Fig.1: Distribution of RING network stations.
Fig. 2 - Examples of geodetic monuments used for the RING network. A) complete RING station, B) antenna mounted on reinforced concrete pillar, C) antenna mounted on surface tripod, D) antenna mounted on building.
The monitoring of ground deformations through networks of Global Navigation Satellite System (GNSS) stations is one of the main institutional tasks of INGV. Globally, the data provided by the GNSS networks have allowed a significant step forward in the knowledge on the processes of accumulation and release of deformation during the various phases of the seismic cycle. The reasons that led to the creation and continuous densification of the RING network are linked to the need to better understand the rates and directions of displacement of the crustal blocks that make up the complex tectonic mosaic of the central Mediterranean, and to measure, in greater detail spatial possible, the deformation rates along the Apennine and Alpine chains, where most of the seismic energy release in our country is concentrated.
The RING network is currently made up of 207 GNSS stations active in Italy, Greece and Malta (Fig. 1). The network has been installed since 2004 for monitoring ground deformations in non-volcanic areas. In fact, the RING is associated with denser GNSS networks for monitoring active volcanoes. The RING network was created as part of various agreements and projects, many of which are now closed; among these, the agreements with DPC 2004-2006 and 2007-2009, the PROSIS and FIRB projects financed by MIUR, the APQ Sicily and recently the Otrions project and the PON Vulcamed. As part of the PON-Grint project, starting from 2019, a significant upgrade of the instrumental park is planned, as well as a densification of the network.
The RING is managed by personnel belonging to various sections, and in particular to the National Earthquake Observatory (ONT), the Bologna Section, the Etna Observatory (OE) and the Vesuvius Observatory (OV). In particular, the maintenance and management of the RING is coordinated by the Geodetic and Seismic Observatory of Grottaminarda which makes use of contributions from the Rome and Bologna offices for central and northern Italy and the Ancona office for the Umbria-Marche area, from 'OV and from the OE, however, for the GPS stations of Sicily and the Campania area respectively. The installation of RING stations in Greece and Malta are the result of scientific collaborations respectively with the National Observatory of Athens and the University of Malta.
Almost all of the GNSS sensors installed transmit data, both in real time and in near real time, at the offices in Rome, Grottaminarda and Ancona. The transmission system mainly makes use of satellite vectors (TCP/IP, UDP, VSAT, Broadsat) and internet or intranet connections, wired or wireless (Wi-Fi and GPRS/UMTS).
Given the geological complexity of the Italian territory, the stations of the RING network have been built over the years using different types of geodetic monuments. Fig. 2 shows some examples. Most of the stations in the RING network were built using a steel surface tripod (https://webring.gm.ingv.it/index.php/ring-infrastructure/#sites).
The quality control and archiving of the GPS data and related information is done in the RING database which is an advanced technological infrastructure aimed at the complete management and sharing of data and related information content. The GPS data of the RING stations, available to the entire scientific community (https://webring.gm.ingv.it:44324/rinex/RING), are processed, together with the data of the other networks operating on the national territory, by three Analysis Centers organized to guarantee processing according to the international standards defined by the International GNSS Service (IGS) and contained latency times, compatibly with the availability of IGS products required by daily data and processing software.
