The zero-difference (ZD) and double difference (DD) approach for processing GNSS observations is mathematically equivalent – meaning that in DD case the huge number of clock parameters are just pre-eliminated. The results for all remaining parameters are identical, if no numerical shortcut is done (e.g., ignoring parts of the correlations introduced by the DD approach). The advantage of processing DD observations is the reduced number of parameters, easier detection and potential correction of cycle slips, and direct access to the integer ambiguities without any phase bias parameter. On the other hand, ZD processing offers greater flexibility in network configuration and parameter handling. This is particularly advantageous when modifying the list of stations in the processing, including Low Earth Orbiting satellites (LEOs), or implementing advanced clock models, e.g., for Galileo satellites.Based on an experimentally developed ZD-based ambiguity resolution method that introduces ambiguity clusters and satellite-wise consistency corrections, the original research prototype was translated into a robust and automated routine processing chain which is suitable for operational use.The new procedure follows the structure of the established CODE DD strategy but adapts the individual processing steps, e.g. pre-processing, estimation of global parameters, handling of receiver-dependent parameters, and ambiguity resolution. Special emphasis is placed on numerical stability, the reliable handling of real-valued ambiguities, and the introduction of quality-control mechanisms designed for long-term autonomous operation. The resulting procedure enables efficient parallelization and delivers consistent orbit, clock, and ambiguity products. We have investigated the requirements on the station density for all these steps in order to optimize also the processing time. Stations, that are not needed in this context can get pre-processed based on the PPP approach and get added to the final solution only.Initial results show that the operational ZD processing chain reaches the accuracy and stability of CODE DD-based products while offering greater flexibility for future extensions. The results demonstrate that the ZD-based GNSS processing is sufficiently mature to generate stable global products on a daily basis and therefore represents a promising foundation for next-generation GNSS solutions computed at CODE.

Within the IGS, it was agreed that Precise Point Positioning (PPP) based on satellite orbit and clock corrections of the IGS analysis centers allow a direct access to the IGS realization of the International Terrestrial Reference Frame (ITRF). This convention is considered convenient for all PPP users and should not be changed in future. On the other hand, the groups determining the GNSS satellite orbits do prefer an origin of the frame that is related to the Earth instantaneous center of mass since this is the reference of the gravitational orbit force model. With this background, some discussions take place to change the convention related to the origin of the terrestrial frame because it is convenient for the orbit determination. This convention is, however, in contradiction to the expected needs of the PPP users that do prefer a stable coordinate origin in time. We will introduce a strategy to serve both needs by applying the center of mass corrections for the orbit determination only.

The CODE Processing Center of IGS produces orbits for the U.S. Global Positioning System (GPS), earth rotation parameters (ERPs), station coordinates, and other data on a regular basis since 21 June 1992. The experience gained at CODE during the first year of IGS operations indicated that at least in some cases our standard orbit model was not sufficient for 3-days-arcs. This was the motivation for the investigation presented here. Our new orbit model contains the following adjustable parameters: (1) six parameters defining the initial state vector (position and velocity), (2) velocity changes at pre-determined times and in pre-determined directions, (3) (at maximum) nine parameters of a new direct radiation pressure model (drp-model), (4) the parameters of the earth’s gravity field, (5) two parameters of a simple earth’s albedo radiation pressure model (arp-model), and (6) the (empirical) resonance terms suggested by (Colombo, 1989). These new orbit models were used in the newly developed computer program ORBIMP, interpreting the IGS precise ephemerides as (pseudo-)observations. Results are presented using IGS data from 17 to 30 January 1993. The new orbit models allowed working with 14-days-arcs instead of 1–3 days-arcs (as it is standard within IGS), the orbital accuracy dropped from about 1 – 2 m rms for the standard model to about 10 cm to 20 cm when using the new radiation pressure model. Computation times and disk storage capacities are crucial when estimating parameters of the satellites’ force field: Each satellite arc is defined by six initial conditions and a certain number of (dynamical) parameters describing the force field. One second order differential equation system has to be solved for each orbital parameter to be determined (initial conditions and dynamical parameters) and for each satellite arc. Our standard procedure so far was to numerically integrate these variational equations together with the equations of motion prior to the actual parameter estimation process, where long integration times and, more important, much disk space is required (because we have to store the solutions of the variational equations). Here we present very efficient algorithms for the integration of the variational equations. Because the integration times are negligible compared to the processing times involved when analyzing global GPS networks the variational equations may be integrated during the parameter estimation process.

With the introduction of the operating system Android 7 Nougat in the year 2016, it became possible to access Global Navigation Satellite System (GNSS) code and carrier phase observations. These observations can be processed with the state-of-the-art GNSS processing software packages, which allows an in-depth evaluation of the smartphone’s GNSS performance. The availability of carrier phase observations enables sub-decimeter-level positioning. A few years ago, smartphones wearing dual-frequency GNSS chipsets hit the mass market. In this study, we investigate the capability of such a device for the estimation of tropospheric delays. Static measurements carried out over the period of two weeks are performed using a Google Pixel 4 XL smartphone. The measurements are processed using relative positioning methods with a baseline length of about 33 kilometers, where a continuously operating reference station (CORS) acts as a base. The estimated differential zenith tropospheric wet delay (dZWD), obtained for the smartphone are then combined with absolute values computed at the reference station, in order to obtain time series of Zenith Total Delay (ZTD). Using this method, we demonstrate that high-precision ZTDs can be successfully determined from smartphone GNSS observations. When comparing the estimated tropospheric delays with those determined at a nearby geodetic receiver to assess the accuracy of the acquired time series of ZTD, differences in the range of few millimeters to a centimeter are visible. We examine the impact of various error sources, such as antenna phase center variations and residual effects of the ionosphere. Given that the obtained accuracies are at the level of a centimeter and below, the suggested method shows the potential to resolve small-scale tropospheric structures in near real-time, and thus, could be an interesting data source for numerical weather prediction models or related GNSS crowdsourcing projects.

The densification of high-quality, permanent GNSS stations in Europe enables a large-scale investigation of deformation processes on the Earth’s surface. This work aims to interpolate the horizontal and vertical GNSS station velocities and thus produce velocity fields showing the land motion for Switzerland, the Alps and Europe. The GNSS station velocities are provided by the EUREF Working Group on European Dense Velocities. The data set contains horizontal (east, north) and vertical velocities for around 8000 stations in Europe. Five interpolation methods are implemented and compared, namely, Inverse Distance Weighting (IDW), Ordinary Kriging, K - Nearest Neighbors (KNN), Random Forest and Multilayer Perceptron (MLP). Latitude and longitude of the station locations are used as input features for the interpolation. Additional input features will be engineered for Random Forest and MLP. Generally, the performance of all five interpolation methods with latitude and longitude as features evaluated on the test data by Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Mean Bias Error (MBE) is comparable for all velocity components in Switzerland, the Alps and Europe. RMSE and MAE vary among the methods by hundredths of a mm/year. The only exceptions are the horizontal velocity components for the extent of Europe, where MLP and Ordinary Kriging perform slightly worse than the other methods. The key findings of the qualitative analysis are that MLP and Ordinary Kriging produce the smoothest velocity fields, while IDW, KNN and Random Forest produce artifacts due to their mode of operation. All methods interpolate similar velocity fields where the station data is dense and greater differences when it is sparse. Especially for extrapolation areas where no data is available their performance is not verified. The interpolation of the GNSS station velocities in Switzerland, the Alps and Europe for this work shows that it is possible to produce velocity fields with accuracy level below 1 mm/year and the different phenomena of land motion can be clearly identified.

This study presents a seismotectonic analysis of the Miocene-aged Bodensee-Hegau Graben, a major tectonic element in the northern foreland of the European Central Alps. The graben is characterized by comparatively low strain rates and low to moderate seismicity. Our study builds on the seismological analysis of earthquakes recorded by a recently densified seismometer network. The derived high-precision absolute and relative hypocenter relocations allow to identify seismogenic structures in the pre-Mesozoic basement, which we relate to bounding faults on either side of the NW-SE striking graben. A cluster of seismicity on the SW side of the graben is associated with the previously mapped Neuhausen Fault. In contrast, the seismogenic, SW-dipping bounding faults on the opposite side of the graben, between the extinct Hegau volcanic field and the Bodanrück peninsula of Lake Constance, cannot be associated with any known fault. A set of 51 focal mechanisms allows for a high-resolution analysis of kinematics and stress regime of the graben. Our results show that the bounding faults of the graben are optimally oriented to be reactivated in transtensional mode in the present-day stress field. Slip rates across the Neuhausen and Randen faults estimated from geodetic data are likely <0.1 mm/yr. In comparison with historic seismicity over the past 600 years and geomorphic field observations, these rates appear overestimated. Nevertheless, historic seismicity over the past 600 years suggests that fault dimensions and slip rates are certainly sufficient to generate MW 5.0 earthquakes within this slowly deforming transtensive fault zone in the foreland of the Alpine collision zone.

Remote sensing of water vapour using the Global Navigation Satellite System (GNSS) is a well-established technique and reliable data source for numerical weather prediction (NWP). However, one of the phenomena rarely studied using GNSS are foehn winds. Since foehn winds are associated with significant humidity gradients between two sides of a mountain range, tropospheric estimates from GNSS are also affected by their occurrence. Time series reveal characteristic features like distinctive minima and maxima as well as a significant decrease in the correlation between the stations. However, detecting such signals becomes increasingly difficult for large datasets. Therefore, we suggest the application of machine learning algorithms for the detection and prediction of foehn events by means of GNSS troposphere products. This initial study develops a new, machine learning-based method for detection and prediction of foehn events at the Swiss station Altdorf by utilising long-term time series of high-quality GNSS troposphere products. Data from the Automated GNSS Network Switzerland (AGNES) and various GNSS sites from neighbouring countries as well as records of an operational foehn index are used to investigate the performance of several different classification algorithms based on appropriate statistical metrics. The two best-performing algorithms are fine tuned and tested in four dedicated experiments using different feature setups. The results are promising, especially when reprocessed GNSS products are utilised and the most dense station setup is used. Detection- and alarm-based measures reach levels between 66 %–80 % for both tested algorithms and thus are comparable to those from studies using data from meteorological stations and NWP. For operational prediction, limitations due to the availability and quality of GNSS products in near-real time (NRT) exist. However, they might be mitigated to a significant extent by provision of additional NRT products and improved data processing in the future. Results also outline benefits for the results when including geographically relevant stations (e.g. high-altitude stations) in the utilised datasets.

Abstract. Remote sensing of water vapor using the Global Navigation Satellite System (GNSS) is a well-established technique and reliable data source for Numerical Weather Prediction (NWP). One of the phenomena rarely studied using GNSS are foehn winds. Since foehn winds are associated with significant humidity gradients between lee/luv side of a mountain range, tropospheric estimates from GNSS are also affected by their occurrence. Time series reveal characteristic features like distinctive minima/maxima and significant decrease in correlation between the stations. However, detecting such signals becomes increasingly difficult for large data sets. Therefore, we suggest the application of machine learning algorithms for detection and prediction of foehn events from GNSS troposphere products. The present study uses long-term time series of high-quality GNSS troposphere products from the Automated GNSS Network Switzerland (AGNES) as well as records of operational foehn index to investigate the performance of several different classification algorithms based on appropriate statistical metrics. The two best-performing algorithms are fine-tuned and employed on two years of test data. The results show very promising results, especially when reprocessed GNSS products are utilized. Detection- and alarm-based measures reach levels of 70–85 % for both tested algorithms and thus are comparable to those from studies using data from meteorological stations and NWP. For operational prediction, some limitations due to the availability and quality of GNSS products in near-real time (NRT) exist. However, they might be mitigated to a significant extend by provision of additional NRT products and improved data processing in the future.

Owing to still ongoing convergence within the Europe-Adria collision zone, Switzerland is affected by heterogeneously distributed moderate seismic activity. The project SeismoTeCH aims to improve the understanding of the links between the seismic activity, existing fault structures and geodynamics in Switzerland and its close vicinity. We started with compiling existing databases on faults (fault densities, lengths and orientations), seismic activity (spatial hypocenter and magnitude distributions, detection of seismic lineaments, focal mechanisms), orientations of mean principal stress axes and recent crustal movements (GNSS, high precision levelling) in order to establish potential correspondences as well as regional variations. Due to the long-lasting Alpine deformation, fault-orientation patterns as well as fault-densities vary between specific tectonic domains (Jura/North-Alpine foreland, Alpine frontal sediment nappe systems, External Crystalline Massifs, inner-Alpine domains and Southern Alps). Despite this variability, the fault patterns show first order correlations with the spatial arrangement of newly mapped seismic lineaments, earthquake focal planes and associated focal mechanisms. This correlation indicates a regional geodynamics-controlled reactivation of the specific fault networks during current crustal movements. In terms of recent surface movements, variations in (i) horizontal GNSS movements with respect to stable Europe and (ii) vertical uplift (from levelling and GNSS data) have to be discriminated. (i) From E to W in southern Switzerland (S-Grisons–Ticino–Valais, S of Rhone-Simplon line), horizontal movements change from NW to SW directions (velocities >0.5-0.8mm/yr). The southern Adria crustal block shows minimal to no lateral motions in the W-part and a clear NE-directed motion that is progressively increasing towards the E. This motion can be correlated with the so-called counter-clockwise rotation of the Adriatic plate. North of aforementioned domain, N- to NW-directed movements dominate but velocities decrease progressively from the central Alpine domains (<0.3-0.5mm/yr) towards southern Germany, where they are generally small (<0.3-0.4mm NE-CH). This variability between southern and central/northern Switzerland as well as that from E to W, respectively, is accommodated by NE-SW (Rhone-Simplon system) and N-S oriented strike-slip systems. (ii) Most substantial vertical uplift occurs in a WSW-ENE oriented central Alpine belt ranging from the Valais to the Grisons. Note that absolute values of this vertical uplift are 2-3 times larger compared to horizontal movements in the corresponding domains. Focal mechanisms in this high uplift belt indicate orogen-parallel NE-SW extension mainly in the S-Valais and Grisons accommodated by active normal faulting S of the Penninic front. Uplift rates gradually decrease towards the N- and S-Alpine foreland as well as towards Austria and France. Data even suggest tendencies of subsidence at very low rates in the Bresse graben, Upper Rhine graben as well as somewhat more pronounced ones in the eastern Po-plane but not in the CH-Molasse basin. Parts of the northern Alpine foreland exhibit upper to lower crustal seismic activity, while in the thick-crustal-root-enhanced high uplift domains upper crustal seismicity dominates and earthquakes below 20km depth do not occur. Overall recent surface movements and seismicity in and along Central Alpine crustal blocks are affected by buoyancy-driven vertical combined with transpressional/-tensional horizontal movements indicating a lithosphere-scale geodynamic forcing.

The atmospheric delay experienced by a signal of the Global Navigation Satellite System (GNSS) is proportional to the water vapour content along the signal path. This fact is typically exploited in GNSS Meteorology by introducing GNSS derived atmospheric parameters like the Zenith Wet Delay (ZWD) in data assimilation schemes. In numerous studies, the positive impact on the (especially precipitation) forecast has been demonstrated. However, while mostly precipitation-related studies represent the current focus of research, other meteorological phenomena might also be investigated by means of GNSS. The present study represents an initial investigation on the detection of another important meteorological phenomena using GNSS time series: Foehn winds. Foehn denotes a gusty, warm fall wind occurring in mountainous regions worldwide, leading to a relatively mild climate in affected areas. On the other hand, Foehn can also be characterized as severe weather leading to disasters, due to the high wind speeds frequently encountered. The proposed detection method of Foehn in ZWD time series is based on the significant drying/wetting effects on the lee/luv side of an affected mountain range associated with Foehn. The comparison of ZWD from stations on both sides of the main Alpine ridge reveals characteristic features like distinctive ZWD minima/maxima and significant decrease in correlation between the stations. In this study we investigate a number of well-documented Foehn events in the Swiss Alps (therefore called Alpine Foehn) using ZWD time series from the Automated GNSS Network Switzerland (AGNES) station network, operated by the Swiss Federal Office of Topography (swisstopo). Based on these case studies, an assessment of the usability of GNSS-ZWD for Foehn detection is presented and possible strengths and weaknesses will be analysed. Finally, an outlook on possible improvements and innovative extensions to the presented approach is given. These range from embedment of ZWD data in operational Foehn classification and the application of Machine-Learning techniques for detection, to the establishment of collocated GNSS/weather stations, which come with a number of scientific benefits - not only for Foehn investigations but GNSS Meteorology in general.

This roadmap is the product of a grassroots effort by the Swiss Geosciences community. It is the first of its kind, outlining an integrated approach to research facilities for the Swiss Geosciences. It spans the planning period 2025-2028. Swiss Geoscience is by its nature leading or highly in-volved in research on many of the major national and global challenges facing society such as climate change and meteorological extreme events, environmental pol-lution, mass movements (land- and rock-slides), earth-quakes and seismic hazards, global volcanic hazards, and energy and other natural resources. It is essential to under- stand the fundamentals of the whole Earth system to pro-vide scientific guidelines to politicians, stakeholders and society for these pressing issues. Here, we strive to gain efficiency and synergies through an integrative approach to the Earth sciences. The research activities of indivi- dual branches in geosciences were merged under the roof of the 'Integrated Swiss Geosciences'. The goal is to facilitate multidisciplinary synergies and to bundle efforts for large research infrastructural (RI) requirements, which will re-sult in better use of resources by merging sectorial acti- vities under four pillars. These pillars represent the four key RIs to be developed in a synergistic way to improve our understanding of whole-system processes and me- chanisms governing the geospheres and the interactions among their components. At the same time, the roadmap provides for the required transition to an infrastructure adhering to FAIR (findable, accessible, interoperable, and reusable) data principles by 2028.The geosciences as a whole do not primarily profit from a single large-scale research infrastructure investment, but they see their highest scientific potential for ground-break-ing new findings in joining forces in establishing state-of-the-art RI by bringing together diverse expertise for the benefit of the entire geosciences community. Hence, the recommendation of the geoscientific community to policy makers is to establish an integrative RI to support the ne- cessary breadth of geosciences in their endeavor to ad-dress the Earth system across the breadth of both temporal and spatial scales. It is also imperative to include suffi-cient and adequately qualified personnel in all large RIs. This is best achieved by fostering centers of excellence in atmospheric, environmental, surface processes, and deep Earth projects, under the roof of the 'Integrated Swiss Geosciences'. This will provide support to Swiss geo-sciences to maintain their long standing and internatio- nally well-recognized tradition of observation, monitor-ing, modelling and understanding of geosciences process-es in mountainous environments such as the Alps and beyond.

Vertically integrated water vapour (IWV) is expected to increase globally in a warming climate. To determine whether IWV increases as expected on a regional scale, we present IWV trends in Switzerland from ground-based remote sensing techniques and reanalysis models, considering data for the time period 1995 to 2018. We estimate IWV trends from a ground-based microwave radiometer in Bern, from a Fourier transform infrared (FTIR) spectrometer at Jungfraujoch, from reanalysis data (ERA5 and MERRA-2) and from Swiss ground-based Global Navigation Satellite System (GNSS) stations. Using a straightforward trend method, we account for jumps in the GNSS data, which are highly sensitive to instrumental changes. We found that IWV generally increased by 2 % per decade to 5 % per decade, with deviating trends at some GNSS stations. Trends were significantly positive at 17 % of all GNSS stations, which often lie at higher altitudes (between 850 and 1650 m above sea level). Our results further show that IWV in Bern scales to air temperature as expected (except in winter), but the IWV–temperature relation based on reanalysis data in the whole of Switzerland is not clear everywhere. In addition to our positive IWV trends, we found that the radiometer in Bern agrees within 5 % with GNSS and reanalyses. At the Jungfraujoch high-altitude station, we found a mean difference of 0.26 mm (15 %) between the FTIR and coincident GNSS data, improving to 4 % after an antenna update in 2016. In general, we showed that ground-based GNSS data are highly valuable for climate monitoring, given that the data have been homogeneously reprocessed and that instrumental changes are accounted for. We found a response of IWV to rising temperature in Switzerland, which is relevant for projected changes in local cloud and precipitation processes.

Water vapour in the atmosphere is not only a strong greenhouse gas, but also affects many atmospheric processes such as the formation of clouds and precipitation. With increasing temperature, Integrated Water Vapour (IWV) is expected to increase. Analysing how atmospheric water vapour changes in time is therefore important to monitor ongoing climate change. To determine whether IWV increases in Switzerland as expected, we asses IWV trends from a tropospheric water radiometer (TROWARA) in Bern, from a Fourier transform infrared (FTIR) spectrometer at Jungfraujoch and from the Swiss network of ground-based Global Navigation Satellite System (GNSS) stations. In addition, trends are assessed from reanalysis data, using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) and the Modern-Era Retrospecitve Analysis for Research and Applications (MERRA-2). Ground-based GNSS data are well suited for IWV trends due to their high temporal resolution and the spatially dense networks. However, they are highly sensitvie to instrumental changes and care has to be taken when determining GNSS based trends. We therefore use a straightforward trend method to account for jumps in the GNSS data when instrumental changes were performed. Our data show mostly positive IWV trends between 2 and 5% per decade in Switzerland. GNSS trends are significant for some stations and the significance has the tendency to increase with altitude. Further, we found that IWV scales on average to lower tropospheric temperatures as expected, except in winter. However, the correlation between IWV and temperature based on reanalysis data is spatially incoherent. Besides our positive IWV trends, we found a good agreement of radiometer, GNSS and reanalysis data in Bern. Further, we found a dry bias of the FTIR compared to GNSS data at Jungfraujoch, due to the restriction of FTIR to clear-sky conditions. Our results are generally consistent with the positive water vapour feedback in a warming climate. We show that ground-based GNSS networks provide a valuable source for regional climate monitoring with high spatial and temporal resolution, but homogeneously reprocessed data and advanced trend techniques are needed to account for data jumps.

ETH Zurich developed an absolute GNSS antenna calibration system based on measurements taken in the field. An industrial robot is used to rotate and tilt the antenna to be calibrated. This procedure ensures good coverage of the antenna hemisphere and reduces systematic errors. The calibration system at ETH Zurich is validated by a direct comparison of the obtained calibrations with calibrations from the anechoic chamber method (University of Bonn) and from another absolute field calibration method (Geo++ ® GmbH). Calibrations by ETH Zurich agree on the sub-millimeter level with both reference calibrations. A second validation was conducted using real measurements on short baselines. Data were acquired on four stations in direct vicinity and processed using different phase center correction models. The experiment shows that individual corrections of ETH Zurich reduce the residuals in the coordinate domain when compared to type-mean calibrations of the International GNSS Service (IGS). However, residual biases between GPS and Galileo coordinates remain. These biases are efficiently reduced when using the new type-mean calibrations from the IGS that include calibration values for all GNSS, including Galileo. The ETH Zurich calibration system is proven to deliver meaningful calibrations that agree with other calibrations on the millimeter level in the azimuth and elevation domain. The field validation shows evidence that the consistency of the Galileo and GPS calibration should be further enhanced by performing a combined GPS and Galileo analysis, which is not yet implemented.

One of the goals of the EUREF working group on Deformation Models is to develop a deformation model for entire Europe. However, the irregular and partly sparse distribution of GPS stations makes it difficult to obtain a complete picture of the horizontal deformation for Europe. The solution for this problem is to use an interpolation. However, most well-known interpolation techniques (e.g., triangulation, spline interpolation) have the disadvantage that the entire signal is used while every signal always includes noise due to unknown errors or local effects. Additionally, those interpolation techniques can only be applied to one component at a time. The least-square collocation solves both problems of dividing the dataset into a signal and noise component and applying different datasets simultaneously. This method of filtering and interpolation is widely used in Physical Geodesy. However, when applied to velocity fields, the advantage of the collocation with using more than one dataset at the same time is not utilized. This implies that no correlation between the horizontal components is assumed. Here, we will show results of applying a combined least-square collocation for the example of Europe. Different European-wide GPS datasets will be tested as well as the effect of reducing a background model for northern Europe due to glacial isostatic adjustment. The effect of interpolation parameters (e.g., choice of covariance function, correlation length) will be presented as well. Systems: ETRS89 EVRS EVRF2019 as new realization of the European Vertical Reference System Martina Sacher, Gunter Liebsch Federal Agency for Cartography and Geodesy martina.sacher@bkg.bund.de Abstract The last realization of EVRS, EVRF2007, was adopted at the EUREF symposium 2008 in Brussels. As announced in the last years, a new realization of EVRS has been computed. It contains new data of many countries and includes for the first time also data of Russia, Belarus and Ukraine. The presentation describes the parameters of the adjustment, the realization of the datum, the treatment of the permanent tides and the reduction to a common epoch. The special treatment of the data of Belgium, France and Great Britain in the computation is explicated. The results of the adjustment are compared with the former realization EVRF2007.The last realization of EVRS, EVRF2007, was adopted at the EUREF symposium 2008 in Brussels. As announced in the last years, a new realization of EVRS has been computed. It contains new data of many countries and includes for the first time also data of Russia, Belarus and Ukraine. The presentation describes the parameters of the adjustment, the realization of the datum, the treatment of the permanent tides and the reduction to a common epoch. The special treatment of the data of Belgium, France and Great Britain in the computation is explicated. The results of the adjustment are compared with the former realization EVRF2007. The preliminary solution of EVRF2019 has been distributed to the participating countries in March 2019, together with a questionnaire, where the individual countries could decide about the publication of their national EVRF2019 heights. The results of the questionnaire are evaluated in the presentation. Systems: ETRS89 EVRS Present and future of European reference frames – (more than) 30 years of EUREF M. Poutanen, Z. Altamimi, E. Brockmann, C. Bruyninx, A. Caporali, R. Dach, J. Dousa, R. Fernandes, A. Kenyeres, J. Legrand, M. Lidberg, T. Liwosz, R. Pacione, M. Sacher, W. Söhne, J. Torres, C. Völksen 1) Finnish Geospatial Research Institute, 2) Institut Géographique National, 3) Swisstopo, 4) Royal Observatory Belgium, 5) University of Padova, 6) University of Berne, 7) Lechner Knowledge Center, 8) University of Beira Interior, 9) Penc Satellite Geodetic Observatory, 10) Lantmäteriet, 11) Warsaw University of Technology, 12) e-GEOS, ASI/CGS, 13) Bundesamt für Kartographie und Geodäsie, 14) Instituto Geográfico Português, 15) Bayerische Akademie der Wissenschaften markku.poutanen@nls.fi Abstract 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). Technical development, new applications and increased accuracy of observations are setting new demands for the realizations of the reference systems. The EUREF community 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. Crustal deformations and movements deteriorate the accuracy of static reference frames and heights. Monitoring the deformation within EUREF is a necessity for the future, but this alone does not answer the question of future reference frames. It is foreseeable an emerging mass market for centimetre level precise positioning services which very much rely on a technical body with an European dimension such as EUREF for validation and compliance with European regulations, such as the INSPIRE Directive.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). Technical development, new applications and increased accuracy of observations are setting new demands for the realizations of the reference systems. The EUREF community 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. Crustal deformations and movements deteriorate the accuracy of static reference frames and heights. Monitoring the deformation within EUREF is a necessity for the future, but this alone does not answer the question of future reference frames. It is foreseeable an emerging mass market for centimetre level precise positioning services which very much rely on a technical body with an European dimension such as EUREF for validation and compliance with European regulations, such as the INSPIRE Directive. We are facing the European-wide question on the future of reference frames and the role of EUREF. The release of the International Terrestrial Reference Frame ITRF2014 raised also the question on needs and ways to renew the realization of the ETRS89 both for practical and scientific purposes. For some years to come we may have a two frame approach where ETRF and ITRF will be used together. Using European-wide 3D deformation models, and a dense network of permanent GNSS stations, we may link these together (semi-kinematic approach). On the gravity related global heights we do not yet have a similar approach, which will take even more time to get adopted. However, on European basis, EUREF keeps very close collaborations with NMCAs with the intent of merging the national high precision levelling data bases and define a European system of gravity related heights with commonly agreed standards. Systems: ETRS89 EVRS Maintenance of the National Realization of ETRS89 in Sweden: re-analysis of 20 years’ GPS data for SWEREF stations Lotti Jivall1, Faramarz Nilfouroushan (1,2), Naim Al Munaizel (1), Christina Lilje (1), Christina Kempe (1) 1-Geodata Division, Lantmäteriet, Gävle, Sweden 2-Department of Computer and Geospatial sciences, University of Gävle, Gävle, Sweden

There has been growing interest in recent years in the use of homogeneously reprocessed ground-based GNSS, VLBI, and DORIS measurements for climate applications. Existing datasets are reviewed and the sensitivity of tropospheric estimates to the processing details is discussed. The uncertainty in the derived IWV estimates and linear trends is around 1 kg m−2 RMS and ± 0.3 kg m−2 per decade, respectively. Standardized methods for ZTD outlier detection and IWV conversion are proposed. The homogeneity of final time series is limited however by changes in the stations equipment and environment. Various homogenization algorithms have been evaluated based on a synthetic benchmark dataset. The uncertainty of trends estimated from the homogenized times series is estimated to ±0.5 kg m−2 per decade. Reprocessed GNSS IWV data are analysed along with satellites data, reanalyses and global and regional climate model simulations. A selection of global and regional reprocessed GNSS datasets and ERA-interim reanalysis are made available through the GOP-TropDB tropospheric database and online service. A new tropo SINEX format, providing new features and simplifications, was developed and it is going to be adopted by all the IAG services.

Over the last decade, near real-time analysis of GPS data has become a well-established atmospheric observing tool, primarily coordinated by the EIG EUMETNET GPS Water Vapour Programme (E-GVAP) in Europe. In the near future, four operational GNSS will be available for commercial and scientific applications with atmospheric science benefiting from new signals from up to 60 satellites observed at any one place and time, however, many challenges remain regarding their optimal combined utilization. Besides raw data streaming, recent availability of precise real-time orbit and clock corrections enable wide utilization of autonomous Precise Point Positioning (PPP), which is particularly efficient for high-rate, real-time and multi-GNSS analyses.