The GNSS velocity field of Central Greece and the Peloponnese

The dataset consists of five tables in CSV format, which are described below and in five attached files:

• Table 1: List of the 920 GNSS points of Central Greece and the Peloponnese for which coordinates are provided in the ITRF-2020 at the epoch 2020.0.
• Table 2: Velocities in the ITRF2020 of 509 points in the studied area.
• Table 3: ITRF2020 coordinates of 424 HMGS pillars remeasured by GNSS.
• Table 4: Estimated coordinates of the HMGS pillars of the investigated area at the epoch 2020.0.
• Table 5: List of the 1:50,000 scale HMGS maps belonging to the study area.

The tables are in CSV format, using a semicolon as separator. To make them correctly readable in all versions of Excel, it may be necessary to add the line  *sep=;*  at the beginning of each file. Note also that Tables 1 and 5 contain Unicode characters (for Greek names).

Content

We provide a comprehensive dataset of 920 coordinates (Table 1) and 509 velocities (Table 2) for geodetic points in Central Greece and the Peloponnese (Figure 1). These were observed during GNSS campaigns conducted between 1990 and 2024. The investigated region is characterised by intense tectonic deformation, either distributed in areas like southern Peloponnese or localised around fault systems such as the Corinth rift and the Katouna-Stamna and Movri fault zones.

The novelty of this dataset lies in the density of campaign stations and the quantity of data accumulated over thirty-five years. The geodetic points are organised into four main categories: permanent stations, triangulation pillars from the Greek national network (HMGS) established in the 1960s-70s, ground markers on stable rock, and some non-HMGS pillars. The pillars of the HMGS and the markers are themselves divided into two categories, depending on whether or not they are equipped with a self-centering system. Non-HMGS pillars all have forced self-centering systems.

The GNSS data are processed using the GIPSY 6.4 software developed by JPL. We correct for co-seismic and post-seismic deformations in the assessment of secular velocities, using earthquake parameters derived from permanent station time series and the methodology developed in Briole et al. (2021).

We show that self-centring systems significantly improve precision, reducing the average coordinate residual variability from 6.15 mm to 4.45 mm. The analysis of the 509 points with velocity determination reveals uncertainties that stabilise between 0.12 and 0.15 mm yr^-1 when the observed time period is more than twenty years. Stations with self-centring achieve 0.2 mm yr^-1 accuracy after twelve years of data, compared to twenty years for those without self-centring. After twenty to thirty years, campaign stations observed eight to ten times practically match the precision level of permanent stations.

Bufféral et al. (2026) analyses the velocity field obtained at the 509 sites. We also find that the calculated velocities further validate the HELVEL model developed in Briole et al. (2021) using permanent stations only. This validation, obtained with nearly four times more points, supports the relevance of the model.

We calculate a robust transformation of historical triangulation coordinates to coordinates in the ITRF2020 system at epoch 2020.0, with an average accuracy of 0.15 m. This transformation, based on 424 coordinate pairs (Table 3), uses seven parameters and determines 1965 as the optimal reference epoch for the triangulation measurements. The transformation formula is then applied to all 9,729 HMGS pillars in the study area (Table 4).

A geoid grid is calculated by comparing GNSS elevations to levelled altitudes at the 424 points with coordinates pairs (Table 3). Its estimated accuracy is 0.3 m. This grid is compared with the official Greek HG2023 grid. Our compilation provides a much more detailed picture of the regional deformation field than with permanent stations alone.

The dataset, entirely referenced to ITRF2020 at epoch 2020.0, enables interoperability with all previous geodetic work, providing a foundation for long-term tectonic studies of the ground deformations. The use of dense arrays of campaign points is particularly important for assessing deformation at the scale of individual active faults in the investigated area, which is not achievable with permanent stations only.

Detailed information concerning the survey campaigns, the processing of data, the application of co-seismic and post-seismic corrections, the accuracy analyses,  the validation of the HELVEL model, the comparison of the GNSS coordinates of the HMGS pillars with their original coordinates, and an analysis of the differences between the altitude and elevation of these pillars and the quasi-geoid of the study area, is provided in Briole et al. (2026).

Please cite this article when using this dataset.

References

Briole, P., Ganas, A., Elias, P. & Dimitrov, D., 2021. The GPS velocity field of the Aegean. New observations, contribution of the earthquakes, crustal block model, Geophysical Journal International, 226(1), 468-492, https://doi.org/10.1093/gji/ggab089

Briole, P., Bufféral, S., Elias, P., Avallone, A., Kamberos, K., Dimitrov, D., Marinou, A. & Ganas, A., 2026. The GNSS velocity field of Central Greece and the Peloponnese, Geophysical Journal International, under review

Bufféral, S., Briole, P., Pubellier, M. & Chamot-Rooke, N., 2026. Slip rates, diffuse deformation and interseismic loading in Central and Southwestern Greece, from GNSS velocities, Geophysical Journal International, in revision

GNSS data

Details and acknowledgements concerning the data from permanent stations can be found in Briole et al. (2021), and those concerning the campaign data in Briole et al. (2026).

Disclaimer

In the attached files, we endeavour to provide the most accurate coordinates, velocities and other relevant information for the geodetic points we measured between 1990 and 2024, as well as to correctly quantify the uncertainties. These products are the result of our scientific work and are not intended for commercial use or, in the case of HMGS points, to replace the official information provided by the HMGS for these points, which is the only information with legal value.