1,721,014 research outputs found
Accuracy and Precision of Shallow-Water Photogrammetry from the Sea Surface
Full text linkMapping shallow-water bathymetry and morphology represents a technical challenge. In fact, acoustic surveys are limited by water depths reachable by boat, and airborne surveys have high costs. Photogrammetric approaches (either via drone or from the sea surface) have opened up the possibility to perform shallow-water surveys easily and at accessible costs. This work presents a simple, low-cost, and highly portable platform that allows gathering sequential photos and echosounder depth values of shallow-water sites (up to 5 m depth). The photos are then analysed in conjunction with photogrammetric techniques to obtain digital bathymetric models and orthomosaics of the seafloor. The workflow was tested on four repeated surveys of the same area in the Western Mediterranean and allowed obtaining digital bathymetric models with centimetric average accuracy and precision and root mean square errors within a few decimetres. The platform presented in this work can be employed to obtain first-order bathymetric products, enabling the contextual establishment of the depth accuracy of the final products
The Innovative Growth of Space Archaeology: A Brief Overview of Concepts and Approaches in Detection, Monitoring, and Promotion of the Archaeological Heritage
No full textSpace Archaeology (SA), also known as Satellite Archaeology, Satellite Remote Sensing for Archaeology, or Archaeology from Space, is part of the wider interdisciplinary field of Remote Sensing for Archaeology. The application of satellite data in archaeological investigations has proven useful for landscape observation and analysis, the detection of archaeological traces, the reconstruction and monitoring of natural and anthropic processes, and the management and promotion of archaeological heritage. During the last few decades, the increasing number of SA studies has demonstrated innovative growth in archaeological disciplines due to the significant enhancement of spatial technologies, the advancement of visual inspection and image processing techniques, the development of data fusion methodologies, and the improvement of multi-temporal analysis methods. Therefore, a broad overview of the current situation in the concepts and approaches of SA is necessary to gain greater awareness of the current potentialities and limitations of this science to better address future studies. The present work provides a review of the scientific literature by exploring the different aspects of SA and the goals achieved to date in three main application fields: Detection, monitoring, and promotion of archaeological heritage. The contributions reviewed were divided within each of these three categories by analyzing the type of SA data and methods applied. The results indicate that (1) most studies aim to detect archaeological sites compared to monitoring and promotion; (2) optical images are used more than SAR data; and (3) techniques of image enhancement and visual interpretation are applied more than other data processing methods. This brief overview allows us to consider SA as an evolving discipline, an engine for cross-skills training, as well as a promising future science that can play a key role in the frontier of sustainable development and the new space economy
When storms stir the Mediterranean depths: chlorophyll a response to Mediterranean cyclones
No full textMediterranean cyclones induce significant biogeochemical perturbations in the Mediterranean Sea, with particularly notable effects on chlorophyll a (Chl a) dynamics. This study examines Chl a variability during twenty Mediterranean cyclones, comparing offshore and nearshore responses. Through an integrated investigation of reanalysis products, ARGO float observations, and Sentinel-2 multispectral satellite imagery, we quantified vertical and surface Chl a concentrations, while concurrently assessing nitrate distribution, currents, and mixed layer depth (MLD) variability. Our results revealed that both tropical-like cyclones and extratropical cyclones generated a pronounced uplift of the deep chlorophyll maximum (DCM) in cyclones exhibiting slow-moving phases. Notably, wind-driven upwelling and air–sea heat exchange critically govern DCM uplift for these cyclones. We demonstrated that these physical mechanisms collectively drive DCM uplift along the trajectories of intense, slow-moving Mediterranean cyclones, with significant implications for nutrient cycling and primary productivity across the Mediterranean basin
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
Optical Flow for Wave Characterization in a 2D Water Flume Using Video Analysis: A Cutting-Edge Tool for Coastal Monitoring
Full text linkCoastal monitoring is a rapidly evolving field essential for understanding meteorological and
marine conditions, which in turn supports the development of effective strategies for managing
coastal areas. This necessity is increasingly critical given the challenges posed by climate change,
rising sea levels, and extreme weather events. Among the tools available, video surveillance,
combined with advanced machine learning and computer vision techniques, has emerged as a
powerful method. It offers detailed spatial and temporal data, essential for analyzing tidal phases,
wave parameters, and storm dynamics across extensive geographic areas.
In this study, we propose an innovative integration of optical flow techniques with video analysis
to accurately quantify wave motion parameters. Optical flow, which evaluates object displacement
between video frames, is applied to determine wavelength, wave height, and flow velocity. This
approach is particularly suited for storm conditions where traditional methods face logistical and
financial constraints. Our method enables high-precision, real-time measurements vital for
analyzing coastal processes during extreme events. To ensure reliability, the results are crossvalidated
with in situ instrument data and verified through environmental reconstructions using
point clouds and ground control points. This dual-validation strategy minimizes video distortions
and enhances measurement accuracy, aligning optical flow results with physical realities.
The proposed system has been tested in a controlled environment at the Coastal Engineering
Laboratory of the University of Palermo. A two-dimensional laboratory flume simulated different
coastal conditions, ranging from calm waters to storm-like scenarios, ensuring the robustness and
adaptability of the methodology. By leveraging optical flow techniques with video surveillance, this
approach promises a transformative impact on coastal monitoring, providing continuous,
automated, and cost-effective data collection even in remote or inaccessible locations. It offers a
scalable alternative to conventional methods, which often demand expensive installations and
extensive manpower. The potential of this method to deliver high-quality real-time data, represent
a significant advancement in coastal management and environmental monitoring
Assessing the impact of vegetation cover changes and post-fire effects through an enhanced sediment flow connectivity index (SfCI)
Full text linkLand cover plays a fundamental role in surface dynamics that involve sediment connectivity. Land cover types can physically mitigate, prevent or increase sediment production and mobility on the surface. Further, changes in land cover, particularly in vegetation classes, can directly affect these processes, especially if they occur over short time periods or even more rapidly after extreme events such as fires. This study analyses vegetation cover changes in the Lama Camaggi catchment (southern Italy) in relation to its sediment connectivity pattern, described by Sediment flow Connectivity Index (SfCI). The Normalized difference vegetation index (NDVI), derived from satellite data, is utilized to detect vegetation cover changes over 8-year interval and following fire events. The main objective is to evaluate how the NDVI improves the flexibility of SfCI in defining surface dynamics on both spatial and temporal scales. The findings indicate that (1) NDVI changes identify vegetation cover changes in a short period in many areas of the catchment, potentially affecting sediment connectivity, and (2) the implementation of NDVI in the SfCI helps detect post-fire effects on sediment mobility and connectivity. Integrating NDVI enhances the SfCI algorithm providing a more dynamic description of sediment patterns
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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