Geomatic techniques for the documentation of the Underwater Cultural Heritage

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The Use of UAVs for Performing Safety-Related Tasks at Post-Disaster and Non-Critical Construction Sites

Thanks to the wide diffusion of unmanned aerial vehicles (UAVs), geomatics solutions have actively contributed to the field of safety enhancement and disaster risk reduction, supporting rapid mapping and documentation activities of the damages that have occurred to heritage buildings after natural disasters (such as earthquakes) where, in this scenario it is even more important to plan and execute disaster assessment and response operations in safe conditions. In fact, the planning and execution of technical countermeasures in a seismic emergency response involve higher risks for the safety of the operators as compared with responses related to the activities performed at non-critical construction sites. After an analysis of the state of the art, this study aims to underline the possibilities offered by the use of UAVs for performing safety-related tasks, both at post-disaster and non-critical construction sites. First, a survey has been conducted concerning the main user expectations and characteristics that an ideal UAV platform should have in order to perform safety-related tasks at construction sites that are created following the initial emergency phases. The answers that were obtained have been compared with similar studies retrieved from the literature validating previously conducted research. The legislative context is also considered, as it is an important factor that influences the applicability of these platforms and technology. Along with a method for assessing and mitigating the intrinsic risk of using an UAV, the results of a survey submitted to experts in the field of safety at construction sites is also discussed, intending to identify requirements of the ideal platform and the related user expectations. The results are reported, together with a summary of considerations on the use of these strategies in the analyzed contexts

Pre- and Self-calibration of underwater cameras for photogrammetric documentation of archaeological sites

Underwater photogrammetry has become one of the most affordable and adopted methods for the documentation and the 3D reconstruction of submerged archaeological assets. In digital photogrammetry, images are captured to exploit (using computer vision-based procedures) their intrinsic metric contents. To preserve the metric consistency and to obtain reliable 3D metric products, this process must be followed according to photogrammetric principles that are even more important in underwater photogrammetry. The wide diffusion of low-cost and non-metric sensors requires that some attention be given to proper geometric calibration of the employed cameras. Via calibration, it is possible to opportunely describe geometric distortions that are observable on final images due to lens shapes and construction characteristics of the cameras and the optics used in the survey operations. This research addresses the importance of pre-calibration in underwater cameras, and for this purpose, three calibration datasets are acquired and compared: the first (A) where the camera is pre-calibrated without any addition (flat or dome ports); the second (B) in which the camera is used in combination with a dome port; and the third (C) where the camera setup has been employed in an underwater environment. For both scenarios (dry and wet), self-calibration and pre-calibration procedures are compared. Moreover, is possible to notice how the use of the right camera and lens combinations, specifically designed for underwater survey purposes, are functional to lower the distortion of the images and consequently improve the accuracy of the final 3D products. Different tests have been performed, and preliminary results are presented and discussed in this work-in-progress paper

UAV multi-image matching approach for architectural survey in complex environments

Photogrammetric survey using UAV shows nowadays some aspects, especially related to the optimization of the operative workflows and best practices, that still need to be investigated. This work concerns the use of a small UAV for the documentation of an historical architectural complex, in which space constraints arises. The adoption of a rapid mapping workflow using frames extracted from videos is discussed, together with the exploitation of an automatic procedure for the acquisition of 360° shots, used for ensuring the minimum required overlap for a reliable and accurate image orientation

UAV photogrammetry and thematic maps for environmental risk assessment in construction safety

The rapid diffusion of UAVs (Unmanned Aerial Vehicles) has played an important role in engineering and assisting a wide range of human activities, often replacing the non-equally cost effective traditional practices. Apart from the economic advantages, these innovative methodologies have found their maximum application in activities where the direct human intervention might be extremely risky or lead to loss of lives. One of the main aims of the EU Occupational Safety and Health (OSH) Strategic Framework 2014-2020 is to improve implementation of existing health and safety rules, putting in place effective and efficient risk prevention strategies. The easiness of flying COTS (Commercial Off-the-Shelf) UAVs and the quasi-automatic flight plan generation are currently key features for monitoring environmental risks in mid hazardous environments, and these platforms are nowadays widely employed, even by non-professional users, in those fields where an aircraft assessment was considered not economically sustainable in the recent past. For the above reasons, UAVs have been successfully used in construction safety planning applications, with particular reference to the evaluation of the risk factors connected to the site, i.e. the context conditions potentially interfering with the safe execution of the working tasks. In the presented research, UAV photogrammetry has been used as a methodology for the environmental risk assessment of the surrounding area of a construction site of hotel facilities, located in the north of Italy, in a place with a high hydrogeological risk. The intrinsic instability of these areas has been analysed, and the support offered by this innovative technology has been used, in combination with the existing geological and geotechnical cartography, for tackling or containing the risks of landslide and avalanches. The above analysis is functional to the adoption of precautions for the safety of the construction operators, which is mandatory according to the Italian Legislative Decree no. 81/2008 “Consolidated text on safety at work”, and the subsequent use of the building for the future users, after its completion. The capability of generating a DEM (Digital Elevation Model) of the terrain is a powerful support for large-scale quantitative estimation of volumes, while the possibility of recognizing suspicious terrain conditions can be useful for the early detection of very old or new (and so not already mapped) landslide or avalanches origin points. The above analysis might be shared with the involved professionals in online repositories, using a free and open source 3D model viewer, both for collecting raw data observations and for assisting the decision-making safety planning. The possible future outcomes and the concrete possibility of implementing these technologies in the already existing traditional practices will be then discussed, outlining strengths and weakness of the proposed methodology

Low-cost sensors for rapid mapping of cultural heritage: first tests using a COTS Steadicamera

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Tecniche di acquisizioni fotogrammetriche per il rilievo speditivo utilizzando una Steadycam commerciale

La rapidità di acquisizione nell’ambito del rilievo metrico 3D è un aspetto fondamentale, soprattutto per quanto riguarda contesti post-emergenziali, che spesso sono connotati da elevata pericolosità; negli ultimi anni, proprio per questo motivo, diverse ricerche applicate sono state sviluppate al fine di ottimizzare nuove metodologie di mapping rapide, flessibili e low-cost. Durante questa ricerca è stata testata una steadycam commerciale con la quale sono stati acquisiti in maniera speditiva dei fotogrammi del soffitto ligneo della Basilica di San Nicola a Tolentino, al fine di valutare l’utilizzo di questo strumento per scopi fotogrammetrici come possibile soluzione speditiva ed economica

L’integrazione di tecniche fotogrammetriche e MMS nel rilievo metrico dei Beni Culturali

I recenti sviluppi dei metodi e delle tecniche di rilievo metrico nel campo della Geomatica prediligono sempre più l’integrazione di dati ottenuti da diversi sensori. Le tecniche range-based da un lato e quelle image-based di fotogrammetria dall’altro si rivelano complementari ogni qualvolta sia richiesta una documentazione metrica specifica, con un’elevata accuratezza e un alto livello di dettaglio. Negli ultimi anni, si è assistito a un consolidamento della tecnologia SLAM (Simultaneous Localization and Mapping) e a una sua crescente diffusione. Con lo scopo di valutare le potenzialità e le criticità dei sistemi che impiegano tale tecnologia, in questo contributo si intende confrontare alcuni set di dati acquisiti, con differenti modalità e sensori, in contesti di rilievo speditivo di beni culturali. Nello specifico, è stato testato il dispositivo Kaarta STENCIL, dotato di un sistema di scansione a base fissa, i cui prodotti sono stati confrontati, in termini di congruenza geometrica e di densità, con quelli ottenuti dal laser scanner terrestre FARO Focus 120 (CAM2), utilizzato come ground truth. Inoltre, noti i limiti dei sistemi range-based nell’acquisizione di dati radiometrici di qualità idonea ai processi di texturizzazione, i dati da questi ottenuti sono stati integrati con quelli acquisiti da fotogrammetria terrestre e aerea (aventi sensori più performanti): ciò ha quindi permesso di associare la componente radiometrica fotogrammetrica a quella geometrica ricavata dal sistema SLAM. Ulteriore test effettuato è stato l’utilizzo delle immagini generate simultaneamente all’acquisizione MMS (Mobile Mapping System) e ottenute dalla camera feature tracker (integrata nel dispositivo Kaarta STENCIL): si è proceduto dapprima all’orientamento del dataset di immagini, successivamente a un confronto tra la posizione dei centri di presa stimati e la traiettoria di acquisizione dello strumento e, infine, alla proiezione delle immagini, precedentemente orientate, sul modello ricavato da tecnica MMS. Si è pertanto dimostrato che è possibile un’efficace integrazione delle tecnologie image-based con quelle range-based, ottenendo dati idonei al rilievo speditivo dei beni culturali

Underwater archaeological surveys in Salento waters: results and methods

This paper is related to the survey carried out in several coastal sites of Puglia in 2020, within the project UnderwaterMuse. The core of the activities took place at the Torre S. Sabina site, on the Adriatic Sea, where an integrated topographic and photogrammetric survey has been conducted on the late-imperial Roman shipwreck. Another activity, always on the Adriatic Sea, are been conducted in the “Le Cesine” Natural Reserve how led to the identification of a big pier from the Augustan period. On the Ionian Sea, furthermore, in Porto Cesareo Marine Protected Area, new evidence has been added to the numerous ones already known, such as some spectacular formations composed uniquely by cemented sherds of Tripolitanian amphorae (2nd cent. AD). This evidence seems to be significant markers of sea-level changes and the evolution of the seascape

UAV data acquisition and analysis for a Cultural Landscape Heritage: the emergency area of the Vallone d’Elva.

In the last decades, the technology progress in the cultural and environmental field has had a loud growth. The authors applied drone and terrestrial photogrammetric techniques for a complete survey on a complex Cultural Landscape Heritage, requiring protection and promoting actions. These technologies were used to obtain even more detailed 3D point clouds, terrain models, orthophotos (also new quasi-vertical product) with a centimetre accuracy, for tourism development and landslide hazard prevention on road and villages, also reducing survey costs in a complex and limited orography site