[Chen, Fulong; Zheng, Wenwu] Hengyang Normal Univ, Cooperat Innovat Ctr Digitalizat Cultural Heritag, Hengyang, Peoples R China.;[Chen, Fulong; Xu, Hang; Zhou, Wei] Chinese Acad Sci, Key Lab Digital Earth Sci, Aerosp Informat Res Inst, Beijing, Peoples R China.;[Chen, Fulong; Zhou, Wei] Int Ctr Space Technol Nat & Cultural Heritage Aus, Beijing, Peoples R China.;[Xu, Hang] Univ Chinese Acad Sci, Coll Resources & Environm, Beijing, Peoples R China.;[Deng, Yunyuan] Hengyang Normal Univ, Coll City & Tourism, Hengyang, Peoples R China.
[Chen, Fulong] H;[Chen, Fulong] C;[Chen, Fulong] I;Hengyang Normal Univ, Cooperat Innovat Ctr Digitalizat Cultural Heritag, Hengyang, Peoples R China.;Chinese Acad Sci, Key Lab Digital Earth Sci, Aerosp Informat Res Inst, Beijing, Peoples R China.
InSAR;numerical simulation;three-dimensional deformation;architectural heritage;angkor Wat
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.
Accurate estimation of ground elevation on a large scale is essential and worthwhile in topography, geomorphology, and ecology. The Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) mission, launched in September 2018, offers an opportunity to obtain global elevation data over the earth's surface. This paper aimed to evaluate the performance of ICESat-2 data for ground elevation retrieval. To fulfill this objective, our study first tested the availability of existing noise removal and ground photon identification algorithms on ICESat-2 data. Second, the accuracy of ground elevation data retrieved from ICESat-2 data was validated using airborne LiDAR data. Finally, we explored the influence of various factors (e.g., the signal-to-noise ratio (SNR), slope, vegetation height and vegetation cover) on the estimation accuracy of ground elevation over forest, tundra and bare land areas in interior Alaska. The results indicate that the existing noise removal and ground photon identification algorithms for simulated ICESat-2 data also work well for ICESat-2 data. The overall mean difference and RMSE values between the ground elevations retrieved from the ICESat-2 data and the airborne LiDAR-derived ground elevations are -0.61 m and 1.96 m, respectively. In forest, tundra and bare land scenarios, the mean differences are -0.64 m, -0.61 m and -0.59 m, with RMSE values of 1.89 m, 2.05 m, and 1.76 m, respectively. By analyzing the influence of four error factors on the elevation accuracy, we found that the slope is the most important factor affecting the accuracy of ICESat-2 elevation data. The elevation errors increase rapidly with increasing slope, especially when the slope is greater than 20 degrees. The elevation errors decrease with increasing SNR, but this decrease varies little once the SNR is greater than 10. In forest and tundra areas, the errors in the ground elevation also increase with increasing vegetation height and the amount of vegetation cover. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
This paper provides a brief history review of the use of ancient weirs in fishing on our planet, as well as a pilot study that involves investigating and mapping the coastal heritage of ancient stone tidal weirs (STWs) in the Penghu Archipelago which is located in the Taiwan Strait. The spatial distribution and morphological features of STWs across Penghu Archipelago were investigated and analyzed using very high-resolution (VHR) and freely available Google Earth (GE) imagery and geographic information system (GIS) analysis tools. A total of 539 ground-truthed STWs were identified from multiple temporal GE images, and these accounted for over 90% of the localized inventory databases. The proposed GE-based method was found to be more efficient, timely and effective compared to field and airborne surveys. This paper illustrates the utility of GE as a source of freely available VHR remote sensing imagery for archaeological surveys and heritage sustainability in coastal areas.