Measuring thermal expansion using X-band persistent scatterer interferometry

Abstract

This paper is focused on the estimation of the thermal expansion of buildings and infrastructures using X-band Persistent Scatterer Interferometry (PSI) observations. For this purpose an extended PSI model is used, which allows separating the thermal expansion from the total observed deformation thus generating a new PSI product: the map of the thermal expansion parameter, named thermal map. The core of the paper is devoted to the exploitation of the information contained in the thermal maps: three examples are discussed in detail, which concern a viaduct, a set of industrial buildings and two skyscrapers. The thermal maps can be used to derive the thermal expansion coefficient of the observed objects and information on their static structure. In addition, the paper illustrates the distortions in the PSI deformation products that occur if the thermal expansion is not explicitly modelled. Finally, an inter-comparison exercise is described, where the thermal expansion coefficients estimated by PSI are compared with those derived by a Ku-band ground-based SAR campaign.

Multi-dimensional SAR tomography for monitoring the deformation of newly built concrete buildings

“…This change leads to a better detection probability according to constant false alarm rate analysis (De Maio et al, 2009). As the shorter wavelength X-band SAR sensors (typically, TerraSAR-X and Cosmo-Skymed) can measure subtle movements, such as thermal expansion, more sensitively (Crosetto et al, 2015), the linear deformation model that is used in 4-D SAR becomes insufficient to approximate the deformation phase, especially when monitoring concrete structures that are sensitive to thermal expansion, leading to so-called underfitting effects (Colesanti et al, 2003). The underfitting effects have a considerably negative impact on the accuracy of the estimated linear velocity in the sense that the linear velocity may include partial nonlinear thermal expansion.…”

“…An alternative for the compensation of thermal expansion is to use a seasonal sinusoidal function (Gernhardt and Bamler, 2012) to approximate the thermal expansion based on the fact that thermal expansion is normally periodic with seasonal temperature variations, which is feasible when the temperature is unknown. Compared with sinusoidal functions, the temperature model is related to physical reality more directly and is thus more accurate (Crosetto et al, 2015). A critical error source of the extended 4-D SAR is the possible correlation between the distributions of time and temperature, which may degrade the accuracy of the estimated linear deformation velocity and thermal amplitude .…”

“…A critical error source of the extended 4-D SAR is the possible correlation between the distributions of time and temperature, which may degrade the accuracy of the estimated linear deformation velocity and thermal amplitude . To overcome this problem, the number of available images should be large enough (the larger, the better) and the total temporal span should be long enough (the longer, the better) (Crosetto et al, 2015;Reale et al, 2013). …”

“…The deformation monitoring of buildings using interferometric SAR (InSAR) methods has been performed in some studies, e.g., (Crosetto et al, 2015;Gernhardt et al, 2010;Gernhardt and Bamler, 2012;Reale et al, 2013;Van Waning, 2014). The primary purpose of this paper is to explore the possibility and potential of MD-TomoSAR for the deformation monitoring of newly built concrete buildings with a special focus on the effects of concrete shrinkage and creep.…”

“…We can see that the derived thermal amplitude is highly related to the building height. This relationship is most likely due to the accumulative effect of thermal expansion along the vertical direction (Crosetto et al, 2015). The fixed foundation and relaxed top result that when the temperature increases, dilation of each concrete member at different heights will accumulate upward, and thus the movement will approach the maximum value at the top of buildings in the upward direction, inducing movements toward the sensor in the radar line of sight (LOS) direction, whereas when the temperature decreases, concrete members will contract and the movement will approach the maximum value at the top of buildings in the downward direction, resulting in movements away from the sensor.…”