Bamahry, Fikri ; Legrand, Juliette ; Bruyninx, Carine ; Fabian, Andras ; Pottiaux, Eric

Poster presented at IAG Symposium Reference Frames for Applications in Geosciences (REFAG2026) , Munich, Germany on 2026-03-02

Abstract: The European Plate Observing System (EPOS) is a research platform that offers multidisciplinary data and services for advancing Solid Earth research. The Global Navigation Satellite Systems (GNSS) component of EPOS (EPOS-GNSS) ensures that the EPOS platform provides access to GNSS data, metadata, and products from as many as possible permanently tracking GNSS stations across Europe. These efforts are made in collaboration with the European Reference Frame (EUREF) community. Currently, EPOS and EUREF are working together to make all daily RINEX data from EUREF stations discoverable through EPOS. This is achieved through a dedicated EPOS data node, one of the twelve distributed data nodes, connected to a central EPOS-GNSS Data Gateway. To support the continuous and long-term assessment of GNSS data quality, the Royal Observatory of Belgium has developed the EPOS-GNSS Data Quality Monitoring Service (DQMS), accessible at https://gnssquality-epos.oma.be. This poster presents the functionality of the DQMS portal, which monitors the availability and quality of daily GNSS data from more than 1,900 stations integrated within the EPOS-GNSS e-infrastructure. Currently, 447 of these stations are EUREF stations, but this will be extended to 511 stations. A comprehensive set of Data Quality Indicators (DQIs)—including the ratio of observed versus expected observations, number of missing epochs, number of tracked satellites, maximum number of observations, number of cycle slips, and code-based multipath values—is visualized online to identify potential degradations in EPOS-GNSS station performance. This poster further demonstrates how degraded tracking at low-elevation angles, an increased number of cycle slips, and higher multipath values can degrade the quality of GNSS position time series. We also highlight how undocumented changes in the elevation cut-off angle can introduce apparent jumps in the GNSS position time series; identifying such changes through the DQIs helps GNSS analysts to correctly interpret these artifacts. Through these examples, we will show that the DQI plots provided in the DQMS portal are valuable tools for GNSS data analysis that support both geophysical research and the maintenance of geodetic reference frames.

Keyword(s): GNSS ; EPOS GNSS data quality
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