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Gabriele Colosimo, Mattia Crespi, Augusto Mazzoni

VADASE (Variometric Approach for Displacements Analysis Stand-alone Engine)

This is a novel strategy consisting of an algorithm able to perform real-time retrieval and estimation of displacement and waveforms based on high-frequency (1Hz or more) carrier phase observations collected by a stand-alone GNSS receiver.

The algorithm works with broadcast products (satellite clocks and orbits) and requires very simple hardware. These characteristics allow our solution to be directly embedded into receiver firmware and permit to estimate, in realtime and without any need for corrections from other sources, the receiver displacements.

Although such an ingenious idea can be applied to several different problems, we focus on two we believe are most important: earthquake risk assessment (and related early-warning systems for tsunamis) and structural monitoring.

Figure: Baja (Mexico) earthquake, MW 7.2, April 04 2010, 22:40:42 UTC. Station P496 - variometric BRD solution over the 200 seconds interval 22:40:40 - 22:44:00, YYDOY 10094 GPS time, for direct comparison with the waveforms and coseismic displacements recovered by Kristine Larson at the University of Colorado at Boulder www.unavco.org

The major advancement of the proposed solution introduces a novel strategy in performing real-time estimation of coseismic displacement and waveforms accurate down to a few centimetres. Given the fact that it requires no centralised data analysis, no external corrections for the algorithm to work, and no particularly powerful hardware, the solution can be embedded directly into receiver firmware. This framework enables VADASE to fulfill some of the recommendations recently adopted by the scientific community (2007, Leavenworth) - in particular, the possibility to achieve 1-cm real-time GNSS displacement accuracy in a global reference frame within three minutes after an earthquake.

The immediate fields of application include high-frequency real-time monitoring in seismology and tsunami early-warning systems, as well as the monitoring of structures and geotechnical engineering; oscillation monitoring for different types of structures (buildings, skyscrapers, dams, etc); and safety monitoring for infrastructure elements (railways, highways, etc) close to potential hazard (landslides, etc).

Public administrations in charge of surveying and monitoring areas susceptible to earthquakes or tsunamis, as well as all civil protection departments responsible for monitoring infrastructures that experience oscillations, can take advantage of this idea. In particular, the real-time capability of the system - together with the possibility to embed VADASE into existing sensors' firmware - makes it a low-cost monitoring solution. In fact, the system is completely self-reliant and needs no additional network infrastructure.

University of Rome „La Sapienza"
Mr Gabriele Colosimo, Mr Mattia Crespi, Mr Augusto Mazzoni
Dipartimento di Ingegneria Civile Edile e Ambientale (DICEA)
Area di Geodesia e Geomatica (AGG), Via Eudossiana 18,
00184 Rome, Italy
phone: +39 06 44 58 30 66, +39 06 44 58 50 97
e-mail: gabriele.colosimo@uniroma1.it, mattia.crespi@uniroma1.it,



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