1,721,130 research outputs found
Wide-Area Egomotion Estimation from Known 3D Structure
No full textWe describe an algorithm that takes as inputs a coarse3D model of an environment, and a video sequence acquiredwithin the environment, and produces as output an estimateof the cameraÂs 6-DOF egomotion expressed in the coordinatesof the 3D model. Our method has several novelaspects: it performs line-based structure-from-motion; italigns the local line constellation to the known model; andit uses off-line visibility analysis to dramatically acceleratethe alignment process.We present simulation results demonstrating themethodÂs operation in a multi-room environment. We showthat the method can estimate metric egomotion accuratelyand could be used for for many minutes of operation andthousands of video frames
Motion Compatibility for Indoor Localization
Get PDFIndoor localization -- a device's ability to determine its location within an extended indoor environment -- is a fundamental enabling capability for mobile context-aware applications. Many proposed applications assume localization information from GPS, or from WiFi access points. However, GPS fails indoors and in urban canyons, and current WiFi-based methods require an expensive, and manually intensive, mapping, calibration, and configuration process performed by skilled technicians to bring the system online for end users. We describe a method that estimates indoor location with respect to a prior map consisting of a set of 2D floorplans linked through horizontal and vertical adjacencies. Our main contribution is the notion of "path compatibility," in which the sequential output of a classifier of inertial data producing low-level motion estimates (standing still, walking straight, going upstairs, turning left etc.) is examined for agreement with the prior map. Path compatibility is encoded in an HMM-based matching model, from which the method recovers the user s location trajectory from the low-level motion estimates. To recognize user motions, we present a motion labeling algorithm, extracting fine-grained user motions from sensor data of handheld mobile devices. We propose "feature templates," which allows the motion classifier to learn the optimal window size for a specific combination of a motion and a sensor feature function. We show that, using only proprioceptive data of the quality typically available on a modern smartphone, our motion labeling algorithm classifies user motions with 94.5% accuracy, and our trajectory matching algorithm can recover the user's location to within 5 meters on average after one minute of movements from an unknown starting location. Prior information, such as a known starting floor, further decreases the time required to obtain precise location estimate
An environmental change detection and analysis tool using terrestrial video
Get PDFThesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, September 2006.Includes bibliographical references (p. 107-108).We developed a prototype system to detect and flag changes between pairs of geo-tagged videos of the same scene with similar camera trajectories. The purpose of the system is to help human video analysts detect threats within a set of videos. While computers cannot differentiate threat from non-threat events, they can assist analysts by guiding their attention to sections of video where interesting events are more likely to appear. The system generates a single output video representing the difference between the input pair as well as a set of regions denoting sections of the world where changes occurred between the input videos. These regions represent segments of video where interesting events are likely to be seen. The difference video allows a video analyst to quickly see the differences between the two input videos and decide whether further analysis is required. The system is based on the video matching work by Seth Teller and Peter Sand [14].by Javier Velez.M.Eng
A mapping system for an autonomous helicopter
Get PDFThesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 127-128).Acknowledgments: This thesis was prepared at The Charles Stark Draper Laboratory, Inc., under Internal Research & Development No. 18598. Publication of this thesis does not constitute approval by Draper or the sponsoring agency of the findings or conclusions contained herein. It is published for the exchange and stimulation of ideas. The work that is described in this document was by no means done all by myself. There are many people that I would like to thank for their support of my education here at MIT and Draper Laboratory during the past few years. I would like to thank the members of the helicopter team, who have greatly influenced my development as an engineer: Paul Debitetto, Christian Trott, Bob Butler, Long Phan, Mike Piedmonte, and Anthony Lorusso. Special thanks goes to Paul Debitetto for his thoughtful critiquing and leadership. Long Phan was my close partner in the design of the scanning laser rangefinder, and this thesis would not have been possible without his inspiration and expertise. During my work on the mapping system, a number of Draper staff took time out of their own busy schedules to help me. I am especially indebted to Chris Sanders, Chris Smith, John Plump. Linda Leonard, John Danis, and Dave Hauger for their patience and helpfulness over the last year. I would also like to thank my MIT advisor, Seth Teller, for helping me to graduate this year. Other Draper fellows and students in the autonomous vehicle lab have also provided me with both technical expertise and encouragement. I would like to thank Mohan Gurunathan, Jonah Peskin, and Bill Kaliardos for their advice and moral support. Finally, I would like to thank my entire family for years of encouragement and support. It is to my mother, father, and sister that I dedicate this thesis. Rusty Sammon May, 1999.by Russell Sammon.M.Eng.and S.B
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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