The INGV Mediterranean GNSS Archive (MGA)

The Global Navigation Satellite System (GNSS) represents a primary data source in Solid Earth
Sciences. In order to investigate the Earth’s crustal deformation, time series of the estimated daily
positions of the stations are routinely analyzed at the Istituto Nazionale di Geofisica e
Vulcanologia (INGV) to investigate the deformation of the Earth’s surface caused by tectonic and
non-tectonic processes. The GNSS observations of the stations are processed using the three main
scientific software: GAMIT/GLOBK, BERNESE, and GIPSY OASIS II. The accuracy and the
strength of geodetic solutions often depend on the geometry and spatial density of the network,
and the availability and quality of GNSS data. In many circumstances, GNSS networks are
deployed for topographic purposes by private or public institutions, and a significant number of
GNSS stations in large regions acquire continuous observations. It may happen that such networks
do not collect and distribute data according to IGS standards, so it could be difficult to analyze
this data using automated data-processing tools. For that reason, this data is often ignored or
partially used by the scientific community, despite their potential usefulness in geodynamic
studies. We have attempted troubleshooting this problem by establishing a centralized storage
facility in order to collect all available GNSS data and standardize both formats and metadata
information. Here we describe the processes and functions that manage this unified repository,
called MGA (Mediterranean GNSS Archive), which regularly collects GNSS RINEX files from alarge number of CORS (Continuously Operating Reference Station) located across a wide region
of mainly the European and African plates. RINEX observation data and metadata information are
provided to the analysts through an FTP server and dedicated web-services. The complete data set
is stored in a PostgreSQL database in order to easily retrieve pieces of information and efficiently
manage the archive content. The system implements many high-level services that include scripts
to download files from remote archives and to detect new available data, web applications such as
API (Application Program Interface) to interact with the system, and background services that
interact with the database. During the development of this product, particular attention was paid to
what has already been achieved by EPOS TCS WP10, whose objective was: "[...] to develop an
open source platform with programmatic and web interfaces to store and disseminate raw data
and metadata from GNSS stations operating in Europe''. Many ideas and tools presented here were
inspired by that project.