Avaliação da precisão de posicionamento inerente à utilização de sistemas GPS de baixo custo, receptores utilizados para navegação

Dissertação de mestrado em Engenharia Municipal (área de especialização em Planeamento Urbanístico)O presente trabalho trata sobre a análise do erro de posição obtido com a utilização de receptores GPS de navegação. Estes aparelhos receptores, como se tornaram de aquisição corrente, podem ser utilizados para outros serviços que não a navegação, quer em estrada quer fora dela, bastando para isso conhecer a precisão associada ao aparelho. Esta precisão pode ser variável, dependendo da qualidade da recepção dos dados. Para objectivos associados a actividades de planeamento e gestão do território, a precisão conseguida com esse tipo de equipamento pode ser utilizada em determinadas situações, dependendo dos respectivos objectivos. Assim, considerou-se pertinente fazer uma avaliação de qual a precisão possível para esse tipo de equipamentos GPS e se o erro associado pode ser minorado recorrendo a técnicas de pós-processamento. Deste modo, desenvolveu-se uma metodologia que, recorrendo a receptores GPS de navegação, permitiu avaliar a viabilidade de efectuar levantamentos com precisão adequada a alguns trabalhos de posicionamento. Para confrontação dos resultados utilizou-se um equipamento GPS para Geodesia, portanto um aparelho com precisão sub-métrica e de custo bastante mais elevado. Os resultados destas comparações são analisados e são apresentadas as conclusões obtidas que revelam a validade de utilização deste equipamento até escalas de 1/5000.The objective of this research is to analyse the position error obtained with the use of GPS receivers for navigation. These device receptors, as they become of general acquisition, may be used for services other than navigation, on road or off-road, if we simple know the accuracy associated with the device. This accuracy can be variable, depending on the quality of reception of data. For purposes related to planning and management activities in territory, the accuracy achieved with this type of equipment can be used in certain situations, depending on their objectives. Therefore, the application in a study has shown the accuracy of this type of GPS equipment and the results highlighted that the associated error can be reduced using post-processing. Thus, the proposed methodology evaluates the accuracy of survey with GPS receivers for navigation. Also a comparative analysis was made with a Geodetic GPS, a device with sub-metric accuracy and a much higher cost. The results of these comparisons are analyzed and the conclusions are presented showing the validity of using this equipment to scales of 1 / 5000

Navigation Recommender:Real-Time iGNSS QoS Prediction for Navigation Services

Global Navigation Satellite Systems (GNSSs), especially Global Positioning System (GPS), have become commonplace in mobile devices and are the most preferred geo-positioning sensors for many location-based applications. Besides GPS, other GNSSs under development or deployment are GLONASS, Galileo, and Compass. These four GNSSs are planned to be integrated in the near future. It is anticipated that integrated GNSSs (iGNSSs) will improve the overall satellite-based geo-positioning performance. However, one major shortcoming of any GNSS and iGNSSs is Quality of Service (QoS) degradation due to signal blockage and attenuation by the surrounding environments, particularly in obstructed areas. GNSS QoS uncertainty is the root cause of positioning ambiguity, poor localization performance, application freeze, and incorrect guidance in navigation applications. In this research, a methodology, called iGNSS QoS prediction, that can provide GNSS QoS on desired and prospective routes is developed. Six iGNSS QoS parameters suitable for navigation are defined: visibility, availability, accuracy, continuity, reliability, and flexibility. The iGNSS QoS prediction methodology, which includes a set of algorithms, encompasses four modules: segment sampling, point-based iGNSS QoS prediction, tracking-based iGNSS QoS prediction, and iGNSS QoS segmentation. Given that iGNSS QoS prediction is data- and compute-intensive and navigation applications require real-time solutions, an efficient satellite selection algorithm is developed and distributed computing platforms, mainly grids and clouds, for achieving real-time performance are explored. The proposed methodology is unique in several respects: it specifically addresses the iGNSS positioning requirements of navigation systems/services; it provides a new means for route choices and routing in navigation systems/services; it is suitable for different modes of travel such as driving and walking; it takes high-resolution 3D data into account for GNSS positioning; and it is based on efficient algorithms and can utilize high-performance and scalable computing platforms such as grids and clouds to provide real-time solutions. A number of experiments were conducted to evaluate the developed methodology and the algorithms using real field test data (GPS coordinates). The experimental results show that the methodology can predict iGNSS QoS in various areas, especially in problematic areas