1,720,976 research outputs found
High-accuracy height differences using a pressure sensor for ground control points measurement in underwater photogrammetry
No full textThree-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
Photogrammetric underwater and UAS surveys of archaeological sites: the case study of the Roman shipwreck of Torre Santa Sabina
Full text linkThe 2020 underwater archaeological research in the inlet of Torre Santa Sabina - Baia dei Camerini (Municipality of Carovigno,
Brindisi, Italy) represented the first phase of the pilot intervention of the Interreg Italia-Croatia UnderwaterMuse project. The project
aims to enhance and make accessible the vast underwater heritage of the areas involved; this will be done by creating submerged
archaeological parks and using virtual reality's narrative and communicative tools and platforms. During the 2020 campaign, different
survey activities were carried out using several techniques and methodology to produce the area's multi-scale documentation. First of
all, the entire stretch of coast was mapped with UASs (Uncrewed Aerial Systems) flights to reconstruct the coastal landscape in various
phases. Furthermore, an underwater photogrammetric survey carried out by expert scuba divers has been achieved in the wreck's aft
area (the site analyzed during the 2020 excavation activities). The fruitful synergy between the various actors involved and the support
of the territory and the community has allowed the achievement of this campaign's objectives, preliminary to the broader and more
articulated intervention foreseen for the following year
DEEP LEARNING FOR AUTOMATIC BUILDING DAMAGE ASSESSMENT: APPLICATION IN POST-DISASTER SCENARIOS USING UAV DATA
Full text linkDuring the last few years, the technical and scientific advances in the Geomatics research field have led to the validation of new mapping and surveying strategies, without neglecting already consolidated practices. The use of remote sensing data for damage assessment in post-disaster scenarios underlined, in several contexts and situations, the importance of the Geomatics applied techniques for disaster management operations, and nowadays their reliability and suitability in environmental emergencies is globally recognized. In this paper, the authors present their experiences in the framework of the 2016 earthquake in Central Italy and the 2019 Cyclone Idai in Mozambique. Thanks to the use of image-based survey techniques as the main acquisition methods (UAV photogrammetry), damage assessment analysis has been carried out to assess and map the damages that occurred in Pescara del Tronto village, using DEEP (Digital Engine for Emergency Photo-analysis) a deep learning tool for automatic building footprint segmentation and building damage classification, functional to the rapid production of cartography to be used in emergency response operations. The performed analyses have been presented, and the strengths and weaknesses of the employed methods and techniques have been outlined. In conclusion and based on the authors' experience, some operational suggestions and best practices are provided and future research perspectives within the same research topic are introduced
Quantitative Evaluation of Color Enhancement Methods for Underwater Photogrammetry in Very Shallow Water: a Case Study
Full text linkUnderwater photogrammetry is often hampered by chromatic aberration, leading to degraded 2D and 3D products. This study investigates the effectiveness of various color enhancement methods in addressing these challenges.
Theoretical considerations indicate that light penetration depth varies inversely with wavelength, causing underwater images to exhibit a blue or green cast with increasing depth. Color enhancement techniques can restore natural colors by compensating for this spectral attenuation. Additionally, scattering, caused by light reflected by particles in the water, can introduce haze into underwater images. Color enhancement can mitigate scatter and improve image clarity. In this contribution, to quantitatively evaluate color enhancement methods, we compare original images with images processed using gray-world assumption methods and physical methods that account for the physical properties of light underwater. Using artificial intelligence (AI) for underwater image color enhancement, a data-driven approach was also employed. These methods were applied to a case study concerning a Roman Navis Lapidaria shipwreck carrying five monumental cipollino marble columns at a depth of 4.5 meters in the Porto Cesareo Marine Protected Area (Italy). These methods were compared quantitatively and qualitatively, and the results are presented and discussed
PHOTOGRAMMETRIC UNDERWATER AND UAS SURVEYS OF ARCHAEOLOGICAL SITES: THE CASE STUDY OF THE ROMAN SHIPWRECK OF TORRE SANTA SABINA
Full text linkThe 2020 underwater archaeological research in the inlet of Torre Santa Sabina – Baia dei Camerini (Municipality of Carovigno, Brindisi, Italy) represented the first phase of the pilot intervention of the Interreg Italia-Croatia UnderwaterMuse project. The project aims to enhance and make accessible the vast underwater heritage of the areas involved; this will be done by creating submerged archaeological parks and using virtual reality's narrative and communicative tools and platforms. During the 2020 campaign, different survey activities were carried out using several techniques and methodology to produce the area's multi-scale documentation. First of all, the entire stretch of coast was mapped with UASs (Uncrewed Aerial Systems) flights to reconstruct the coastal landscape in various phases. Furthermore, an underwater photogrammetric survey carried out by expert scuba divers has been achieved in the wreck's aft area (the site analyzed during the 2020 excavation activities). The fruitful synergy between the various actors involved and the support of the territory and the community has allowed the achievement of this campaign's objectives, preliminary to the broader and more articulated intervention foreseen for the following year
RAPID MAPPING FOR BUILT HERITAGE AT RISK USING LOW-COST AND COTS SENSORS. A TEST IN THE DUOMO VECCHIO OF SAN SEVERINO MARCHE
Full text linkIn the last years, the researchers in the field of Geomatics have focused their attention in the experimentation and validation of new
methodologies and techniques, stressing especially the potential of low-cost and COTS (Commercial Off The Shelf) solutions and
sensors. In particular, these tools have been used with purposes of rapid mapping in different contexts (ranging from the construction
industry, environmental monitoring, mining activities, etc.). The Built Heritage, due to its intrinsic nature of endangered artefact, can
largely benefit from the technological and methodological innovations in this research field. The contribute presented in this paper will
highlight these main topics: the rapid mapping of the Built Heritage (in particular the one subjected to different types of risk) using
low-cost and COTS solutions. Different sensors and techniques were chosen to be evaluated on a specific test site: the Duomo Vecchio
of San Severino Marche (MC - Italy), that was partially affected by the earthquake swarm that hit the area of Central Italy starting from
the 24th of August 2016. One of the main aims of this work is to demonstrate how low-cost and COTS sensors can contribute to the
documentation of the Built Heritage for its safeguard, for damage assessment in case of disastrous events and operations of restoration
and preservation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
UAV strategies validation and remote sensing data for damage assessment in post-disaster scenarios
Full text linkThe recent seismic swarms, occurred in Italy since August 2016, outlined the importance of deepen Geomatics researches for the validation of new strategies aimed at rapid-mapping and documenting differently accessible and complex environments, as in urban contexts and damaged built heritage. In the emergency response, the crucial exploitation of technological advances should obtain and efficiently organize high-scale reliable geospatial data for the early warning, impact, and recovery phases. Fulfilling these issues, among others, the Copernicus EMS, has played by now an important role in immediate and extensive damage reconnaissance, as in the case of Centre Italy. Nevertheless, the use of remote sensing data is still affected by a problem of point-of-view, scale and detectable detail. Nadir images, airborne or satellite, in fact, strongly limited the confidence level of these products. The subjectivity of the operator involvement is still an open issue, both in the first fieldwork assessment, and in the following operational approach of interpretative damage detection and rapid mapping production. To overcome these limits, the introduction of UAV platforms for photogrammetric purposes, has proven to be a sustainable approach in terms of time savings, operators’ safety, reliability and accuracy of results: the nadir and oblique integration can provide large multiscale models, with the fundamental information related to the façades conditions. The presented research, conducted within the Central Italy earthquakes events, will focus on potentialities and limits of UAV photogrammetry in the two documented sites: Pescara del Tronto and Accumoli. Here, the aim is not limited to describe a series of strategies for georeferencing, blocks orientation and multitemporal co-registration solutions, but also to validate the implemented pipelines as a workflow that could be integrated in the operative intervention for emergency response in early impact activities. Thus, it would be possible to use this 3D metric products as a reference-data for significative improvements of reliability in typical visual inspection and mapping, flanking the traditional nadir airborne- or satellite-based products. The UAV acquisitions performed in two damaged villages are displayed, in order to underline the implication of the spatial information embedded in DSM reconstruction and 3D models, supporting more reliable damage assessments
- …
