GNSS VarioPy: A Comprehensive Tool for Enhancing Early-Warning Systems for Geophysical and Atmospheric Events Through GNSS Permanent Stations Networks

Rachele Fratini, Alessandra Maria De Pace, Marco Fortunato, Michela Ravanelli, Mattia Crespi, and Augusto Mazzoni

Abstract:	The GNSS (Global Navigation Satellite Systems) Variometric Approach first implementation was proposed in 2011 (Colosimo et al., 2011) in the VADASE (Variometric Approach for Displacement Analysis Stand-Alone Engine) algorithm, in the field of GNSS Seismology. At its core, the variometric approach relies on single-epoch differences of dual-frequency phase observations, collected by a stand-alone receiver. Variometric parameters estimates are performed through the sole use of broadcast products, achieving accuracy levels within the millimeters-per-second range. Despite the well-established effectiveness of the Variometric Approach, there has been a lack of a fully comprehensive variometric tool available to the scientific community. This work aims to address this gap by introducing GNSS VarioPy, a Python-based package designed to implement the real-time GNSS Variometric Approach for static and quasi-static applications. GNSS VarioPy is designed to support the streaming of RTCM-3 data through a socket connection to a NTRIP caster, allowing for real-time data collection and processing for permanent station networks and any additional receiver available. Key features of GNSS VarioPy are three-dimensional ground velocity field estimation (VADASE) and ionospheric slant TEC variometric estimation (VARION). Recent enhancements to the algorithm include the incorporation of receiver clock offset drift estimation, derived from the variometric equation applied in a pure static scenario. Through the application of the variometric algorithm in static scenario, the variometric residuals can be derived for individual satellites, and potentially be used as a real-time descriptor of the timely evolution of local tropospheric conditions with respect to a GNSS receiver. Residual analysis implications and limitations are further explored into the article.
Published in:	Proceedings of the ION 2024 Pacific PNT Meeting April 15 - 18, 2024 Hilton Waikiki Beach Honolulu, Hawaii
Pages:	46 - 53
Cite this article:	Fratini, Rachele, De Pace, Alessandra Maria, Fortunato, Marco, Ravanelli, Michela, Crespi, Mattia, Mazzoni, Augusto, "GNSS VarioPy: A Comprehensive Tool for Enhancing Early-Warning Systems for Geophysical and Atmospheric Events Through GNSS Permanent Stations Networks," Proceedings of the ION 2024 Pacific PNT Meeting, Honolulu, Hawaii, April 2024, pp. 46-53. https://doi.org/10.33012/2024.19609
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