The IAG's Global Geodetic Observing System (GGOS) provides the means for integrating ground- and space-based geodetic and gravimetric observations. Modernizing the existing geodetic and gravimetric infrastructure homogenizing the processing of data are essential for consistent observations of Earth's time-variable shape, rotation, and gravity. This session is a forum for discussing ongoing and planned improvements to the geodetic and gravimetric observing systems and for using the observations from those systems to improve our understanding of the dynamic Earth. We particularly welcome contributions on the observation and determination of essential geodetic variables, including essential variables for global climate and ocean studies. We also welcome general contributions on GGOS including the progress and plans for building next generation geodetic and gravimetric stations.

The goal of this session is to provide a forum to discuss reference systems theory, realization and applications in geosciences and society, with a special emphasis on the scientific applications of the International Terrestrial Reference Frame (ITRF), and namely the ITRF2014. Participants can discuss concerns not only related to the contributing technique services, but also all ITRF uses, ranging from local, regional to global applications. Contributions are sought from the individual technique services and various ITRF users, covering the complete range of topics, such as data analysis, parameter estimation and correction models. Of special interest is the assessment of the impact of non-linear station motions, e.g. periodic signals and post-seismic deformations. Contributions by the technique services focusing on identifying and mitigating technique systematic errors in preparation for the ITRF2020 are most welcome.

Since 1989, the IAG regional reference frame sub-commission 1.3a EUREF has merged efforts of National Mapping and Cadastral Agencies (NMCA), Universities and Research Institutes to define, realize and maintain the European Terrestrial Reference System 1989 (ETRS89) and the European Vertical Reference System (EVRS) for scientific and practical purposes in Europe. Technical development, new applications and increased accuracy of observations are setting new demands for the realizations of the reference systems.

The EUREF community, mainly consisting of National Mapping Agencies and research institutes, is providing a large variety of data and data products. The product catalogue covers file-based and real-time GNSS data, position and velocity estimates from multi-year solutions, position time series, zenith path delay estimates, and real-time GNSS corrections (see http://www.euref.eu/euref_pr.html for details). Many products are based on improved results coming from repeated GNSS re-processing.

Many applications, in particular those covering global or worldwide aspects will most likely use global reference systems like the International Terrestrial Reference Frame (ITRF). In this session we would like to figure out the potential of specific continental reference frame realizations. We are looking for contributions using EUREF data and/or products, in particular (but not limited to)
- Usage of ETRS89 and EVRS
- Potential of the EPN Densification
- Investigations on position time series and on velocities
- Crustal deformation and modelling for deformation
- National realizations of the ETRS89 or EVRS
- Future on regional reference frame realisation

Precise orbit determination is of central importance for many applications of geodesy and earth science. The challenge is to determine satellite orbits in an absolute sense at the centimeter or even sub-centimeter level, and at the millimeter or even sub-millimeter level in a relative sense. New constellations of GNSS satellites are currently being completed and numerous position-critical missions (e.g. altimetry, gravity, SAR and SLR missions) are currently in orbit. All together outstanding data are available offering new opportunities to push orbit determination to the limit and to explore new applications.

This session aims to make accessible the technical challenges of orbit determination and modelling to the wider community and to quantify the nature of the impact of dynamics errors on the various applications. Contributions are solicited but not limited to the following areas: (1) precise orbit determination and validation; (2) satellite surface force modelling; (3) advances in modelling atmospheric density and in atmospheric gravity; (4) advances in modelling earth radiation fluxes and their interaction with space vehicles; (5) analysis of changes in geodetic parameters/earth models resulting from improved force modelling/orbit determination methods; (6) improvements in observable modelling for all tracking systems, e.g. SLR, DORIS, GNSS and their impact on orbit determination; (7) advances in combining the different tracking systems for orbit determination; (8) the impact of improved clock modelling methods/space clocks on precise orbit determination; (9) advances in modelling satellite attitude.

The geodetic products that describe the system Earth are of high quality. However, there are limiting factors that need to be detected, analyzed, quantified, and possible improvements need to be investigated. In this context, the usage of selected observations only, degrading station equipment quality, limitations in the observing concepts, limitations in the analysis and combination methods evoke the question whether and how the derived Earth system products can be improved. Most of these questions can be answered only by carrying out simulation studies.

This session provides a platform for presentations of various simulation studies that seek to improve the observation and the determination of Earth system parameters. We welcome papers that describe simulations investigating the impact of extending the ground networks and space segment to better determine geodetic and geodynamic parameters (e.g., station coordinates and velocities, Earth rotation parameters, satellite orbits, geocenter, scale, gravity field, sea level). The Terrestrial Reference Frame (TRF) being the foundation of all Earth observations, we also seek papers that simulate space geodetic observations such as Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) with a view of better understanding systematic sources of error. In addition, we welcome papers that describe simulations that either follow contemporary approaches (e.g., combination by applying local ties) or focus on alternative concepts such as co-location in space, clock ties, time transfer by laser link, and atmospheric ties to improve the TRF. For this session we also seek to stimulate presentations of novel observation concepts such as VLBI satellite tracking, inclusion of Low Earth Orbit (LEO) satellites, use of ultra-precise clocks (chronometric geodesy), and inter-satellite links to be used for determining the Earth system parameters including gravity field, geocenter and Earth orientation. Simulation studies focused on developing new satellites or measurement concepts are also welcome to contribute to this session. Furthermore, the session is also open for contributions based on the analysis of real data in order to support and confirm the simulation results.

Many of the aspects mentioned are brought together within the Global Geodetic Observing System (GGOS) standing committee PLATO (Performance Simulations and Architectural Trade-Offs). Therefore, contributions related to the activities carried out within the PLATO group are also highly appreciated.

The availability of high spatial resolution Synthetic Aperture Radar (SAR) data, the advances in SAR processing techniques (e.g. interferometric, polarimetric, and tomographic processing), and the fusion of SAR with optical imagery as well as geophysical modelling allow ever increasing use of Imaging Geodesy using SAR/InSAR as a geodetic method of choice for earth system monitoring and investigating geohazard, geodynamic and engineering processes. In particular, the exploitation of data from new generation SAR missions such as Sentinel-1 that provide near real-time measurements of deformation and changes in land cover/use has improved significantly our capabilities to understand natural and anthropogenic hazards and then helped us mitigate their impacts. The development of high-resolution X-band SAR sensors aboard missions such as Italian COSMO-SkyMed (CSK) and German TerraSAR-X (TSX) has also opened new opportunities over the last decade for very high-resolution radar imaging from space with centimetre geometric accuracy for detailed analysis of a variety of processes in the areas of the biosphere, geosphere, cryosphere and hydrosphere. All scientists exploiting radar data from spaceborne, airborne and/or ground-based SAR sensors are cordially invited to contribute to this session. The main objective of the session is to present and discuss the progress, state-of-the-art and future perspectives in scientific exploitation of SAR data, mitigating atmospheric effects and error sources, cloud computing, machine learning and big data analysis, and interpretation methods of results obtained from SAR data for various types of disasters and engineering applications such as earthquakes, volcanoes, landslides and erosion, infrastructure instability and anthropogenic activities in urban areas. Contributions addressing scientific applications of SAR/InSAR data in biosphere, cryosphere, and hydrosphere are also welcome.