhard Euler, Carl Friedrich Gauss, Pierre-Simon Laplace, Friedrich Wilhelm Bessel, and modern contributors such as Ivan I. Mueller and large projects like International GNSS Service, International Association of Geodesy, International Earth Rotation and Reference Systems Service, International Union of Geodesy and Geophysics, Global Geodetic Observing System, European Plate Observing System, Plate Boundary Observatory, and UN-GGIM.

Principles and Techniques

Fundamental techniques employ observations from satellite constellations including Global Positioning System, GLONASS, Galileo (satellite navigation), BeiDou Navigation Satellite System, combined with methods developed in the spirit of pioneers like Carl Friedrich Gauss, Adrien-Marie Legendre, and later specialists at Jet Propulsion Laboratory, Scripps Institution of Oceanography, Geological Survey of Canada, British Geological Survey, Lawrence Livermore National Laboratory. Observational methods draw on Very Long Baseline Interferometry, Satellite Laser Ranging, Doppler (measurement), Radio occultation, and techniques used in projects such as TOPEX/Poseidon, Landsat program, GRACE, GOCE. Geodetic strategies include static geodesy, rapid-static, kinematic positioning, precise point positioning, network adjustment, and deformation monitoring as practiced by teams at California Institute of Technology, Columbia University, University of Texas at Austin, Pennsylvania State University, and agencies like US Geological Survey.

Data Processing and Models

Processing pipelines rely on precise ephemerides from International GNSS Service, clock products from Bureau International des Poids et Mesures, and reference frames such as International Terrestrial Reference Frame and World Geodetic System 1984. Modeling includes atmospheric corrections using models like Saastamoinen model, ionospheric models from Center for Orbit Determination in Europe, ocean loading corrections based on FES (ocean tide models), and solid Earth tide models informed by standards from International Earth Rotation and Reference Systems Service. Analysts use software developed at institutions such as Natural Resources Canada, GFZ German Research Centre for Geosciences, National Geospatial-Intelligence Agency, NOAA's National Centers for Environmental Information, and projects like Bernese GNSS Software, GAMIT/GLOBK, GIPSY-OASIS to perform ambiguity resolution, least-squares adjustment, Kalman filtering, and time series analysis.

Applications

Applications span crustal deformation monitoring for events like 2011 Tōhoku earthquake and tsunami, 1994 Northridge earthquake, Great Chilean earthquake of 1960, volcanic deformation studies at Mount St. Helens, Eyjafjallajökull, and hazard assessment in regions overseen by agencies such as United States Geological Survey, Geological Survey of Japan, Instituto Geofísico del Perú. GPS geodetic products support sea level studies linked to Intergovernmental Panel on Climate Change, plate tectonics research involving Pacific Plate, North American Plate, Eurasian Plate, and infrastructure applications used by Federal Aviation Administration, International Civil Aviation Organization, U.S. Army Corps of Engineers, European Commission, World Bank, and projects like Smart Cities Mission.

Accuracy, Errors, and Uncertainty

Error sources include satellite clock and ephemeris errors managed by International GNSS Service, multipath influenced by urban arrays studied by Massachusetts Institute of Technology teams, ionospheric delay during events like solar storm of 1859 analogues modeled by NOAA Space Weather Prediction Center, tropospheric delay calibrated with radiosonde networks at World Meteorological Organization stations, and systematic biases addressed through reprocessing campaigns by International Association of Geodesy and the International Earth Rotation and Reference Systems Service. Uncertainty quantification employs statistical approaches influenced by works at National Institute of Standards and Technology, European Space Agency, and academic groups at University of Colorado Boulder.

Instrumentation and Networks

Key hardware includes dual- and multi-frequency GNSS receivers manufactured by companies represented at conventions like Intergeo, antennas complying with standards from International Telecommunication Union, and timing standards traceable to International Bureau of Weights and Measures. Global and regional networks include International GNSS Service, EUREF Permanent Network, CORS, SONEL, IGS Real-time Service, APRS (Asia-Pacific Reference Frame), and national networks maintained by institutions such as Ordnance Survey, Geoscience Australia, Instituto Geográfico Nacional (Spain). Field campaigns reference benchmarks from efforts like Great Trigonometrical Survey and use platforms including unmanned aerial systems evaluated by Federal Aviation Administration.

History and Development

Origins tie to orbital mechanics of Johannes Kepler and Isaac Newton, radio-ranging experiments by Guglielmo Marconi era groups, navigation advances during World War II, the satellite age initiated by Sputnik 1, system architecture shaped by agencies including United States Department of Defense and NASA, and the civilian expansion through policy decisions influenced by leaders such as President Ronald Reagan after the Korean Air Lines Flight 007 incident. The maturation of precise GNSS techniques was driven by collaborations among Jet Propulsion Laboratory, Scripps Institution of Oceanography, National Geodetic Survey, and international research networks culminating in standardized products from International GNSS Service and reference frames like International Terrestrial Reference Frame.

Category:Geodesy