Scientific Sessions


Session 1: Current and Future Satellite Gravity Missions
Session chairs: David Wiese, Frank Flechtner, Adrian Jäggi

Satellite gravimetry is unique in providing a global view of mass distribution and its variation in the system Earth. While the Gravity Recovery and Climate Experiment (GRACE) mission has paved the way for observing the time variable gravity field from space over the last two decades, the Gravity Field and Ocean Circulation Explorer (GOCE) mission provided a consistent global model of the static gravity field. These complementary missions triggered a large number of new applications in the fields of oceanography, continental hydrology, polar and mountain glacier ice mass monitoring, solid Earth geophysics, geodetic height systems etc. With the launch of GRACE Follow-On (GRACE-FO) on May 22, 2018, the GRACE-FO data record is now being seamlessly integrated with the 15-year GRACE data record that has become indispensable for wide variety of geophysical process and climate studies. As a continuity mission, GRACE-FO is nearly identical to GRACE, with the exception of flying a technology demonstration laser interferometer to more accurately measure the distance variations between the two spacecraft. The community is preparing for future gravity mission after GRACE-FO, engaging in variety of studies on mission requirements, improved instrumentation, innovative satellite concepts, and new data processing strategies.

This session solicits contributions on analysis techniques for past and current satellite gravimetry mission data (including GRACE/GRACE-FO, GOCE, and other LEO GPS data, combinations with other data types, etc.); future mission concepts and architectures (including satellite-to-satellite tracking, gradiometry, connections between applications and architectures, constellation design, etc.); and relevant instrumentation and technologies (e.g. inertial sensing, cold-atom interferometry, optical interferometry, cubesat/smallsat technologies etc.)

Session 2: Global Gravity Field Modelling
Session chairs: Jianliang Huang, Yan Wang

Gravity field models of global extent and very high resolution encapsulate critical information for a wide range of applications, from a unified World Height System to Inertial Navigation. The development of such gravity models requires the effective combination of heterogeneous terrestrial, shipboard, airborne and satellite-derived gravity information of widely differing resolution, coverage and accuracy. The goal of the combination is to produce gravity data and gravity models ideally of uniformly high accuracy, high resolution and covering the entire Earth. An essential element of such model developments is the availability of global digital topographic models, which are necessary for both the processing of raw gravity observations and for providing supplemental gravity information over regions or in spectral bandwidth where gravity observations are unavailable. The error assessment of any global gravity solutions is of equal importance. Very high-resolution global gravity models require formidable number of parameters (e.g., spherical harmonic coefficients) for their representation, making compressed representation of model functionals and error properties appealing for many applications.

This session solicits contributions that focus on all aspects of global very high resolution gravity model developments and assessment, from methodological issues to modeling results and applications. We also seek contributions that focus on effective parsimonious representations of global gravity model functionals and their errors.

Session 3: Local/Regional Gravity Field Modelling
Session chairs: Riccardo Barzhagi, Hussein Abd-Elmotaal, Georgios Vergos

This session will focus on the practical solution of various formulations of geodetic boundary-value problems to yield precise local and regional high-resolution geoid models. Contributions describing recent developments in theory, processing methods, downward continuation of satellite and airborne data, treatment of altimetry and shipborne data, DEM compilation and validation, terrain modeling, software development and the combination of gravity data with other signals of the gravity field for a precise local and regional gravity field determination and validation are welcome. Topics such as the comparison of methods and results, the interpretation of residuals as well as geoid applications to satellite altimetry, oceanography, vertical datums and local and regional geospatial height registration are of a special interest.

Session 4: Absolute, Relative and Airborne Gravity – Instrumentation, Analysis, and Applications
Session chairs: Derek van Westrum, Przemyslaw Dykowski

New developments are occurring at a rapid pace for both “classic” and quantum absolute instruments as well as novel relative instruments and are of great interest to the geodetic community. In the next ten years, we can expect to see continuous absolute instruments, mobile quantum instruments, combined gravimetric and gradiometric instruments, as well as routine deployment of inertial systems on moving platforms (including aerial and marine drones). In addition, linked optical atomic clocks will provide direct observations of geopotential differences. Improvements to spring-based relative gravity meters will also allow for improved surveys at reduced costs. These advancements will support a vast range of research: biologic processes, ice melt modeling, geophysical exploration, and geoid change to name but a few. These changes will also require redoubled efforts in cooperation and communication. This will include common software tools and file formats as well as certified comparisons of instruments. These comparisons, operated in conjunction with our colleagues in meteorology, will finally lead to the realization of the International Terrestrial Gravity Reference Frame (replacing IGSN71). We welcome contributions on topics such as advances in instrumentation (gravimetry, gradiometry, geopotential measurements), acquisition techniques, processing methods, as well as other novel data applications and models. Submissions on work related to gravity, such as the gravity gradient, deflection of vertical, and geopotential values, are also welcomed.

Session 5: Height Systems and Vertical Datum Unification
Session chairs: David Avalos, Davey Edwards, Laura Sanchez

The session focuses on the unification of the existing height systems around the world. This can be achieved through the realization of an international vertical reference system that supports geometrical (ellipsoidal) and physical (normal, orthometric) heights with centimeter precision in a global frame, enables the unification of all existing physical height systems, and provides high-accuracy and long-term stability of the vertical coordinates. A first step towards this was the release of an IAG resolution for the definition and realization of an International Height Reference System (IHRS) during the 2015 IUGG General Assembly. The next challenge is the realization of the International Height Reference Frame (IHRF), that is expected to include a global network with regional and national densifications, with known geopotential numbers referring to the global IHRS. To guarantee a precise combination of physical and geometric parameters and to support the vertical datum unification worldwide, this reference network should be collocated with fundamental geodetic observatories, geometrical reference stations, reference tide gauges, local levelling networks, and gravity reference stations.

Contributions are invited related to the International Height Reference Frame and System (IHRF/IHRS); refinement of standards and conventions for the definition and realization of vertical reference systems; strategies for the establishment of precise vertical reference frames, precise determination and modelling of the time-dependent changes of the vertical coordinates and the datum itself; and theory and methodology for height system unification. In addition topics such as detection of edge effects, regional vertical datum and their unification, including the connection of vertical datums over oceans, and strategies for collocation of vertical reference stations with existing reference frames (GGOS core stations, ITRF, gravity stations, existing levelling networks, etc.).

Session 6: Satellite Altimetry And Applications
Session chairs: Don Chambers, Ole Andersen

The long-term time series of altimeter measurements has revolutionized the knowledge of many interdisciplinary scientific research fields including the marine gravity field, oceanic dynamics, terrestrial hydrology, ice sheet mass balance, sea level changes, and solid Earth geodynamics. New missions employing innovative technological improvements will provide higher resolution observations of the cryosphere, sea-ice, ice-covered oceans, open oceans and inland water bodies. The session solicits contributions that focus on validation and (cross-) calibration of satellite altimeter data, new technologies, improvement in global marine gravity field from new altimetry data, derivation of sea surface height and mean dynamic topography, improvements in near-coastal areas (retracking), derivation of sea level and sea level extremes, determination of inland water levels and deflection of the vertical from conventional altimetry and SAR as well as connection to height systems, and bathymetry estimation.

Session 7: Gravity for Climate & Natural Hazards: Inversion, Modeling, and Processes
Session chairs: Mark Tamisiea, Annette Eicker, Carmen Blackwood

A wide range of Earth system processes cause transport and re-distribution of mass, including the melting of ice sheets and glaciers, river runoff, changes in precipitation, evapotranspiration, soil moisture and groundwater, post-glacial rebound and flow in the Earth mantle. Observations of gravity and inferred estimates of mass change allow interpretation and direct understanding these processes. Assimilation of mass change information into geophysical models allows disaggregation of signal into contributing processes and allows downscaling of geodetic contributions to other spatio-temporal scales of interest. Results from such analyses are applied towards climate studies, model validations, and understanding and assessments of natural hazards (e.g. earthquakes, flood, drought, etc).

We invite contributions dealing with the interpretation, application and innovative use of gravity and inferred mass change for improved understanding of climate processes and natural hazards. Contributions that include the use of complimentary data (such as obtained from global GNSS networks, terrestrial gravimetry, InSAR, SLR, VLBI, and ocean bottom pressure sensors) and encouraged. We welcome contributions on the use of geodetic data sets for the improvement of geophysical and climate models – both in terms of model evaluation, calibration and data assimilation.