Διερεύνηση πλοήγησης και προγραμματισμού πτήσης με μη επανδρωμένο σύστημα αεροφωτογράφισης

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Προστασία Μνημείων” Β΄ Κατεύθυνση: Υλικά και Επεμβάσεις Συντήρηση

An Updated Comparison on Contemporary Approaches for Digitization of Heritage Objects

Continuous developments on sensors, data acquisition techniques, algorithms and computational systems have enabled automation, higher processing velocities and increased metric accuracy regarding the modeling of tangible heritage. For applications on heritage artefacts or architectural details, scanning and photogrammetric systems based on structure-from-motion (SfM) approach have prevailed, due to lower costs, fast acquisition and processing, re-producibility of workflows and ability to capture high-resolution texture. This study presents an updated comparison of contemporary digitization approaches to examine in extent required processing stages, compare costs and evaluate produced 3D results according to their metric properties, quality of texture and visual fidelity

UAS-Based Archaeological Remote Sensing: Review, Meta-Analysis and State-of-the-Art

Over the last decade, we have witnessed momentous technological developments in unmanned aircraft systems (UAS) and in lightweight sensors operating at various wavelengths, at and beyond the visible spectrum, which can be integrated with unmanned aerial platforms. These innovations have made feasible close-range and high-resolution remote sensing for numerous archaeological applications, including documentation, prospection, and monitoring bridging the gap between satellite, high-altitude airborne, and terrestrial sensing of historical sites and landscapes. In this article, we track the progress made so far, by systematically reviewing the literature relevant to the combined use of UAS platforms with visible, infrared, multi-spectral, hyper-spectral, laser, and radar sensors to reveal archaeological features otherwise invisible to archaeologists with applied non-destructive techniques. We review, specific applications and their global distribution, as well as commonly used platforms, sensors, and data-processing workflows. Furthermore, we identify the contemporary state-of-the-art and discuss the challenges that have already been overcome, and those that have not, to propose suggestions for future research

Near-infrared modeling and enhanced visualization, as a novel approach for 3D decay mapping of stone sculptures

Representation of the surface pathology of heritage objects imposes a problematic task. It usually involves the implementation of on-site visual inspections, and diagnostic procedures on-site, and after sampling, through minimally destructive laboratory tests, to produce area-specific results or two-dimensional mapping visualizations. Mapping of stone weathering is usually performed manually with time-consuming two-dimensional approaches, thus losing the importance of topology and, in general, its threedimensional metric quality. The recent introduction of modified cameras to heritage science has enabled enhanced observation at higher resolutions, concomitantly having the capacity to produce datasets that can be used for direct image-based three-dimensional reconstruction. With this article, we present a novel work combining near-infrared imaging using a modified sensor, and contemporary dense multiple-image reconstruction software, to produce spectral models of historical stone sculptures. This combined approach enables the simultaneous capturing of the shape of the historical stone surfaces and the different responses of deteriorated materials in the near-infrared spectrum. Thus, we investigate the capacity of the suggested method to assist threedimensional diagnosis and mapping of stone weathering. We explore the usability of produced spectral textures via classification and three-dimensional segmentation techniques to obtain and assess different types of visualization. We additionally evaluate the produced models for their metric and radiometric properties, by comparing them with models produced with visible spectrum imagery, acquired with similar capturing parameters

Documenting the State of Preservation of Historical Stone Sculptures in Three Dimensions with Digital Tools

Protection of stone heritage requires detailed records of the state-of-preservation to ensure accurate decision-making for conservation interven-tions. This short paper explores the topic of using digital tools to better visual-ize and map in three-dimensional (3D) representations the deterioration state of stone statues. Technical photography, geomatics techniques, and 3D visualiza-tion approaches are combined to propose reproducible and adaptable solutions that can support the investigation of historical materials' degradation. The short paper reports on the application of these multi-technique approaches regarding a bust sculpture from the Accademia Carrara in Bergamo (Italy)

Close-Range Sensing and Data Fusion for Built Heritage Inspection and Monitoring - A Review

Built cultural heritage is under constant threat due to environmental pressures, anthropogenic damages, and interventions. Understanding the preservation state of monuments and historical structures, and the factors that alter their architectural and structural characteristics through time, is crucial for ensuring their protection. Therefore, inspection and monitoring techniques are essential for heritage preservation, as they enable knowledge about the altering factors that put built cultural heritage at risk, by recording their immediate effects on monuments and historic structures. Nondestructive evaluations with close-range sensing techniques play a crucial role in monitoring. However, data recorded by different sensors are frequently processed separately, which hinders integrated use, visualization, and interpretation. This article’s aim is twofold: i) to present an overview of close-range sensing techniques frequently applied to evaluate built heritage conditions, and ii) to review the progress made regarding the fusion of multi-sensor data recorded by them. Particular emphasis is given to the integration of data from metric surveying and from recording techniques that are traditionally non-metric. The article attempts to shed light on the problems of the individual and integrated use of image-based modeling, laser scanning, thermography, multispectral imaging, ground penetrating radar, and ultrasonic testing, giving heritage practitioners a point of reference for the successful implementation of multidisciplinary approaches for built cultural heritage scientific investigations

Image-based metric heritage modeling in the near-infrared spectrum

Digital photogrammetry and spectral imaging are widely used in heritage sciences towards the comprehensive recording, understanding, and protection of historical artifacts and artworks. The availability of consumer-grade modified cameras for spectral acquisition, as an alternative to expensive multispectral sensors and multi-sensor apparatuses, along with semi-automatic software implementations of Structure-from-Motion (SfM) and Multiple-View-Stereo (MVS) algorithms, has made more feasible than ever the combination of those techniques. In the research presented here, the authors assess image-based modeling from near-infrared (NIR) imagery acquired with modified consumergrade cameras, with applications on tangible heritage. Three-dimensional (3D) meshes, textured with the non-visible data, are produced and evaluated. Specifically, metric evaluations are conducted through extensive comparisons with models produced with image-based modeling from visible (VIS) imagery and with structured light scanning, to check the accuracy of results. Furthermore, the authors observe and discuss, how the implemented NIR modeling approach, affects the surface of the reconstructed models, and may counteract specific problems which arise from lighting conditions during VIS acquisition. The radiometric properties of the produced results are evaluated, in comparison to the respective results in the visible spectrum, on the capacity to enhance observation towards the characterization of the surface and under-surface state of preservation, and consequently, to support conservation interventions