1,720,963 research outputs found
Finding camera overlap in large surveillance networks
No full textRecent research on video surveillance across multiple cameras has typically focused on camera networks of the order of 10 cameras. In this paper we argue that existing systems do not scale to a network of hundreds, or thousands, of cameras. We describe the design and deployment of an algorithm called exclusion that is specifically aimed at finding correspondence between regions in cameras for large camera networks. The information recovered by exclusion can be used as the basis for other surveillance tasks such as tracking people through the network, or as an aid to human inspection. We have run this algorithm on a campus network of over 100 cameras, and report on its performance and accuracy over this network. © Springer-Verlag Berlin Heidelberg 2007.Anton van den Hengel, Anthony Dick, Henry Detmold, Alex Cichowski and Rhys Hil
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
Automatic camera placement for large scale surveillance networks
No full textAutomatic placement of surveillance cameras in arbitrary buildings is a challenging task, and also one that is essential for efficient deployment of large scale surveillance networks. Existing approaches for automatic camera placement are either limited to a small number of cameras, or constrained in terms of the building layouts to which they can be applied. This paper describes a new method for determining the best placement for large numbers of cameras within arbitrary building layouts. The method takes as input a 3D model of the building, and uses a genetic algorithm to find a placement that optimises coverage and (if desired) overlap between cameras. Results are reported for an implementation of the method, including its application to a wide variety of complex buildings, both real and synthetic.Anton Van den Hengel, Rhys Hill, Ben Ward, Alex Cichowski, Henry Detmold, Chris Madden, Anthony Dick, and John Bastia
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
Empirical evaluation of the exclusion approach to estimating camera overlap
No full textMaking intelligent decisions on the basis of the video captured by a large network of surveillance cameras requires the ability to identify overlap between their fields of view. Without this information it is impossible to perform even simple analysis, such as distinguishing between repeated behaviours and multiple views of the same behaviour. Large-scale intelligent video surveillance thus requires a means of understanding the relationships between the fields of view of the cameras involved. The exclusion approach is the only method currently capable of performing online estimation of camera overlap for networks of more than 50 cameras, with a version of the algorithm applicable to 1000 camera networks having been published. Empirical evaluation of every such algorithm is critical to assessing its performance, and essential if comparisons between methods are to be made. This paper presents a method by which such an empirical evaluation may be carried out, and makes publicly available the data (including ground truth) on which it based in order that competing methods might be compared equally. Precision vs recall curves are reported for a series of experiments comparing the results of exclusion to ground truth. These results demonstrate the strengths and limitations of the exclusion-based estimation process, but show that the performance of the method exceeds the requirements of surveillance applications.Rhys Hill, Anton van den Hengel, Anthony Dick, Alex Cichowski, Henry Detmol
Surprisal-aware scheduling of PTZ cameras
No full textAn approach is presented for scheduling PTZ cameras on guard tours with two or more fields of view. In contrast to the target tracking of previous work, this approach seeks to optimise the coverage of the area under surveillance. Specifically, the aim is to minimise the surprisal (self-information) of events in unobserved fields of view. An entropy driven scheduler based on Kullback-Leibler divergence (information gain) is presented, and compared with three naive schedulers (random, round robin and constant selection of one field of view). Experiments investigate its performance on networks of ten cameras. These are evaluated over factors including four different scheduling approaches, different numbers of fields of view, and different inactive times whilst switching views. They demonstrate the efficacy of the entropy driven scheduler as it outperforms the naive schedulers by a significant margin by favouring certain fields of view that are more likely to reveal events with high surprisal value. The scheduler is target agnostic, as it operates on low level properties of the video signal, specifically, occupancy as determined by background subtraction. This permits an efficient implementation that is independent of the number of targets in the area under surveillance. As each camera is scheduled independently, the approach is scalable via distributed implementation, including on smart cameras.Henry Detmold, Anton van den Hengel, Anthony Dick, Christopher Madden, Alex Cichowski and Rhys Hil
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