GPS has become very popular in recent years. It is used in wide range of applications including aircraft navigation, search and rescue, space borne attitude and position determination and cellular network synchronization. Each application places demands on GPS for various levels of accuracy, integrity, system availability and continuity of service. Radio frequency interference (RFI) which results from many sources such as TV/FM harmonics, radar or mobile satellite systems, presents a challenge to the use of GPS. It can affect all the service performance indices mentioned above. To improve the accuracy of GPS positioning, a continuously operating reference station (CORS) network can be used. A CORS network provides all the enabled GPS users in an area with corrections to the fundamental measurements, producing more precise positioning. A threat to these networks is a threat to all high-accuracy GPS users. It is therefore necessary to monitor the quality of the received signal with the objective of promptly detecting the presence of RFI and providing a timely warning of the degradation of system accuracy, thereby boosting the integrity of GPS. This research was focused on four main tasks: a) Detection. The focus here is on a power spectral density fluctuation detection technique, in which statistical inference is used to detect narrowband continuous-wave (CW) interference in the GPS signal band after being captured by the RF front-end. An optimal detector algorithm is proposed. At this optimal point, for a fixed Detection Threshold (DT), probability of false alarm becomes minimal and for a fixed probability of false alarm, we can achieve the minimum value for the detection threshold. Experiments show that at this point we have the minimum computational load. This theoretical result is supported by real experiments. Finally this algorithm is employed to detect a real GPS interference signal generated by a TV transmitter in Sydney. b) Characterization. In the characterization section, using the GNSS signal structure and the baseband signal processing inside the GNSS receiver, a closed formula is derived for the received signal quality in terms of effective carrier to noise ratio ( ). This formula is tested and proved by calculating the C/No using the I and Q data from a software GPS receiver. For pulsed CW, a similar analysis is done to characterize the effect of parameters such as pulse repetition period (PRP) and also duty cycle on the received signal quality. Considering this characterization and the commonality between the GPS C/A code and Galileo signal as a basis to build up a common term for satellite availability, the probability of satellite availability in the presence of CW interference is defined and for the two currently available satellite navigation systems (GPS L1 signal and Galileo signal (GIOVE-A BOC(1, 1) in the E1/L1 band)) it is shown that they can be considered as alternatives to each other in the presence of different RFI frequencies as their availability in the presence of CW RFI is different in terms of RFI frequency. c) Mitigation. The last section of the research presents a new concept of ?Satellite Exclusion Zone?. In this technique, using our previously developed characterization techniques, and considering the fact that RFI has different effects on different satellite signals at different times depending on satellite Doppler frequency, the idea of excluding the most vulnerable satellite signal from positioning calculations is proposed. Using real data and real interference, the effectiveness of this technique is proven and its performance analyzed. d) Hardware implementation. The above detection technique is implemented using the UNSW FPGA receiver board called NAMURU.

"Author biographies are available in the expanded on-line version of this article [http://www.insidegnss.com/auto/julyaug09-tetewsky-final.pdf]" / "July/August 2009." Web site title: Making Sense of GPS Inter-Signal Corrections : Satellite Calibration Parameters in Legacy and Modernized Ionosphere Correction Algorithms.

The objective of this thesis is to design a model for a multi global navigation satellite system using Simulink. It explains a design procedure which includes the models for transmitter and receiver for two different navigation systems. To overcome the problem, where less number of satellites are visible to determine location degrades the performance of any positioning system significantly, this research has done to make use of multi GNSS satellite signals in one navigation receiver.

No description available.

Despite significant progress in GPS/INS integration-based direct geo-referencing (DGR) technology over the past decade, its performance still needs to be improved in terms of accuracy and tolerance to GPS outages. This is mainly due to the limited geometric strength of the GPS satellite constellation, the quality of INS and the system integration technology. This research is focused on pseudolite (PL) augmentation to enhance the geometric strength of the GPS satellite constellation, and the Neural Network (NN) aided Kalman filter (KF) system integration algorithm to improve the geo-referencing system's performance during GPS outages. The main research contributions are summarized as below: a) Systematic errors introduced by pseudolites have been investigated. Theoretical and numerical analyses reveal that errors of troposphere delay modelling, differential nonlinearity and pseudolite location are sensitive to pseudolite receiver geometry. Their effect on final positioning solutions can be minimised by selecting optimal pseudolite and receiver locations, which is referred to as geometry design. Optimal geometry design for pseudolite augmented systems has been proposed based on simulation results in airborne surveying scenarios. b) Nonlinear geometry bias, or nonlinearity, exists in single difference processes when the unit vectors from the reference and user receivers to a satellite or pseudolite are non-parallel. Similar to long baseline differential GPS (DGPS), nonlinearity is a serious issue in pseudolite augmentation. A Projected Single Difference (PSD) method has been introduced to eliminate nonlinear geometry bias. An optimized expression has been derived to calculate the direction of project vectors, and the advantages of applying PSD in pseudolite augmented airborne DGPS have been demonstrated. c) A new method for pseudolite tropospheric delay modelling has been proposed, which is based on single-differenced GPS tropospheric delay models. The performance of different models has been investigated through simulations and field testing. The advantages and limitations of each method have been analysed. It is determined that the Bouska model performs relatively well in all ranges and elevations if the meteorological parameters in the models can be accurately collected. d) An adaptive pseudolite tropospheric delay modelling method has been developed to reduce modelling error by estimating meteorological parameters in real-time, using GPS and pseudolite measurements. Test results show that pseudolite tropospheric delay modelling errors can be effectively mitigated by the proposed method. e) A novel geo-referencing system based on GPS/PL/INS integration has been developed as an alternative to existing GPS/INS systems. With the inclusion of pseudolite signals to enhance availability and geometry strength of GPS signals, the continuity and precision of the GPS/INS system can be significantly improved. Flight trials have been conducted to evaluate the system performance for airborne mapping. The results show that the accuracy and reliability of the geo-referenced solution can be improved with the deployment of one or more pseudolites. f) Two KF and NN hybrid methods have been proposed to improve geo-referenced results during GPS outages. As the KF prediction diverges without measurement update, the performance of a GPS/INS integrated system degrades rapidly during GPS outages. Neural networks can overcome this limitation of KF. The first method uses NN to map vehicle manoeuvres with KF measurement in a loosely coupled GPS/INS system. In the second method, an NN is trained to map INS measurements with selected KF error states in a tightly coupled GPS/INS system when GPS signals are available. These training results can be used to modify KF time updates. Optimal input/output and NN structure have been investigated. Field tests show that the proposed hybrid methods can dramatically improve geo-referenced solutions during GPS outages.

Despite significant progress in GPS/INS integration-based direct geo-referencing (DGR) technology over the past decade, its performance still needs to be improved in terms of accuracy and tolerance to GPS outages. This is mainly due to the limited geometric strength of the GPS satellite constellation, the quality of INS and the system integration technology. This research is focused on pseudolite (PL) augmentation to enhance the geometric strength of the GPS satellite constellation, and the Neural Network (NN) aided Kalman filter (KF) system integration algorithm to improve the geo-referencing system's performance during GPS outages. The main research contributions are summarized as below: a) Systematic errors introduced by pseudolites have been investigated. Theoretical and numerical analyses reveal that errors of troposphere delay modelling, differential nonlinearity and pseudolite location are sensitive to pseudolite receiver geometry. Their effect on final positioning solutions can be minimised by selecting optimal pseudolite and receiver locations, which is referred to as geometry design. Optimal geometry design for pseudolite augmented systems has been proposed based on simulation results in airborne surveying scenarios. b) Nonlinear geometry bias, or nonlinearity, exists in single difference processes when the unit vectors from the reference and user receivers to a satellite or pseudolite are non-parallel. Similar to long baseline differential GPS (DGPS), nonlinearity is a serious issue in pseudolite augmentation. A Projected Single Difference (PSD) method has been introduced to eliminate nonlinear geometry bias. An optimized expression has been derived to calculate the direction of project vectors, and the advantages of applying PSD in pseudolite augmented airborne DGPS have been demonstrated. c) A new method for pseudolite tropospheric delay modelling has been proposed, which is based on single-differenced GPS tropospheric delay models. The performance of different models has been investigated through simulations and field testing. The advantages and limitations of each method have been analysed. It is determined that the Bouska model performs relatively well in all ranges and elevations if the meteorological parameters in the models can be accurately collected. d) An adaptive pseudolite tropospheric delay modelling method has been developed to reduce modelling error by estimating meteorological parameters in real-time, using GPS and pseudolite measurements. Test results show that pseudolite tropospheric delay modelling errors can be effectively mitigated by the proposed method. e) A novel geo-referencing system based on GPS/PL/INS integration has been developed as an alternative to existing GPS/INS systems. With the inclusion of pseudolite signals to enhance availability and geometry strength of GPS signals, the continuity and precision of the GPS/INS system can be significantly improved. Flight trials have been conducted to evaluate the system performance for airborne mapping. The results show that the accuracy and reliability of the geo-referenced solution can be improved with the deployment of one or more pseudolites. f) Two KF and NN hybrid methods have been proposed to improve geo-referenced results during GPS outages. As the KF prediction diverges without measurement update, the performance of a GPS/INS integrated system degrades rapidly during GPS outages. Neural networks can overcome this limitation of KF. The first method uses NN to map vehicle manoeuvres with KF measurement in a loosely coupled GPS/INS system. In the second method, an NN is trained to map INS measurements with selected KF error states in a tightly coupled GPS/INS system when GPS signals are available. These training results can be used to modify KF time updates. Optimal input/output and NN structure have been investigated. Field tests show that the proposed hybrid methods can dramatically improve geo-referenced solutions during GPS outages.

Made available in DSpace on 2015-03-26T13:28:36Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1996865 bytes, checksum: 80a7a778bb6c66c23c06d757b2a4c310 (MD5) Previous issue date: 2015-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Among the technologies of spatial positioning, highlight the GNSS (Global Navigation Satellite System), which is widely used in various applications in the area of Geodesy, among others. The precise point positioning (PPP) has been shown to be a powerful tool for geodetic and geodynamics. applications Relative positioning is still the most widely used method for determination of coordinates in precision geodetic surveys. However, the PPP is increasingly in evidence and has provided satisfactory results. Given the above, remains to be seen, among the techniques mentioned, which provides more accurate results currently. The data used in this study were collected by the stations of RBMC (Brazilian Network for Continuous Monitoring of GNSS Systems) provided by IBGE (Brazilian Institute of Geography and Statistics), for the date January 01, 2014. For PPP analysis was used the free service online IBGE-PPP, and for analysis of static relative positioning was used the free online placement service AUSPOS, that processes network data, using the scientific software Bernese, and commercial software LGO (Leica Geo Office), which was used for processing single baselines and multiple baselines (vector adjustment).The GPS data were processed by varying the trace interval, covering the intervals of 1, 2, 4, 6, 8, 10 and 12 hours. In IBGE-PPP and AUSPOS the results provided was referenced to IGb08 (ITRF2008) at the time of data collection. To process the data in the LGO, the coordinates of the base stations, available in SIRGAS2000, epoch 2000.4, were transformed and updated to the reference system IGb08 (ITRF2008) at the time of data collection.Thus, the estimated coordinates at LGO were also estimated in IGb08 at the time of data collection. In sequence, the coordinates estimated in LGO, IBGE-PPP and AUSPOS were compared with the coordinates provided in descriptive of RBMC stations,which were also transformed and updated to the same reference system and time of coordinates estimated. With that, the movement of tectonic plates over time was minimized. In this way, from the calculation of discrepancies (trends) and with the clarifications provided in the adjustment, it was possible to perform the calculation of accuracies. According to the results, it was concluded that the method of relative positioning with the use of computational application and commercial use of receivers of dual frequency continues to be the most accurate method, regardless of the length of the baseline. The performance of relative positioning with a frequency receivers, involving short baselines also showed excellent results. In this case, at 64.3% of the results the accuracy was millimeter. It should be noted the potential of the IBGE-PPP and AUSPOS, which showed good results. In addition, these processing services are free and the users need only a receiver. / Dentre as tecnologias espaciais de posicionamento, destaca-se o GNSS (Global Navigation Satellite System), que é amplamente empregado em diversas aplicações na área de Geodésia, entre outras. O Posicionamento por Ponto Preciso (PPP) tem se mostrado uma poderosa ferramenta para aplicações geodésicas e geodinâmicas. O posicionamento relativo é ainda o método mais utilizado para determinação de coordenadas em levantamentos geodésicos de precisão. Contudo, o PPP está cada vez mais em evidência e tem proporcionado resultados satisfatórios. Diante do exposto, resta saber, dentre as técnicas mencionadas, qual apresenta resultados mais acurados atualmente. Os dados utilizados neste trabalho foram coletados pelas estações da RBMC (Rede Brasileira de Monitoramento Contínuo dos Sistemas GNSS) disponibilizados pelo IBGE (Instituto Brasileiro de Geografia e Estatística), referentes à data 01 de janeiro de 2014. Para análise do PPP foi utilizado o serviço gratuito online IBGE-PPP, e para análise do posicionamento relativo estático foram utilizados o serviço de posicionamento online gratuito AUSPOS, que processa os dados em rede, com uso do software científico Bernese, e o software comercial LGO (Leica Geo Office), que foi utilizado para processamento de linhas de base simples e de múltiplas linhas de base (ajustamento vetorial). Os dados GPS foram processados variando o intervalo de rastreio, abrangendo os intervalos de 1, 2, 4, 6, 8, 10 e 12 horas. No IBGE- PPP e no AUSPOS os resultados fornecidos são referenciados ao IGb08 (ITRF2008) na época de coleta dos dados. Para o processamento dos dados no LGO as coordenadas das estações base, disponibilizadas em SIRGAS2000, época 2000,4, foram transformadas e atualizadas para o sistema de referência IGb08 (ITRF2008) na época de coleta dos dados. Assim, as coordenadas estimadas no LGO também foram estimadas no IGb08 na época de coleta dos dados. Na sequência, as coordenadas estimadas no LGO, IBGE-PPP e AUSPOS foram comparadas com as coordenadas disponibilizadas nos descritivos das estações da RBMC, que também foram transformadas e atualizadas para o mesmo sistema de referência e época das coordenadas estimadas. Com isso, o deslocamento das placas tectônicas ao longo do tempo foi minimizado. Desta forma, a partir do cálculo das discrepâncias (tendências) e com as precisões disponibilizadas no ajustamento, foi possível realizar o cálculo das acurácias. De acordo com os resultados obtidos, conclui-se que o método de posicionamento relativo com o uso de aplicativo computacional comercial e uso de receptores de dupla frequência continua sendo o método mais acurado, independentemente do comprimento da linha de base. A performance do posicionamento relativo com receptores de uma frequência, envolvendo linhas de base curtas, também apresentou ótimos resultados. Neste caso, em 64,3% dos resultados a acurácia foi milimétrica. Deve-se salientar a potencialidade do IBGE-PPP e do AUSPOS, que apresentaram bons resultados. Além disso, esses serviços de processamento são gratuitos e o usuário deve dispor de apenas um receptor.

Made available in DSpace on 2015-03-26T13:28:35Z (GMT). No. of bitstreams: 1 texto completo.pdf: 8031518 bytes, checksum: 187f1c8078747afc55195475e89c6e44 (MD5) Previous issue date: 2014-07-22 / Over time has increased the need for low cost positioning of the populatio, and for this reason the demand for navigation devices has grown considerably in all levels of users of these devices, the population in general has greater access to smartphones because of its many features. Smartphones using micro GNSS receiver has a main component of positioning, where the pseudorange is its basic observable. The data sources for GPS corrections are increasingly available to the community through institutions as the IBGE with the Brazilian Network for Continuous Monitoring (RBMC). Thus, there is a greater possibility of improvement in accuracy of positioning these devices with the post- processed relative positioning and even in real time. With these possibilities and needs, this study aims the establishment of methodology that improves the accuracy in the positioning devices using micro GNSS receiver with a recursive least squares estimation with the Kalman gain matrix applied in relative positioning static by double difference of pseudorange in short baselines. To verify the effectiveness of this methodology is used SiRFstar IV micro receiver data which receives data only in L1 frequency GPS constellation. Was used reference RBMC stations to process these data. With tracking 15 minutes in known points had a mean deviation in the horizontal component of the plane coordinates 29 cm for post-processing and 98 cm for the real time processing, and, for the single point positioning average deviation was 6 meters. With this, it was concluded that the use of static methods for processing on recursive least squares estimation improves the accuracy of positioning significantly, where mobile devices that were previously given only to navigation may also be used for mapping. / Com o passar do tempo aumentou a necessidade da população em posicionamento a baixo custo, e por este motivo a procura por aparelhos de navegação tem crescido consideravelmente em todos os níveis de usuários. Destes dispositivos, a população no geral tem maior acesso aos smartphones devido a suas diversas funcionalidades. Os smartphones utilizam de microrreceptor GNSS como principal componente de posicionamento, sendo que sua observável básica é a pseudodistância derivada do código C/A. As fontes de dados para correções GPS estão cada vez mais disponíveis para a comunidade por meio de instituições como o IBGE com a Rede Brasileira de Monitoramento Continuo dos Sistemas GNSS (RBMC). Com isso, tem-se uma maior possibilidade de melhorias na acurácia do posicionamento destes dispositivos com o posicionamento relativo pós-processado e até mesmo em tempo real. Com estas possibilidades e necessidades, este trabalho tem como objetivo o estabelecimento de metodologia que melhore a acurácia no posicionamento de dispositivos móveis que utilizam microrreceptor GNSS, utilizando a estimativa de mínimos quadrados recursiva com a matriz de ganho de Kalman aplicada no posicionamento relativo estático por dupla diferença da pseudodistância em linhas de base curtas. Para verificar a eficácia desta metodologia utilizou-se dados do microrreceptor SiRFstar IV que recebe dados na frequência L1 da constelação GPS. Foram utilizadas as estações de referência da RBMC para o processamento destes dados. Com rastreios de 15 minutos em pontos de coordenadas conhecidas teve-se um desvio médio na componente horizontal das coordenadas planas de 29 centímetros para o pós- processamento e 98 centímetros para o processamento em tempo real, sendo que, para o posicionamento por ponto simples o desvio médio foi de 6 metros. Com isso, concluiu-se que a utilização da metodologia de processamento relativo estático por estimativa dos mínimos quadrados recursiva melhorou a acurácia do posicionamento de forma significativa, onde dispositivos móveis 14que até então eram indicados somente para navegação podem ser utilizados também para mapeamento.