1,721,112 research outputs found
The Sheldonian Theatre 3D model
No full textIn Spring 2022 Oxford Robotics Institute collaborated with Hilti Group and the Sheldonian Theatre to create a high quality 3D reconstruction of Grade 1 listed building. A Z&F Imager scanner was used to collect hundreds of high definition scans of the facility.
The result is a 3D point cloud of millions of points with millimetre accuracy using techniques developed for construction surveying. This enables the viewer to interactively 'visit' every corridor, room, and staircase within the theatre - from the basement to the attic and cupola.
Take the opportunity to visit the theatre directly from your computer!
Contact Prof. Maurice Fallon [email protected] for more details about this model
Cooperative Localization for Autonomous Underwater Vehicles
Full text linkThis paper describes an algorithm for distributed acoustic navigation for Autonomous Underwater Vehicles
(AUVs). Whereas typical AUV navigation systems utilize pre-calibrated arrays of static transponders, our work
seeks to create a fully mobile network of AUVs that perform acoustic ranging and data exchange with one another to
achieve cooperative positioning for extended duration missions over large areas. The algorithm enumerates possible
solutions for the AUV trajectory based on dead-reckoning and range-only measurements provided by acoustic modems
that are mounted on each vehicle, and chooses the trajectory via minimization of a cost function based on these
constraints. The resulting algorithm is computationally efficient, meets the strict bandwidth requirements of available
AUV modems, and has potential to scale well to networks of large numbers of vehicles. The method has undergone
extensive experimentation, and results from three different scenarios are reported in this paper, each of which utilizes
MIT SCOUT Autonomous Surface Craft (ASC) as convenient platforms for testing. In the first experiment, we utilize
three ASCs, each equipped with a Woods Hole acoustic modem, as surrogates for AUVs. In this scenario, two ASCs
serve as Communication/Navigation Aids (CNAs) for a third ASC that computes its position based exclusively on
GPS positions of the CNAs and acoustic range measurements between platforms. In the second scenario, an undersea
glider is used in conjunction with two ASCs serving as CNAs. Finally, in the third experiment, a Bluefin12 AUV
serves as the target vehicle. All three experiments demonstrate the successful operation of the technique with real
ocean data.United States. Office of Naval Research (grants N00014-02-C-0210, N00014-97-1-0202 and N00014-05-G-0106)MIT Sea Grant College Program (grant NA86RG0074 (project RD-24)
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
Mapping Complex Marine Environments with Autonomous Surface Craft
Full text linkThis paper presents a novel marine mapping system using an Autonomous
Surface Craft (ASC). The platform includes an extensive sensor suite for mapping
environments both above and below the water surface. A relatively small hull size
and shallow draft permits operation in cluttered and shallow environments. We address the Simultaneous Mapping and Localization (SLAM) problem for concurrent
mapping above and below the water in large scale marine environments. Our key
algorithmic contributions include: (1) methods to account for degradation of GPS
in close proximity to bridges or foliage canopies and (2) scalable systems for management of large volumes of sensor data to allow for consistent online mapping
under limited physical memory. Experimental results are presented to demonstrate
the approach for mapping selected structures along the Charles River in Boston.United States. Office of Naval Research (N00014-06-10043)United States. Office of Naval Research (N00014-05-10244)United States. Office of Naval Research (N00014-07-11102)Massachusetts Institute of Technology. Sea Grant College Program (grant 2007-R/RCM-20
Cooperative localization of marine vehicles using nonlinear state estimation
No full textThis paper investigates the problem of cooperative navigation of autonomous marine vehicles using range-only acoustic measurements. We consider the use of a single maneuvering autonomous surface vehicle (ASV) to aid the navigation of one or more submerged autonomous underwater vehicles (AUVs), using acoustic range measurements combined with position measurements for the ASV when data packets are transmitted. The AUV combines the data from the surface vehicle with its proprioceptive sensor measurements to compute its trajectory. In previous work, we presented an experimental demonstration of this approach, using an extended Kalman filter (EKF) for state estimation. In the present paper, we analyze the observability properties of the cooperative ASV/AUV localization problem and present experimental results comparing several different state estimators. Using the weak observability theorem for nonlinear systems, we demonstrate that this cooperative localization problem is best attacked using nonlinear least squares (NLS) optimization. We present experimental results for this new approach and compare it to alternative state estimators, demonstrating superior performance
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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