Multi-temporal satellite interferometric technique for structures 3D rigid motion assessment with uncertainty estimation

In the last decade, with the launch of high-resolution and short revisit time Synthetic Aperture Radar (SAR) satellite missions new possibilities arose in the structure and infrastructure monitoring field. In particular, with the use of multi-temporal interferometric techniques applied to high-resolution SAR data, the displacement time series of stable ground targets (the Persistent Scatterers or PS) can be reconstructed with an accuracy of 1-2 mm/yr and a spatial resolution of few meters. The information extracted from SAR products could be relevant both for the preventive conservation and maintenance and for the health assessment of the existing built heritage, in particular when exposed to ground deformation phenomena. Some issues related to the use of multi-temporal satellite interferometric techniques in structural applications need to be carefully investigated; in particular, the reliability of SAR-derived data in these applications needs to be assessed due to the small displacements affecting a damaged structure.

The proposed work investigates the potentialities of multi-temporal satellite interferometric techniques in the structural monitoring field. In particular, the 3D rigid motion of isolated buildings is reconstructed computing the motion parameters from a dual-orbit set of Persistent Scatterers. The uncertainties affecting the estimated parameters are also assessed on the basis of an error model taking into account the uncertainties related to the displacement measurements from the interferometric technique and the expected errors in the positioning of the scatterers.

The method has been tested on COSMO-SkyMed SAR data processed with a SNAP-StaMPS open-source procedure complemented by in-house procedures for the calibration of SAR products with velocities from GNSS observations. Moreover, the topographic error affecting the elevation of the Persistent Scatterers was estimated and the planimetric coordinates of the scatterers were corrected accordingly, since an accurate 3D positioning of the scatters is fundamental when dealing with structural investigations.

The obtained results show that 3D rigid motions can be estimated in the order of few mm/yr for the displacements and mrad/yr for the rotations with corresponding precision at one order of magnitude smaller than the associated parameters.

Funding

The methodology adopted in the present research was developed in the frame of the FAR Mission Oriented 2021 Project (Satellite Methods for Structural Monitoring, SM4SM, contract E95F21002900007) with the financial support of the University of Modena and Reggio Emilia and Fondazione di Modena.