KEYWORDS: 3D modeling, Laser scanners, Data modeling, Cultural heritage, Data acquisition, Clouds, Unmanned aerial vehicles, Gold, 3D imaging standards, Atomic force microscopy
The digital twin is among the Top 10 of the strategic technological trends for the period 2007-2019, and it represents a powerful tool for the conservation and enhancement of cultural heritage. It reproduces with "precision" a physical asset, thus allowing to investigate its structure and to analyze the deformations that occur over the years. Various techniques have been introduced to obtain high-resolution 3D models. Among these, the Terrestrial Laser Scanner (TLS) is widely recognized as the gold standard to generate accurate 3D metric reconstructions. TLS allows acquiring a lot of data (point cloud) in a fast way, being not in physical contact with the objects of investigation. By integrating the point cloud coming from the TLS with the one coming from the photogrammetric processes based on the Structure from Motion (SfM) and Multi View Stereo (MVS) techniques, it is possible to obtain a complete model of the object under investigation. The Unmanned Aerial Vehicles (UAV) photogrammetric technique allows to investigate possible elements not detectable by TLS. Both techniques, if well performed, can show comparable accuracies. Data fusion approach, based on multi-sensor and multi-scale integration, was proposed in the present work as the optimal solution to exploit the potential of the various techniques. A high-quality virtual twin from the All Saints' Monastery of Cuti (Puglia) was produced. The resulting detailed 3D textured model was generated by integrating digital photogrammetry with laser scanning data. A discussion on data acquisition procedures, modeling approaches and accuracy of results is provided.
The monitoring of archaeological sites declared World Heritage Sites is a fundamental activity to protect and safeguard cultural heritage. In this context, monitoring with sensors mounted on a satellite platform represents a valuable tool. The availability of satellite images at high temporal frequency allows a continuous monitoring of the areas to be protected. The images acquired with the Sentinel-2 constellation are available free of charge and with a high temporal frequency; this mean that it is possible a continuous monitoring of the areas to be protected. In addition, the change-detection techniques and, in particular, the "Image Differencing" technique may be used, thanks to its simplicity and speed of application, in the monitoring activity. This technique provides that to each radiance value of an image acquired on a given date, the corresponding values of another image dating back to a high date are subtracted; in other words, to each pixel of an image is subtracted the value of the corresponding pixel of a second image acquired on a different date from the first one. The investigation was conducted on the archaeological site of the Temple of "Ain Dara" located in Syria, which is recognized in 2011 as a UNESCO World Heritage Site. The temple was destroyed in January 2018.
The research is focused on the study of the applicability of remote sensing techniques (specifically using ASTER data) for marine environmental analysis, relative to the determination of the surface temperatures. Using a multitemporal approach, two images (classified as level-1B), acquired in August 2000 and in 2005, were considered. The thermal maps were realized by means of the emissivity spectral normalization method, defining the thermal gradients in the area under investigation. The spatial and temporal anomalies related to the temperature distribution were highlighted; these anomalies represent an important parameter for the identification of probable groundwater pollution and soil contamination. To define the map of the surface temperature using thermal infrared ASTER channels, a numerical model dedicated to ASTER data was implemented during the experimentation. This model is based on the principle of interpolation of the type “least square interpolation (linear),” and it implies a reduction in the number of unknowns to obtain an acceptable solution to the problem. This experimental model has provided good results in the phase of implementation and in the tests on a synthetic image that were simulated in the laboratory. However, further verifications and modifications are necessary for the processing of real ASTER images.
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