1,720,994 research outputs found
Geomatic techniques for the documentation of the Underwater Cultural Heritage
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
L'impiego dei droni per la sicurezza nei cantieri post-sisma
No full textL’articolo presenta un’analisi dello stato dell’arte e del contesto normativo in merito all’impiego dei droni nei cantieri edili emergenziali (post-sisma), e fornisce un metodo per valutare e mitigare il rischio intrinseco connesso al loro utilizzo. L’obbiettivo dello studio è far emergere le possibilità offerte per il miglioramento della sicurezza degli operatori e la mitigazione dei rischi derivanti dai disastri naturali. Queste nuove tecnologie da anni supportano le attività di rilievo speditivo e di documentazione dei danni occorsi al patrimonio costruito, garantendo la sicurezza degli operatori durante le operazioni di consolidamento e ricostruzione
The Use of UAVs for Performing Safety-Related Tasks at Post-Disaster and Non-Critical Construction Sites
Full text linkThanks 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
Georeferencing Strategies in Very Shallow Waters: A Novel GCPs Survey Approach for UCH Photogrammetric Documentation
Full text linkThe growing interest of the scientific community in surveying and monitoring submerged assets is motivated by the increasing demand for high-resolution products with certified accuracies. While many instrumental and methodological solutions for documenting, monitoring, and studying archaeological and cultural heritage through geomatics techniques are already available for the terrestrial environment, the challenge remains open to the underwater context. High-resolution capability and accurate positioning are still difficult to achieve in these environments. This paper discusses the limitations of positioning and georeferencing techniques in the underwater environment. It explores how existing methods and new instruments can be used to perform accurate topographic surveys of ground control points (GCPs) in very shallow waters (within 5 m depths), which can support the photogrammetric reconstruction of underwater assets. This research presents two innovative prototypes: a self-built plastic marker for topographic use in the underwater environment and a self-built aluminum pole for topographic use in the marine environment. The prototypes are tested and validated with a tilt-compensating smart antenna to reduce planar and altimetric errors when the pole is not perfectly level and to work independently of the shore proximity required when using a total station to perform said measurements
Underwater Cultural Heritage Documentation Using Photogrammetry
Full text linkUnderwater cultural heritage (UCH) is an irreplaceable resource with intrinsic value that requires preservation, documentation, and safeguarding. Documentation is fundamental to increasing UCH resilience, providing a basis for monitoring, conservation, and management. Advanced UCH documentation and virtualization technologies are increasingly important for dissemination and visualization purposes, domain expert study, replica reproduction, degradation monitoring, and all other outcomes after a metric survey of cultural heritage (CH). Among the different metric documentation techniques, underwater photogrammetry is the most widely used for UCH documentation. It is a non-destructive and relatively inexpensive method that can produce high-resolution 3D models and 2D orthomosaics of underwater sites and artifacts. However, underwater photogrammetry is challenged by the different optical properties of water, light penetration, visibility and suspension, radiometric issues, and environmental drawbacks that make underwater documentation difficult. This paper introduces some of the recent applications of photogrammetric techniques and methods for UCH documentation, as well as the needs and shortcomings of the current state of the art
An adhoc UW image colour correction method and the impact on image feature matching & SfM-MVS 3D reconstruction
No full textThe problem of colour correction of underwater images concerns not only surveyors, who primarily use images for photogrammetric purposes, but also archaeologists, marine biologists, and many other experts of different disciplines whose aim is to study objects and lifeforms underwater. For this reason, this study aims to address and quantify the impact of an ad-hoc underwater image restoration algorithm regarding image feature matching and 3D reconstruction of the scene. The datasets used for the purpose of this study consist of the original and colour corrected images captured in two different sites located in Cyprus with different depths and different water conditions. The images were colour corrected following a simple mathematical model that utilizes the scene's geometry while considering also the absorption and backscattering of light in order to restore the missing colour information
High-accuracy height differences using a pressure sensor for ground control points measurement in underwater photogrammetry
Full text linkThree-dimensional reference points (RPs) are fundamental for datum definition and metric validation in many photogrammetric applications, often used as ground control points (GCPs) to constrain the bundle adjustment solution. Nevertheless, survey operations underwater present challenges due to the physical characteristics of the water itself and the technological limitations of available instruments. Traditional methods to collect RPs underwater rely on direct geodetic measurements like slope distances, height differences, and depths from a dive computer. These methods can be time-consuming and impractical to scale up to large areas, particularly in deeper waters. This paper reports on the use of a custom-developed low-cost pressure sensor to measure depths and height differences of underwater RPs with survey-grade accuracy. Laboratory and open water tests demonstrated the method's potential, achieving an RMSEZ of less than 1 mm over a 1.5 m height range in the laboratory in static water and a sub-centimetre RMSE of relative depth differences in shallow water tests carried out in two different locations at sea with maximum significant wave height of 9 cm. The sensor proved its effectiveness also for constraining a corridor-like underwater photogrammetric survey reducing the bending of the 3D model with respect to the free network solution (RMSEZ lowered from 10 cm to less than 1 cm). The preliminary tests with the presented approach proved several advantages against other consolidated methods, including cost reduction (compared to commercial survey instruments), rapidity, safety, and accuracy, especially at depths greater than 3–5 m where other approaches (e.g., GNSS or topographic measures) cannot be applied
Low-cost sensors for rapid mapping of cultural heritage: first tests using a COTS Steadicamera
Full text linkOne of the last and more pressing requests to the researchers working in the field of Geomatics is to research, validate, and propose new strategies for the rapid mapping of different contexts, with low-cost solutions. The continuous implementation of image-matching algorithms and their use in structure from motion (SfM) software allow using new sensors and implementing new strategies for the production of 3D models starting from an image-based approach. In the last years, another central issue for the researchers has been related with the documentation of cultural heritage (CH) artifacts using different sensors and techniques. In the experience presented in this paper, the attention was focused on these two central aspects: a test of a commercial off-the-shelf (COTS) steadicamera for the rapid 3D documentation of two cultural heritage artifacts was proposed. The two sites chosen to evaluate this mass market sensor were as follows: the Basilica of San Nicola (Tolentino, MC, Marche Region, Central Italy) and the Castello del Valentino (Torino, TO, Piedmont Region, North Italy). The metric products obtained with the Steadicam were compared with more consolidated techniques such as close-range photogrammetry (CRP) and terrestrial laser scanner (TLS). The products derived from the different techniques were then evaluated and compared, and an overall assess of the use of this new solution was made
An Action-Camera Based Stereo System for MicroROV for Monitoring Coralline Algae in the Mediterranean Sea: Preliminary Assessment
No full textUnderwater monitoring and surveying are fundamental activities spanning various fields, each contributing significantly to managing marine environments. These activities are crucial in marine ecology, providing essential conservation, management, and research data. The importance of underwater monitoring extends to several key areas, including marine ecology, environmental science, archaeology, and resource management. In marine ecology, monitoring activities are crucial for conserving biodiversity, assessing habitat health, understanding the impacts of climate change, and mitigating human impacts. Stereo-vision systems can be decisive for several underwater activities, such as monitoring, research, and exploration. Commercial stereo-vision systems often involve high costs and complex setups, which limit their accessibility. The proposed approach leverages the affordability of action cameras to create an accessible and effective solution. Indeed, this paper presents the design, implementation, and preliminary testing of a low-cost stereo-vision system utilizing two GoPro 11 for underwater applications on a micro ROV. The design process involved synchronizing two action cameras and developing a mounting rig to ensure a stable relative position between the cameras. The stereo system is calibrated in-air and underwater to test different calibration strategies. The obtained performances will guide practical considerations on using the low-cost, off-the-shelf stereo system based on action cameras for monitoring challenging underwater environments
Il rilievo metrico integrato della Valle dei Re: software open-source per la documentazione del patrimonio archeologico in Egitto
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