# 3D Monitoring of Buildings Using TerraSAR-X InSAR, DInSAR and PolSAR Capacities
###### Abstract  
The rapid expansion of cities increases the need of urban remote sensing for a large scale monitoring. This paper provides greater understanding of how TerraSAR-X (TSX) high-resolution abilities enable to reach the spatial precision required to monitor individual buildings, through the use of a 4 year temporal stack of 100 images over Paris (France). Three different SAR modes are investigated for this purpose. First a method involving a whole time-series is proposed to measure realistic heights of buildings. Then, we show that the small wavelength of TSX makes the interferometric products very sensitive to the ordinary building-deformation, and that daily deformation can be measured over the entire building with a centimetric accuracy, and without any a priori on the deformation evolution, even when neglecting the impact of the atmosphere. Deformations up to 4 cm were estimated for the Eiffel Tower and up to 1 cm for other lower buildings. These deformations were analyzed and validated with weather and in situ local data. Finally, four TSX polarimetric images were used to investigate geometric and dielectric properties of buildings under the deterministic framework. Despite of the resolution loss of this mode, the possibility to estimate the structural elements of a building orientations and their relative complexity in the spatial organization are demonstrated. SAR; InSAR; DInSAR; PolSAR; urban areas; deformation monitoring; scatterers orientation +
Footnote †: journal: Remote Sensing  
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satellites can offer meter resolution, which were not previously available. This evolution opens the opportunity of building-scale monitoring for a large number of applications. The purpose of this article is to analyze three common complementary techniques for building-scale monitoring: the across-track interferometry SAR (InSAR) for building height estimation, differential interferometry SAR (DInSAR) for deformation monitoring, and polarimetry SAR (PolSAR) for analysis of materials and structures. In this paper, 96 Very High Resolution (VHR) TerraSAR-X images acquired over more than 4 years are considered for the InSAR and DInSAR study. This dataset is extended with 2 PolInSAR images acquired 3 years after the end of the interferometric time serie, leading to the longest monitoring of urban structure using SAR images. Using X-band images allows first to access meter resolution images. It can also improve the monitoring of deformation through DInSAR since the precision of this technique is inversely proportional to the wavelength as pointed out in [1]. However, these progresses should not obscure the fact that relatively little knowledge exists on the phenomenology of the X-band wave scattering in urban areas especially for these resolutions. Among the pioneer works for building monitoring, the height of buildings using interferometric techniques has already been estimated. When airborne data with a sub-metric resolution are available, 3D-model of buildings can be computed, as already demonstrated in [2; 3; 4]. In all these papers, 3D estimation have been made using single-pass acquisitions. Repeat pass across-track interferometry enabled to measure the height of emblematic buildings such as the Eiffel Tower [5; 6]. As part of the subsidence of cities, the notion of subsidence has also been extended to the estimation of deformations distributed over a structure [7]. When images with a coarse resolution are used to this aim, the deformation measurement is based on very few pixels [8; 9]. In [10], this limitation has been overcome using images with one-meter resolution, but deformation is measured assuming a linear evolution through time, that constraints a priori the deformation causes. Most of the earlier works related to building deformation by DinSAR uses a selection of pixels before deformation estimation, and a priori over deformation evolutions [9; 11]. Finally, Ref.