Dissertations / Theses on the topic 'GNSS data'
To see the other types of publications on this topic, follow the link: GNSS data.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 49 dissertations / theses for your research on the topic 'GNSS data.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Ortolani, Alberto <1969>. "Probabilistic tomography of atmospheric parameters from GNSS data." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3922/1/ortolani_alberto_tesi.pdf.
Full textAbstract:
The objective of the work is the evaluation of the potential capabilities of navigation satellite signals to retrieve basic atmospheric parameters. A capillary study have been performed on the assumptions more or less explicitly contained in the common processing steps of navigation signals. A probabilistic procedure has been designed for measuring vertical discretised profiles of pressure, temperature and water vapour and their associated
errors. Numerical experiments on a synthetic dataset have been performed with the main objective of quantifying the information that could be gained from such approach, using
entropy and relative entropy as testing parameters. A simulator of phase delay and bending of
a GNSS signal travelling across the atmosphere has been developed to this aim.
2
Ortolani, Alberto <1969>. "Probabilistic tomography of atmospheric parameters from GNSS data." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3922/.
Full textAbstract:
The objective of the work is the evaluation of the potential capabilities of navigation satellite signals to retrieve basic atmospheric parameters. A capillary study have been performed on the assumptions more or less explicitly contained in the common processing steps of navigation signals. A probabilistic procedure has been designed for measuring vertical discretised profiles of pressure, temperature and water vapour and their associated
errors. Numerical experiments on a synthetic dataset have been performed with the main objective of quantifying the information that could be gained from such approach, using
entropy and relative entropy as testing parameters. A simulator of phase delay and bending of
a GNSS signal travelling across the atmosphere has been developed to this aim.
3
Bertani, Federico. "Reconstruction of vehicle dynamics from inertial and GNSS data." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16105/.
Full textAbstract:
The increasingly massive collection of data from various types of sensors installed on vehicles allows the study and reconstruction of their dynamics in real time, as well as their archiving for subsequent analysis.
This Thesis describes the design of a numerical algorithm and its implementation in a program that uses data from inertial and geo-positioning sensors, with applications in industrial contexts and automotive research. The result was made usable through the development of a Python add-on for the Blender graphics program, able to generate a three-dimensional view of the dynamics that can be used by experts and others.
Throughout the Thesis, particular attention was paid to the complex nature of the data processed, introducing adequate systems for filtering, interpolation, integration and analysis, aimed at reducing errors and simultaneously optimizing performances.
4
Horn, Matti. "En analys av webbtjänster för bearbetning av GNSS-data." Thesis, KTH, Geoinformatik och Geodesi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-46743.
Full text
5
Romano, Vincenzo. "Ionospheric scintillation effects on GNSS : monitoring and data treatment development." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33909/.
Full textAbstract:
The increasing importance of satellite navigation technologies in modern society implies that a deeper knowledge and a reliable monitoring of the scintillation phenomena are essential to warn and forecast information to the end users and system designers. In fact, warnings, alerts and forecasting of ionospheric conditions may wisely tune the development of GNSS-based services to obtain the necessary levels of accuracy, integrity, and immediacy for reliable life-critical applications. The PhD research project is within the framework of the longstanding NGI-INGV collaboration, increasingly consolidated in the framework of many international projects. NGI pioneered GPS ionospheric scintillation monitoring in Northern Europe with GISTM (GPS ionospheric scintillation and TEC monitor, Van Dierendonck et al., 1993; Van Dierendonck, 2001) receivers. Between June 2001 and December 2003, four units were installed in the UK and Norway mainland, covering the geographic latitudes from 53° N to 70° N. Data was stored and analysed, focusing on statistical analyses and impact for GNSS users (Rodrigues et al., 2004, Aquino et al., 2005a, Aquino et al., 2005b). These units were decommissioned in 2004 and, then, re-deployed together with additional new receivers, in UK, Norway, Italy and Cyprus. An additional station was deployed by the NGI in Dourbes, Belgium (in collaboration with the Royal Meteorological Institute of Belgium) between 2006 and 2011. INGV leads the ISACCO (Ionospheric Scintillation Arctic Campaign Coordinated Observations) project in the Arctic, started in 2003, in which frame the management of three GISTM receivers in Svalbard (De Franceschi et al., 2006) and another two at European mid-latitudes, Chania (Greece) and Lampedusa (Italy), is currently undertaken. The PhD research project contributed to the reinforcement of the NGI-INGV GISTM network developing monitoring, data management and quality tools. Such activities have supported the continuity and the control of the receiving stations, as well as the access and the preservation of the both real-time and historical data acquired. In fact, a robust, continuous data acquisition and a wise management of the GISTM network are of paramount importance for Space Weather applications, as they are the basis on which reliable forecasting and now-casting of possible effects on technological systems lean. Moreover, the possibility to use the data for scientific and applicative purposes depends upon well-established data quality procedures and upon a detailed knowledge of the sites in which each receiver comprising the network are deployed. Starting from these considerations, and in the framework of the aforementioned collaborative context, the PhD work aimed at improving the monitoring techniques and developing novel data processing to improve the data quality. Scintillation measurements are contaminated by multiple scattering encountered by the GNSS signal due to buildings, trees, etc. Such multipath sources need to be identified to keep the quality of the scintillation and TEC data as higher as possible. This can be achieved by removing these sources of errors or mitigating their effects by filtering the data. A novel station characterization technique has been introduced, developed and discussed in this thesis. The results demonstrated that this is a promising method to improve the quality of data (Romano et. al 2013). The results obtained so far motivated the development of the data filtering procedures. The filtering was aimed at filtering-out spurious, noisy data based on general assumptions about statistical data analysis (outlier analysis), thus efficiently removing multipath affected measurements and reducing the data loss with respect to applying a fixed elevation angle cut-off threshold. This is particularly important in case of not well covered regions (e.g. forests, deserts, oceans, etc.), as the field of view spanned by each antenna is optimized. During the PhD activities, the filtering technique has been also tested and validated against real and simulated data. To show how the development of the filtering method is able to efficiently clean multipath and signal degradation from GNSS data, it was applied in two different cases: - First, it was applied to the data published in a climatological study (Alfonsi et al. 2011), carried out with the NGI-INGV GISTM network at high-latitudes. Each station was characterized using the station characterization method, and then the data were filtered using the filtering method. Then, the new climatological maps were generated and compared to the original ones. The percentage of the filtered-out data obtained by applying the standard threshold of 20° on the elevation angle and the filtering technique for each station demonstrated how the latter is able to meaningfully reduce the data loss. The filtering extends the field of view of the network and, then, improves the capability of investigating the dynamics of the ionosphere over larger areas. - Second, the data used in this application were acquired by the CIGALA/CALIBRA network of PolaRxS receivers during the whole year of 2012. The elevation angle cut-off significantly reduced the capability of the network to depict the ionosphere northward of the geomagnetic equator and above the Atlantic Ocean, east of Brazil. This approach limited the data loss to 10-20%, while the traditional cut off of 15°-30° on the elevation angle led to losses of 35-45%. This method not only optimized the capability of GNSS networks, but also helped in planning the installation of additional new receivers aiming to enlarge network coverage in the framework of the CALIBRA project. The enlarged field of view made it possible to identify the increased occurrence of scintillation along the northern crest of the Equatorial Ionospheric Anomaly (EIA). To summarize and to introduce the reader into this thesis, specific issues here addressed are: - Development of software procedures and hardware designs to optimize the station configurations of the existing measurement network of GISTM (GPS Ionospheric Scintillation and TEC Monitor). - Development of techniques for remote, automatic instrument control and setting. - Development of data management tools to achieve quasi real-time data accessibility. - Development of data analysis methods to assess station characterization. - Development of techniques to perform data quality filtering. - Perform acquisition of experimental and simulation data. - Support scientific investigations through the high quality of the NGI-INGV network data.
6
Khodabandeh, Amir. "Precise multi-GNSS point positioning: theory, algorithm and data analysis." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/159.
Full textAbstract:
In this thesis we study the principles and intricacies of the new state-of-the-art precise positioning technique, the PPP-RTK. Both its network- and user-components are discussed. The concept of array-based PPP-RTK is introduced, where its efficiency is demonstrated by multi-Global Navigation Satellite Systems (GNSS) results. Finally an optimal recursive filter is developed to process observation equations of the network- and user-components.
7
Yan, Thomas Surya Sanjaya Surveying & Spatial Information Systems Faculty of Engineering UNSW. "Analysis on distribution of real-time GNSS data over IP networks." Publisher:University of New South Wales. Surveying & Spatial Information Systems, 2008. http://handle.unsw.edu.au/1959.4/41286.
Full textAbstract:
This thesis examines the current implementations for the distribution of real-time GNSS data over IP networks such as the public Internet, focusing on two essential components of the system, data format and transport protocol. The provision of a suitable data format will allow users to take full advantage of the real-time GNSS data distribution system. Types of GNSS supported, message sizes, data rates, data precision levels, hardware and software support and possible future developments are investigated. An analysis is carried out on commonly known GNSS data formats, highlighting the most suitable standard for each evaluation criterion. A similar investigation is carried out on the transport protocols. An analysis is conducted on various design aspects of NTRIP and RT-IGS protocols, covering factors such as data latency, integrity, firewalls and proxy server compatibility and scalability. The analysis also covers the design aspects of the new draft Version 2 of NTRIP. The latter parts of this thesis report on the experiment results aimed at providing assessment of the current level of implementation of NTRIP. Data latency and integrity using NTRIP over the Internet are examined. Their impacts on users applications as the quality of real-time kinematic positioning is assessed. The results show that the performance of the system satisfies the rigorous requirement of the end-user application. The draft version of the new NTRIP indicates that UDP will be also supported. A similar investigation is carried out, providing the first experiment results on the new option. Tests using similar metrics, data latency and integrity, were carried out to verify the inherent differences between TCP and UDP. It was ascertained that, in most cases, UDP does offer improvement in terms of reduced latency over TCP. However this improvement is not significant enough to affect the performance of users applications tested. Compatibility tests were also carried out and the test results show that the new option experiences some compatibility issues with firewalls and wireless networks.
8
Polezel, Wesley Gildo Canducci [UNESP]. "Investigações sobre o impacto da modernização do GNSS no Posicionamento." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/86810.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:22:26Z (GMT). No. of bitstreams: 0
Previous issue date: 2010-02-25Bitstream added on 2014-06-13T20:09:31Z : No. of bitstreams: 1
polezel_wgc_me_prud.pdf: 1240950 bytes, checksum: 142fe3cb11a3c5af3d674c07f9b8cc46 (MD5)Com a inclusão de novos sinais nos satélites GPS e o advento do sistema Galileo, o posicionamento por satélite entrará em uma nova era, trazendo inovações tecnológicas e científicas, principalmente nas combinações entre diferentes sistemas. Logo, verifica-se a importância de analisar a qualidade dos novos sinais, quantificando suas contribuições na acurácia do posicionamento. Visando contribuir com essa demanda, este trabalho tem o intuito de dar continuidade às pesquisas no Brasil sobre a qualidade advinda da modernização do GNSS utilizando os novos sinais transmitidos pelos satélites. O GNSS engloba o GPS, o GLONASS, o Galileo, o SBAS, o Beidou e o LAAS. Entretanto, neste trabalho apenas os sistemas GPS, GLONASS e Galileo serão abordados. Com esses três sistemas é possível realizar combinações lineares para integrá-los no posicionamento por ponto e relativo. Alguns problemas nessa combinação foram detectados com indicações de soluções para os efeitos não modelados. No que concerne aos efeitos da ionosfera, uma combinação ion-free utilizando três freqüências foi apresentada, permitindo eliminar os efeitos de primeira e segunda ordem da ionosfera. Apresenta-se também uma revisão bibliográfica do estado da arte da solução da ambigüidade utilizando esses três sistemas. Além disso, foi realizado um experimento a fim de analisar a qualidade do novo sinal L2C. Nas análises, tal como esperado, os satélites modernizados apresentaram melhores resultados do que os satélites não modernizados. Como o sistema Galileo ainda não está operacional, foi implementado no software GPSeq a interoperabilidade dos sinais GPS e GLONASS e realizadas análises comparando tais sistemas no posicionamento relativo. Além disso, comparou-se os resultados do software GPSeq com softwares comerciais. Os resultados, em alguns momento...
With the addition of new signals in GPS satellites and the advent of Galileo system, the satellite positioning will start a new era, which will require technologic and scientific innovations mainly in combinations of these systems. Therefore, analyzing the new signal quality and quantifying their contribution in the positioning accuracy are very important. Thus, this research points out the importance of continuing investigations in Brazil about GNSS modernization using the new signals transmitted by the satellites. The GNSS include GPS, GLONASS, Galileo, SBAS, Beidou and LAAS. However, in this work only GPS, GLONASS and Galileo system are taken into account. In order to integrate these three systems it is possible to accomplish linear combinations in absolute and relative positioning. Some problems in these combinations were detected and solutions for the unmodeled effects were recommended. For the ionospheric effect, an ion-free combination using three frequencies was performed. This combination can eliminate the ionosphere effects of first and second order. In this paper a bibliographical revision of the ambiguity solution using three systems is accomplished. Furthermore, an experiment was carried out to analyze... (Complete abstract click electronic access below)
9
Takahashi, Atsushi. "Hierarchical Cluster Analysis of Dense GNSS Data and Interpretation of Cluster Characteristics." Kyoto University, 2019. http://hdl.handle.net/2433/244510.
Full text
10
Polezel, Wesley Gildo Canducci. "Investigações sobre o impacto da modernização do GNSS no Posicionamento /." Presidente Prudente : [s.n.], 2010. http://hdl.handle.net/11449/86810.
Full textAbstract:
Resumo: Com a inclusão de novos sinais nos satélites GPS e o advento do sistema Galileo, o posicionamento por satélite entrará em uma nova era, trazendo inovações tecnológicas e científicas, principalmente nas combinações entre diferentes sistemas. Logo, verifica-se a importância de analisar a qualidade dos novos sinais, quantificando suas contribuições na acurácia do posicionamento. Visando contribuir com essa demanda, este trabalho tem o intuito de dar continuidade às pesquisas no Brasil sobre a qualidade advinda da modernização do GNSS utilizando os novos sinais transmitidos pelos satélites. O GNSS engloba o GPS, o GLONASS, o Galileo, o SBAS, o Beidou e o LAAS. Entretanto, neste trabalho apenas os sistemas GPS, GLONASS e Galileo serão abordados. Com esses três sistemas é possível realizar combinações lineares para integrá-los no posicionamento por ponto e relativo. Alguns problemas nessa combinação foram detectados com indicações de soluções para os efeitos não modelados. No que concerne aos efeitos da ionosfera, uma combinação ion-free utilizando três freqüências foi apresentada, permitindo eliminar os efeitos de primeira e segunda ordem da ionosfera. Apresenta-se também uma revisão bibliográfica do estado da arte da solução da ambigüidade utilizando esses três sistemas. Além disso, foi realizado um experimento a fim de analisar a qualidade do novo sinal L2C. Nas análises, tal como esperado, os satélites modernizados apresentaram melhores resultados do que os satélites não modernizados. Como o sistema Galileo ainda não está operacional, foi implementado no software GPSeq a interoperabilidade dos sinais GPS e GLONASS e realizadas análises comparando tais sistemas no posicionamento relativo. Além disso, comparou-se os resultados do software GPSeq com softwares comerciais. Os resultados, em alguns momento... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: With the addition of new signals in GPS satellites and the advent of Galileo system, the satellite positioning will start a new era, which will require technologic and scientific innovations mainly in combinations of these systems. Therefore, analyzing the new signal quality and quantifying their contribution in the positioning accuracy are very important. Thus, this research points out the importance of continuing investigations in Brazil about GNSS modernization using the new signals transmitted by the satellites. The GNSS include GPS, GLONASS, Galileo, SBAS, Beidou and LAAS. However, in this work only GPS, GLONASS and Galileo system are taken into account. In order to integrate these three systems it is possible to accomplish linear combinations in absolute and relative positioning. Some problems in these combinations were detected and solutions for the unmodeled effects were recommended. For the ionospheric effect, an ion-free combination using three frequencies was performed. This combination can eliminate the ionosphere effects of first and second order. In this paper a bibliographical revision of the ambiguity solution using three systems is accomplished. Furthermore, an experiment was carried out to analyze... (Complete abstract click electronic access below)
Orientador: João Francisco Galera Monico
Coorientador: Eniuce Menezes de Souza
Banca: Helio Koiga Kuga
Banca: Daniela Barrocá Marra Alves
Mestre
11
Gessi, Luca. "Analisi e implementazione di tecniche di data fusion GNSS/IMU per localizzazione di precisione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
L'elaborato affronta l'implementazione di una tecnica di fusione dei dati inerziali, provenienti da accelerometro, giroscopio e magnetometro, con misure satellitari ricavate da scheda GNSS/RTK. Il sistema di posizionamento monta su carrello elevatore operante in ambito industriale.
Viene affrontata la modellazione dei sensori inerziali e la loro calibrazione.
Successivamente è stato implementato un generatore di traiettorie tramite il quale vengono simulate le misure dei sensori inerziali.
Infine, l’algoritmo di fusione, implementato tramite filtro di Kalman, è stato analizzato utilizzando i dati simulati.
12
Quan, Yiming. "A new machine learning based method for multi-GNSS data quality assurance and multipath detection." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39748/.
Full textAbstract:
Global Navigation Satellite Systems (GNSS) based high-precision positioning techniques have been widely used in geodesy, attitude determination, engineering survey and agricultural applications. With the modernisation of GNSS, the number of visible satellites and new signals are increasing. Multi-constellation and multi-frequency data provide users with more observations, and hence increase redundancy in parameter estimation. However, increased number of satellites may increase the chance of multipath errors, especially in difficult environments. Therefore, this thesis aims at characterising the measurement signal quality of all available and new signals of multi-GNSS (GPS, GLONASS, Galileo, BDS, and QZSS) with real data. Also, a new multipath detection model based on machine learning methods is developed. The measurement noise levels in all currently available signals have been studied by investigating their double difference (DD) carrier phase residuals. The positioning precision, accuracy, and ambiguity success rate have been assessed using the selected individual GNSS constellations and their selected combinations with static and kinematic antennas in low multipath and severe multipath environments. The statistical results show the residuals vary from 0.5 mm to 2 mm with different signals and models of receivers. Short baseline tests show that in ideal conditions (i.e., a low multipath environment), using a single GNSS constellation (GPS, GLONASS, Galileo, or BDS) or their combinations can usually achieve millimetre-level precision and centimetre-level accuracy with almost 100% ambiguity success rates, regardless if the rover antenna is static or kinematic. In realistic condition (i.e. a severe multipath environment) the positioning precision and accuracy reduce to the centimetre level or even worse with a kinematic antenna. Multipath effect is one of the major error sources in GNSS positioning. Most of the currently available multipath detection and mitigation methods are based on stochastic modelling, advanced techniques in data processing, spatial geometry modelling, and special hardware designs. A new machine learning based multipath detection model is developed for undifferenced measurements (a single receiver approach). The approach is based on the fact that the multipath signature can be found in the multipath contaminated time series, and the features of multipath signature can be learned and identified by machine learning methods. The proposed model has been trained and validated with simulated data in an urban canyon environment with different satellite geometries. Moreover, the model has been trained and tested with real kinematic LoS and multipath data collected with a rotating arm rig in a multipath environment, and tested with multipath data collected near solar panels and near a building. The model has been tested using all available GNSS signals. The results show the model can achieve accuracy of 80%-90% with the simulated GNSS (GPS, Galileo, and BDS) data, and accuracy of 65%-70% with the real data collected using rotating arm rig on GPS L1 and GLONASS L1 signals. Real data collected near solar panels and near a building show that the well-trained model can achieve accuracy of about 60% in completely different multipath environments. The test results show the model was not well trained on GLONASS L2 and BDS data due to their carrier multipath errors are close to their carrier measurement error in ideal environment (low multipath environment).
13
Alshawaf, Fadwa [Verfasser], and S. [Akademischer Betreuer] Hinz. "Constructing water vapor maps by fusing InSAR, GNSS and WRF data / Fadwa Alshawaf. Betreuer: S. Hinz." Karlsruhe : KIT-Bibliothek, 2013. http://d-nb.info/1048384888/34.
Full text
14
Morkel, Izak Gerhardus. "A GPS-based method for pressure corrections to neutron monitor data / Izak G. Morkel." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2054.
Full text
15
Peixoto, da Rocha Cesar. "Proposta de uma tecnologia para levantamento da morfologia costeira com aplicação de tecnologia GNSS." Universidade Federal de Pernambuco, 2009. https://repositorio.ufpe.br/handle/123456789/8196.
Full textAbstract:
Made available in DSpace on 2014-06-12T22:58:05Z (GMT). No. of bitstreams: 2
arquivo1446_1.pdf: 4391997 bytes, checksum: cf2f9970dc31e357b9bdb19b4ffdf45b (MD5)
license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5)
Previous issue date: 2009Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O ambiente costeiro é berçário natural para um grande número de espécies marinhas, principalmente onde ocorrem mangues e recifes, que funcionam como abrigo natural para a desova e início de vida de muitas espécies marinhas. A linha de costa está inserida nesse ambiente, pois representa o limite entre o mar e o continente, no alcance máximo das ondas, onde cessa a ação marinha efetiva. Entretanto, a dinâmica de movimentação das marés torna esse limite uma zona de fronteira de difícil demarcação e monitoramento. Além disso, as alterações geomorfológicas, muitas vezes catalisadas pelas interferências antrópicas, diminuem a capacidade de regeneração natural das praias, dificultando o gerenciamento desse ambiente. Em virtude disso, essa tese desenvolveu alguns experimentos para localizar e monitorar linhas de costa nas praias de Sauaçui e Japaratinga, localizadas no Estado de Alagoas Brasil, aplicando tecnologia de posicionamento dos sistemas GNSS (Global Navigation Satellite System), com base em um indicador de linha de costa com representação matemática, correspondente à máxima altura alcançada pelas marés nos últimos 20 anos, acrescida do run-up, correspondente ao espraio das ondas. O GPS (Global Positioning System), que a partir deste ponto será designado apenas GPS, consiste em um sistema de posicionamento por satélite pertencente ao GNSS e pode gerar posicionamentos no modo dinâmico relativo, com precisão de poucos centímetros e suas técnicas já vem sendo aplicadas em programas de gerenciamento costeiro em várias partes do mundo. Entretanto, as alturas geradas pelo GPS são elipsoidais e representam um problema para o uso desse sistema em aplicações que envolvem altitudes, como é o caso das linhas de costa, que são relacionadas com o nível do mar. A técnica proposta nessa tese gera o modelo de elevação digital da praia, com base em perfis de praia, no mesmo referencial de nível das marés e nele identifica a linha de costa. Para isso, os referenciais verticais de maré e do GPS são correlacionados através de um artifício apropriado que requer o conhecimento das alturas de maré e do GPS em um mesmo local. Os perfis de praia aqui referidos são constituídos de pontos coordenados gerados pelo deslocamento de uma antena GPS em ziguezague ao longo da praia. Essa metodologia mostrou-se adequada para localizar e monitorar linhas de costa com precisão sub-métrica e tem como principal vantagem o fato desse modelo facilitar a visualização do comportamento da linha d´água, sendo apropriado para simular o deslocamento do mar sobre o continente. Os resultados mostram a localização geográfica das linhas de costa das praias objeto desse estudo, expressas no Sistema de Projeção Cartográfica Universal Transverso de Mercator (UTM). O monitoramento da linha de costa provém da comparação do seu traçado, superpondo-se os modelos produzidos em diferentes épocas e indica comportamento sazonal das linhas de costas tanto nas praias de Japaratinga (máximo de 6,0 m), como na praia de Sauaçui (máximo de 8,0 m). Além disso, como o referencial do GPS tem grande estabilidade, ele pode ser usado no monitoramento da estabilidade dos marcos de apoio, cujas coordenadas são suscetíveis de alterações, em havendo subsidências do solo e/ou movimentações de placas da crosta terrestre
16
SHAIKH, MUHAMMAD MUBASSHIR. "GNSS Radio Occultation for Ionospheric Monitoring – Impact and Mitigation of High Solar Activity Effects." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2586161.
Full textAbstract:
The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth, stretching from a height of about 50 km to more than 1000 km. It owes its existence primarily to ultraviolet radiation from the sun. The ionosphere is becoming more relevant to human society with its reliance on modern technology, since the accuracy of navigation and quality of telecommunication is influenced by ionospheric conditions.
The free electrons in the ionosphere affect the propagation of radio waves. Below about 30 MHz the ionosphere acts like a mirror, bending the path traveled by a radio wave back toward the Earth. At higher frequencies, such as those used by GPS, radio waves pass right through the ionosphere. They are, nevertheless, affected by it. Disruption of communications and navigation systems can have severe societal consequences. Even though the ionospheric observational techniques and the ionospheric models have gone through considerable development sustained over many decades, accurate monitoring and forecasting of the ionosphere conditions still presents stubborn challenges.
The global navigation satellite system (GNSS)-based radio occultation (RO) has been proven to be a powerful technique for remotely sensing the earth’s troposphere, stratosphere, and ionosphere in the past decade [8]. Radio occultation is a relatively new technique that can be used to study the ionosphere, offering potentially global and continuous measurements. MARINER IV first applied the RO observation technique to observe the Mars atmosphere and ionosphere in 1965 [48]. MicroLab-1 GPS/MET was launched in 1995 and applied to monitor the Earth’s atmosphere and ionosphere by using GPS RO technique [37,50]. The Global Positioning System (GPS) to Low Earth Orbit (LEO) satellite paths essentially make long, near-horizontal measurements of the integrated content of ionospheric electron density; namely total electron content (TEC). These measurements are not simple to interpret, since the satellite transmission paths map out a complicated and continuously changing measurement geometry. Nevertheless, a strong advantage of this system is that it provides measurements over the oceans and into remote polar caps, thus enabling the ionosphere to be studied on a truly global-scale. The FORMOSAT-3/COSMIC (the most recent and advanced RO mission in operation) was launched in April 2006, and has six micro satellites in different orbital planes. The GPS radio occultation experiment (GOX) is one of the satellite mission objectives, and observes the ionosphere and atmosphere vertical structure by using the RO observation technique. RO observations, particularly from FORMOSAT-3/COSMIC, have significantly improved our capability of monitoring the global ionosphere.
In the ionosphere, the important scientific RO data product is the retrieved electron density profile (Ne(h)) along the tangent points during an occultation event. The Abel inverse transform is the conventional method to analyze the tropospheric occultations and it was natural to adopt this approach for the ionospheric studies. It allows the vertical profile of electron concentration to be obtained, nominally at a single location between the GPS and LEO (onboard RO receiver). The resulting profile is therefore some average of the ionosphere traversed by the occulting ray paths between the two satellites. However, the classical approach of the Abel inversion assumes spherical symmetry of the electron density field in the vicinity of an occultation. In practice, the footprint of an occultation generally covers wide regions and averages any spatial variations connected with variable declinations of the magnetic field from the horizontal direction along the occulted ray path. Indeed, inhomogeneous electron density in the horizontal direction for a given occultation is believed to be the main source of error when using the Abel inversion.
Large amount of research has been done, in last couple of decades, to improve the Abel inversion by removing or reducing the effect of ionospheric asymmetry. One potential and frequently studied and revised method is the Abel inversion aided by other horizontal information such as the global ionospheric map (GIM) [9,30,32,36,42,49,72]. However, due to variability of available maps and the fact that not much attention was paid to the large-scale Abel retrieval error, as illustrated by [54,92,93], no standard procedure have been globally accepted and Abel inversion is still the most widely used technique to produce the ionospheric products using RO technique.
In our research, we have thoroughly investigated the spherical symmetry problem of Abel inversion; qualitatively as well as quantitatively. This was done to first understand what actually is happening when we apply such algorithm for RO data inversion. In the process of this investigation, we were able to find an effective way of quantifying the impact of ionospheric asymmetry on the final product of RO data inversion, i.e., vertical electron density profile. The asymmetry index is based on the electron density variation along the occulted ray path. It efficiently incorporates electron density gradients along the RO ray path to find a number that sums-up the impact of prevailing ionospheric condition, on the final RO product, by giving it a number on a scale from 0 to 1. Our results, based on model simulations, show that the designed algorithm is proving to be an effective technique to find such information quickly and accurately.
Using the knowledge gained during this thorough investigation, to mitigate the impact of spherical symmetry hypothesis from RO data inversion, we have also implemented a very effective technique based on the NeQuick2 (electron density model) adaptation to RO-derived TEC. It relies on the minimization of a cost function involving experimental and model-derived TEC data to determine the NeQuick2 input parameters (local ionization parameters) at the wanted locations and time. These parameters are then used to evaluate the electron density profile along the ray perigee positions associated to the relevant RO event. The results indicate that the technique significantly improved the RO inversion product and is able to avoid the presence of negative electron density values in the reconstructed profiles. Furthermore, no external data, such as GIM maps or other data, is required to apply the technique. The technique is currently under development and, when fully developed, will not only provides a solution to a long awaited problem (spherical symmetry hypothesis) to be solved related to RO data processing, but also defines some new concepts on which RO technique may be used in future research related to the ionosphere. This will be a significant contribution for RO scientific community, specifically, when a large increase in RO observations (from approximately 1,500 to 12,000 per day) is expected with the launch of COSMIC-2 RO mission in the next few years.
17
Dejan, Vasić. "Model geodetskog premera savremenim akvizicionim tehnologijama." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2018. https://www.cris.uns.ac.rs/record.jsf?recordId=106256&source=NDLTD&language=en.
Full textAbstract:
Prikupljanje prostornih podataka se danas, u projektima premera i obnovepremera, različitim projektima iz oblasti inženjerske geodezije, realizujekonvencionalnim metodama, koje najčešće obezbeđuju traženu tačnostizlaznih podataka. Sa druge strane, razvojem novih tehnologija i uređaja zaprikupljanje podataka nameću se i nove metode rada koje obezbeđujuneuporedivo veći nivo detaljnosti od konvencionalnih metoda pa veomačesto imaju prednost u odnosu na konvencionalne metode naročito uprojektima inženjerske geodezije. U disertaciji je dat predlog modelageodetskog premera savremenim akvizicionim tehnologijama koji ispunjavakriterijume kvaliteta definisane pravilnikom o premeru zemljišta i kriterijumeinženjerske geodezije.The collection of spatial data is carried out today by conventional methods,which usually provide the required accuracy of the output data in the projectsof diameter and diameter reconstruction, by various projects in the field ofengineering geodesy. On the other hand, the development of newtechnologies and data collection devices imposes new methods of work thatprovide an incomparably higher level of detail than conventional methods,and they often have an advantage over conventional, especially inengineering projects. In the dissertation, the model of geodetic diametermodel was presented with modern acquisition technologies that meets thequality criteria defined by the Land Regulations Rulebook and the criteria ofengineering geodesy.
18
Guner, Dunya Rauf Levent. "Inertial Navigation Sytem Improvement Using Ground Station Data." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615036/index.pdf.
Full textAbstract:
Missile navigation systems rely on hybrid INS/GPS systems to employ lower grade inertial sensors for the sake of cost and availability. Current inertial navigation systems on missiles can perform accurately for a limited time without GPS aiding. However, GPS is the most likely system that is going to be jammed in a crisis or war by low cost jammers by any opposing force. Missiles do not have adequate equipment to maintain accuracy when GPS is jammed completely in the battle area.
In this thesis, a new method is proposed to improve performance of INS systems onboard missiles and autonomous aerial vehicles with EO sensors in a GPS denied environment. Previously laid ground based beacons are used by the missile EO/IIR seeker for bearing-only measurements and position updates are performed by the use of modified artillery survey algorithms based on triangulation techniques which involve angle measurements.
For mission planning, two main problems are identified as deployment problem and path planning problem and a tool for the optimal laying of beacons for a given desired trajectory and optimal path planning for a given network of beacons is developed by using evolutionary algorithms and results for test scenarios are discussed.
19
Haselmaier, Lawrence H. "Computation of a Virtual Tide Corrector to Support Vertical Adjustment of Autonomous Underwater Vehicle Multibeam Sonar Data." ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2080.
Full textAbstract:
One challenge for Autonomous Underwater Vehicle (AUV) multibeam surveying is the limited ability to assess internal vertical agreement rapidly and reliably. Applying an external ellipsoid reference to AUV multibeam data would allow for field comparisons. A method is established to merge ellipsoid height (EH) data collected by a surface vessel in close proximity to the AUV. The method is demonstrated over multiple collection missions in two separate areas. Virtual tide corrector values are derived using EH data collected by a boat and a measured ellipsoid to chart datum separation distance. Those values are compared to measurements by a traditional tide gauge installed nearby. Results from the method had a mean difference of 6 centimeters with respect to conventional data and had a mean total propagated uncertainty of 15 centimeters at the 95% confidence interval. Methodologies are examined to characterize their accuracies and uncertainty contribution to overall vertical correction.
20
Hannay, Peter. "A non-device specific framework for the development of forensic locational data analysis procedure for consumer grade small and embedded devices." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2017. https://ro.ecu.edu.au/theses/2026.
Full textAbstract:
Portable and wearable computing devices such as smart watches, navigation units, mobile phones, and tablet computers commonly ship with Global Navigation Satellite System (GNSS) supported locational awareness. Locational functionality is no longer limited to navigation specific devices such as satellite navigation devices and location tracking systems. Instead the use of these technologies has extended to become secondary functionality on many devices, including mobile phones, cameras, portable computers, and video game consoles. The increase in use of location aware technology is of use to forensic investigators as it has the potential to provide historic locational information. The evidentiary value of these devices to forensic investigators is currently limited due to the lack of available forensic tools and published methods to properly acquire and analyse these data sources. This research addresses this issue through the synthesis of common processes for the development of forensic procedure to acquire and interpret historic locational data from embedded, locationally aware devices.
The research undertaken provides a framework for the generation of forensic procedure to enable the forensic extraction of historical locational data. The framework is device agnostic, relying instead on differential analysis and structured testing to produce a validated method for the extraction of locational history. This framework was evaluated against five devices, selected on a basis of market penetration, availability and a stage
of deduplication.
The examination of the framework took place in a laboratory developed specifically for the research. This laboratory replicates all identified sources of location data for the devices selected. In this case the laboratory is able to simulate cellular (2G and 3G), GNSS (NAVSTAR and GLONASS), and Wi-Fi locationing services. The laboratory is a closed-sky facility, meaning that the laboratory is contained within a faraday cage and all signals are produced and broadcast internally.
Each selected device was run through a series of simulations. These simulations involved the broadcast of signals, replicating the travel of a specific path. Control data was established through the use of appropriate data recording systems, for each of the simulated location signals. On completion of the simulation, each device was forensically acquired and analysed in accordance with the proposed framework.
For each experiment carried out against the five devices, the control and experimental data were compared. In this examination any divergence less than those expected for GNSS were ignored. Any divergence greater than this was examined to establish cause.
Predictable divergence was accepted and non-predictable divergence would have been noted as a limitation. In all instances where data was recovered, all divergences were found to be predictable.
Post analysis, the research found that the proposed framework was successful in producing locational forensic procedure in a non-device specific manner. This success was confirmed for all the devices tested.
21
Raabe, Armin, Michael Bender, and Jens Wickert. "Final results of the DFG funded project “Development of a tomographic water vapour sounding system based on GNSS data”." Universität Leipzig, 2013. https://ul.qucosa.de/id/qucosa%3A16410.
Full textAbstract:
Since 2008 a group of scientists of the Leipzig Institute of Meteorology (LIM) and the German Research Centre for Geosciences Potsdam (GFZ) develops a method to derive water vapour profiles out of continuously available GNSS data (Global Navigation Satellite System). The aim of this project - supported by the Deutsche Forschungsgemeinschaft (DFG) - was to develop a processing system with related scientific algorithms, which uses data of regional GNSS ground networks to derive 3D water vapour distributions above these stations. This systems use the line of sight water vapour information from each ground station to every GNSS satellite in view (slants) as basis of a 3D tomographic reconstruction. At this time these reconstructions are based on GNSS data of about 330 German or near Germany located groundstations. This leads to a horizontal resolution of the
reconstructed 3D water vapour field up to 40km and a vertical resolution of about 0.5km from the upper part of troposphere down to the atmospheric boundary layer (1km height).Seit 2008 befasst sich eine Arbeitsgruppe von Wissenschaftlern am LIM und dem GFZ in Potsdam im Rahmen eines DFG-geförderten Projektes mit der Ableitung von dreidimensionalen Wasserdampfverteilungen in der Atmosphäre aus Beobachtungsdaten regionaler GNSS-Bodennetze (GlobaleNavigationsSatellitenSysteme). Die Wasserdampfverteilungen können aus der atmosphärischen Information entlang der Sichtlinien zwischen den Bodenstationen und den sichtbaren GNSS-Satelliten (sogenannte Slants) berechnet werden. Diese zahlreichen Sichtlinien ermöglichen eine tomographische Verarbeitung der Daten. Der entwickelte tomographische Algorithmus nutzt derzeit bis zu 330 deutsche und nahe Deutschland gelegene GNSS-Stationen, was eine horizontale Auflösung der resultierenden 3D-Felder von 40km und einer vertikalen Auflösung von 0,5km bis hinab zur atmosphärischen Grenzschicht (bis 1 km über dem Boden) ermöglicht
22
Tonetto, Leonardo. "A Particle Filter approach to GPS signals." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177320.
Full textAbstract:
Localization systems nowadays are extensively used by a growing number of mobile devices, such as smartphones and tablets integrated with various applications, and their use for traditional purposes such as navigation and geodesy have pushed the development of new techniques and improved algorithms. The combination of multiple techniques is the most common approach. Global Navigation Satellite Systems, such as GPS are well known and established localization systems that have great accuracy but are limited to locations where the strength of the signal is good. Therefore a new approach that could increase the sensitivity and even the accuracy by using GPS could benet a large group of users. This thesis originally proposes a new approach for these signals, based on Particle Filters that proved to work well in mitigating problems in an audio-based localization system. The results obtained show that this approach can increase the sensitivity of the system as a whole and positions estimations can be achieved under conditions that previous systems were not able to.
23
Orliac, Etienne J. "Development of azimuth dependent tropospheric mapping functions, based on a high resolution mesoscale numerical weather model, for GNSS data processing." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10861/.
Full textAbstract:
This thesis is dedicated to the development of two new tropospheric mapping functions for GNSS data processing, based on a high resolution mesoscale numerical weather model (NWM). NWMs have proven to be beneficiary in the processing of GNSS and VLBI data, both for deriving mapping functions and for providing a priori information such as zenith hydrostatic delay (ZHD). The mapping functions derived here make a greater use of the NWM information than the mapping functions currently recommended by the International GNSS Service. In addition to using a single vertical pro¯le at the site in order to derive mapping functions under the assumption of an azimuthally symmetric atmosphere, the NWM was also ray traced every thirty degrees in azimuth. This way, a complete volume of the atmosphere is sensed, and better modelling is expected if the NWM does indeed provide an accurate representation of the atmosphere, by accounting for azimuthal variations. An emphasis was put in this thesis on assessing the mathematical models used to vertically interpolate meteorological information, as they play a key role in computing the refractivities in the ray tracing algorithm. Error sources were identified and quantified. As expected, water vapour is the major source of error. However, the results showed that the model used for the total pressure induced a systematic bias. To derive an azimuth dependent mapping function, the Marini model traditionally used had to be left in favor of a cubic spline interpolation (CSI). This new approach was validated by comparing the performance of the new azimuthally symmetric mapping functions against the updated Vienna mapping functions (VMF1), the best mapping functions currently available. Similar positioning performances were obtained, therefore validating the CSI based approach. The performance of new azimuth dependent mapping functions (AMF) in handling the troposphere asymmetry were compared to those obtained when estimating horizontal tropospheric gradients with an azimuthally symmetric mapping function. Results show a good agreement in the modelling of the asymmetry, and that estimating gradients is justified. The gradient solution performed better overall, although it failed for some sites, and better inter-station consistency was obtained with the AMF. This thesis also investigated the role of the tropospheric modelling in the retrieval of the atmospheric pressure loading (APL) in GNSS data processing, which is now part of the IGS 2008 recommendations. The results show that differential height time series obtained with different tropospheric modelling can correlate with the APL signal to a level up to 0.7. In other words, the choice of tropospheric modelling strategy does greatly influence the retrieval of the APL.
24
Caparra, Gianluca. "Authentication and Integrity Protection at Data and Physical layer for Critical Infrastructures." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3421920.
Full textAbstract:
This thesis examines the authentication and the data integrity services in two prominent emerging contexts such as Global Navigation Satellite Systems (GNSS) and the Internet of Things (IoT), analyzing various techniques proposed in the literature and proposing novel methods.
GNSS, among which Global Positioning System (GPS) is the most widely used, provide affordable access to accurate positioning and timing with global coverage. There are several motivations to attack GNSS: from personal privacy reasons, to disrupting critical infrastructures for terrorist purposes.
The generation and transmission of spoofing signals either for research purpose or for actually mounting attacks has become easier in recent years with the increase of the computational power and with the availability on the market of Software Defined Radios (SDRs), general purpose radio devices that can be programmed to both receive and transmit RF signals.
In this thesis a security analysis of the main currently proposed data and signal level authentication mechanisms for GNSS is performed. A novel GNSS data level authentication scheme, SigAm, that combines the security of asymmetric cryptographic primitives with the performance of hash functions or symmetric key cryptographic primitives is proposed. Moreover, a generalization of GNSS signal layer security code estimation attacks and defenses is provided, improving their performance, and an autonomous anti-spoofing technique that exploits semi-codeless tracking techniques is introduced.
Finally, physical layer authentication techniques for IoT are discussed, providing a trade-off between the performance of the authentication protocol and energy expenditure of the authentication process.Questa tesi esamina i servizi di autenticazione e la protezione di integrità in due contesti emergenti come Global Navigation Satellite Systems (GNSS) e the Internet of Things (IoT), analizzando varie tecniche proposte in letteratura e proponendone di originali. I sistemi di navigazione satellitare, di cui il più conosciuto ed utilizzato è GPS, forniscono servizi di posizionamento e sincronizzazione temporale con copertura globale. Esistono vari motivi per attaccare GNSS: dai motivi legati alla privacy, all’attaccare infrastrutture critiche per scopi terroristici. La generazione e trasmissione di segnali GNSS contraffatti, per scopi di ricerca o per effettuare attacchi, è diventata più semplice negli ultimi anni con l’aumento della potenza computazionale e la disponibilità di Software Defined Radios (SDRs), dispositivi radio general purpose che possono essere programmati sia per ricevere che per trasmettere segnali RF. Questa tesi fa una analisi di sicurezza delle principali tecniche di autenticazione per GNSS proposte in letteratura, sia al livello dati che al livello di segnale. È proposto uno schema originale di autenticazione al livello dati, SigAm, che combina la sicurezza delle primitive crittografiche asimmetriche con le performance delle funzioni di hashing o di funzioni crittografiche simmetriche. Inoltre, è proposta una generalizzazione degli attacchi security code estimation and replay e delle rispettive tecniche di difesa, migliorando le prestazioni in entrambi i versanti, ed è proposta una tecnica anti-spoofing autonoma che usa semi-codeless tracking. Infine, sono discusse tecniche di autenticazione a livello fisico applicate ad IoT, mettendo in risalto il trade-off tra le performance e il costo energetico del processo di autenticazione.
25
Hotta, Kohei. "Style and process of magma intrusion based on combined ground deformation data in and around Sakurajima volcano, southern Kyushu, Japan." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215323.
Full text
26
Leksell, Torbjörn. "A Comparison of Smartphone GPSL1 and Galileo E1-B/C Spoofing Resilience." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292950.
Full textAbstract:
Location-based services have grown in importance as smartphones, and location-based applications have become an integral part of everyday life. While Global Navigation Satellite Systems (GNSSs) provide the most accurate position determination, open service GNSS signals remain unprotected and susceptible to spoofing attacks. Previous work within the domain highlighted this issue, with many smartphone receivers shown susceptible to GPS L1 spoofing, suggesting that their resilience experiments should be extended to include other GNSS signals in the future. Given that multi-GNSS receivers now have become the norm in smartphones, this thesis investigates whether smartphone GNSS receiver spoofing resilience depends on the type of signal; by conducting a series of comparative spoofing experiments involving GPS L1 and Galileo E1-B/C signals. To conduct the experiments, we developed a Galileo E1-B/C signal simulator that, together with the open-source GPS-SDR-SIM signal simulator, was the basis for conducting a series of experiments designed to identify the potential presence of anti-spoofing measures. The result of our experiments indicates that smartphone multi-GNSS receivers were significantly more resilient towards Galileo E1-B/C spoofing attacks, often accepting GPS L1 signals with significant position, time, and data errors, while refusing to accept corresponding Galileo E1-B/C signals. While we never observed cases of E1-B/C signals being accepted while rejecting GPS L1 signals, external factors limited the scope of the investigation and do not allow a generalized conclusion. As such, to deepen our understanding of these issues and how they relate to the development of anti-spoofing measures and trust in different signals, it is essential to extend this research to include more devices and other GNSS signals.Positionstjänster har växt i betydelse allteftersom smarttelefoner och positionsapplikationer har blivit en integral del av våran vardag. Även om satellitpositionering utger det mest precisa och vedertagna positionsbestämningen av tillgängliga positionstjänser så är de publika satellitnavigeringssignalarna oskyddade och sårbara för förfalskningsattacker. Tidigare forskning inom området har evaluerat dessa sårbarheter och visat att ett betydande antal smarttelefoner var sårbara för GPS-L1 förfalskningsattacker och att denna forskning borde utökas i framtiden allteftersom satellitnavigeringsmottagare med förmåga att mottaga olika satellitsignaler integreras i smarttelefoner. Givet att en majoritet av nya smarttelefoner nu integrerar denna typ av mottagare så utvärderar detta arbete hur sårbarheten mot förfalskningsattacker beror på typ av satellitsignal genom en komparativ jämförelse av sårbarhet mellan GPS-L1 och den nyare Galileo E1-B/C signalen. För att genomföra utvärderingen så utvecklade vi en Galileo E1-B/C signalsimulator som tillsammans med GPS-L1 signalsimulatorn (GPS-SDR-SIM) utgjorde grunden för en serie av experiment designade för att identifiera och utvärdera sårbarheter och potentiella motåtgärder i smarttelefoner. Våra resultat indikerar att smarttelefoner är betydligt mer sårbara for GPS-L1 forfalskningsattacker då de accepterade GPS-L1 signaler med betydande position, tid, och datafel medans motsvarande Galileo E1-B/C signaler ej accepterades. Trots resultaten så är det viktigt att inte dra för starka slutsatser då underlaget var kraftigt begränsat givet rådande omständigheter (Covid), som gjorde det svårt/omöjligt att på ett säkert sätt samla volontärer med olika smarttelefoner för våra experiment. Därav så är det viktigt att i framtiden utöka arbetet med ett större underlag och fler signaltyper.
27
Suneson, Oscar. "Spatial Variability in the Ionosphere and GNSS Signal Delays in the L-band: A Direct Comparison of In-Situ Satellite- and Swepos-Data." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448889.
Full textAbstract:
It has been shown that ionospheric irregularities can disturb our GNSS (Global Navigation Satellite System) communication. This disturbance is caused by scintillation of the radio signals when they pass through the ionosphere, leading to lock-on difficulties or in worst case, a loss of position for the GNSS-receiver. In this study, a large number of ground based GNSS reference stations spread across Sweden (known as the Swepos-network) was used to measure the variability of the GNSS-signal. These measurements were then combined with observations of ionospheric irregularities made by the Langmuir probes on ESA’s SWARM satellites. The study is a collaboration between Uppsala University and the Swedish Institute of Space Physics and covers five events between December 2013 to Mars 2021, when both datasets were available. The purpose is to determine the shape and extension of these ionospheric irregularities and how localized in time and space they are. The study also tries to answer whether it is possible to draw any conclusions regarding physical models such as diffraction or refraction from this comparison. It was found that during the event days, there was in general a clear increase (of often several hundred percent) of the spatial variability on different scales according to the standard deviation. This increase was seen for both the lower orbiting SWARM A and C satellites and the higher orbiting SWARM B. It was also possible to see that the increase of spatial variability was spread across all the studied latitudes, (magnetic latitude 49° to 70°). This corresponds well with the fact that all the analysed event days had an GNSS-signal variability above average for the same latitudes. There seems to be a clear connection between increased GNSS-signal variability and ionospheric irregularities, although more studies need to be done to be able to draw more accurate conclusions.
28
Bedada, Tullu Besha. "Absolute geopotential height system for Ethiopia." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4726.
Full textAbstract:
This study used airborne gravity data, the 2008 Earth Gravity Model (EGM08) and Shuttle Radar Topographic Mission (SRTM) digital elevation data in a ‘Remove-Compute-Restore’ process to determine absolute vertical reference system for Ethiopia. This gives a geopotential height at any isolated field point where there is a Global Navigation Satellite System (GNSS) measurement without reference to a vertical network or a regional datum point. Previously, height was determined conventionally by connecting the desired field point physically to a nearby bench mark of a vertical network using co-located measurements of gravity and spirit levelling. With the use of precise GNSS positioning and a gravity model this method becomes obsolesce. The new approach uses the ‘Remove-Restore’ process to eliminate longer to shorter wavelengths from the measured gravity data using EGM08 and geometrical and condensed gravity models of the SRTM data. This provides small, smooth and localised residuals so that the interpolation and integration involved is reliable and the Stokes-like integral can be legitimately restricted to a spherical cap. A very fast, stable and accurate computational algorithm has been formulated by combining ‘hedgehog’ and ‘multipoint’ models in order to make tractable an unavoidably huge computational task required to remove the effects of about 1.5 billion! SRTM topographic mass elements representing Ethiopia and its immediate surroundings at 92433 point airborne gravity observations. The compute stage first uses an iterative Fast Fourier Transform (FFT) to predict residual gravity at aircraft height as a regular grid on to the surface of the ellipsoidal Earth and then it used a Fourier operation equivalent to Stokes’ integral to transform the localised gravity disturbance to residual potential. The restore process determines the geopotential number on or above the Earth’s surface where practitioners need it by restoring the potential effects of the removed masses. The accuracy of the geopotential number computed from gravity and topography was evaluated by comparing it with the one derived directly from EGM08 and precise geodetic levelling. The new model is in a good agreement across 100 km baseline with a standard deviation of 56 10−2 2 −2 × m s and 39 10−2 2 −2 × m s relative to EGM08 and levelling, respectively ( 10−2 2 −2 m s is approximately equivalent to 1mm of height). The new method provides an absolute geopotential height of a point on or above the Earth’s surface in a global sense by interpolating from geopotential models prepared as the digital grids carried in a chip for use with the GNSS receiver in the field.
29
Itoh, Yuji. "Crustal Deformation Model of the Southern Kurile Subduction Zone Inferred from Geodetic Observation Data." Kyoto University, 2020. http://hdl.handle.net/2433/253092.
Full text
30
Waqar, Adnan. "Enhancing the capabilities of electronic performance tracking system for applications in sports." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2562.
Full textAbstract:
The success of electronic technologies has sparked interest in sports amongst coaches, athletes and sports scientists. Consequently, the sporting world has witnessed a rapid rise in sports technologies in recent years. In sports, technologies can assist in a variety of ways, ranging from winner selection to athlete injury prevention. In recent years, wearable technologies have become popular in sports. Wearable microtechnology devices, commonly known as electronic performance tracking system (EPTS) in sports, can be used to monitor and improve an athlete's performance. EPTSs can also play an important role in injury prevention. This thesis investigates the performance of wearable EPTSs and presents solutions to improve the accuracy of EPTSs in sports.
For an EPTS to capture and accurately quantify important athlete-related parameters, such as speed, distance covered, number and intensity of sprints, change of direction (COD), and positioning and movement, data is of vital importance. Whilst satellite-based positioning systems require a relatively short setup time, their accuracy and reliability are often low. Wearable inertial sensors may be able to track an athlete's movements, but they can also be noisy and their error accumulates over time. Consequently, designing an accurate and wearable EPTS is a complex task and requires critical investigation. This featured as the key motivation for this research, whose findings are presented in this thesis.
In this thesis, a new ultra-wide band (UWB)-based positioning system is proposed to increase the accuracy of an EPTS in indoor sports. A close analysis of real-world experiments is presented, and limitations associated with the UWB-based positioning systems are highlighted. In forming an economical hardware solution, geometric and machine learning algorithms are introduced. The accuracy of the developed solution is compared against conventional positioning systems. To mitigate errors in UWB-based indoor positioning systems, a range error reduction technique is introduced. The optimal hardware setup and complexity for implementing the proposed positioning solution are also discussed.
In order to track an athlete's movements using real-world data, a multi-sensor data fusion approach is introduced for measuring/tracking athletes' change of direction (COD) detection and quantification. This COD data is then used to reduce divergence errors incurred in state estimation-based particle filter algorithms. The developed solution achieves significant improvements as compared to existing techniques. Overall, the proposed EPTS solution offers higher accuracy in tracking an athlete's position and movement data. Further, the proposed solution enables the use of EPTS in indoor environments.
31
Jílek, Tomáš. "Pokročilá navigace v heterogenních multirobotických systémech ve vnějším prostředí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-234530.
Full textAbstract:
The doctoral thesis discusses current options for the navigation of unmanned ground vehicles with a focus on achieving high absolute compliance of the required motion trajectory and the obtained one. The current possibilities of key self-localization methods, such as global satellite navigation systems, inertial navigation systems, and odometry, are analyzed. The description of the navigation method, which allows achieving a centimeter-level accuracy of the required trajectory tracking with the above mentioned self-localization methods, forms the core of the thesis. The new navigation method was designed with regard to its very simple parameterization, respecting the limitations of the used robot drive configuration. Thus, after an appropriate parametrization of the navigation method, it can be applied to any drive configuration. The concept of the navigation method allows integrating and using more self-localization systems and external navigation methods simultaneously. This increases the overall robustness of the whole process of the mobile robot navigation. The thesis also deals with the solution of cooperative convoying heterogeneous mobile robots. The proposed algorithms were validated under real outdoor conditions in three different experiments.
32
Gentilini, Lorenzo. "Kalman Filters: Linear and Nonlinear applications in Sensor Fusion." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Find full textAbstract:
Autonomous navigation is nowadays one of the hottest topic among engineering research fields and, as a matter of facts, the number of researches which are working on this field increased a lot in last years and it is expected to increase even more in future. One of the main problem, which can be encountered when facing with autonomous navigation, is the gathering of information coming from different sensors. The autonomous devices are, in fact, equipped with a large number of perception tools useful to build a model of the surrounding environment. The main question to which this dissertation aims to found an answer, is: how can this large number of data be combined in order to exploit all the available information and to obtain an improved, unique and more reliable estimation of the interesting variable?
Therefore, the objective of this dissertation is the study of different techniques of state estimation which can be used to build different data fusion algorithms. In particular the focus is on Kalman-based data fusion techniques, the theory behind this kind of algorithms is deeply analyzed and the performances of them are tested by means of a real application: a Kalman-based method is used to combine data coming from visual odometry, IMU, GNSS module and encoders in order to estimate the absolute position of a UGV within a semistructured environment, such as an orchard.
33
Sorge, Alberto. "Analisi di sensibilità di strumentazione GNSS a basso costo ed elaborazione dati mediante software libero GoGPS." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13994/.
Full text
34
DI, PIETRA VINCENZO. "Seamless Positioning and Navigation in Urban Environment." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2732878.
Full text
35
Lassoued, Khaoula. "Localisation de robots mobiles en coopération mutuelle par observation d'état distribuée." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2289/document.
Full textAbstract:
On étudie dans cette thèse des méthodes de localisation coopérative de robots mobiles sans utilisation de mesures extéroceptives relatives, comme des angles ou des distances entre robots. Les systèmes de localisation considérés sont basés sur des mesures de radionavigation sur des balises fixes ou des satellites. Pour ces systèmes, on observe en général un écart entre la position observée et la position réelle. Cet écart systématique (appelé biais) peut être dû à une mauvaise position de la balise ou à une différence entre la propagation réelles des ondes électromagnétiques par rapport aux conditions standard utilisées pour établir les modèles d’observation. L’influence de ce biais sur la localisation des robots est non négligeable. La coopération et l’échange de données entre les robots (estimations des biais, estimations des positions et données proprioceptives) est une approche qui permet de corriger ces erreurs systématiques. La localisation coopérative par échange des estimations est sujette aux problèmes de consanguinité des données qui peuvent engendrer des résultats erronés, en particulier trop confiants. Lorsque les estimations sont utilisées pour la navigation autonome à l’approche, on doit éviter tout risque de collision qui peut mettre en jeu la sécurité des robots et des personnes aux alentours. On doit donc avoir recours à un mécanisme d’intégrité vérifiant que l’erreur commise reste inférieure à une erreur maximale tolérable pour la mission. Dans un tel contexte, il est nécessaire de caractériser des domaines de confiance fiables contenant les positions des robots mobiles avec une forte probabilité. L’utilisation des méthodes ensemblistes à erreurs bornées est considérée alors comme une solution efficace. En effet, ce type d’approche résout naturellement le problème de consanguinité des données et fournit des domaines de confiance fiables. De surcroît, l’utilisation de modèles non-linéaires ne pose aucun problème de linéarisation. Après avoir modélisé un système coopératif de nr robots avec des mesures biaisées sur des balises, une étude d’observabilité est conduite. Deux cas sont considérés selon la nature des mesures brutes des observations. En outre, des conditions d’observabilité sont démontrées. Un algorithme ensembliste de localisation coopérative est ensuite présenté. Les méthodes considérées sont basées sur la propagation de contraintes sur des intervalles et l’inversion ensembliste. La coopération est effectuée grâce au partage des positions estimées, des biais estimés et des mesures proprioceptives.L’échange des estimations de biais permet de réduire les incertitudes sur les positions des robots. Dans un cadre d’étude simple, la faisabilité de l’algorithme est évaluée grâce à des simulations de mesures de distances sur balises en utilisant plusieurs robots. La coopération est comparée aux méthodes non coopératives. L’algorithme coopératif ensembliste est ensuite testé sur des données réelles en utilisant deux véhicules. Les performances de la méthode ensembliste coopérative sont enfin comparées avec deux méthodes Bayésiennes séquentielles, notamment une avec fusion par intersection de covariance. La comparaison est conduite en termes d’exactitude et d’incertitudeIn this work, we study some cooperative localization issues for mobile robotic systems that interact with each other without using relative measurements (e.g. bearing and relative distances). The considered localization technologies are based on beacons or satellites that provide radio-navigation measurements. Such systems often lead to offsets between real and observed positions. These systematic offsets (i.e, biases) are often due to inaccurate beacon positions, or differences between the real electromagnetic waves propagation and the observation models. The impact of these biases on robots localization should not be neglected. Cooperation and data exchange (estimates of biases, estimates of positions and proprioceptive measurements) reduce significantly systematic errors. However, cooperative localization based on sharing estimates is subject to data incest problems (i.e, reuse of identical information in the fusion process) that often lead to over-convergence problems. When position information is used in a safety-critical context (e.g. close navigation of autonomous robots), one should check the consistency of the localization estimates. In this context, we aim at characterizing reliable confidence domains that contain robots positions with high reliability. Hence, set-membership methods are considered as efficient solutions. This kind of approach enables merging adequately the information even when it is reused several time. It also provides reliable domains. Moreover, the use of non-linear models does not require any linearization. The modeling of a cooperative system of nr robots with biased beacons measurements is firstly presented. Then, we perform an observability study. Two cases regarding the localization technology are considered. Observability conditions are identified and demonstrated. We then propose a set-membership method for cooperativelocalization. Cooperation is performed by sharing estimated positions, estimated biases and proprioceptive measurements. Sharing biases estimates allows to reduce the estimation error and the uncertainty of the robots positions. The algorithm feasibility is validated through simulation when the observations are beacons distance measurements with several robots. The cooperation provides better performance compared to a non-cooperative method. Afterwards, the cooperative algorithm based on set-membership method is tested using real data with two experimental vehicles. Finally, we compare the interval method performance with a sequential Bayesian approach based on covariance intersection. Experimental results indicate that the interval approach provides more accurate positions of the vehicles with smaller confidence domains that remain reliable. Indeed, the comparison is performed in terms of accuracy and uncertainty
36
Toledo, Moreo Rafael. "Un sistema de navegación de alta integridad para vehículos en entornos desfavorables." Doctoral thesis, Universidad de Murcia, 2006. http://hdl.handle.net/10803/10923.
Full textAbstract:
Algunas aplicaciones de carretera actuales, tales como los servicios de información al viajero, llamadas de emergencia automáticas, control de flotas o telepeaje eletrónico, requieren una solución de calidad al problema del posicionamiento de un vehículo terrestre, que funcione en cualquier entorno y a un coste razonable. Esta tesis presenta una solución a este problema, fusionando para ello la información procedente principalmente de sensores de navegación por satélite y sensores inerciales. Para ello emplea un nuevo filtro de fusion multisensorial IMM-EKF. El comportamiento del sistema ha sido analizado en entornos reales y controlados, y comparado con otras soluciones propuestas. Finalmente, su aplicabilidad al problema planteado ha sido verificada.Road applications such as traveller information, automatic emergency calls, freight management or electronic fee, collection require a onboard equipment (OBE) capable to offer a high available accurate position, even in unfriendly environments with low satellite visibility at low cost. Specifically in life critical applications, users demand from the OBEs accurate continuous positioning and information of the reliability of this position. This thesis presents a solution based on the fusion of Global Navigation Satellite Systems (GNSS) and inertial sensors (GNSS/INS), running an Extended Kalman Filter combined with an Interactive Multi-Model method (IMM-EKF). The solution developed in this work supplies continuous positioning in marketable conditions, and a meaningful trust level of the given solution. A set of tests performed in controlled and real scenarios proves the suitability of the proposed IMM-EKF implementation, as compared with low cost GNSS based solutions, dead reckoning systems and single model extended Kalman filter (SM-EKF) solutions.
37
Chiriaco, Isabella. "Sviluppo e caratterizzazione di metodi numerici per la stima del ritardo ionosferico tramite dati GNSS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22946/.
Full textAbstract:
In questo elaborato di tesi, tramite lo sviluppo di un software in Matlab, verrà mostrata la procedura di stima del ritardo ionosferico a partire dai dati originali GNSS e la creazione di calibrazioni ionosferiche in formato CSP, compatibili con i software di determinazione orbitale. Verranno mostrati diversi algoritmi di stima basati sull’estrazione del Vertical Total Electron Content da mappe bidimensionali globali, assumendo tutta la ionosfera terrestre condensata su un guscio sottile ad una determinata altezza. Confrontando i diversi metodi, verranno selezionati i parametri per la generazione delle CSP. Infine, il ritardo ionosferico stimato verrà confrontato con le calibrazioni generate indipendentemente da JPL, relative ad una serie di passaggi di Juno presso le stazioni DSN di Madrid, Canberra e Goldstone. Si mostrerà che il ritardo ionosferico stimato sarà compatibile in prima approssimazione con il ritardo generato da JPL, mantenendo però un valore dei residui troppo alto, tale da non poter validare il metodo proposto. Per cui, per studiare e analizzare i motivi della differenza nei risultati, sarà necessario effettuare ulteriori approfondimenti.
38
Tonna, Arianna. "Sviluppo e caratterizzazione di metodi numerici per la stima del ritardo troposferico tramite dati GNSS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22852/.
Full textAbstract:
Lo scopo di questo elaborato finale consiste nella realizzazione di un software in Matlab per la stima del ritardo troposferico a partire da dati GNSS (Global Navigation Satellite System) e da misure meteorologiche locali raccolte presso le stazioni di terra.
Nello specifico, verranno descritti in dettaglio i metodi utilizzati per la stima delle componenti del ritardo troposferico e le procedure che portano alla realizzazione dei prodotti finali di calibrazione, compatibili con i principali software di determinazione orbitale.
Come verifica dei metodi e delle assunzioni proposte, si effettuerà un confronto tra le calibrazioni ottenute e in particolare, verranno analizzati una serie di passaggi dello spacecraft Juno presso le stazioni di terra del DSN (Deep Space Network) di Goldstone, Canberra e Madrid, per i quali verranno caratterizzate le performances tramite un’analisi statistica dei valori di RMS (scarto quadratico medio) dei residui.
I risultati proposti risultano compatibili con le calibrazioni del JPL (Jet Propulsion Laboratory) a meno di un offset nella componente idrostatica che sono stati caratterizzati e che richiederanno un’ulteriore analisi.
39
Varli, Dogan. "Modulation Coding In A Radio Link And Data Transfer Application Using L2 VPN Ethernet Over MPLS In A Large Network." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-20961.
Full textAbstract:
In this thesis work, the locations where we are unable to reach via fiber are considered for wireless transmission links. In the practical part of this thesis different modulation techniques and antenna sizes were analyzed in order to provide the most efficient way of data transmission. The data between this wireless links was transfered using MPLS L2 VPN solution. According to improving technology and increasing internet usage, the communication speed, which is between users and providers, becomes more inevitable for transmitting data without any delays. More than one users might use same connection line for transmitting their packets and it is able to be caused an online traffic and some delays and data loss could occur. In this circumstance, high rate internet demands would lead extra costs for Internet Service Providers (ISPs) and users. In the introduction part, a brief description for the history of communications and basic equipments for Radio Link and Fiber Optic cable are done. In the theory part, detailed information was provided about modulation techniques and multiplexing techniques followed by general information about computer networks and comprehensive information about OSI layers. In the process and result parts, program outputs for Path Loss design which was used for R/L was mentioned in a detailed way. After that, Ethernet Over MPLS L2 VPN was highlighted and a simulation from point-to-point "Ethernet Over MPLS L2 VPN” was conducted in GNS3 software. Furthermore, the simulation for point-to-multipoint case was then applied in a laboratory environment in order to achieve the desired result. In the result part, different R/L simulation results are compared to determine the optimized modulation technique and antenna sizes which could then be merged with simulation results from the previous part.
40
Planta, Giorgia. "Analisi delle prestazioni di un codice di calcolo open-source per l'elaborazione dati GNSS in modalità cinematica finalizzata al monitoraggio di strutture e applicazione di filtri sequenziali." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10436/.
Full textAbstract:
Il presente lavoro di tesi si pone come obbiettivo l’elaborazione di dati GNSS in modalità cinematica post-processing per il monitoraggio strutturale e, in una seconda fase, lo studio delle precisioni raggiungibili delle soluzioni ottenute utilizzando algoritmi di post-elaborazione del dato.
L’oggetto di studio è la torre Garisenda, situata in piazza Ravegnana, accanto alla torre Asinelli, nel centro storico di Bologna, da tempo oggetto di studi e monitoraggi per via della sua inclinazione particolarmente critica. Per lo studio è stato utilizzato un data set di quindici giorni, dal 15/12/2013 al 29/12/2013 compresi.
Per l’elaborazione dei dati è stato utilizzato un software open source realizzato da ricercatori del Politecnico di Milano, goGPS. Quest'ultimo, essendo un codice nuovo, è stato necessario testarlo al fine di poter ottenere dei risultati validi.
Nella prima fase della tesi si è quindi affrontato l’aspetto della calibrazione dei parametri che forniscono le soluzioni più precise per le finalità di monitoraggio considerando le possibili scelte offerte dal codice goGPS. In particolare sono stati imposti dei movimenti calibrati e si è osservata la soluzione al variare dei parametri selezionati scegliendo poi quella migliore, ossia il miglior compromesso tra la capacità di individuare i movimenti e il rumore della serie.
Nella seconda fase, allo scopo di poter migliorare le precisioni delle soluzioni si sono valutati metodi di correzione delle soluzioni basati sull'uso di filtri sequenziali e sono state condotte analisi sull'incremento di precisione derivante dall'applicazione di tali correzioni.
41
Gambuzzi, Ilaria. "Rilevamento con Laser Scanner Terrestre e restituzione 3D del monastero di San Domenico sito in Montecreto (MO): integrazione con dati da interferometria satellitare e possibili cause del quadro fessurativo." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23277/.
Full textAbstract:
La tesi propone un processo di indagine per il rilievo di edifici storici e la generazione di prodotti a valenza metrica, al fine di ottenere una modalità di analisi completa, che si avvale di un’alta precisione di misura, per lo studio geometrico del manufatto d’interesse.
I principali obiettivi di questa trattazione sono: la documentazione e caratterizzazione geometrica dell'edificato, tramite rilevamento laser scanning e GNSS; lo studio degli spostamenti al suolo del territorio circostante il sito di indagine, tramite interferometria satellitare; la ricerca e lo studio di eventuali relazioni tra gli spostamenti a scala territoriale e i risultati delle indagini a scala di edificio. Si propone l’integrazione di queste tecniche come strumento per l’analisi strutturale dell’edificio allo stato di fatto e per il monitoraggio delle evoluzioni future della struttura, in rapporto con quelle dell’ambiente circostante.
Per testare le potenzialità del processo, lo si applica al Monastero di San Domenico sito in Montecreto, Modena (MO). Ottenuta la restituzione del rilievo laser scanner del Complesso, si vuole mettere in relazione lo spostamento del suolo con il rilievo fotografico del quadro fessurativo acquisito in loco, tramite l’analisi geometrica condotta attraverso il modello elaborato.
Il processo d’indagine proposto offre grandi vantaggi: l’alta risoluzione ed accuratezza delle misure effettuate e l’alta densità di dato rilevato creano un continuum spaziale di dati, restituendo una documentazione completa del sito indagato. L'integrazione con altre tecniche topografiche (ad esempio GNSS) permette, di arricchire il prodotto finale e di verificarne la bontà del processo di elaborazione. Sebbene non sia stato possibile identificare una relazione diretta tra dato di spostamento al suolo e quadro fessurativo, il modello elaborato è uno strumento di analisi geometrica che, in confronto con indagini pregresse o future, agevolerà l’identificazione di criticità strutturali.
42
Hsu, Chih-Ting, and 徐稚婷. "GNSS RO data assimilation of ionospheric numerical weather prediction." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/yhcyqx.
Full textAbstract:
博士國立中央大學
太空科學研究所
106
This dissertation evaluates the ability of the Formosa Satellite-3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) and the FORMOSAT-7/COSMIC-2 Global Navigation Satellite System (GNSS) Radio Occultation (RO) data to improve ionospheric specification and forecasting in the contest of ionospheric Numerical Weather Prediction (NWP) aided by data assimilation. For this purpose, both electron density profile and slant Total Electron Content (sTEC) data provided by the FORMOSAT-3/COSMIC and the FORMOSAT-7/COSMIC-2 missions are assimilated into a coupled first-principles model of the thermosphere and ionosphere by using ensemble square root filters. Along with evaluation of observational data, the dissertation investigates roles of incorporating ion-neutral coupling into data assimilation processes and the impact of different auxiliary ensemble data assimilation methods. The role of ion-neutral coupling to ionospheric NWP systems is addressed first in this study. The FORMOSAT-3/COSMIC electron density profiles are assimilated into the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM), using Ensemble Adjustment Kalman Filter (EAKF) implemented in the Data Assimilation Research Testbed (DART). Combining the EAKF and the TIE-GCM allows a self-consistent treatment of ion-neutral coupling in both analysis and forecast steps of data assimilation. Both thermospheric and ionospheric variables are updating according to the background error covariance in the EAKF, and the updated state variables further affect other state variables through the physical ion-neutral coupling processes described by the TIE-GCM in Observing System Simulation Experiments (OSSEs). By updating different combinations of thermospheric and ionospheric variables in OSSEs, the impact of coupling processes on ionospheric NWP can be assessed. It is demonstrated that the incorporation of ion-neutral coupling can significantly improve the ionospheric electron density analysis and forecast, with the thermospheric composition being the most significant state variable. Next, in the second part of this study, RO sTEC data, instead of electron density profiles, are attempted with the goal of further enhancing the ability of the FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2 to improve ionospheric specification and forecasting by eliminating the errors in electron density profiles that are introduced by the assumption of a spherical symmetric ionospheric electron density distribution in retrieval processes. Since the upper boundary of the TIE-GCM is 500-700 km, which is too low for assimilation of GNSS RO sTEC, another data assimilation system, the Community Gridpoint Statistical Interpolation (GSI) Ionosphere is used. The GSI Ionosphere is constructed using the GSI Ensemble Square Root Filter (EnSRF) and the Global Ionosphere Plasmasphere/TIE-GCM (GIP/TIE-GCM). Because the EAKF and the EnSRF are methodologically equivalent, the major difference between the DART/TIE-GCM and the GSI Ionosphere is the first-principles models employed in these two systems. The GIP/TIE-GCM is a coupled model of the thermosphere, ionosphere, and plasmasphere, and the plasma in the GIP/TIE-GCM are simulated along geomagnetic flux tubes, allowing the model to be extended to the plasmasphere, which adds flexibility for various future applications, such as incorporating the model with observation at higher altitude or studying the role of coupling of plasmasphere and ionosphere on ionospheric NWP. In order to make quantify assessments of capability of the GSI Ionosphere to improve the low- and mid-latitude ionospheric specification and forecasting through assimilation of GNSS RO sTEC, a number of OSSEs are carried out by using synthetic FORMOSAT-7/COSMIC-2 data. An additional question addressed with the GSI ionosphere is the comparative evaluation of the FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2 observing systems. The effect of major EnSRF parameters, including the ensemble size and covariance localization schemes, on the assimilation analysis is investigated extensively, and are optimized to yield the highest quality assimilation analysis within the parameter range explored in this dissertation. The result shows that assimilation of sTEC data from the FORMOSAT-7/COSMIC-2 mission through the use of the GSI Ionosphere could potentially improve the low- and mid-latitude ionospheric specification considerably. In the third part of this study, for the purpose of demonstrating the ability of the GSI Ionosphere data assimilation system to improve low- and mid-latitude ionospheric monitoring and forecasting with actual data rather than synthetic data, a case study is carried out under geomagnetically quiet and low solar activity conditions with the FORMOSAT-3/COSMIC GNSS RO sTEC data. Real FORMOSAT-3/COSMIC GNSS RO sTEC data during January 01, 2013 and January 02, 2013 is assimilated into the GSI Ionosphere, and the result is compared with the Center of Orbit Determination in Europe (CODE) Global Ionosphere Maps (GIMs). Result shows that, by assimilating sTEC data into the GSI Ionosphere, the feature of the Equatorial Ionization Anomaly (EIA) in the GSI Ionosphere becomes closer to that of the CODE GIMs. However, the correction of EIA magnitude by using EnSRF still need to be addressed. Comparing with the FORMSAT-3/COSMIC, the FORMOSAT-7/COSMIC-2 will be able to provide more dens data volume in low- and mid-latitude region. As a result, this issue can be solved by incorporating the FORMOSAT-7/COSMIC-2 data into the GSI Ionosphere in the future, since the sTEC data volume will be increased considerably
43
(9354989), Feixiong Huang. "Assimilation of GNSS-R Delay-Doppler Maps into Weather Models." Thesis, 2020.
Find full textAbstract:
Global Navigation Satellite System Reflectometry (GNSS-R) is a remote sensing technique that uses reflected satellite navigation signals from the Earth surface in a bistatic radar configuration. GNSS-R observations have been collected using receivers on stationary, airborne and spaceborne platforms. The delay-Doppler map (DDM) is the fundamental GNSS-R measurement from which ocean surface wind speed can be retrieved. GNSS-R observations can be assimilated into numerical weather prediction models to improve weather analyses and forecasts. The direct assimilation of DDM observations shows potential superiority over the assimilation of wind retrievals.
This dissertation demonstrates the direct assimilation of GNSS-R DDMs using a two-dimensional variational analysis method (VAM). First, the observation forward model and its Jacobian are developed. Then, the observation's bias correction, quality control, and error characterization are presented. The DDM assimilation was applied to a global and a regional case.
In the global case, DDM observations from the NASA Cyclone Global Navigation Satellite System (CYGNSS) mission are assimilated into global ocean surface wind analyses using the European Centre for Medium-Range Weather Forecasts (ECMWF) 10-meter winds as the background. The wind analyses are improved as a result of the DDM assimilation. VAM can also be used to derive a new type of wind vector observation from DDMs (VAM-DDM).
In the regional case, an observing system experiment (OSE) is used to quantify the impact of VAM-DDM wind vectors from CYGNSS on hurricane forecasts, in the case of Hurricane Michael (2018). It is found that the assimilation of VAM-DDM wind vectors at the early stage of the hurricane improves the forecasted track and intensity.
The research of this dissertation implies potential benefits of DDM assimilation for future research and operational applications.
44
Gonçalves, Hugo Valentim Figueira. "Automatization of Real Time GNSS Data Acquisition, Validation, Processing for Water Vapor Estimation NUVEM." Master's thesis, 2016. http://hdl.handle.net/10400.6/6077.
Full textAbstract:
In the recent years, Global Navigation Satellite Systems (GNSS), in particular Global Positioning
Systems (GPS), have proved their capacity to monitor atmospheric water vapor with an accuracy
that is comparable to the accuracy of other conventional meteorological sensors. GNSS has
several significant advantages compared to the traditional observational systems, including low
operating expense, all-weather operability and high temporal/spatial coverage. As a result, the
provision of Zenith Total Delay (ZTD) and derived Precipitable Water Vapor (PWV) from GNSS
data has become established as a standard and valid technique. These atmospheric parameters
are currently assimilated into regional weather forecast models (Meteo Office UK; Meteo France
and German Research Center for Geosciences (GFZ)). However, the accuracy of the near realtime
estimates for these values is still in active research issue.
This dissertation describes the implementation and testing of the estimation of PWV in near-real
time that was carried out at SEGAL in framework of the NUVEM project during 2015-2016. The
scheme to estimate the atmospheric parameters (ZTD and PWV) and to deliver them timely to
the Portuguese Meteo Office (IPMA - Instituto Português do Mar e da Atmosfera) is described in
detail. The focus was on the computational component of the scheme but some studies using
the estimated solutions were also necessary to be performed in order to obtain some necessary
parameters for the operational phase of the project.
The timely estimation of the solutions depends of several processes, which needed to be analysed
and optimized separately (but considering always their integration in the full schema),
namely:
• download of the GNSS data from external providers since the project relies on the data
acquired by different GNSS networks in Portugal and Spain.
• download of the additional products (orbits and clocks) necessary to process the GNSS
data.
• retrieve from numerical models the values (temperature & pressure) necessary to convert
from ZTD to PWV (done at IPMA).
• processing of the GNSS solutions as soon as the data and products were available.
• uploading of numerical and graphical solutions to IPMA and to the dedicated website.
• redundancy of the system in order to guarantee a maximum operational (online) time.
Additional features and improvements can be implemented in the future in order to further optimize
the use of GNSS-PWV in Portugal for nowcasting. Nevertheless, the goals were achieved
since the NUVEM system is currently running in operational mode at SEGAL providing IPMA with
timely PWV estimates that can be used to help the analysis of atmospheric events in near-real
time.Nos últimos anos, Sistemas de Navegação Global por Satélite (GNSS), em particular o Sistema de Posicionamento Global (GPS), têm provado a sua capacidade para monitorizar o vapor de agua existente na atmosfera, com uma precisão ao nível de outras soluções mais tradicionais. Este tipo de sistemas tem várias vantagens comparado com os tradicionais sistemas de observação. Entre estas vantagens estão o baixo custo de operacionalização, e a alta cobertura espacial e temporal. Como resultado a previsão de Atraso Total de Zenith (ZTD) e a previsão de Vapor de Água Precipitável (PWV) foi estabelecido como uma técnica de observação standard. ZTDs e PWVs já são hoje em dia utilizados em vários países (nomeadamente Reino Unido, França e Alemanha) como um dos factores que ajuda nos modelos de meteorologia. No entanto, a precisão das estimativas de ZTD/PWV em tempo quase real baseadas em orbitas ultra rápidas do sistema GPS, encontra-se ainda em estudo. Nesta dissertação é descrita a implementação e os testes de validação da computação de PWV em tempo quase real feita pelo SEGAL no âmbito do projecto NUVEM que ocorreu entre 2015 e 2016, o esquema de cálculo dos parâmetros atmosféricos (ZTD e PWV) e o seu envio atempadamente ao Instituto Português do Mar e da Atmosfera (IPMA) é descrito em detalhe. O foco centrou-se na componente informática. No entanto alguns estudos, relativos aos resultados obtidos, foram realizados de forma a poder definir alguns parâmetros necessários na fase operacional do projecto. A computação das soluções está dependente de vários processos. Houve a necessidade destes serem analisados e optimizados separadamente. Eles são: • download dos dados GNSS dos provedores externos, uma vez que o projecto depende desses dados, adquiridos em diferentes redes GNSS em Portugal e Espanha; • download dos dados adicionais (órbitas e relógios) necessários à computação dos dados GNSS; • obtenção via modelos de previsão numérica dos valores de pressão e temperatura necessários para a conversão de ZTD em PWV (feito pelo IPMA); • computação das soluções GNSS tão rápido quanto possível; • upload das soluções (numéricas e gráficas) para o IPMA e para o website; • redundância dos recursos computacionais. Existem funcionalidades e melhorias que podem ser implementadas no futuro de forma a optimizar o uso de GNSS-PWV para o nowcasting em Portugal. Contudo, os objectivos foram atingidos, uma vez que, o sistema NUVEM está em modo operacional, sendo executado no SEGAL e providenciando ao IPMA as soluções que são depois usados na análise de eventos atmosféricos em tempo quase real.
45
SHENG, HSU CHIH, and 許志生. "The Study of Using GNSS data in Network Adjustment Analysis and Reservoir Deformation Monitoring." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55822599767649263632.
Full textAbstract:
碩士國防大學理工學院
空間科學碩士班
101
Recently, the technology of GNSS(Global Navigation Satellites System) positioning is rapidly developed. This work shows that more positioning accuracy of monitored points of Geodetic Datum could be achieved by GNSS data with suitable network adjustment model, it’s proved that the technology of GNSS positioning really could be applied on the deformation monitoring. This study is combined GNSS with Robotic Total Station(RTS)for Reservoir Deformation Monitoring. Selected experimental area as Shihmen Reservoir located in Daxi Township, Taoyuan County, it organize 3 individual network adjustment models which applied 7 Taiwan’s satellite tracking stations and 1 international satellite tracking station(TWTF) as reference points. With RTS verified, the differential values between RMS values by using Bernese 5.0 software and published values by MOI (Ministry of the Interior) can be computed, and the best network model can be achieved for Reservoir Deformation Monitoring. Results show that first model (including 8 satellite tracking station as reference points) is the best method of the others, and it shows systematic differential value between GNSS and RTS is about 0～-3.2cm. It also can be expected to provide the relationship of reliability in three-dimensional dynamic coordinates, and the average changeable values are estimated to be 0.18～0.61, -0.15～-0.55 and 12.05～69.59 cm at N, E and U moments. From result’s figures, almost changeable values of monitored points are detected about below centimeter degrees, and it’s corresponded with requirement of accuracy of Reservoir Deformation Monitoring.
46
Chi-MingLee and 李啓民. "Coastal Sea Level Variations Derived from GNSS SNR Data - A Case Study in Taiwan." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/8y45bu.
Full textAbstract:
碩士國立成功大學
測量及空間資訊學系
105
Global sea level rise (SLR) has caused many kinds of disasters, damaging the lives and properties of numerous human beings, especially in low-lying coastal regions. Therefore, understanding and monitoring coastal sea level variations are of great importance for human society. This research used Global Navigation Satellite System (GNSS) signal-to-noise ratio (SNR) data from the GNSS stations located in Taiwan (Kaohsiung, Suao and TaiCOAST) and Sweden (Onsala Space Observatory, OSO) to compute sea level heights (SLH) by using three different methods, including Lomb Scargle Periodogram (LSP) aided with tidal harmonic analysis, LSP-only and inverse modeling (IM). The GNSS-derived sea level variations are compared with those from co-located or nearby traditional tide gauges. In Taiwan, the GNSS-derived sea level variations in Kaohsiung and Suao show good agreement with those from tide gauges with the standard deviations (STDs) of differences ranging from 7.1 - 11.1 cm and the correlation coefficients of 0.94-0.97. In addition, more than 80 % of SLH can be successfully achieved during the SNR available periods. Besides, the absolute sea level trend in Kaohsiung during 2006-2011 calculated by combining the vertical motion and the relative sea level from GNSS, is mm/yr, which agrees with that derived from satellite altimetry of mm/yr. However, this comparison is not robust because the uncertainty is almost the same level with the estimate, resulting from the short time coverage of data. In contrast, merely 40 % of SLH can be successfully provided by TaiCOAST and the STD of differences between GNSS-derived and tide gauge sea level changes is 1.12 m with a correlation coefficient of 0.13. TaiCOAST has poor performance for monitoring sea level changes since the GNSS signals may be reflected from intertidal zone when sea level ebbs. On the other hand, the GNSS-based tide gauge in Sweden can offer over 90 % of SLH by both LSP and IM methods. The STD of differences between sea level changes derived from GNSS SNR by IM and the tide gauge decreases about 2 cm compared with that by LSP and the correlation coefficient increases from 0.91 to 0.97. From the bottom line, the GNSS stations in Taiwan except for TaiCOAST demonstrate the potential of serving as GNSS-based tide gauges to measure sea level changes like a specially designed one (e.g. OSO) does.
47
Liu, Jung-Shan, and 劉榮山. "Implementation of e-GNSS and Multi-Map Data for Land Survey Corretion：Two Cases Study of Taoyuan District and Gueishan District." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/726uyw.
Full textAbstract:
碩士國防大學理工學院
空間科學碩士班
104
Land survey correction is the main duties of government of land affairs departments in Taiwan. Because of the rapidly of economy development and the raisely of land price, people require more accuracy surveying results.Due to distribution of control points, mistakes of reliable land boundary coordinates and analysis of overlap mapping , traditional procedures of land survey correctionwould make different results.It brings about lots of land disputation and decrease of government credibility. Therefore, NLSC (National Land Surveying and Mapping Center) provides e-GNSS(ElectronicGlobalNavigationSatellite system) technology that not only save time of surveying but avoid surveying mistakes, toupgrade the quality of surveying results. Existing graphic informations for survey works of topographic maps, orthophoto images maps, cadastral digital maps, base-status-point maps, city planning maps and electronic-global mapseffectively supplied to cadastral survey of overlap mapping. Collecting with all graphic information, those data uniformly translated intothe TWD97 (Taiwan Datum 1997)coordinate system. It alsoassists works of land survey correctionand the graphic information could be provided the good valuation reference. This study established new SOP (Standard Operation Procedure), select Taoyuan District and Gueishan District which are 1/1200in proportiongraphics of the cadastral map in the range of the study area.Using high precision ofe-GNSS technology and multi-map data to handle affairs oftopographical densified control surveying,cadastral surveying and land survey correction. Because there is no accumulationresiduals of traditional densified topographicalcontrol surveying, measured points can be translated into a TWD97 coordinate system by 6-parameter translations and least square collocation method. It is proved that not onlyreduce of the operating time but also improve of working efficiency, new SOP corresponds with the rules of operating procedures and the accuracies of related specifications.
48
Lüer, Juliana. "Design and Development of a Measurement System to Track the Motion of a Point Absorber." Thesis, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416222.
Full textAbstract:
Because of climate change renewable energy field is becoming more and more relevant. Renewable energy can be gained from the sun, from wind but also from ocean waves. To support the research and development in this field reliably measured wave data is collected through a measurement system that shows the exact position of a buoy. The project consists of the design, development and implementation of such a measurement system. It is divided into three subtasks: The power supply based on a solar panel and a battery The measurement part including a sensor and its implementation to the circuit The deployment of a module for data transmission and communication between the measurement system and the on-shore computer The power supply is capable to power the system and to maintain the battery voltage. A suggested stronger power supply will be used in a later state of the project to increase the reliability. The results of the charging test are good. The power supply system is connected to the circuit and the battery charges. For the measurement system the altitude and heading reference system (AHRS) “Ellipse2-D” from SBG Systems has been selected and connected to an Arduino Mega 2560. The AHRS provides raw data and values processed by a Kalman filter. Both data sets are picked up by the microcontroller. The raw data is backed up on a secure digital memory card (SD-card). For the evaluation of the sensor unit, static and dynamic tests are applied to the sensor. In the end it can be seen that the measurement series are aligned with each other. The information from the Kalman model of the AHRS is transmitted with the Adeunis ARF868 ultra-long range (ULR) modem. The transmitter is linked to the Arduino Mega 2560 and the sensor data is transmitted to the receiver. The first field test already shows the reliability of the system for a range of about 3 km. The results of the tests are as expected and in the future this system will be implemented on a buoy.
49
Raděj, Karel. "Využití a výběr monitorovacího systému ve speciální tělesné přípravě AČR." Master's thesis, 2012. http://www.nusl.cz/ntk/nusl-306709.
Full textAbstract:
AABBSSTTRRAACCTT TTiitteell:: Use and selection of monitoring system in special physical training of Army of the Czech Republic GGooaallss:: The goal of this thesis is to give a complex, integrated and comprehensive overview about functional options and effective utilization of Monitoring System in selected areas of special physical training of Czech Army. MMeetthhooddss:: Study, analysis, synthesis and comparison of published findings of professionals from the fields of Geography, Geodesy and Special Physical Training were used in this thesis. Secondary research consisted of interviews with experts on mentioned areas and disciplines. RReessuullttss:: The main subject of this work is the utilization of Monitoring System in special physical training process. Usage of MS in selected areas of special physical training will result in effective support in terms of planning, safety and overall evaluation of its individual parts. KKeeyy wwoorrddss:: GNSS (Global Navigation Satellite System) GPS (Global Positioning System) GIS (Geographic Information System) Special physical training Load Monitoring system Date