1,720,958 research outputs found
Definizione automatica da rilievi lidar di attributi geometrici per il GIS 3D urbano
No full textSi descrive una procedura per aggiornare ed estendere un SIT 2D urbano esistente, ricavando mediante l’uso di funzioni disponibili in ambiente GIS, attributi geometrici 3D di interesse
urbanistico, desumendoli in modo automatico da rilievi LiDAR opportunamente classificati.
Si illustra inoltre come sul dato LiDAR si possa costruire un supporto tridimensionale, il 3D city model, da integrare al SIT 2D, che permetta di navigare in un ambiente virtuale e di interrogare la banca dati aggiornata selezionando oggetti 3D
Produzione e verifica di DTM da rilievi LiDAR aerei su aree montane ricoperte da foresta
No full textIl sistema Lidar da aeromobile si propone in molti casi come la tecnica piu' efficace per effettuare rilievi del terreno su aree montane ricoperte da foresta, grazie alla possibilita' del raggio laser di insinuarsi tra i varchi della copertura fogliare e di raggiungere il suolo. In tali casi, la nube di punti prodotta dalla scansione presenta una morfologia arbitraria e complessa, e per una corretta individuazione e rappresentazione del terreno notevole importanza riveste la fase di filtraggio dei dati. Il lavoro svolto ha inteso verificare la precisione e la fedelta' di un modello digitale del terreno (DTM) ad elevata definizione, prodotto mediante scansione laser da elicottero su un area campione della Foresta di Pramosio, nelle Alpi Carniche. Il confronto e' stato effettuato nei riguardi del corrispondente DTM ottenuto da rilievo topografico a terra, eseguito sotto chioma mediante stazione totale ad inseguimento automatico e prisma riflettore. L articolo illustra gli esiti delle verifiche metriche e morfologiche condotte, offrendo anche un confronto critico tra le problematiche logistiche e operative delle tecniche impiegate, a conferma dei notevoli vantaggi offerti dal LiDAR
Esperienze di filtraggio, classificazione, segmentazione e modellazione di dati spaziali da rilievo laser aereo
No full textThe paper describes the operative steps of an aerial laser scanning survey; among these, the initial procedures for acquisition and geo-referencing are briefly illustrated, while more attention is given to the filtering, classification, segmentation, and modelling phases. For these last topics, several fundamental aspects on the basis of experiences developed processing different kinds of laser data are reported.
For every phase, the analytical models, the implemented algorithms and numerical experimentation realized by the research group of the University of Udine are described. This last activity is within the INTERREG IIIA Phare/CBC Italy-Slovenia project “Cadastral map updating and regional technical map integration for the Geographical Information
Systems of regional agencies by testing advanced and innovative survey techniques” in cooperation with the Geodetski Institut Slovenije
of Ljubljana
Esperienze di integrazione di dati laserscannig aerei ed iperspettrali per lo studio del manto nevoso
No full textTelerilevamento e scansione laser costituiscono strumenti comprovati per lo studio qualitativo e quantitativo del manto nevoso. L’articolo descriveun esperimento di impiego sinergico delle due tecnologie, nel quale la componente radiometrica ad alta risoluzione viene acquisita assieme a quella geometrica mediante l’utilizzo simultaneo di un sensore iperspettrare AISA Eaglee di un laserscanner Optech ALTM 3100 montati su elicottero. L’area di studio riguarda la zona del Monte
Canin, nelle Alpi Giulie Occidentali. I primi risultati dell’esperimento consentono di quantificare
con precisione la copertura e l’altezza della neve al suolo, e di impostare una possibile mappatura di alcune sue caratteristiche fisiche di superficie
3D virtual model of the Gorizia downtown (Italy) by matching aerial and terrestrial surveying techniques
No full textLikelihood and accuracy analyses of 3D building models from airborne laser data
No full textAirborne laser scanning can be employed today for the production of large scale maps and the creation of detailed 3D city models. For this purpose, several solutions have been proposed, also available in commercial software, to make easier and semi-automated the extraction and the geometric modeling of buildings from LIDaR data. As a consequence, while 3D urban modeling is gaining popularity among architects, engineers and urban designers, proper investigations are addressed to evaluate the likelihood and the accuracy of this new kind of survey products. In this paper, after a concise analysis of the possible errors affecting the building model construction, and a brief description of the
principal methods to achieve it, we illustrate our experience in the realization of a detailed 3D model of the city of Gorizia (NE Italy), using the TerraScan software on two different laser scan datasets taken at different sampling densities (2 points/sm and 15 points/sm, respectively). Finally, we discuss the results of a test involving one set of 25 buildings, extracted from the city model and
topographically surveyed by reflectorless EDMs and GPS equipment, in order to establish their effective size and shape. The comparison between the models obtained from the LIDaR and the real ones from the conventional survey outline that the likelihood and accuracy of the models derived from a 15 points/sm laser surveys are equivalent to those obtained by topographic measures
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
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
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