There is no doubt that Greece is an interesting area for the Solid Earth Science community because it is tectonically active. From this historical place, the birthplace of philosophy, democracy, literature and major cultural and art manifestation, scientific and mathematical principles, this cradle of Western civilization came the first signed GNSS data supplier letter, on January 25, 2018.
According to Dr Athanassios Ganas, from National Observatory of Athens (NOA) and a member of the EPOS GNSS Data and Products Working Group, as the one who mediated the local negotiations states that “the NOA´s signed letter contains 27 GNSS stations (all located in Greece), that are continuously operating stations equipped with geodetic equipment and delivering GNSS data on a daily basis”.
For Carine Bruyninx, from Royal Observatory of Belgium (ROB) and EPOS GNSS, this signed data supplier letter has a relevant meaning for the EPOS GNSS Group as it is the first step towards the EPOS´s project accomplishment. As she explains: “This signed letter is a protocol and means that the agency, NOA, agrees to make available to EPOS the data from the GNSS stations that this observatory is operating”.
Benefits and bonuses – Besides the actual EPOS project, the benefit of having the signed data supplier letter is that each country will provide a piece of the European puzzle with relation to “ground and plate movements”. “If each country provides access to the GNSS data in their region, then using this data, the GNSS TCS is able to better compute the ground movements at the station locations”, says Bruyninx explaining that “together, all the GNSS stations in all the countries will give a cross-boundary overview of ground movements. It is just one more input to the full scale of observations that EPOS offers to study the Solid Earth”.
For Machiel Bos, from UBI and from EPOS GNSS “as a bonus, people get access to GNSS that can be used to study the motion of the tectonic plates which can create areas of stress in the Earth’s crust which eventually may lead to earthquakes, especially important to Greece as it is a tectonically active area”.
Harmonization and open access – Scientists in Europe have been collecting GNSS data for over 20 years on a regional or national level. EUREF was one of the first initiatives to collect GNSS data on the European scale. However, they used a subset of stations since their prime objective is to define a European reference frame for which you don’t need all stations, only a few hundreds.
In the scope of EPOS, which is for the Solid Earth Science community, the objective is to harmonize and make available all GNSS data in Europe. At the same time EUREF also started a densification project to include more GNSS stations so, both EUREF and EPOS are now working together.
Machiel Bos clarifies this as an enormous task and to do it properly, taking all legal aspects into account, we need a supplier letter that states the data provider is the owner of the data and that EPOS is permitted to release the data under the Creative Commons 4.0 CC:BY license. The letter ensures that the data will be open access, in line with the guidelines of the European commission. “To have the first supplier letter signed is thus a very positive first step in our goal to receive GNSS (Global Navigation Satellite System) from all of Europe, all of them accompanied with a supplier letter”, celebrates Bos.
Metadata used for scientific purpose – Station metadata is the chronological description of the equipment at a GNSS station. Incorrect station metadata can cause errors in the computed coordinate positions. To avoid such errors, it is important that the researcher who analyses the GNSS data from the station has access to the full set of station metadata. Each data supplier must make sure that the metadata of its GNSS stations are properly maintained. The GNSS TCS is developing a dedicated tool (M3G) for that.
GNSS – The term Global Navigation Satellite System (GNSS) refers to several constellations of navigation satellites that can be used to determine positions on Earth.
EPOS GNSS Data and Products Portal – EPOS GNSS Data and Products portal is an e-infrastructure to disseminate the continuous GNSS data from existing Research Infrastructures.
NOA – The National Observatory of Athens facing the Parthenon and Thission is one of the landmarks of Athens; it has long been used by Greek and foreign Astronomers as the basis for astronomical, meteorological, cartographical and geodynamical measurements and observations in the more than 170 years long course of its history. Today the buildings of NOA at Thission include an Astrogeophysics Museum, housing clocks, telescopes and other instruments of the 19th century, as well as an extensive 19th century library. The activities of the National Observatory of Athens are organized in 3 research Institutes: Institute of Astronomy, Astrophysics, Space Applications and Remote Sensing, the Institute of Environmental Research and Sustainable Development, and the Geodynamics Institute.
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