1,721,007 research outputs found
Monitoring natural resources in conflict using an object-based multiscale image analysis approach
No full textSuper-resolution mapping for extraction of urban tree crown objects from VHR satellite images
No full textContext-sensitive extraction of tree crown objects in urban areas using VHR satellite images
Get PDFMunicipalities need accurate and updated inventories of urban vegetation in order to manage green resources and estimate the profit of urban forestry activities. Earlier studies using high resolution satellite images have shown that automatic tree detection in urban areas using traditional classification techniques remains a very difficult task. This is mainly due to intra-crown spectral variation, heterogeneity of tree species and the complex spatial arrangement of individual trees with respect to other vegetated surfaces and elements of the urban space. This study aims to develop a reproducible object based image analysis (OBIA) methodology to locate and delineate individual tree crowns in urban areas using high resolution imagery and existing topographic maps. We propose an OBIA approach that considers the spectral, spatial and contextual characteristics of tree objects in the urban space. The classification strategy is implemented with classification rules that exploit object features at multiple segmentation levels such as spectral response, texture, size, geometry, roundness, and distance to shadow, which are used to modify the labeling and shape of image objects. The classification procedure was tested in a QuickBird image acquired over a city in The Netherlands with results indicating an identification rate of 75% for individual trees and a commission rate of 39%. For the group of trees the identification rate was 100%. We equally report on the geometrical and positional accuracy of the identified tree crown objects
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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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