UAV (Unmanned Aircraft Vehicle) har revolutiontionerat ortofotoframställningen med sitt bidrag till ökad säkerhet, lägre kostnader samt effektivare arbetsgång vid framställning av ortofoton. Den traditionella flygfotogrammetrin med flygplan och utplacering av flygsignaler har varit den givna metoden i många år. Att flyga med UAV istället för flygplan sparar tid och pengar däremot är utplacering och inmätning av flygsignaler fortfarande tidskrävande och därför kostsamt. Företaget DJI har tagit fram en ny UAV med namnet DJI Phantom 4 RTK vilken stödjer möjligheten att använda satellitbaserad positionering för direkt georeferering. Den här studien har jämfört två olika georefereringsmetoder för framställning av ortofoton med UAV: direkt georeferering med NRTK (satellitbaserad positionering och nätverks-RTK) samt indirekt georeferering med olika antal markstödspunkter. Studien utfördes vid Högskolan i Gävle på en yta av åtta hektar. En undersökning av avvikelser i plan och höjd resulterade i acceptabla värden enligt de riktlinjer som följdes i HMK – Ortofoto (2017) samt de kontroller som genomfördes enligt SIS-TS 21144:2016. RMS-värdet i plan för den indirekta georefereringsmetoden ligger på 0,0102m. För den direkta georefereringsmetoden ligger RMS-värdet i plan vid användning av markstödpunkter mellan 0,0132 och 0,0148 m. Slutligen för den direkta georefereringsmetoden utan markstödpunkter är RMS-värdet i plan på 0,0136 m. RMS i höjd ligger inom intervallet 0,008-0,025 m. Det som redovisas i studien visar att en accepterad kvalitet av ortofoton går att erhålla baserat på de RMS-värden i plan och höjd med samtliga georefereringsmetoder som testats. Efter genomförda kontroller och utvärdering av de resultat kan det konstateras att de olika georefereringsmetoderna skiljer inte mycket åt varandra kvalitetsmässigt.Dock är den direkta georefereringsmetoden utan markstödpunkter mycket effektivare ur ett tidsperspektiv. Phantom 4 RTK är ny på marknaden och det behöver utföras mer forskning för att få en större insikt av dess potential. Dock krävs det mer forskning kring direkt georeferering för utvärdering av orotofotons kvalitet. / UAV (Unmanned Aircraft Vehicle) has revolutionized the creation of orthophotos with its contribution to increased safety, lower costs and more effective ways when making orthophotos. The traditional aerial photogrammetry with airplanes and placement of flight signals has been the standard method for years. To fly with UAV instead of an airplane is cheaper and saves time, however, the placement and measurements of flight signals is still time consuming and therefore expensive. The company DJI has developed a new UAV called Phantom 4 RTK that supports satellite based technology for direct georeferercing. This study compared two different measuring methods when producing orthophotos with UAV: direct georeferencing with NRTK (Network Real Time Kinematic) and indirect georeferencing when using different number of Ground Control Points (GCP). The study was conducted at the University of Gävle over an area of eight hectares. An investigation of the deviation in plane and height resulted in acceptable units based on the guidelines that were followed in HMK – Ortofoto and the controls that were followed from SIS- TS 21144:2016. The RMS value in plane for the indirect georeferencing method is 0,0102 m. For the direct georeferencing method the RMS value in plane when using ground control points is between 0,0132 and 0,0148 m. At last the RMS value for the direct georeferencing method without ground control points is 0,0136m. The RMS value in height is between the intervals 0,008-0,025 m. The data presented in this study show that an accepted quality in the orthophotos can be acquired based on the RMS values in plane and height for every georeferencing that was tested. After accomplished controls and evaluation the results show that the different georeferencing methods doesn´t differantiate too much from each other based on their quality. However, the direct georeferencing method with ground control points is more effective from a time perspective. Phantom 4 RTK is new on the market and more research is necessary in order to understand the potential of this technology and its posibility to integrate into society. More research is recquired for the direct georeferencing method in order to evaluate the quality of orthophotos.

This master‘s thesis deals with development and realisation of robotic lawn mower with satelite navigation. It begins with preparation of a platform for outdoor mobile robot navigation and it’s control HW and SW. There are discussed different options of navigation both commercial and experimental. Further on I have chosen the right GNSS receiver based on market research and user experience. The GNSS receiver’s parameters are measured with different antennas. Following with the choice of suitable open-source control unit and it’s software implementation. Furthermore control from a companion computer is described and physical realisation is done. In the end of the thesis activation of the whole mower is performed and described. Lastly there are discussed possible ways of future development.

In this thesis two methods were developed for precise maritime landing of an autonomous multirotor aircraft based on real-time kinematic (RTK) Global Navigation Satellite System (GNSS). The first method called RTK-localized method (RLM) uses RTK GNSS measurements to localize a sea vessel and execute the landing. RLM was demonstrated outdoors in hardware and landed on a physically simulated boat called a mock-boat with an average landing error of 9.7 cm. The mock-boat was actuated to have boat-like motion and a forward velocity of ~2 m/s. This method showed that accurate landing is possible with RTK GNSS as the primary means of localizing a sea vessel. The localization was unaided by non-GNSS sensors or an estimator, but lacked full attitude estimation and measurement smoothing. The second method was called RTK-Estimation Method (REM) and provides a more complete and robust solution, particularly at sea. It includes a base (landing pad) estimator to fuse RTK GNSS measurements with a dynamic model of a sea vessel. In contrast to RLM, the estimator provides full attitude estimation and measurement smoothing. The base estimator consists of an EKF in conjunction with a complimentary filter and estimates the relative position, attitude, and velocity of a moving target using RTK GNSS and inertial measurements alone. REM was demonstrated outdoors in hardware for 18 flight tests. The same mock-boat from RLM was used as a substitute for a sea vessel, and the boat motion varied between tests. These dynamics were recorded and performances were compared. The rate of success was high given moderate mock-boat motion and degraded with more aggressive motion. Tests were conducted with forward velocities from 0 to 3 m/s and moderate to high wave like motion. Over all tests for REM, the multirotor landed with an average accuracy of 12.7 cm. The methods described depart from common methods given that the only sensors involved for tracking the sea vessel were RTK GNSS receivers and inertial measurement units. Most current methods rely on computer vision, and can fail in poor lighting conditions, in the presence of ocean spray, and other scenarios. The given solutions do not fail under such conditions. The multirotor was equipped with a standard off-the-shelf autopilot, PX4, and the methods function with common control and estimation schemes. The two methods are capable of landing on relatively small landing pads, on the order of 1 m by 1 m, at sea using measurements from satellites thousands of kilometers away.

Advance Driver Assistance System (ADAS) are becoming the main issue in today’s automotive industry. The new generation of ADAS aims at focusing on more details and obtaining more accuracy. To achieve this objective, the research and development parts of the automobile industry intend to utilize Global Positioning System (GPS) by integrating it with other existing tools in ADAS. There are several driving assistance systems which are served by a digital map as a primary or a secondary sensor. The traditional techniques of digital map generation are expensive and time consuming and require extensive manual effort. Therefore, having frequently updated maps is an issue. Furthermore, the existing commercial digital maps are not highly accurate. This Master thesis presents several algorithms for automatically converting raw Universal Serial Bus (USB)-GPS and Real Time Kinematic (RTK) GPS traces into a routable road network. The traces are gathered by driving 20 times on a highway. This work begins by pruning raw GPS traces using four different algorithms. The first step tries to minimize the number of outliers. After the traces are smoothed, they tend to consolidate into smooth paths. So in order to merge all 20 trips together and estimate the road network a Trace Merging algorithm is applied. Finally, a Non-Uniform Rational B-Spline (NURBS) curve is implemented as an approximation curve to smooth the road shape and decrease the effect of noisy data further. Since the RTK-GPS receiver provides highly accurate data, the curve resulted from its GPS data is the most sufficient road shape. Therefore, it is used as a ground truth to compare the result of each pruning algorithm based on data from USB-GPS. Lastly, the results of this work are demonstrated and a quality evaluation is done for all methods.

This master’s thesis describes the design, implementation and testing of an active antenna intended for use with global navigation satellite systems. The active antenna is composed of two major parts, a dual-band circular patch antenna and a dual-band low-noise amplifier. To streamline the design process, a modular solution was adopted. This enabled the functionality of every part in the signal path to be verified before the final active antenna was designed. A practical method to develop dual-band stacked circular patch antennas, along with a systematic way to tune the resonant frequencies and impedance of the antenna, is also presented. Testing of the antenna in realistic scenarios shows that the active antenna performs as expected and predicted by simulations. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>

No description available.

Ego-motion sensors are commonly used for pose estimation in Simultaneous Localization And Mapping (SLAM) algorithms. Inertial Measurement Units (IMUs) are popular sensors but suffer from integration drift over longer time scales. To remedy the drift they are often used in combination with additional sensors, such as a LiDAR. Pose estimation is used when scans, produced by these additional sensors, are being matched. The matching of scans can be computationally heavy as one scan can contain millions of data points. Methods exist to simplify the problem of finding the relative pose between sensor data, such as the Normal Distribution Transform SLAM algorithm. The algorithm separates the point cloud data into a voxelgrid and represent each voxel as a normal distribution, effectively decreasing the amount of data points. Registration is based on a function which converges to a minimum. Sub-optimal conditions can cause the function to converge at a local minimum. To remedy this problem this thesis explores the benefits of combining IMU sensor data to estimate the pose to be used in the NDT SLAM algorithm.

The oncogene Anaplastic Lymphoma Kinase (ALK) is a Receptor Tyrosine Kinase (RTK) and was initially discovered as the fusion protein NPM (nucleophosmin)-ALK in a subset of Anaplastic Large Cell Lymphomas (ALCL). Since then more fusion proteins have been identified in a variety of cancers. Further, overexpression of ALK due to gene amplification has been observed in many malignancies, amongst others neuroblastoma, a pediatric cancer. Lately, activating point mutations in the kinase domain of ALK have been described in neuroblastoma patients and neuroblastoma cell lines. In contrast, the physiological function of ALK is still unclear, but ALK is suggested to play a role in the normal development and function of the nervous system. By employing cell culture based approaches, including a tetracycline-inducible PC12 cell system and the in vivo D. melanogaster model system, we aimed to analyze the downstream signalling of ALK and its role in neuroblastoma. First, we wished to analyze whether ALK is able to activate the small GTPase Rap1 contributing to differentiation/proliferation processes. Activated ALK recruits a complex of the GEF C3G and CrkL and activates C3G by tyrosine phosphorylation. This activated complex is able to activate Rap1 resulting either in neurite outgrowth in PC12 cells or proliferation of neuroblastoma cells suggesting a potential role in the oncogenesis of neuroblastoma driven by gain-of-function mutant ALK. Next, we could show that seven investigated ALK mutations with a high probability of being oncogenic (G1128A, I1171N, F1174L, F1174S, R1192P, F1245C and R1275Q), are true gain-of-function mutations, respond differently to ALK inhibitors and have different transforming ability. Especially the F1174S mutation correlates with aggressive disease development. However, the assumed active germ line mutation I1250T is in fact a kinase dead mutation and suggested to act as a dominant-negative receptor. Finally, ALK mutations are most frequently observed in MYCN amplified tumours correlating with a poor clinical outcome. Active ALK regulates mainly the initiation of MYCN transcription in human neuroblastoma cell lines. Further, ALK gain-of-function mutants and MYCN synergize in transforming NIH3T3 cells. Overall, somatic mutations appear to be more aggressive than germ line mutations, implying a different impact on neuroblastoma. Further, successful application of ALK inhibitors suggests a promising future for the development of patient-specific treatments for neuroblastoma patients.

Activated receptor tyrosine kinases recruit many signalling proteins to initiate downstream cell proliferation and survival pathways, including phosphatidylinositol 3-kinase (PI3K), a heterodimer consisting of a p85 regulatory protein and a p110 catalytic protein. Our laboratory has previously shown the p85α protein also has in vitro GTPase activating protein (GAP) activity towards Rab5 and Rab4, small GTPases that regulate vesicle trafficking events for activated receptors. Expression of a p85α protein containing an arginine to alanine substitution at position 274 (p85R274A) that affects its GAP activity, caused sustained levels of activated platelet-derived growth factor receptors (PDGFRs), enhanced downstream signalling, and resulted in cellular transformation. Together with other data, this suggested that in p85R274A-expressing cells, PDGFRs are more rapidly trafficked through the endocytic pathway, which reduces opportunities for sorting events necessary for receptor degradation. Our laboratory has observed previously that p85 was capable of binding to both Rab5-GDP, as well as Rab5-GTP, which is an atypical characteristic of GAP proteins, whereas p110β had previously been reported to bind Rab5-GTP selectively. Based on these observations, this thesis project was designed to test the hypothesis that both proteins contributed GAP activity towards Rab5, with p85 providing a catalytic arginine residue (R274) and p110β providing switch stabilization functions specific to the GTP-bound state. To accomplish the thesis objective, cells expressing individual p85 defects (lacking GAP activity, R274A; or lacking p110-binding ability through deletion of residues 478-513, Δ110) were compared to cells expressing a double mutant missing both functions. Stable clonal NIH 3T3 cell lines were generated and selected in G418 and clones expressing similar levels of FLAG-tagged p85 wild type or mutants compared to the control cell lines (NIH 3T3, FLAG-vector control, p85 wild type, and p85R274A) were chosen for analysis. A time-course of PDGF stimulation showed that cells expressing p85R274A or p85Δ110+R274A have sustained phosphorylation levels of the PDGFR, reduced rates of PDGFR degradation and sustained MAPK/Erk signalling. Contrary to the cellular transformation previously reported for p85R274A-expressing cells, expression of p85Δ110+R274A did not lead to cellular transformation. These divergent results suggest that p85-associated p110 serves two functions. As the catalytic subunit of PI3K, one function is the localized generation of PI3,4,5P3 lipids at the plasma membrane for Akt activation, and possibly during receptor endocytosis where it could impact MAPK/Erk activation/deactivation kinetics and cell transformation. These results support a second function for p110 in the regulation of PDGFR activation/deactivation kinetics and PDGFR half-life, both strongly influenced by alterations in PDGFR trafficking. This suggests that p110β may regulate PDGFR trafficking by providing Rab5-GTP switch stabilization that complements the catalytic arginine residue (R274) within p85, and that p85α and p110β work together as a Rab5 GAP. The role of PDGFR in the localization of the RabGAP function of p85 to specific subcellular compartments was also examined. It was hypothesized that PDGFR may help localize the RabGAP function of p85 to vesicles containing Rab5 or Rab4 through the binding of p85 to phosphorylated tyrosine residues on activated PDGFR. Stable cell lines expressing individual p85 defects (lacking GAP activity, R274A; or lacking PDGFR-binding ability through site-directed mutation of residues 358 and 649 from arginine to alanine, ΔR; or a double mutant missing both functions) demonstrated that p85R274A or p85ΔR+R274A expression leads to sustained PDGFR activation and signalling, and to delayed PDGFR degradation in response to PDGF stimulation. The sustained signalling observed resulted in cellular transformation in cells expressing p85R274A or p85ΔR+R274A. The data suggests that PDGFR does not play a role in the localization of the RabGAP activity of p85. The findings of this study elucidates important non-canonical functions of the PI3K heterodimer and contributes to our understanding of how specific mutations in both p85 and p110β within regions implicated in the regulation of RabGAP activity can alter signalling events and lead to enhancement of tumour-associated phenotypes.

Submitted by Paulo Sérgio de Oliveira Júnior null (psergio.jr@hotmail.com) on 2017-11-17T14:41:41Z No. of bitstreams: 1 d_oliveira-jr_ps_thesis.pdf: 14260833 bytes, checksum: ebcb000a304456bb9bc42d8d1ccaa566 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-11-17T17:10:17Z (GMT) No. of bitstreams: 1 oliveirajunior_ps_dr_prud.pdf: 14260833 bytes, checksum: ebcb000a304456bb9bc42d8d1ccaa566 (MD5) / Made available in DSpace on 2017-11-17T17:10:17Z (GMT). No. of bitstreams: 1 oliveirajunior_ps_dr_prud.pdf: 14260833 bytes, checksum: ebcb000a304456bb9bc42d8d1ccaa566 (MD5) Previous issue date: 2017-09-05 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / PPP (Precise Point Positioning) is a positioning method by GNSS (Global Navigation Satellite Systems), based on SSR (State Space Representation) concept that can provide centimeter accuracy solutions. Real-time PPP (RT-PPP) is possible thanks to the availability of precise products, for orbits and clocks, provided by the International GNSS Service (IGS), as well as by its analysis centers such as CNES (Center National d'Etudes Spatiales). One of the remaining challenges on RT-PPP is the mitigation of atmospheric effects (troposphere and ionosphere) on GNSS signals. Thanks to recent improvements in atmospheric models, RT-PPP can be enhanced, allowing accuracy and centimeter initialization time, comparable to the current NRTK (Network Real-Time Kinematic) method. Such performance depends on topology of permanent stations networks and atmospheric conditions. The main objective of this project is to study the RT-PPP and the optimized infrastructure in terms of costs and benefits to realize the method using atmospheric corrections. Therefore, different configurations of a dense and regular GNSS network existing in France, the Orpheon network, are used. This network has about 160 sites and is owned by Geodata-Diffusion (Hexagon Geosystems). The work was divided into two main stages. Initially, ‘float PPP-RTK’ was evaluated, it corresponds to RT-PPP with improvements resulting from network corrections, although with ambiguities kept float. Further on, network corrections are applied to improve “PPP-RTK” where ambiguities are fixed to their integer values. For the float PPP-RTK, a modified version of the RTKLib 2.4.3 (beta) package is used to take into account for the network corrections. First-order ionospheric effects were eliminated by the iono-free combination and zenith tropospheric delay estimated. The corrections were applied by introducing a priori constrained tropospheric parameters. Periods with different tropospheric conditions were chosen to carry out the study. Adaptive modeling based on OFCs (Optimal Fitting Coefficients) has been developed to describe the behavior of the troposphere, using estimates of tropospheric delays for Orpheon stations. This solution allows one-way communication between the server and the user. The quality of tropospheric corrections is evaluated by comparison to external tropospheric products. The gains achieved in convergence time to 10 centimeters accuracy were statistically quantified. Network topology was assessed by reducing the number of reference stations (up to 75%) using a sparse Orpheon network configuration to perform tropospheric modeling. This did not degrade the tropospheric corrections and similar performances were obtained on the user side. In the second step, PPP-RTK is realized using the PPP-Wizard 1.3 software and CNES real-time products for orbits, clocks and phase biases of satellites. RT-IPPP (Real-Time Integer PPP) is performed with estimation of tropospheric and ionospheric delays. Ionospheric and tropospheric corrections are introduced as a priori parameters constrained to the PPP-RTK of the user. To generate ionospheric corrections, it was implemented a solution aligned with RTCM (Real-Time Maritime Services) conventions, regarding the transmission of ionospheric parameters SSR, which is a standard Inverse Distance Weighting (IDW) algorithm. The choice of the periods for this experiment was made mainly with respect to the ionospheric activity. The comparison of the atmospheric corrections with the external products and the evaluation of different network topologies (dense and sparse) were also carried out in this stage. Statistically, the standard RT-IPPP takes ~ 25 min to achieve a 10 cm horizontal accuracy, which is significantly improved by our method: 46% (convergence in 14 min) with dense network corrections and 24% (convergence in 19 min) with the sparse network. Nevertheless, vertical positioning sees its convergence time slightly increased, especially when corrections are used from a sparse network solution. However, improvements in horizontal positioning due to external SSR corrections from a (dense or sparse) network are promising and may be useful for applications that depend primarily on horizontal positioning. / O PPP (Precise Point Positioning) é um método de posicionamento pelo GNSS (Global Navigation Satellite Systems), baseado no conceito SSR (State Space Representation) o qual pode fornecer soluções de acurácia centimétrica. O PPP em tempo real (RT-PPP) é possível graças à disponibilidade de produtos precisos, para órbitas e relógios, fornecidos pelo IGS (International GNSS Service), bem como por seus centros de análise, como o CNES (Centre National d’Etudes Spatiales). Um dos desafios restantes no RT-PPP é a mitigação dos efeitos atmosféricos (troposfera e ionosfera) nos sinais GNSS. Graças às melhorias recentes nos modelos atmosféricos, o RT-PPP pode ser aprimorado, permitindo tempo de inicialização com acurácia centimétrica, comparável ao atual método NRTK (Network Real-Time Kinematic). Esse desempenho depende da topologia das redes de estações permanentes e das condições atmosféricas. O objetivo principal deste projeto é estudar o RT-PPP e a infraestrutura optimizada em termos de custos e benefícios para realizar o método usando correções atmosféricas. Portanto, são utilizadas diferentes configurações de uma rede GNSS densa e regular existente na França, a rede Orphéon. Esta rede tem cerca de 160 estações, sendo propriedade da Geodata-Diffusion (Hexagon Geosystems). O trabalho foi dividido em duas etapas principais. Inicialmente, foi avaliado o "float PPP-RTK", que corresponde ao RT-PPP com melhorias resultantes de correções de rede, embora mantendo as ambiguidades como float. Em um segundo momento, as correções de rede são aplicadas para aprimorar o "PPP-RTK", onde ambiguidades são fixadas para seus valores inteiros. Para o float PPP-RTK, uma versão modificada do software RTKLib 2.4.3 (beta) é empregada de modo a levar em consideração as correções de rede. Os efeitos ionosféricos de primeira ordem são eliminados pela combinação iono-free e atraso zenital troposférico é estimado. As correções são aplicadas introduzindo parâmetros troposféricos a priori injuncionados. Períodos com diferentes condições troposféricas foram escolhidos para realizar o estudo. Uma modelagem adaptativa baseada em OFCs (Optimal Fitting Coefficients) foi implementada para descrever o comportamento da troposfera, utilizando estimativas de atraso troposférico para estações da rede Orphéon. Tal solução permite a comunicação unidirecional entre o servidor e o usuário. A qualidade das correções troposféricas foi avaliada através de comparação com produtos externos troposféricos. Os ganhos alcançados no tempo de convergência para acurácia de 10 centímetros foram quantificados estatisticamente. A topologia de rede foi avaliada reduzindo o número de estações de referência (em até 75%) usando uma configuração da rede Orphéon esparsa para realizar a modelagem troposférica. Isso não degradou as correções troposféricas e foram obtidas performances similares para os usuários simulados. Na segunda etapa, o PPP-RTK é realizado usando o software PPP-Wizard 1.3, bem como os produtos para tempo real do CNES de órbitas, relógios e biases de fase dos satélites. O RT-IPPP (Real-Time Integer PPP) é realizado com estimativa de atrasos troposféricos e ionosféricos. As correções ionosféricas e troposféricas são introduzidas como parâmetros a priori injuncionados no PPP-RTK do usuário. Para gerar correções ionosféricas, foi implementada uma solução alinhada com as convenções RTCM (Real-Time Maritime Services), em relação à transmissão de correções ionosféricas SSR, o qual é um algoritmo baseado na ponderação pelo inverso da distância (IDW – Inverse Distance Weighting). A escolha dos períodos para este experimento foi realizada principalmente em relação à atividade ionosférica. A comparação das correções atmosféricas com produtos externos, assim como a avaliação de diferentes topologias de rede (densa e esparsa) também foram realizadas nesta etapa. Estatisticamente, o RT-IPPP padrão leva ~ 25 min para alcançar uma acurácia horizontal de 10 cm, a qual é significativamente melhorada pelo método implementado: 46% (convergência em 14 min) com correções de rede densa e 24% (convergência em 19 min) com a rede esparsa. No entanto, o posicionamento vertical vê o seu tempo de convergência ligeiramente aumentado, especialmente quando as correções são usadas a partir de uma solução de rede esparsa. No entanto, as melhorias no posicionamento horizontal com o uso das correções de SSR externas de uma rede (densa ou esparsa) são promissoras e podem ser úteis para aplicações que dependem principalmente do posicionamento horizontal. / Le PPP (Precise Point Positioning) est une méthode de positionnement par GNSS (Global Navigation Satellite Systems), basée sur le concept SSR (State Space Representation), qui peut générer solutions de précision centimétrique. Le PPP en temps réel (RT-PPP) est possible grâce à la disponibilité des produits précis, pour les orbites et horloges, fournis par l’IGS (International GNSS Service), ainsi que par ses centres d'analyse, tels que le CNES (Centre National d'Etudes Spatiales). Un des défis restants sur le RT-PPP est la mitigation des effets atmosphériques (troposphère et ionosphère) sur les signaux GNSS. Grâce aux améliorations récentes des modèles atmosphériques, le RT-PPP peut être amélioré, ce qui permet une précision et un temps d'initialisation au niveau du centimètre, comparables à la méthode NRTK (Network Real-Time Kinematic) actuelle. De telles performances dépendent de la topologie du réseau de stations GNSS permanentes et des conditions atmosphériques. L'objectif principal de ce projet est d'étudier le RT-PPP et l'infrastructure optimisée en termes de coûts et d'avantages pour réaliser la méthode en utilisant des corrections atmosphériques. Pour cela, différentes configurations d'un réseau GNSS dense et régulier existant en France, le réseau Orphéon, sont utilisées. Ce réseau compte environ 160 sites, propriété de Geodata-Diffusion (Hexagon Geosystems). Le travail est divisé en deux étapes principales. Dans un premier temps, le mode «PPP-RTK flottant» a été évalué, il correspond au RT-PPP avec des améliorations issues des corrections de réseau, mais avec les ambiguïtés flottantes. Ensuite, des corrections de réseau sont appliquées pour améliorer le mode « PPP-RTK » où les ambiguïtés sont fixées à leurs valeurs entières. Pour le PPP-RTK flottant, une version modifiée du package RTKLib 2.4.3 (beta) est utilisée pour prendre en compte les corrections réseau. Les effets ionosphériques de premier ordre ont été éliminés par la combinaison iono-free et le retard troposphérique zénithal est estimé. Les corrections ont été appliquées en introduisant des paramètres troposphériques a priori contraints. Des périodes avec différentes conditions troposphériques ont été choisies pour réaliser l'étude. Une modélisation adaptative basée sur les OFCs (Optimal Fitting Coefficients) a été mise en place pour décrire le comportement de la troposphère, en utilisant des estimations des retards troposphériques pour les stations Orphéon. Cette solution permet une communication mono-directionnelle entre le serveur et l'utilisateur. La qualité des corrections troposphériques est évaluée par comparaison avec des produits troposphériques externes. Les gains réalisés sur le temps de convergence pour obtenir un positionnement de 10 centimètres de précision ont été quantifiés statistiquement. La topologie du réseau a été évaluée, en réduisant le nombre de stations de référence (jusqu'à 75%), via une configuration de réseau Orphéon lâche pour effectuer la modélisation troposphérique. Cela n'a pas dégradé les corrections troposphériques et des performances similaires ont été obtenues du côté de l'utilisateur. Dans la deuxième étape, le PPP-RTK est réalisé grâce au logiciel PPP-Wizard 1.3 et avec les produits temps réel CNES pour les orbites, les horloges et les biais de phase des satellites. Le RT-IPPP (Real-Time Integer PPP) est réalisé avec estimation des délais troposphériques et ionosphériques. Les corrections ionosphériques et troposphériques sont introduites en tant que paramètres a priori contraints au PPP-RTK de l'utilisateur. Pour générer des corrections ionosphériques, il a été mis en place une solution alignée avec les conventions RTCM (Real-Time Maritime Services) pour la transmission des paramètres ionosphériques SSR, un algorithme standard d'interpolation à distance inversée (IDW – Inverse Distance Weighting). Le choix des périodes pour cette expérience a été fait principalement en regard de l'activité ionosphérique. La comparaison des corrections atmosphériques avec les produits externes et l'évaluation de différentes topologies de réseau (dense et lâche) ont également été effectuées dans cette étape. Statistiquement le RT-IPPP standard prend ~25 min pour atteindre une précision horizontale de 10 cm, ce que nous améliorons significativement par notre méthode : 46% (convergence en 14 min) avec le réseau dense et 24% (convergence en 19 min) avec le réseau restreint. Néanmoins le positionnement vertical voit son temps de convergence légèrement augmenté, en particulier lorsque l'on utilise des corrections à partir d'une solution de réseau lâche. Cependant, les améliorations apportées au positionnement horizontal dues aux corrections atmosphériques SSR externes provenant d’un réseau (dense ou lâche) sont prometteuses et peuvent être utiles pour les applications qui dépendent principalement du positionnement horizontal. / CNPq: 229828/2013-2