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Optimisation of MF DGNSS, maritime and aeronautical radiobeacon coverage by frequency re-assignmentTurhan, Birol Erdem January 1999 (has links)
No description available.
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Implementation and optimization of a Global Navigation Satellite System software radioBhanot, Sunil January 1998 (has links)
No description available.
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Investigating the effect of the DGNSS SCAT-I data link on VOR signal receptionLi, Jian January 1996 (has links)
No description available.
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System level performance of ATM transmission over a DS-CDMA satellite linkTimotijevic, Tijana January 1999 (has links)
No description available.
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Determinação de um modelo geoidal local para o Distrito FederalSilva, Denis Vinicius Ricardo da 17 July 2017 (has links)
Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geociências Aplicadas, 2017. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-11-20T16:13:23Z
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Previous issue date: 2018-01-04 / O modelo geoidal é parte fundamental na transformação entre as altitudes ortométricas e geométricas. Existem aspectos positivos na sua utilização quando comparados a métodos clássicos de levantamento. O surgimento das técnicas de posicionamento por GNSS (Global Navigation Satellite System) impulsionou de maneira significativa diversas linhas de pesquisa, na busca de um modelo geoidal cada vez mais preciso. A disponibilidade de dados altimétricos, gravimetria terrestre e orbital também contribuíram neste sentido. Deste então, várias abordagens para a obtenção de um modelo geoidal tem sido apresentadas. Atualmente a integração de diferentes métodos se mostra uma alternativa promissora para o cálculo do geoide. Neste contexto, o emprego da técnica Remove-Calcula-Restaura (RCR) tem demonstrado resultados importantes no Brasil e em outras partes do mundo. A base de todas as formulações da técnica RCR envolve métodos gravimétrico e orbital, por isto, utiliza Modelos Digitais de Terreno (MDT), dados gravimétricos terrestres, Modelos do Geopotencial Global (MGG) e valor de densidade para o cálculo de modelos geoidais. Neste trabalho é apresentado um levantamento das diferentes formulações utilizadas no processo de redução gravimétrica. Também uma análise das principais variáveis que possam influenciar no cálculo das anomalias gravimétricas e na elaboração de modelos geoidais, a partir da técnica RCR. Para o cálculo, utilizou-se um pacote denominado GRAVTool, baseado no software MATLAB®. No final da pesquisa, tem-se também, como marco, a determinação de um modelo geoidal local para o Distrito Federal. / The geoidal model is a fundamental part of the transformation between orthometric and geometric heights. There are positive aspects in its use when compared to classical survey methods. The emergence of GNSS (Global Navigation Satellite System) positioning techniques has significantly boosted several lines of research in the search for an increasingly accurate geoidal model. The availability of altimetric data, terrestrial and orbital gravimetry also contributed in this sense. From this, several approaches to obtaining a geoid model have been presented. Currently the integration of different methods shows a promising alternative for the calculation of the geoid. In this context, the use of the Remove-Compute-Restore technique (RCR) has shown important results in Brazil and in other parts of the world. The basis of all RCR technique formulations is derived from gravimetric and orbital methods, using Digital Terrain Models (DTM), terrestrial gravimetric data, Global Geopotential Models (GGM) and density value for the calculation of geoid models. This work presents a revision of the different formulations used in the gravimetric reduction process. Also an analysis of the main variables that can influence the calculation of the gravimetric anomalies and the elaboration of geoid models from the RCR technique. For the calculation, a package called GRAVTool, based on the MATLAB® software, is used. At the end of the research, we also have as a landmark, the determination of a local geoidal model for the Brazilian Federal District.
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Performance analysis of assisted-GNSS receiversCouronneau, Nicolas January 2013 (has links)
The goal of this thesis is to improve the understanding of the performance of Global Navigation Satellite System (GNSS) receivers that use assistance data provided by cellular networks. A typical example of such a receiver is a mobile phone including a Global Positioning System (GPS) receiver. Using assistance data such as an accurate estimate of the GPS system time is known to improve the availability and the time-tofirst- fix performance of a GNSS receiver. However, the performance depends on the architecture of the cellular network and may vary significantly across networks. This thesis presents three new contributions to the performance analysis of assisted-GNSS receivers in cellular networks. I first introduce a mathematical framework that can be used to calculate a theoretical lower bound of the time-to-first-fix (TTFF) in an assisted-GNSS receiver. Existing methods, for example the flow-graph method, generally focus on calculating the theoretical mean acquisition time of a pseudo-noise signal for one satellite only. I extend these methods to calculate the full probability distribution of the joint acquisition of several satellites, as well as the sequential acquisition of satellites, which is commonly performed in assisted receivers. The method is applied to real measurements made in a multipath fading channel. I next consider time assistance in unsynchronised cellular networks. It is often argued that unsynchronised networks can not provide fine-time aiding since they do not have a common clock, although few experimental results have been reported in the existing literature. I carried out experiments on a GSM network, a second-generation cellular network, in Cambridge, UK, in order to measure the time stability of the synchronisation signals. The results showed a large variability in the time stabilities across different base stations and I evaluated the performance of an ensemble filter that combines the measurements into a single, more accurate, estimate of the universal time. The main contribution is to show that the performance of such a filter is adequate to provide fine-time assistance to a satellite navigation receiver. Finally, I address the positioning performance of an assisted receiver in synchronised cellular networks. Cellular positioning has been often investigated in the literature, but few results on real networks have been presented. Many positioning methods are proprietary and little information about their performance in real networks haven been published publicly. A CDMA2000 cellular network in Calgary, Canada, was used to collect experimental data. The time stability and the synchronisation of the CDMA2000 pilot signals were excellent and were used to evaluate the performance of CDMA2000-based cellular positioning system. I then developed a method to combine the pseudo-range measurements from the GPS signals and the CDMA2000 base stations. I evaluated the performance of positioning in both outdoor and indoor environments, and I analysed the effects and the possible mitigation of non-line-of-sight signals. The main contribution is to show that additional satellite navigation signals can improve the accuracy of cellular positioning beyond what is theoretically expected from the improvement in the geometry.
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Analysis of integrity monitoring for the local area augmentation system using the global navigation satellite systemLiu, Fan January 1998 (has links)
No description available.
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Calculations for positioning with the Global Navigation Satellite SystemCheng, Chao-heh January 1998 (has links)
No description available.
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A software radio approach to Global Navigation Satellite System receiver designAkos, Dennis M. January 1997 (has links)
No description available.
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GROUND SUPPORT FOR THE SPACE-BASED RANGE FLIGHT DEMONSTRATION 2Burkes, Darryl A. 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The primary objective of the NASA Space-Based Range Demonstration and Certification
program was to develop and demonstrate space-based range capabilities. The Flight
Demonstration 2 flights at NASA Dryden Flight Research Center were conducted to
support Range Safety (commanding and position reporting) and high-rate (5 Mbps)
Range User (video and data) requirements. Required ground support infrastructure
included a flight termination system computer, the ground-data distribution network to
send range safety commands and receive range safety and range user telemetry data and
video, and the ground processing systems at the Dryden Mission Control Center to
process range safety and range user telemetry data and video.
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