Joint measurement of height and deformation by radar Interferometry: the example of the Eiffel Tower

Abstract

International audienceThe measurement of altitude and ground movements are well-known problems in InSAR. With the refinement of the resolution, the same techniques can be considered for monitoring individual buildings. Since the measure of the height and the deformations are interlinked in the interferometric phase, a measure of the height is necessary to obtain the deformations. In this article, we monitor the deformations of the Eiffel Tower using 50 images acquired by TerraSAR-X, with a metric resolution. The height is obtained using a single pass interferogram acquired by TerraSAR-X and TanDEM-X. Then these measures are compared to weather data and optical strand fixed to the Eiffel Tower by the company OSMOS. The normalized correlation of the measured deformations with the minimum temperature measured on the acquisition dates is 0.5 for the Eiffel Tower and the deformation measured by InSAR have the same order of magnitude than the deformation measured by the optical strands. To achieve local deformations measurement by interferometry, it is necessary to have the height of each pixel of the structure. This height can be obtained using a 3D model, provided that the acquisition geometry and backscattering effects are taken into account. The deformations maps obtained using a 3D model or a single pass interferogram have similar orders of magnitude