The Interferometric Use of Radar Sensors for the Urban Monitoring of Structural Vibrations and Surface Displacements

Abstract

In this paper, we propose a combined use of real aperture radar (RAR) and synthetic aperture radar (SAR) sensors, within an interferometric processingchain, to provide a new methodology for monitoring urban environment and historical buildings at different temporal and spatial scales. In particular, ground-based RAR measurements are performed to estimate the vibration displacements and the natural oscillation frequencies of structures, with the aim of supporting the understanding of the building dynamic response. These measurements are then juxtaposed with ground-based and space-borne SAR data to monitor surface deformation phenomena, and hence, point out potential risks within an urban environment. In this framework, differential interferometric SAR algorithms are implemented to generate short-term (monthly) surface displacement and long-term (annual) mean surface displacement velocity maps at local (hundreds m 2 ) and regional (tens km 2 ) scale, respectively. The proposed methodology, developed among the activities carried out within the national project Programma Operativo Nazionale MASSIMO (Monitoraggio in Area Sismica di SIstemi MOnumentali), is tested and discussed for the ancient structure of Saint Augustine compound, located in the historical center of Cosenza (Italy) and representing a typical example of the Italian Cultural Heritage.

Landslides and Subsidence Assessment in the Crati Valley (Southern Italy) Using InSAR Data

“…On the other hand, for the eastern sector, a weak subsidence (up to 1.6 mm/year) was instead observed for the areas that were built on Quaternary alluvial deposits. No significant surface deformation was observed in the correspondence of Cosenza old town with COSMO-SkyMed and ground-based radar sensors data by [50]. In particular, we observed vertical component values of 0.23, 0.02, and −0.37 mm/year (Figure 8a) close to the Saint Augustine Monumental compound.…”

“…From these data, we derived a map of water table variations during the periods 1979-1992, 1990-2005, and 1979-2005 (Figure 7a-c). During the first period, the main piezometric level decreased in proximity of the Quattromiglia, Taverna di Montalto, and Torano station areas (Figure 7a No significant surface deformation was observed in the correspondence of Cosenza old town with COSMO-SkyMed and ground-based radar sensors data by [50]. In particular, we observed vertical component values of 0.23, 0.02, and −0.37 mm/year (Figure 8a) close to the Saint Augustine Monumental compound.…”

“…In particular, we observed vertical component values of 0.23, 0.02, and −0.37 mm/year (Figure 8a) close to the Saint Augustine Monumental compound. This area was investigated in detail by Montuori, A. et al [50]. In the western sector of Cosenza, the vertical component showed a weak uplift (max value 2.3 mm/year; mean value 0.76 mm/year) for parts of the town that were built on Pliocene deposits (clay, sandstone, and conglomerate) and the Quaternary conglomerates representing fluvial terraces (Figure 8b).…”

Dynamic Monitoring and Vibration Analysis of Ancient Bridges by Ground-Based Microwave Interferometry and the ESMD Method

“…, where  is the length of the electromagnetic wave and   is the phase shift [31]. For IBIS-S, the Ku-band of the working Radar is between 16.6-16.9…”

“…In general, amplitude and phase information can be acquired for each measurement using ground-based microwave interferometry. Therefore, considering a single target, a tiny displacement d along the radar line-of-sight direction can be calculated through comparing the phase shift at different times by d = λ∆ϕ 4π , where λ is the length of the electromagnetic wave and ∆ϕ is the phase shift [31]. For IBIS-S, the Ku-band of the working Radar is between 16.6-16.9 GHz, the approximate value of λ = c/ f is 18.07 mm, the maximum value of ∆ϕ is π, and therefore, the maximum range of displacement d along the radar line-of-sight direction is about 4.5175 mm for the adjacent sampling interval.…”