Os sistemas de aumento, conhecidos como SBAS (Satellite-Based Augmentation System) fornecem informações de integridade e acurácia em tempo real para seus usuários, utilizando-se das correções diferenciais que são transmitidas pelos satélites geoestacionários e estão disponíveis em algumas regiões do globo terrestre. Fora da sua região de abrangência o sistema ainda não disponibiliza os dados de correção em tempo real. Entretanto, o sinal é transmitido na mesma frequência L1 do GPS, o qual fica disponível aqui no Brasil, e alguns receptores GNSS possuem canais de frequência especifica que captam este sinal, com a perspectiva de que os dados destes satélites melhoram as condições do rastreio, além da melhoria na acurácia das coordenadas. Partindo deste princípio, foi utilizada a observável fase da onda portadora (L1) para inferir sobre a sua contribuição para o posicionamento. Os rastreios foram realizados em diferentes localidades devido à elevação dos satélites SBAS variar em função da latitude e longitude. Contudo, este estudo foi direcionado para os dados dos satélites PRN 138 (WAAS), PRN 120 e 124 (EGNOS), pois foram os únicos visíveis durante todo o rastreio, tendo simultaneidade dos dados entre os receptores base e móvel. Durante a etapa de processamento, o qual foi utilizado o software GNSS Solution, alguns experimentos foram realizados, tais como: 1) Processamento com todas as observáveis L1 dos satélites disponíveis (GPS e SBAS), análise dos desvios-padrão e comparação das coordenadas obtidas com as consideradas verdadeiras; 2) Processamento sem as observáveis L1 dos satélites SBAS, análises e comparações; 3) Retirada gradativa dos satélites GPS e reprocessamento em conjunto (GPS+SBAS) e separadamente (apenas GPS). A finalidade principal desses experimentos foi verificar a potencialidade da observável L1 dos satélites SBAS processadas em conjunto com a observável L1 do GPS, no posicionamento relativo. Análises estatísticas, como tendência e erro médio quadrático (RMS), foram aplicadas para verificar a existência de erros sistemáticos e a acurácia das coordenadas. Os resultados mostram que, especificamente nos locais de rastreio, as observáveis L1 dos satélites SBAS ao serem adicionados ao processamento, combinado com as observáveis L1 dos satélites GPS, não são determinantes para melhoria da acurácia das coordenadas. / The augmentation systems, known as SBAS (Satellite-Based Augmentation System) provide information for completeness and accuracy in real time to its users, using the differential corrections that are transmitted by geostationary satellites. They are available in specific regions of the globe such as USA, Canada and Europe. Outside their region of coverage the system still does not provide the correction data in real time. However, the signal is transmitted at the same frequency L1 GPS, which is available here in Brazil, and some GNSS receivers have specific frequency channels that capture this signal, with the prospect that the data from these satellites improve the conditions of screening, besides improving the accuracy of the coordinates. With this assumption, we used the observed phase of the carrier wave (L1) to infer its contribution to the placement. The surveys were conducted in various locations due to rising SBAS satellites vary with latitude and longitude. However, this study was directed to the data from the WAAS satellites (PRN 138) and EGNOS (PRN 120 and 124) because they were the only visible throughout the screening taking simultaneity between the base and mobile receivers. During the processing stage, which was used the software GNSS Solution, some experiments were performed, such as: 1) Processing with all the L1 observable from available satellites (GPS and SBAS), analysis of standard deviations and comparison of the coordinates obtained with the true, 2) processing without observable L1 SBAS satellites, analysis and comparisons, 3) gradual withdrawal of the GPS satellites and reprocessing together (GPS + SBAS) and separately (GPS only). The main purpose of these experiments was to investigate the potential of the L1 observable processed SBAS satellites together with GPS L1 observable in the relative positioning. Statistical analysis such as trending and root mean square (RMS) were applied to verify the existence of systematic errors and accuracy of these coordinates. The results show that, specifically at sites of screening, the observables L1 SBAS satellites to be added to the processing, combined with the L1 observable GPS satellites, are not decisive for improving the accuracy of the coordinates.

Ao se efetuar levantamentos utilizando a tecnologia GNSS, o processamento desses dados, bem como uma análise dos fatores oriundos dos processamentos e a correta interpretação dos resultados obtidos, consiste em fator primordial para se definir a qualidade de um levantamento. Contudo, os resultados estatísticos fornecidos pelos softwares comerciais após o processamento e ajustamento dos dados, apesar de garantir maior confiabilidade aos levantamentos, não fornecem a acurácia das coordenadas encontradas, apresentando apenas a sua precisão. Assim, este trabalho tem por objetivo final, fornecer uma tabela onde seja possível, através de uma comparação dos resultados oriundos dos processamentos, classificar a acurácia dos mesmos. Para tanto, foram efetuados os processamentos e ajustamentos de dados inerentes as quatro estações do ano, durante os anos de 2006, 2007 e 2008, e após adequada análise dos mesmos, foi implementada uma Tabela de Acurácia Recomendada, onde os profissionais da área de mensuração poderão, através de uma comparação entre os relatórios de processamento fornecidos e os itens da referida tabela, efetuar a classificação da acurácia dos trabalhos de interesse. / When making surveys using GNSS technology, the processing of these data, as well as an analysis of the factors resulting from the processing and the correct interpretation of results, is to prime factor for defining the quality of a survey. However, the statistics provided by commercial software after processing and adjustment of the data, while ensuring high reliability of surveys, do not provide the accuracy of the coordinates found, showing only its precision. This paper aims to provide a table where possible, by comparing the results from the processing, The classification accuracy of them. To do so, we made adjustments and the processing of data relating the four seasons, during the years 2006, 2007 and 2008, and after proper analysis of the same purpose, a Table of Accuracy Recommended where professionals in the area of measurement may, through a comparison between the reports provided and processing the items of the tariff, to perform the classification accuracy of the work of interest.

La navigation par satellite pour les applications critiques telles que l'aviation civile nécessite un dispositif de contrôle d'intégrité pour garantir un certain niveau de précision et de fiabilité des informations fournies au pilote. Au delà des informations de position, le système de navigation doit donc fournir des alertes lorsque les exigences opérationnelles ne sont pas respectées. Cette perte de performance peut être due aux dysfonctionnements des satellites. Cette thèse traite donc du contrôle d'intégrité des systèmes de navigation en présence de pannes satellite multiples. Le contexte étudié est celui où les mesures satellitaires sont hybridées avec les données cinématiques provenant d'une centrale inertielle. Les contributions apportées à cette problématique sont diverses. Différents algorithmes sont proposés en tenant compte des contraintes de charge de calcul limitée liées aux applications embarquées. Parmi eux, l'utilisation de la fusion d'informations permet d'améliorer les performances de contrôle d'intégrité. Les imperfections du modèle d'erreur de mesure sont également traitées dans cette thèse. D'une part, nous proposons de détecter et de compenser les potentiels sauts de variance du bruit de mesure. D'autre part, des approches robustes sont utilisés afin d'améliorer le contrôle d'intégrité en présence de bruit de mesure non-gaussien. / Critical applications such as civil aviation require a navigation system including an integrity monitoring function to provide accurate and reliable information. Thus, the navigation system has to raise an alert when the operational requirements are not met. This loss of performance can be due to satellite failures. This thesis deals with integrity monitoring of navigation system assuming multiple satellite failures. Moreover, we consider herein the satellite measurements are hybidized with the kinematic information providing by an inertial navigation system.The contributions to this issue are manifold. Several algorithms are proposed accounting for the limited computing load of the embedded applications. Among them, information fusion allows to improve the integrity monitoring performance. Errors in measurement noise model are also treated in this thesis. On the one hand, we propose to detect and compensate the measurement noise variance jumps. On the other hand, robust approaches are used to improve the integrity monitoring when the measurement noise is not gaussian distributed.

Radio Occultation (RO) is a remote sensing technique which uses Global Navigation Satellite System (GNSS) signals tracked by a Low-Earth Orbit (LEO) satellite to sound the earth's atmosphere both in low (troposphere, stratosphere) and high (ionosphere) altitudes. GNSS-RO provides global coverage and SI traceable measurements of atmospheric data with high-vertical resolution. Refractivity, dry temperature, pressure and water vapour profiles retrieved from RO measurements have a relevant contribution in Numerical Weather Prediction (NWP) systems and in climate-monitoring. Due to the partial propagation through the ionosphere, a systematic bias is added to the lower atmospheric data product. Most of this contribution is removed by a linear combination of data for two frequencies. In climatology studies, one can apply a second-order correction - so called κ-correction - which relies on a priori information on the conditions in the ionosphere. However, both approaches do not remove high-order terms in the error due to horizontal gradient and earth's geomagnetic fields. The remaining residual ionospheric error (RIE) and its systematic bias in RO atmospheric data is a well-known issue and its mitigation is an open research topic. In this licentiate dissertation, the residual ionospheric error after the standard correction is evaluated with computational simulations using a wave optics propagator (WOP). Multiple Phase Screen (MPS) method is used to simulate occultation events in different ionospheric scenarios, e.g. quiet and disturbed conditions. Electron density profiles (EDP) assumed in simulations are either defined by analytical equations or measurements. The disturbed cases are modelled as small-scale irregularities within F-region in two different ways: as sinusoidal fluctuations; and by using a more complex approach, where the irregularities follow a single-slope power-law that yields moderate to strong scintillation in the signal amplitude. Possible errors in MPS simulations assuming long segment of orbit and ionosphere are also evaluated. The results obtained with the sinusoidal disturbances show minor influence in the RIE after the standard correction, with the major part of the error due to the F-region peak. The implementation of the single-slope power-law is validated and the fluctuations obtained in simulation show good agreement to the ones observed in RO measurements. Finally, an alternative to overcome limitations in MPS simulations considering occultations with long segment of orbit and ionosphere is introduced and validated. The small-scale irregularities modelled in F-region with the power-law can be added in simulations of a large dataset subjected to κ-correction, in order to evaluate the RIE bending angle and the consequences in atmospheric parameters, e.g. temperature. / NRPF-3, Rymdstyrelsen, 241/15

In this study, the connection of a local levelling network to the national height system in Sweden, RH 2000, with GNSS-techniques is investigated. The SWEN 08 is applied as geoid model. Essentially, the method is precise normal height determination with GNSS. The accuracy, repeatability and the affecting elements are tested. According to the statistics,the proposed method achieves 1-cm accuracy level. Suggestions on the general methodology and settings of several elements are proposed based on the statistics for the future application.

La réflectométrie GNSS (GNSS-R) est une technique d'observation de la Terre reposant sur un système radar bi-statique passif qui utilise, comme signaux d'opportunité, les signaux GNSS en bande L. Les travaux présentés dans ce manuscrit de thèse ont pour but de développer des méthodes de traitement du signal dédiées à l'altimétrie au sol par GNSS-R. L'altitude entre le récepteur GNSS-R et la surface de réflexion est déduite de la différence de chemin entre les signaux direct et réfléchi. On propose trois méthodes d'estimation dédiées à l'altimétrie par GNSS-R, pour un récepteur mono-fréquence, utilisant respectivement les observables de code, de puissance (carrier-to-noise ratio C/N₀) et de phase des signaux GNSS observés. Nous proposons un estimateur de la pseudo-distance qui utilise la mesure de délais de code sous-échantilloné aidée par la mesure de phase. On montre que l'estimateur sub-résolution proposé permet d'obtenir une précision qui est inférieure à la résolution en délai de code. Le deuxième estimateur s'appuie sur une méthode de calibration qui normalise la puissance de la somme des signaux direct et réfléchi (Interférence Pattern Technique). On montre par l'étude des bornes de Cramèr-Rao que l'estimateur proposé permet de réduire le temps de mesure et de conserver une précision centimétrique. La mesure de phase est une grandeur circulaire qui évolue linéairement avec l'élévation du satellite. Dans ce contexte, nous proposons deux estimateurs qui s'appuient sur un modèle de régression circulaire et la distribution circulaire de von Mises. Des expérimentations sur données réelles viennent conclure ce manuscrit de thèse et montrent la faisabilité des trois méthodes d'estimation proposées. La précision centimétrique est atteinte. / The Global Navigation Satellite Systems Reflectometry (GNSS-R) is an Earth observation technique. It is based on a passive bi-static radar system using the L-band signal coming directly from a GNSS satellite and this same signal reflected by the Earth surface. The aim of the presented work is to develop signal processing methods for altimetry measurements using ground based GNSS-R. The altitude is derived from the difference of path between the direct and reflected signals. We propose three estimators for GNSS-R altimetry measurement using respectively the code observations, the carrier-to-noise ratio C/N₀ observations, and the phase observations obtained by a mono-frequency receiver. Firstly, we define a pseudo-range estimator using under-sampling code delay observations aided by phase measurements. We show that the proposed estimator allows avoiding accuracy limitations due to the receiver resolution. Secondly, a calibration method has been developed for the Interference Pattern Technique, for normalizing the C/N₀ of the combination of the direct and reflected signals. The Cramèr-Rao Lower Bound of this estimation technique is studied. We show that the proposed estimator allows reducing the observation duration while keeping the centimeter accuracy. Thirdly, a last method is proposed in order to evaluate the difference of path between the direct and reflected signals using phase measurement.The phase measurement is an angular data evolving linearly with the satellite elevation. In this context, we propose two estimators based on a circular-linear regression and the von Mises distribution. Experimentation on real data conclude this manuscript and show the feasibility of these methods. The centimeter accuracy is reached.

Lorsqu'une grandeur est observée par une série temporelle de mesures périodiques, telles que des mesures d'angles, les outils statistiques du domaine linéaire ne sont plus adaptés à l'estimation des paramètres statistiques de cette série. Nous proposons des filtres et un opérateur de fusion adaptés aux grandeurs aléatoires circulaires. Ils sont développés dans un cadre bayésien avec la distribution circulaire normale de von Mises. De plus, on propose un estimateur circulaire GLR (Global Likehood Ratio) de ruptures dans un signal angulaire s'appuyant sur un filtre particulaire défini dans le domaine circulaire. Le traitement des signaux GNSS repose traditionnellement sur l'estimation récursive, en boucles fermées, de trois paramètres : le délai de code, la phase et la fréquence porteuse du signal reçu. On montre dans cette thèse que l'estimation de la phase et de la fréquence en boucle fermée est à l'origine d'imprécisions et de perturbations additionnelles. On propose une nouvelle approche pour l'estimation de ces paramètres en boule ouverte. Dans ce cas, les mesures de phase sont des angles, définis entre ‒π et π. Statistiquement, elles peuvent être modélisées par la distribution circulaire de von Mises et l'on utilise donc les outils d'estimation circulaire développés dans cette thèse pour les traiter. On montre l'intérêt de l'approche proposée pour le positionnement et pour l'altimétrie par réflectométrie des signaux GNSS. La précision obtenue est de l'ordre du centimètre, pour des durées d'intégrationd'une milliseconde. On propose également une technique de résolution de l'ambiguïté de phase, utilisable dans une approche mono-récepteur et mono-fréquence. / When a value is observed by a temporal series of periodic measurements, such as angle measurements, the statistic tools of the linear domain are no longer adapted to the estimation of the statistical parameters of this series. We propose several filters and a fusion operator adapted to angular random variables estimation. They are developed in a Bayesian framework with the von Mises circular normal distribution. Moreover, we propose a Global Likelihood Ratio circular change estimator which relies on a particle filter defined in the circular domain. GNSS signal procedding traditionnaly relies on the recursive estimation of three parameters in lock loops : the code delay, the phase and the frequency of the received signal carrier. We show in this thesis that the phase and frequency estimations, when realized in a lock loop, cause imprecisions and additional perturbations. We proposea new approach for the estimation of these parameters in an open loop. in this context, the phase measurements are angles defined between ‒π et π. They can be modeled using the von Mises distribution, thus we use the developed circular estimation tools in order to process them. We show the benefit of the proposed approach for positioning and for height estimation using the GNSS-Reflectometry technique. The obtained precision is of the centimeter order, for integration times of one millisecond. We also propose a phase ambiguity resolution technique which can be used in a mono-receiver , mono-frequency approach.

The aim of this diploma thesis was to evaluate a precision of spatial position of chosen services from Czepos and TopNET providers. The chosen services were virtual reference station generated by MAC concept from Czepos provider and virtual reference station NVR3 from TopNET provider. Testing measurement was measured by RTK method with GNSS instrument from Leica System 1200. There were measured long-standing observations which lasts 24 hours and short observations which lasts five and twenty seconds. The short observations were measured at five points in area of Brno. Result of the thesis is comparisons of precisions in position and height.

Orientador: Daniele Barroca Marra Alves / Resumo: Uma das principais fontes de erro sistemático no posicionamento pelo GNSS (Global Navigation Satellite System) é a ionosfera, a qual está relacionada ao conteúdo total de elétrons (TEC - Total Electron Content). O TEC por sua vez é influenciado por diversas variáveis, entre elas os ciclos solares, época do ano, hora local, localização geográfica, atividade geomagnética, além de irregularidades. Com o intuito de minimizar os efeitos causados pela ionosfera vários modelos têm sido desenvolvidos. Os GIMs (Global Ionospheric Maps) são um exemplo, disponibilizados por diversos centros, como o CODE (Center for Orbit Determination in Europe) o qual tem maior concentração de estações na Europa e sua precisão varia de acordo com o número de estações, a região do globo, o período dos dados, além de outros fatores. Por isso a precisão dos GIMs pode variar de 2 a 8 TECU (TEC Unit). Mas, devido sua característica global, apenas parte dos erros ionosféricos são reduzidos quando empregados para fins de posicionamento. Portanto, nessa pesquisa, foram utilizados dados da RBMC (Rede Brasileira de Monitoramento Contínuo dos Sistemas GNSS), do IGS e da RAMSAC (Red Argentina de Monitoreo Satelital Contínuo) durante o período de baixa e de alta intensidade de elétrons, no ciclo solar 24, a fim de gerar mapas ionosféricos por meio do software científico Bernese 5.2: MIBB (Mapa Ionosférico Brasileiro a partir do Bernese). Após a geração dos MIBBs, os mesmos puderam ser comparados com os disponibiliz... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The ionosphere is one of the main sources of systematic errors in GNSS (Global Navigation Satellite System), and is directly related to the TEC (Total Electron Content). The TEC is influenced by several variables: solar cycle, time of the year, local time, geographic position, geomagnetic activity, and other irregularities. In order to minimize the effects caused by the ionosphere different models have been developed, among them we can highlight the GIMs (Global Ionospheric Maps). They are provided by several centers, such as CODE (Center for Orbit Determination in Europe). In general, the accuracy of models varies with the number of stations, the region of the globe, the data period, and other factors. According to some authors, the GIMs’ accuracy can go from 2 to 8 TECU (TEC Unit). However, due to its global characteristic, few parts of the ionospheric errors are reduced when employed for positioning purposes. In this sense, we propose a strategy that combines data derived from RBMC (Brazilian Network for Continuous Monitoring of GNSS), IGS (International GNSS Service) and RAMSAC (Red Argentina de Monitoreo Satelital Contínuo) to generate a regional ionospheric map using Bernese 5.2 software. The ionospheric maps generated by proposed strategy are called Brazilian Ionospheric Map from Bernese (Mapa Ionosférico Brasileiro a partir do Bernese - MIBB). In the conducted experiments we used GNSS data derived from low and high electron intensity periods, in the solar cycle 24. A ... (Complete abstract click electronic access below) / Mestre

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