## 7 Conclusions  
An experimental campaign has been planned within the 2019-2021 DPC-Reluis Project with the aim of setting up new protocols to merge information retrieved from satellite data and on-site vibrational measurements. The \"Ponte della Musica-Armando Trovajoli\" bridge has been selected as test site. With reference to the satellite data, analyses of LOS displacement time series, retrieved through the multi-temporal SBAS-DInSAR technique, show a substantially stable behavior of the bridge structural elements. The deformation trends of the foundations observed in the 2011-2019 time interval reflect the response in term of small settlement of the subsoil due to the load of bridge itself imposed not before of 2009. During the experimental campaign velocimetric acquisitions were also performed on the bridge. Collected data allowed us to observe that the monitored structure exhibits, in the considered time interval, a stable behavior. The main structural eigenfrequencies were estimated: the first mode is characterized by a frequency equal to 0.92 Hz, the second mode is characterized by a frequency equal to 1.01 Hz, and the third one is characterized by a frequency equal to 1.33 Hz. These values could be used in future as a reference to detect possible anomalous dynamic behavior. The analysis of satellite data relating to both the ascending and descending orbits showed that there are no measuring points detected by the satellite on the deck. Same measurements performed on masonry arch bridges located close to the Ponte della Musica show data both on the support and on along the deck. Bridges with high stiffness and with the piles in the riverbed (Ponte Matteotti, Ponte Pietro Nenni, Ponte Flaminio and Ponte Milvio) are completely covered by the satellite measurement points whereas on Ponte Risorgimento and Ponte Duca d'Aosta the points detected by the satellite are not located on the deck, as observed for Ponte della Musica. In the case of bridge monitoring, the associated displacements are on the order of magnitude of millimeters and are continuously varying in time due to temperature and traffic loads. However, heavy traffic loads, strong wind, temperature changes and other second-order events may lead to large unexpected vibration effects on the bridge, which sometimes jeopardize the correct retrieval of displacements associated to the investigated bridge or some parts of it. In the specific case of Ponte della Musica, some further investigations to detect the possible causes (for instance, sudden temperature variations, strong winds) that led to the observed lack of coherent DInSAR measurements on the bridge deck need to be further investigated. Accordingly, future numerical and experimental studies are envisaged to correlate structural eigenfrequencies with temperature, displacements and satellite data, with the aim to: (i) update protocols to merge information retrieved by using different techniques, on site and remote-sensing data; (ii) define structural behavior thresholds to identify and locate damages on structural and non-structural components. Finally, it must be remarked that the combination of SAR satellite and in situ techniques represents a monitoring level able on the one hand to follow the trend of the infrastructure over time, identifying variations that may herald criticalities, and on the other hand to identify, in the presence of a seismic event, infrastructures that do not present critical issues that require further investigation. Conceptualization, C.I., R.D., F.C.P., M.B., R.L., F.S., V.C. and F.B. ; experimental campaign of ambient vibration measurements, C.I., R.D. and F.C.P. ; velocimetric data acquisition and processing, C.I., R.D. and F.C.P. ; satellite data acquisition and processing, M.B., R.L., F.S. and V.C. ; geological analysis, F.B., P.C. and M.R. ; writing original draft, C.I., R.D. and F.C.P. ; writing review and editing, all authors; funding acquisition, F.C.P. All authors have read and agreed to the published version of the manuscript.