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Partnership renewal IGN – EXAGONE

Partnership renewal IGN – EXAGONE

Partnership renewal IGN – EXAGONE

Partnership renewal IGN – EXAGONE

Partnership renewal IGN – EXAGONE

Partnership renewal IGN – EXAGONE

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The signing of the RGP partnership: a technical and scientific partnership

On 20 June, EXAGONE and IGN signed a partnership agreement to integrate TERIA network stations into the GNSS Permanent Network (RGP).

This network, coordinated by the IGN, comprises 526 geodetic stations operated by some fifty partners in mainland France and the French overseas territories.

The RGP is essential for monitoring the territory, helping to observe phenomena such as sea levels, the rising of the Alps and seismic movements in Mayotte.

A partnership for quality and excellence

From the outset, the TERIA network has enjoyed a close partnership with the IGN.

TERIA offered IGN the incorporation of all its stations into the RGP network (Permanent GNSS Network). As a result, the network rapidly covered the whole of mainland France and offered a post-processing service for all users. Reciprocally, the IGN has certified TERIA’s stations, providing users with a guarantee of geo-referencing in the RGF 93 system and stability monitoring over time.
RGF 93 is a three-dimensional, geocentric system with centimetric accuracy that complements the traditional GPS system.

The status of certified TERIA stations can be consulted in real time 24/7 on the iTERIA application, as can all the areas covered by the network.

The TERIA – IGN partnership has resulted in a public-private partnership agreement between the OGE and the IGN. Attached to this agreement is a protocol setting out the technical terms and conditions for data transfer.

As part of EXAGONE’s Quality policy, the IGN provides an independent external source of control, ensuring maximum security for the service.

RGP – Permanent GNSS Network

The Permanent GNSS Network (RGP) is an essential tool for the geodetic community and the production of geographic data in France, integrating all GNSS surveys into the national reference system, which has been mandatory since the decree of 5 March 2019. It is also used to monitor land movements for the scientific community.

Created in 1998 as a federative network, the RGP brings together 25 of the IGN’s own stations and other stations integrated via partnerships. The IGN offers these partners its expertise, the determination of official coordinates, regular monitoring, quality control and open distribution of GNSS data.

EXAGONE, with more than 200 stations in the TERIA network, is the largest part of the RGP, which comprises 526 stations. It provides its subscribers with a real-time GNSS positioning service with centimetre accuracy.

Focus on Overseas France

Earthquake in Mayotte

Since May 2018, the archipelago of Mayotte has been the scene of an almost uninterrupted series of large-scale seismic events. The intensity of this seismic activity has attracted the attention of scientists, who are seeking to understand the causes. Geodetic observations from the four Permanent GNSS Network (PNG) stations on the island have played a crucial role in this. These include a station managed by CNES, two TERIA stations and a Lél@ station. These high-precision instruments have made it possible to detect a significant displacement of the island since July 2018.

The data collected show that Mayotte is moving eastwards at a rate of around 1.5 cm per month. At the same time, the island is also sinking at a rate of around 1.2 cm per month, indicating significant vertical deformation. Faced with these abnormal movements, geophysicists were quick to formulate a hypothesis in November 2018: the origin of these phenomena could be volcanic.

This hypothesis, initially based on geodetic data, was confirmed in May 2019 thanks to a major discovery. During an expedition led by the oceanographic vessel Marion-Dufresne, researchers identified an underwater volcano some fifty kilometres east of Mayotte. This discovery corroborates previous observations, providing a tangible explanation for the tectonic movements and seismic activity that have been shaking the archipelago for several months.

In response to a call for projects launched by the CNRS, the Institut national de l’information géographique et forestière (IGN) and EXAGONE-TERIA have joined forces with several other partners to contribute to a better understanding of the geological phenomena underway in Mayotte. The project is based ongeodetic observations using the GNSS (Global Navigation Satellite System). As part of the project, new measuring stations have been installed not only on the island of Mayotte, but also in strategic areas of the surrounding territories, notably on the Glorieuses islands and in Madagascar.

These GNSS stations collect precise data on ground movements and other geodetic parameters, which are essential for monitoring the evolution of the phenomenon in question. All the data collected is then made available to the scientific community, so that researchers can study and analyse it in depth. This initiative is part of a crisis management context in which a detailed understanding of the geological processes underway is crucial for the safety of the population and for informed decision-making by local and international authorities.