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(July 8-19, 2019)

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IAG symposia


G01 Reference Frames

Convener: Tonie van Dam (Luxembourg, Luxembourg)
Gary Johnston (Canberra, Australia)


Accurate reference frames are fundamentally important for Earth science studies, for satellite navigation, for applications relying on geo-spatial information, and increasingly for commercial applications such as agriculture, aviation, construction, public safety, and transportation. The primary goal of this symposium, is to bring together

  • the many individuals and government representatives responsible for funding, installing, and maintaining the global International Terrestrial Reference Frame infrastructure;
  • scientists from all disciplines and branches studying and using geodetic reference frames, and
  • representatives from industry who use geo-referencing to address the most important questions and issues that the community must consider regarding theoretical and practical implementation of improved reference frames for science, surveying, and commerce.

Contributions are solicited that will address the underlying limiting factors, systematic errors and novel approaches for future improvements to the ITRF. Additionally, papers addressing reference frame requirements, geoscience and commercial usage, and applications will be of great importance to the G1 symposium.

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G02 Static Gravity Field Models and Observations

Convener: Urs Marti (Wabern, Switzerland)

Co-conveners: Hussein Abd-Elmotaal (Minia, Egypt), Thomas Gruber (Munich, Germany), Jianliang Huang (Ottawa, Canada), Leonid Vitushkin (St. Petersburg, Russia), Yan Ming Wang (Washington, USA)


The determination of the Earth's gravity field and its temporal variations is one of the principal tasks of geodesy. After the successful completion of the GOCE mission and the release of its final products, new applications in high precision global and regional gravity field modelling became possible. In combination with new satellite altimetry missions, terrestrial and airborne gravity data, digital elevation and density models or GPS/levelling measurements, new insights are given in the field of oceanography, physical height systems, solid Earth sciences and others. This session invites contributions in the field of generation of global and regional static gravity field models. Specifically, the application of GOCE data and models and their combination with other gravimetric satellite missions is one of the key topics. The spatial resolution of such global satellite-only models can be further increased through the combination with terrestrial and airborne gravity data and with topographic gravity models and are usually verified by independent sources such as GPS/levelling or deflections of the vertical. Further topics include but are not limited to:

  • advances in the methodology and application of combining heterogeneous data sets and the generation of regional and local geoid models and the modelling of topographic gravity effects;
  • recent progress in the development of instrumentation and application of absolute and relative gravity measurements (terrestrial, airborne and shipborne) and their combination and processing;
  • establishment of the global gravity reference system and metrological support of absolute gravity measurements;
  • new applications of GOCE models in geophysics;
  • topography and density models and their effect on the gravity field;
  • investigations for modelling the gravity field of the moon and the planets. 

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G03 Variations of the Gravity Field

Convener: Srinivas Bettadpur (Austin, USA)

Co-conveners: Frank Flechtner (Potsdam, Germany), Shuanggen Jin (Shanghai, China), Paul Tregoning (Canberra, Australia)


The Earth science community has enjoyed more than a decade of new insights into the Earth system through the geodetic remote-sensing of time-variations of Earth gravity field from the joint US/German GRACE mission. Even further gains are anticipated with the planned 2017 launch of the US/German GRACE Follow-On mission, as well as the other next generation gravity missions envisaged in the post-2020 time-frame. At the same time, there is renewed interest in the geodetic re-analysis of satellite laser ranging and GNSS tracking of low-Earth orbiter (LEO) satellites as a means of extended data records into the past, or for bridging between dedicated gravity missions. Complementary outcomes from geophysical modeling, and terrestrial positioning/loading and gravimetry are deployed to help interpret, disaggregate, or validate time-variable gravity measurements. On the applications front, the geodesy community is examining the use of historical and low-latency satellite gravity data sets for both research as well as operational applications. This session invites contributions reporting on the state of the art pertinent to the full range of this subject. Topics of interest include, but are not limited to: new results from the studies of time-variable Earth gravity time-series; developments in the methods of global and regional satellite gravity data analysis; use of complementary geodetic methods for data collection and analysis of time-variable gravity field; development of applications and technologies for current and future gravity missions; innovations in algorithms, computation, and analysis; and other related subjects.

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G04 Earth Rotation and Geodynamics

Convener: Richard Gross (Pasadena, USA)

Co-conveners: Aleksander Brzezinski (Warsaw, Poland), Manabu Hashimoto (Kyoto, Japan), Matt King (Tasmania, Australia), Haluk Özener (Istanbul, Turkey), Maik Thomas (Potsdam, Germany)


The Earth is a dynamic system: it has a fluid, mobile atmosphere and oceans, a continually changing global distribution of ice, snow, and water, a fluid core that is undergoing some type of hydromagnetic motion, a mantle both thermally convecting and rebounding from the glacial loading of the last ice age, and mobile tectonic plates. In addition, external forces due to the gravitational attraction of the Sun, Moon, and planets act upon the Earth. These internal dynamical processes and external gravitational forces exert torques on the solid Earth, or displace its mass, thereby causing the Earth's rotation, gravitational field, and shape to change.
Geodetic observing systems, both space-based and ground-based, provide the measurements of the Earth's rotation, gravitational field, and shape that are used to study the response of the Earth to these dynamical forces. This symposium will be a forum for discussing the theory, modeling, and observations of these geodynamical processes and their effect on the Earth's rotation. In particular, contributions are solicited on tidal phenomena; on global and regional crustal deformation including intraplate deformation, the earthquake deformation cycle, aseismic phenomena such as episodic tremor and slip, and volcanic deformation; on loading effects associated with the space-time variation of atmospheric pressure, seafloor pressure, and the hydrological cycle; on the Earth's instantaneous and delayed responses to ice mass changes; and on the integration of space and terrestrial approaches for studying the kinematics and mechanics of tectonic plate boundary zones, and in particular of the Eurasian/African/Arabian boundary zone. Contributions on the theory, modeling, and observations of the Earth's rotation itself are also sought.

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G05 GNSS++: Emerging Technologies and Applications

Convener: Dorota Grejner-Brzezinska (Columbus, USA)

Co-conveners: Allison Kealy (Melbourne, Australia), Vassilis Gikas (Athens, Greece), Joao F. Galera Monico (Presidente Prudente, Brazil)


The Symposium will deal with the following topics:

  • Advanced GNSS processing techniques and algorithms including multi-constellation and multi-frequency implementations and estimation, and stability of inter-constellation biases and reference frame alignment;
  • Algorithms and methods for improving the performance of network-based RTK and PPP techniques;
  • Integrity monitoring techniques and navigation performance, including software tools;
  • Interoperability among augmentation systems (e.g. GBAS with SBAS ranging, GBAS with integrated inertial, transitions between GBAS, SBAS and RAIM/FDE etc.);
  • Practical applications of alternatives and backups to GNSS using multi-sensor systems and multi-agent collaborative navigation;
  • Novel algorithms and techniques for positioning and timing in GNSS-challenged environments;
  • Design, construction, characterization, and installation of imaging and non-optical imaging sensors, including optical, IR, SAR, IfSAR, LiDAR, etc;
  • Investigation and development of integration algorithms for imaging techniques and RF-based technologies (such as, Wi-Fi, UWB, RFID, etc.) for different navigation problems;
  • Real-time implementation of a vision based navigation algorithms;
  • System architectures and algorithms for data fusion of multi-sensor systems (GNSS, radio, magnetic, inertial, visual).
  • Concepts and algorithms for remote sensing using GNSS signals to probe the earth’s atmosphere and surface and the use of GNSS-based positioning to support observations made by other sensors. Topics include: ground-based, airborne, and spaceborne GNSS reflectometry, GNSS radio occultations (GNSS-RO), airborne laser scanning, digital photogrammetry and synthetic aperture radar applications;
  • Modern PNT and its applications: autonomous navigation and guidance, collaborative navigation based on vehicle-to-vehicle or vehicle-to-cloud communication, advanced driver assistance and collision avoidance;
  • UAS, augmented reality, location-based services, road tolling, liability issues associated with commercial delivery of positioning services; science-based future role of PNT in society;
  • New technology, products, and applications in precise positioning and RTK for civil applications; Applications for construction, agriculture, survey, infrastructure, OEM, GIS, and other emerging precise positioning, precise agriculture, geo-sensor networks, field robotics etc.

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G06 Unifying Height Systems

Convener: Laura Sánchez (Munich, Germany)

Co-conveners: Michael Sideris (Calgary, Canada), Matthew Amos (Wellington, New Zealand), Silvio Freitas (Curitiba, Brazil), Yan Ming Wang (Silver Spring, USA)


The scope of the Symposium is the unification of the existing vertical reference systems around the world to be achieved through the definition and realization of a global vertical reference system that supports geometrical (ellipsoidal) and physical (normal, orthometric) heights world-wide with centi­metre precision (10-9) in a global frame, enables the unification of all existing physical height systems, i.e., referring all geopotential differences to one and the same reference equipotential surface with potential W0, and provides high-accuracy and long-term stability of the temporal height changes (dh/dt, dH/dt, dN/dt) with millimetre precision. A World Height System (WHS) shall be realized with a global combined network, which will integrate at a set of terrestrial reference stations high-precision absolute and relative gravity, levelling with gravity reductions, and GNSS and tide gauge observations. For this purpose, it will use contributions from all IAG Commissions, and the available databases, standards and infrastructure of the IAG/GGOS Services.

Contributions are invited to all aspects of height system unification, i.e.,

  • Refinement of standards and conventions for the definition and realisation of vertical reference systems;
  • Establishment of a global vertical reference level;
  • Recommendations for a global vertical reference frame;
  • Guidelines/procedures for height system unification;
  • Development of a registry (metadata) containing the existing height systems and their connections to a global one;
  • Determination and modelling of the temporal changes of the reference frame.

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G07 Geohazards Monitoring

Convener: Ioannis Doukas (Thessaloniki, Greece)

Co-conveners: Cheng Wang (Xiamen, China), Ruth Neilan (Pasadena, USA), Barbara Theilen-Willige (Berlin, Germany)


Mitigating the impact on human life and property of natural hazards such as earthquakes, volcanic eruptions, debris flows, landslides, land subsidence, tsunamis, floods, storm surges, hurricanes and extreme weather is an important scientific task to which GGOS can make fundamental con-tributions. The symposium will concentrate on:

  • Techniques and methods (terrestrial, air- and spaceborne measurements, monitoring, analysis, assessment, decision support and management);
  • Interdisciplinary, integration, geoinformatics;
  • Other “modern” geosensorics/geosensor networks, sensor fusion, SLAM (Simultaneous Localization and Mapping), SLAMMOT (Simultaneous Localization, Mapping and Moving Object Tracking), artificial intelligence, unmanned vehicles (UAV, USV, AUV-UUV, UGV), mobile mapping etc., where the above could relate to any of the “Disaster Cycle”-components (preparedness, response, recovery, mitigation, prevention).

Contributions are invited to geohazards studies includind (in alphabetic order):
Cascading effects of geohazards (poisonous gas releases, nuclear accidents, etc.); Climate change (sea-level changes, increasing heatwaves, drought, lightning); Desertification, Deforestation; Dry mass movements (avalanches of debris, snow); Earthquakes; Floods (flash floods, inundations); Fires (forest fires, firestorms, bushfires, wildfires); Glaciers; Ground/soil erosion; Icebergs; Lake (exploding, overturn); Mine fires; Rip currents; Salinization; Seawater (inundation, intrusion, infall, tidal and storm waves, tsunami waves); Slope failure (earthflow, debris flow, rock falls, block gliding); Subsidence (ground, land); Sinkholes (karst, mining, etc.); Variation of underground water; Volcanic eruptions (lahar, falls, lava flow).

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G08 Sea-Level Observation and Modelling

Convener: Tilo Schöne (Potsdam, Germany)

Co-conveners: Xiaoli Deng (Newcastle, Australia), Chalermchon Satirapod (Bangkok, Thailand), Simon D.P. Williams (Liverpool, U.K.)


Changes in sea level are one of the major indicators of climate variability as well affecting society in various ways, such as saltwater intrusion, coastal erosion and inundation. In particular, nations with heavy population, long coastlines, low-lying coastal areas, and significant marine industry will face strong economic and socio-economic impacts. To find the patterns, fingerprints and to predict future sea level changes, different monitoring and modelling techniques have been developed. Today global and regional observing systems provide the necessary background information to assess sea level trends; over decades tide gauges and space-borne altimetry provided continuous observations. In many areas, the slow long-term change in sea level is superimposed by artificial and natural land changes, which sometimes have much higher rates than the sea level rise itself. This calls for additional or new observation technologies (e.g., GNSS or InSAR), but also require modelling and forecasting of sea level and associated quantities.
The Global Geodetic Observing System (GGOS) can help to provide the necessary scientific information. GGOS contributes in many ways to the monitoring of the sea level or interacts with groups contributing external information. This ranges from tide gauge and satellite altimetry observations, estimation of gravity changes, GNSS-control of tide gauges, river discharge monitoring, InSAR/PSI observations, monitoring and maintaining of International and regional reference system and frames.
The symposium will aim to bring together the disciplines involved in sea-level research with a focus on geodetic observing techniques, modelling of sea level related quantities, modelling of impacts on coastal societies, and the interpretation of sea level related results. The long-term monitoring and the combination of different observation technologies will be a priority. We also encourage submissions about how geodetic derived sea level information interacts with socio-economic studies and policy advice.

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