1,721,274 research outputs found
Subpixel motion estimation from sequences of video images
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 105-107).by Samson J. Timoner.S.M
Iterative altitude-aiding algorithm for improved GNSS positioning
No full textThe system proposed in this study relies on a WAVE P2P network, which is a proper standard to fit the vehicular environment wireless communications requests. Starting from the chance to exchange information given by this infrastructure, the possibility to improve the performance of a global navigation satellite system (GNSS) receiver based on a Kalman filter is considered. This improvement is obtained exploiting the external altitude measurements provided by other peers in the network, equipped with GNSS receivers. The topic of an altitude-aided system has been described in a previous work, that highlighted the need for a parameter that points out the effectiveness and the consistency of the computed aiding measurement, namely the altitude-aiding reliability index. A detailed analysis of this reliability index led to the development of an iterative algorithm to be used in the presence of three satellites and of a biased aiding, in order to overcome the issues related to this peculiar scenario, which is the main result of this wor
Experimental assessment of Distance Measuring Equipment and Tactical Air Navigation interference on GPS L5 and Galileo E5a frequency bands
No full textThis paper will provide an experimental assessment of Global Navigation Satellite System (GNSS) receiver operations under interference generated by other Aeronautical Radio Navigation Systems (ARNS) such as Distance Measuring Equipment (DME) and Tactical Air Navigation (TACAN) transmitting within the GPS L5 and Galileo E5a frequency bands. In detail, results in terms of C/N0 degradation and error on the pseudorange measurements will be presented. Afterwards, an innovative interference mitigation technique will be introduced and its benefits against the aviation interference environment considered, will be assessed at receiver level by means of software implementation and simulation. Finally, a quick analysis of the potential DME/TACAN interference impact on GNSS receiver in demodulating the Space Based Augmentation System (SBAS) navigation messages, will be describe
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
Performance assessment of pulse blanking mitigation in presence of multiple Distance Measuring Equipment/Tactical Air Navigation interference on Global Navigation Satellite Systems signals
Full text linkIt is known that the Aeronautical Radio Navigation Systems sharing the Global Navigation Satellite Systems (GNSS)
frequency band represent a threat to the satellite-based navigation services. Distance Measuring Equipment (DME) and Tactical
Air Navigation (TACAN) systems broadcast strong pulsed ranging signals within the Global Positioning System L5 and Galileo
E5a frequency bands where the aviation positioning aids services are allocated. This study provides an experimental assessment
of the DME/TACAN interference effect on the GNSS receivers performance in scenarios where the presence of several
transmitters in view generates radio-frequency interference hard to mitigate by means of the classical solutions. In detail,
analysis in terms of the receiver performance will be presented by showing the effect of the non-ideal pulse blanking on the
GNSS signal quality. The optimal set-up of the mitigation process, investigated by means of a software simulation, is provided
Performance comparison of transformed-domain techniques for pulsed interference mitigation
No full textWith the growth of a new European Satellite Navigation System and with the modernization of the currently existent Satellite Navigation Systems as the American GPS or Russian GLONASS, a wider range of new signals will guarantee better performance enabling a plethora of new applications. However, due to the weakness of the GNSS signal reaching the antenna users and a crowded frequency spectrum, GNSS-based services will be always vulnerable to the presence of interfering signals generated by other communication systems. A recent example of these risks was the Lightsquared case in the USA, where the GPS receivers operations in L1 GPS band have been seriously threatened. The new modernized GPS L5 and the Galileo E5 frequency bands, which will be the frequencies allocated for GNSS-based aviation aids, will deal with a harsh interference environment in the airport areas due to the sharing of the bandwidth with other Radio Navigation Systems (RNSS) The issue of the interference potentially affects all the frequency bands allocated to GNSS, and for this reason it is crucial to provide the user receivers of proper countermeasures, in particular if devoted to support services related to personal safety. In the last years, the research on new interference detection and mitigation techniques has been focused on more complex algorithms working at higher rate with measurements performed by the receiver and not only assessing the reliability of the position solution. A recent class of such signal processing algorithms aims at processing the received digital signals in domains different from the classical time or frequency representation. In this paper, a general classification of possible unintentional interference for GNSS receivers will be provided, focusing on the aeronautical environment. Then, a comparative analysis of different transformed-domain techniques will be presented. A wavelet-based mitigation approach will be introduced, as well as a new Karhunen-Loève Transform based algorithm and their application on pulsed interference will be described
Sistema di posizionamento geo-spaziale cooperativo operante con sistemi di navigazione globale satellitare e reti di telecomunicazione wireless, relativo procedimento e apparato di posizionamento geo-spaziale
No full textPeer to peer equation augmentation for an altitude aided GNSS receiver
No full textThis paper considers the possibility to integrate external altitude measurements with a Kalman based Global Navigation Satellite System (GNSS) receiver in a peer to peer scenario. The performance of such a system is investigated for different characteristics of the aiding measurement and for different degree of trust of the receiver upon the aiding measurement. The aiding measurement is obtained starting from the altitude measurements that the other peers in the network send to the aided user. The experiments highlight the need for a parameter that points out the effectiveness and the consistency of the computed aiding measurement. To this purpose, a reliability index is proposed, on the basis of some considerations on the variance and on the number of the received measurements
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
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