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Showing 1 to 7 of 7 (0.105 seconds)Spelling suggestions: "subject:"dilution off precision"" "subject:"dilution oof precision""
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Wireless Location Tracking Algorithms based on GDOP in the Mobile EnvironmentKuo, Ting-Fu 31 August 2011 (has links)
The thesis is to explore wireless location tracking algorithms based on geometric dilution of precision (GDOP) in the mobile environment. The GDOP can be used as an indication of positioning accuracy, affected by the geometric relationship between the target and sensing units. The smaller the GDOP is, the better positioning accuracy. By using the information of sensing units and time difference of arrival (TDOA) positioning method, we use extended Kalman filter as an estimator to track and predict the state of a moving target. From previous research, the lowest GDOP value, located at the center of a regular polygon, represents the best positioning accuracy in 2-D scenario with numerous sensing units. It is important to find the best locations for the sensing units. Simulated annealing algorithm was used in previous studies. However, it only finds a location at a time, and consumes computation load and time. Due to the above-mentioned reasons, we propose a location tracking system, which consists of a base traiver station and numerous mobile sensing units. By using the information of a base transceiver station and the predicted position of target, we can obtain the best locations for all the mobile sensing units with the calculation of rotation matrix. The locations can also be used as beacons for relocating mobile sensing units. It may take many cycles to move mobile sensing units to the best locations. We have to perform path planning for mobile sensing units. Due to the location change of the moving target, the routes need adjustment accordingly. If the predicted stay of a mobile sensing unit is inside the obstacle, we adjust the route of the mobile sensing unit to make it stay out of the obstacle. Therefore, we also propose a path planning scheme for mobile sensing units to avoid obstacles. Through simulations, the proposed method decreases the tracking time effectively, and find the best locations precisely. When mobile sensing units move toward the best locations, they successfully avoid obstacles and move toward the position with the minimum GDOP. Through the course, good positioning accuracy can be maintained.
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Mobile Base Station for Improvement of Wireless LocationYen, Yun-ting 18 August 2009 (has links)
In wireless location system, geometric relationship between the base station (BS) and the mobile station (MS) may affect the accuracy of MS location estimate. The effect is called Geometric Dilution of Precision (GDOP). Given the information of geometric configuration of BS and MS locations, the GDOP value can be calculated accordingly. In fact, the GDOP value is considered as ratio factor between the location error and measurement noise. A higher GDOP value indicates larger location error in the location estimator. Therefore the GDOP can be utilized as an index for observing the location precision of the MS under different geometric layout. The accuracy of location estimation can be improved by changing the BS device element locations. In the thesis, a time different of arrival (TDOA) wireless location system with mobile base station (MBS) is considered. Changing the geometric layout between the BS and the MS by relocating the MBS, the GDOP effect can be reduced and the accuracy of location estimation also can therefore be improved. Since the simulated annealing (SA) is capable of escaping the local minimum and finding the global minimum in an objective function, the SA algorithm is used in finding the best solution in a defined function based on the GDOP distribution. The best solution is then the destination of an MBS in the process of MS location estimation. When relocating an MBS from its initial location to the best location, it is likely that the MBS enters regions with high GDOP effects. To avoid the problem, the steepest descent (SD) algorithm is utilized for path planning. First, we establish the objective function which consists of the GDOP information and the angle of movement. A nearby location that has the minimum value of objective function is selected as the next move. The process continues until the MBS reaches the destination. A variety of cases are investigated by computer simulations. Simulation results show that the proposed approach can effectively find the best locations for MBSs to relocate. Based on the relocation and path planning, the GDOP effects can be reasonably reduced, and therefore the higher location accuracy is achieved.
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Problems in GPS AccuracyVodhanel, Michael Thomas 01 January 2011 (has links)
Improving and predicting the accuracy of positioning estimates derived from the global positioning system (GPS) continues to be a problem of great interest. Dependable and accurate positioning is especially important for navigation applications such as the landing of commercial aircraft. This subject gives rise to many interesting and challenging mathematical problems. This dissertation investigates two such problems. The first problem involves the study of the relationship between positioning accuracy and satellite geometry configurations relative to a user's position. In this work, accuracy is measured by so-called dilution of precision (DOP) terms. The DOP terms arise from the linear regression model used to estimate user position from GPS observables, and are directly related to user position errors. An analysis of the statistical properties explaining the behavior of the DOP terms is presented. The most accurate satellite geometries and worst configurations are given for some cases. The second problem involves finding methods for detecting and repairing cycle-slips in range delay data between a satellite and a receiver. The distance between a satellite and a receiver can be estimated by measuring the difference in the carrier frequency phase shift experienced between the satellite and receiver oscillators. Cycle-slips are discontinuities in the integer number of complete cycles in these data, and are caused by interruptions or degradations in the signal such as low signal to noise ratio, software failures, or physical obstruction of the signals. These slips propagate to errors in user positioning. Cycle-slip detection and repair are crucial to maintaining accurate positioning. Linear regression models and sequential hypothesis testing are used to model, detect, and repair cycle-slips. The effectiveness of these methods is studied using data obtained from ground-station receivers.
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Influência da geometria dos satélites na precisão das coordenadas geodésicas obtidas com o sistema GPS / Influence of satellite geometry on the geodetic coordinates precision from GPS determinationsSilveira, Gustavo Cruz da 27 August 2008 (has links)
A precisão que pode ser obtida com levantamentos com uso do Sistema de Posicionamento Global (GPS) depende de uma série de fatores, devido à grande quantidade de fontes de erros. Em geral, estas interferências podem ser modeladas e considerações são feitas de acordo com a contribuição de cada uma destas fontes de erros. Nos primórdios dos sistemas de posicionamento, o planejamento de missões era essencial para encontrar os horários em que haveria satélites suficientes para determinação da posição. Desde que o GPS foi declarado operacional, essa questão perdeu importância. Dessa forma, não há estudos conclusivos sobre a possível influência que suas posições relativas à antena do receptor causam nos resultados dos levantamentos. Esta questão foi investigada usando como ferramenta os indicadores de precisão (DOP) disponíveis. Considerações a respeito da interpretação da figura geométrica (tetraedro), cujo volume é considerado proporcional ao DOP foram estudadas. Foi verificada a confiabilidade e a contribuição da geometria nos resultados. Comparações entre valores de planejamento e levantamento foram realizadas para o posicionamento por ponto e relativo. A influência que o comprimento da linha-base tem na obtenção dos valores de indicação foi analisada assim como a influência na precisão causada por instantes de alto valor de DOP. A questão da expectativa de que horários com bons valores de DOP possam contribuir para a fixação da ambigüidade também foi esclarecida. / The obtaining precision of GPS (Global Positioning System) surveying depends on of many factors, due the several error fonts. In general, these interferences can be modeled and considerations are made as each one contributes. In the beginning of the positioning systems, the mission planning was essential to find the period of the day that would possible to have satellites enough to position determination. Since the GPS was declared operational this issue lost importance. Hence there is a lack of conclusive researches about the influence of the satellites positioning regarding the receptor antenna position may cause on the results. This issue was investigated using tools like the available precision indicators (DOP - Dilution of Precision). Considerations regarding interpretation of the geometric figure (thetraedron), that its volume is considered proportional to the DOP were analyzed. The reliability and the geometry contribution in the results were verified. Comparisons between planning and surveying values were done to the absolute and relative positioning. The influence of the baseline in indicator values determination was analyzed as the influence in the accuracy by DOP spikes. The issue regarding the expectative that the periods with good DOP values may contribute to the ambiguity fix status was also clarified.
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Influência da geometria dos satélites na precisão das coordenadas geodésicas obtidas com o sistema GPS / Influence of satellite geometry on the geodetic coordinates precision from GPS determinationsGustavo Cruz da Silveira 27 August 2008 (has links)
A precisão que pode ser obtida com levantamentos com uso do Sistema de Posicionamento Global (GPS) depende de uma série de fatores, devido à grande quantidade de fontes de erros. Em geral, estas interferências podem ser modeladas e considerações são feitas de acordo com a contribuição de cada uma destas fontes de erros. Nos primórdios dos sistemas de posicionamento, o planejamento de missões era essencial para encontrar os horários em que haveria satélites suficientes para determinação da posição. Desde que o GPS foi declarado operacional, essa questão perdeu importância. Dessa forma, não há estudos conclusivos sobre a possível influência que suas posições relativas à antena do receptor causam nos resultados dos levantamentos. Esta questão foi investigada usando como ferramenta os indicadores de precisão (DOP) disponíveis. Considerações a respeito da interpretação da figura geométrica (tetraedro), cujo volume é considerado proporcional ao DOP foram estudadas. Foi verificada a confiabilidade e a contribuição da geometria nos resultados. Comparações entre valores de planejamento e levantamento foram realizadas para o posicionamento por ponto e relativo. A influência que o comprimento da linha-base tem na obtenção dos valores de indicação foi analisada assim como a influência na precisão causada por instantes de alto valor de DOP. A questão da expectativa de que horários com bons valores de DOP possam contribuir para a fixação da ambigüidade também foi esclarecida. / The obtaining precision of GPS (Global Positioning System) surveying depends on of many factors, due the several error fonts. In general, these interferences can be modeled and considerations are made as each one contributes. In the beginning of the positioning systems, the mission planning was essential to find the period of the day that would possible to have satellites enough to position determination. Since the GPS was declared operational this issue lost importance. Hence there is a lack of conclusive researches about the influence of the satellites positioning regarding the receptor antenna position may cause on the results. This issue was investigated using tools like the available precision indicators (DOP - Dilution of Precision). Considerations regarding interpretation of the geometric figure (thetraedron), that its volume is considered proportional to the DOP were analyzed. The reliability and the geometry contribution in the results were verified. Comparisons between planning and surveying values were done to the absolute and relative positioning. The influence of the baseline in indicator values determination was analyzed as the influence in the accuracy by DOP spikes. The issue regarding the expectative that the periods with good DOP values may contribute to the ambiguity fix status was also clarified.
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Deployment Strategies for High Accuracy and Availability Indoor Positioning with 5GAhlander, Jesper, Posluk, Maria January 2020 (has links)
Indoor positioning is desired in many areas for various reasons, such as positioning products in industrial environments, hospital equipment or firefighters inside a building on fire. One even tougher situation where indoor positioning can be useful is locating a specific object on a shelf in a commercial setting. This thesis aims to investigate and design different network deployment strategies in an indoor environment in order to achieve both high position estimation accuracy and availability. The investigation considers the two positioning techniques downlink time difference of arrival, DL-TDOA, and round trip time, RTT. Simulations of several deployments are performed in two standard scenarios which mimic an indoor open office and an indoor factory, respectively. Factors having an impact on the positioning accuracy and availability are found to be deployment geometry, number of base stations, line-of-sight conditions and interference, with the most important being deployment geometry. Two deployment strategies are designed with the goal of optimising the deployment geometry. In order to achieve both high positioning accuracy and availability in a simple, sparsely cluttered environment, the strategy is to deploy the base stations evenly around the edges of the deployment area. In a more problematic, densely cluttered environment the approach somewhat differs. The proposed strategy is now to identify and strategically place some base stations in the most cluttered areas but still place a majority of the base stations around the edges of the deployment area. A robust positioning algorithm is able to handle interference well and to decrease its impact on the positioning accuracy. The cost, in terms of frequency resources, of using more orthogonal signals may not be worth the small improvement in accuracy and availability.
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GIS-based Episode Reconstruction Using GPS Data for Activity Analysis and Route Choice Modeling / GIS-based Episode Reconstruction Using GPS DataDalumpines, Ron 26 September 2014 (has links)
Most transportation problems arise from individual travel decisions. In response, transportation researchers had been studying individual travel behavior – a growing trend that requires activity data at individual level. Global positioning systems (GPS) and geographical information systems (GIS) have been used to capture and process individual activity data, from determining activity locations to mapping routes to these locations. Potential applications of GPS data seem limitless but our tools and methods to make these data usable lags behind. In response to this need, this dissertation presents a GIS-based toolkit to automatically extract activity episodes from GPS data and derive information related to these episodes from additional data (e.g., road network, land use).
The major emphasis of this dissertation is the development of a toolkit for extracting information associated with movements of individuals from GPS data. To be effective, the toolkit has been developed around three design principles: transferability, modularity, and scalability. Two substantive chapters focus on selected components of the toolkit (map-matching, mode detection); another for the entire toolkit. Final substantive chapter demonstrates the toolkit’s potential by comparing route choice models of work and shop trips using inputs generated by the toolkit.
There are several tools and methods that capitalize on GPS data, developed within different problem domains. This dissertation contributes to that repository of tools and methods by presenting a suite of tools that can extract all possible information that can be derived from GPS data. Unlike existing tools cited in the transportation literature, the toolkit has been designed to be complete (covers preprocessing up to extracting route attributes), and can work with GPS data alone or in combination with additional data. Moreover, this dissertation contributes to our understanding of route choice decisions for work and shop trips by looking into the combined effects of route attributes and individual characteristics. / Dissertation / Doctor of Philosophy (PhD)
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