Three-dimensional deformation monitoring and simulations for the preventive conservation of architectural heritage: a case study of the Angkor Wat Temple, Cambodia

Architectural heritage has important historical, artistic, and technological value. However, these sites are subject to long-term degradation and are sensitive to disturbances from the surrounding landscape, resulting in the potential deterioration of the architecture. Deformation is a quantitative indicator of the vulnerability of architectural heritage. The extraction of three-dimensional (3D) deformation via existing geodetic approaches, such as global navigation satellite systems (GNSS) and interferometric synthetic aperture radar (InSAR), proves to be a challenging task. In this study, we proposed an adaptable methodology for the preventive monitoring of architectural heritage by integrating differential SAR tomography (D-TomoSAR) and a finite element method (FEM) to overcome the limitations of current geodetic approaches in cultural applications (i.e., sparse measurements in space; time- and labor-intensive). The Angkor Wat Temple, a well-known monument at the Angkor World Heritage site, Cambodia, was selected as the investigation target. We used D-TomoSAR to calculate the deformation, height, and thermal dilation of the structure using 46 TerraSAR-X images acquired during 2011-2013. InSAR deformation measurements were used as the constraint for the 3D deformation simulation and structural monitoring using an integrated approach to diagnose the soundness of the architectural structure. The experimental results demonstrate the following: 1) the integration of InSAR measurements prevented the underestimation of structural instabilities and linked the simplified physical model and mechanical parameters to the FEM simulation. 2) The Angkor Wat Temple appeared stable; however, structural instabilities were detected with an absolute deformation rate of up to 3 mm/yr. 3) Daily changes in thermal-related deformations caused by incoming frontal and posterior solar radiation-induced the bending of the architecture and the risk of structural defects. Our study reveals the defect mechanism of the Angkor Wat Temple and demonstrates the potential of the proposed method for the health diagnosis and preventive safeguarding of architectural heritages across the globe.