1,721,062 research outputs found
Investigation on roof segmentation for 3D building reconstruction from aerial LIDAR point clouds
Full text linkThree-dimensional (3D) reconstruction techniques are increasingly used to obtain 3D representations of buildings due to the broad range of applications for 3D city models related to sustainability, efficiency and resilience (i.e., energy demand estimation, estimation of the propagation of noise in an urban environment, routing and accessibility, flood or seismic damage assessment). With advancements in airborne laser scanning (ALS), 3D modeling of urban topography has increased its potential to automatize extraction of the characteristics of individual buildings. In 3D building modeling from light detection and ranging (LIDAR) point clouds, one major challenging issue is how to efficiently and accurately segment building regions and extract rooftop features. This study aims to present an investigation and critical comparison of two different fully automatic roof segmentation approaches for 3D building reconstruction. In particular, the paper presents and compares a cluster-based roof segmentation approach that uses (a) a fuzzy c-means clustering method refined through a density clustering and connectivity analysis, and (b) a region growing segmentation approach combined with random sample consensus (RANSAC) method. In addition, a robust 2.5D dual contouring method is utilized to deliver watertight 3D building modeling from the results of each proposed segmentation approach. The benchmark LIDAR point clouds and related reference data (generated by stereo plotting) of 58 buildings over downtown Toronto (Canada), made available to the scientific community by the International Society for Photogrammetry and Remote Sensing (ISPRS), have been used to evaluate the quality of the two proposed segmentation approaches by analysing the geometrical accuracy of the roof polygons. Moreover, the results of both approaches have been evaluated under different operating conditions against the real measurements (based on archive documentation and celerimetric surveys realized by a total station system) of a complex building located in the historical center of Matera (UNESCO world heritage site in southern Italy) that has been manually reconstructed in 3D via traditional Building Information Modeling (BIM) technique. The results demonstrate that both methods reach good performance metrics in terms of geometry accuracy. However, approach (b), based on region growing segmentation, exhibited slightly better performance but required greater computational time than the clustering-based approach
Geospatial methods and tools for natural risk management and communications
Full text linkIn the last decade, real-time access to data and the use of high-resolution spatial information have provided scientists and engineers with valuable information to help them understand risk. At the same time, there has been a rapid growth of novel and cutting-edge information and communication technologies for the collection, analysis and dissemination of data, re-inventing the way in which risk management is carried out throughout its cycle (risk identification and reduction, preparedness, disaster relief and recovery). The applications of those geospatial technologies are expected to enable better mitigation of, and adaptation to, the disastrous impact of natural hazards. The description of risks may particularly benefit from the integrated use of new algorithms and monitoring techniques. The ability of new tools to carry out intensive analyses over huge datasets makes it possible to perform future risk assessments, keeping abreast of temporal and spatial changes in hazard, exposure, and vulnerability. The present special issue aims to describe the state-of-the-art of natural risk assessment, management, and communication using new geospatial models and Earth Observation (EO)architecture. More specifically, we have collected a number of contributions dealing with: (1) applications of EO data and machine learning techniques for hazard, vulnerability and risk mapping; (2) natural hazards monitoring and forecasting geospatial systems; (3) modeling of spatiotemporal resource optimization for emergency management in the post-disaster phase; and (4) development of tools and platforms for risk projection assessment and communication of inherent uncertainties
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
Improving flood risk analysis for effectively supporting the implementation of flood risk management plans: The case study of “Serio” Valley
No full textThe EU Flood Directive 2007/60 requires the assessment and delineation of flood risk maps. The latter should provide the required knowledge for the development of flood risk management plans (FRMPs), that should deal with all features of risk management: e.g. preparation, protection and prevention, comprising also the phase of the flood forecasting and warning systems, in addition to the emergency management. The risk maps, delineated through the expert-drive qualitative (EDQ) approach currently adopted in several European countries, such as Italy, fail to represent the information base that needed by stakeholders for selecting the suitable objectives and designing the appropriate mitigation actions for flood risk management. In the EDQ approach, the flood hazard and the potential damage degree maps are combined by means of a matrix to obtain a qualitative flood risk map. However, the performance of the risk matrix is not usually rigorous validated and, therefore, presents limits, such as subjective and not careful explained interpretation of rating and poor resolution, (due to range compression), that can produce errors in comparative ranking of risk areas. In this context, this paper proposes the FloodRisk approach that aims to improve the efficacy of flood risk map overcoming the limits of EDQ approach in supplying the knowledge base that allow to analyze costs and benefits of potential mitigation measures. However, the proposed approach is also able to involve the citizens in the flood management process, enhancing their awareness. An application of FloodRisk procedure is showed on a pilot case in “Serio” Valley, (North Italy), and its strengths and limits, in terms of additional efforts required in its application compared with EDQ procedure, have been discussed focusing on the efficacy of the outcomes provided for the fulfillment of FRMPs. The results have demonstrated the ability of FloodRisk, respect to EDQ approach, to distinguish successfully different levels of vulnerability of exposure elements, thanks to the use of asset value and depth-damage curves, that allows a suitably evaluation of the effectiveness of risk mitigation strategies. In this light, a successfully application of a cost-benefit analysis of FloodRisk approach on a portfolio of alternative mitigation actions, (i.e. structural and non-structural measurements), has been demonstrated on the proposed study case. However, FloodRisk requires additional information, e.g. water depths assessment and assets values, and it needs a proper analysis and communication of the uncertainty in its results. Although they still exist limitations that impede, at present, the FloodRisk application without an adequate understanding and a critical consideration of the hazard, exposure and vulnerability characteristics of the study area, considerations are supplied on how the utilization of this approach can be maximized in the light of the next flood risk maps revision due by December 2019
Organizzazione: parole chiave per l'analisi e la ricerca
No full textNella ricerca e nell’analisi organizzativa, l’uso di un termine o di una locuzione non individua di per sé un particolare modo di vedere, di descrivere, di interpretare l'oggetto di studio. Non basta dunque evocare un concetto per qualificare un approccio, una teoria, un modello di analisi: occorre chiarire a quale modo di concepire il concetto si sta facendo riferimento. Per far ciò, è necessario spostare la riflessione dal piano dei concetti, e delle teorie in cui questi sono inseriti, a quello dell’epistemologia che li sottende. Su queste basi, il libro si propone come “bussola” per orientare chi si occupa di analisi e ricerca in ambito organizzativo. Alcune delle parole-chiave che tipicamente si trovano nella letteratura di settore, sono illustrate sinteticamente e secondo una struttura costante, che fa riferimento al dibattito epistemologico in campo organizzativo e, più in generale, delle scienze sociali. Il lettore è guidato quindi a distinguere per ciascuna voce tra definizioni tipiche di teorie di matrice oggettivista , soggettivista e processuale. Per coloro che già da tempo si occupano di organizzazione (docenti, ricercatori, practitioner), il testo può essere uno strumento utile a mettere in luce i fondamenti epistemologici spesso impliciti, del proprio agire sulle e nelle organizzazioni
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
- …
