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The estimation of target moving trajectory by the multiple receivers based on global positioning system (GPS) forward scattering radar has been first presented in the study, which cannot be obtained by the traditional method. A new estimation approach has been considered using the following information. First, the starting and ending time at which the target pass through the baseline of GPS transmitter–receiver can be obtained. Second, the azimuth and elevation angles of GPS satellites are extracted in combination with the satellite sky map at the recording time. On the basis, the target moving trajectory can be obtained by the established model. In order to validate its feasibility, the experiment has been completed in the open area of Beihang University, which regards the human as the target. Four GPS receivers have been employed to record the data. The experimental results show that the estimation of target trajectory is consistent with the real situation, which proves the practical applicability of the proposed technique.

В статье рассматриваются вопросы строительства подстанции 500/220/10 кВ «Алма». Целью работы является оценка точности методов разбивочных работ и усовершенствовании методики разбивочных работ путем рационального сочетания традиционного метода и метода GPS – измерений. Усовершенствование методики разбивочных работ при строительстве подстанции с использованием GPS технологий позволяет увеличить точность разбивочных работ и производительность труда., The article discusses the construction of a substation 500/220/10 kV "Alma". The aim of the work is to assess the accuracy of the methods of center work and to improve the methods of center work by a rational combination of the traditional method and the method of GPS measurements. The improvement of the methods of center work during the construction of a substation using GPS technologies allows to increase the accuracy of center work and labor productivity.

A primary concern of intelligent traffic management systems (ITMS) is to collect necessary traffic data. Vehicle position is one of the most important data types to manage traffic effectively. Most current approaches to localize modern vehicles (MVs) fall into three categories. The first category uses standalone reference stations, such as the wide-area augmentation system (WAAS), which are expensive modules. The second category uses multiple expensive localization sensors such as the global positioning system (GPS), global navigation satellite system (GNSS), and inertial measurement unit (IMU). However, such expensive solutions may not be applicable in all vehicles, impacting generalizability. The third category is a software-based approach. As opposed to the abovementioned approaches using expensive hardware, the third category uses software, such as map-matching techniques, to augment noisy localization sensors. In this study, we investigated map-matching software in some case studies and found that it cannot locate the vehicle effectively if the positional data are collected by a low-cost and too noisy GPS receiver. Therefore, this paper analyzes and highlights the impact of GPS receiver’s noise in applying self-localization. It also proposes a new methodology by integrating cross-GPS validation, interpolation/best fit, and map-matching techniques to localize a vehicle in the presence of GPS signal noise and investigate it in real traffic data from a metropolitan area. Our proposed methodology is able to identify the more accurate GPS receiver dynamically, by considering the fixed distance between the two GPS receivers. Our evaluations indicate that the proposed methodology can significantly improve vehicle self-localization performance.

Цунами являются одними из самых катастрофических природных явлений, приносящих колоссальные разрушения и уносящих большое число человеческих жизней. Причины возникновения цунами могут быть различными: подводные землетрясения, подводные оползни, извержения вулканов. Даже известны случаи возникновения цунами в результате обрушения в море больших оползней и обвалов. Изучением физики возникновения и развития цунами занимались с древности и продолжают заниматься учёные разных стран. Основное направление исследований связано с построением краткосрочного прогноза землетрясений. В настоящее время традиционные методы краткосрочного прогнозирования цунами основаны только на сейсмологической информации (магнитуде землетрясения, времени главного толчка и местоположении эпицентра). Магнитуда землетрясения, превышающая установленное пороговое значение, которое различается для разных цунамигенных зон, обычно приводит к выдаче предупреждения о цунами. Научная значимость и актуальность обозначенной проблемы очень высока, более того, она жизненно необходима для большинства населения планеты, живущего в прибрежных районах. Как показывает история последних десятилетий, особенно события 2004 и 2011 годов и последних лет, эффективность работы службы предупреждений о цунами далека от своего совершенства. Не предсказанные катастрофические цунами, плохая оценка энергии возникающих цунами, объявления ложных тревог приводят к большим экономическим и социальным потерям. Это связано, прежде всего, с отсутствием достоверного краткосрочного прогноза цунами. Работы последних лет, основанные на применении распределённой сети GPS-приёмников, системы DART, спутниковых технологий, направлены на решение данной проблемы, но итоговые результаты этих исследований пока не видны. Мы считаем, что решение задачи краткосрочного прогноза цунами, основанного на дистанционной регистрации деформационных процессов, происходящих в очаговой области места возникновения цунами, является самым перспективным направлением исследований., Tsunamis are one of the most catastrophic phenomena, causing tremendous destruction and claiming a significant number of lives. The causes of tsunamis can be different: water-quake, underwater landslides and volcanic eruptions. Even cases of tsunami are known as a result of the collapse of a huge mass of rocks in the sea. Scientists from different countries since antiquity have been studying the physics of the occurrence and development of tsunamis. The main direction of research is related to the construction of a short-term forecast of earthquakes. Currently, the traditional method of short-term tsunami forecasting is based only on seismological information (earthquake magnitude, main shock time and epicenter location). An earthquake magnitude exceeding a predetermined threshold value that differs between tsunamigenic zones usually results to a tsunami warning. The scientific significance and relevance of this problem is very high, moreover, it is vital for the majority of the world's population living in coastal regions. As the history of recent decades, especially the events of 2004 and 2011, and even recent years, shows, the efficiency of the tsunami service, to put it mildly, is far from perfect. The misses of catastrophic tsunamis, poor estimation of the energy of the arising tsunamis, false alarms, lead to very sad consequences. This is primarily due to the lack of a reliable short-term tsunami forecast. The works of recent years, based on the use of a distributed network of GPS receivers, DART systems, satellite technologies, are aimed at solving this problem, the final results of which are not yet visible. We believe that solving the problem of short-term tsunami forecast based on remote registration of deformational processes occurring in the source area of the tsunami origin is the most promising area of research, which will be partially confirmed in this paper., Гидросфера. Опасные процессы и явления, Выпуск 3 2020, Pages 260-271

К числу важнейших сведений кадастра недвижимости относят геодезические материалы. Геодезические данные представляют собой значения координат характерных точек, описывающих границы пространственного положения объекта недвижимости. Традиционные геодезические приборы и технологии не способны сегодня обеспечить качественное и оперативное геодезическое сопровождение кадастровых работ. В то время как внедряемые новые технологии геодезических измерений и построений обладают рядом преимуществ и могут заменить традиционные технологии. Благодаря оснащению приборов современным программным обеспечением и вводу в эксплуатацию роботизированных станций, позволяющих без участия человека производить измерения, работа кадастровых инженеров стала более эффективной. В данной статье описываются основы геодезических работ кадастра земель. Поставлена цель рассмотреть технологические этапы инженерногеодезических изысканий. Для достижения цели поставлены следующие задачи: рассмотреть методы геодезических съемок с применением GNSSтехнологий, уделить внимание конструктивным особенностям приборов и оборудования для этого вида работ, а также программным продуктам, которые применяются для обработки информации., Among the most important information of the real estate cadastre include geodetic materials. These data represent the coordinate values of the characteristic points describing the boundaries of the spatial position of the property. Traditional surveying instruments and technologies are not able today to provide highquality and operational geodetic support of cadastral works. While the introduction of new technologies of geodetic measurements and constructions have a number of advantages and can replace traditional technologies. Thanks to the equipment of devices with modern software and commissioning of robotic stations, allowing without human intervention to make measurements, makes the work of cadastral engineers more efficient. This article describes the basics of surveying land cadastre. The aim is to consider the technological stages of engineering and geodetic surveys. To achieve the goal, the following tasks: to consider methods of surveying using GNSS technologies, to pay attention to the design features of devices and equipment for this type of work, as well as software products that are used for information processing., №1(15) (2019)

GPS-based systems have been widely used in different critical sectors, including civilian and military applications. Despite of being able to provide great benefits, under certain circumstances they show to be highly vulnerable to intentional interferences. In this context, this article aimed to evaluate the susceptibility of different complex GPS-dependent systems to intentional interferences, focusing on the technique known as spoofing. This technique presents a high complexity and a great potential for damaging/deceiving complex systems, besides being difficult to identify and to implement countermeasures. Complex systems, like mobile phones, automobile receivers and aircraft receivers were submitted to different levels of spoofing, in free space and in a semi-anechoic chamber, being corrupted with low power levels of interference.

GPS-based systems have been widely used in different critical sectors, including civilian, military and commercial applications. Despite of being able to provide great benefits, under certain circumstances they show to be highly vulnerable to intentional interferences. In this context, this article aimed to evaluate the vulnerability range of this kind of systems, focusing on different kinds of environments and based on different propagation models, to which the simulations were performed. Results show high vulnerabilities of GPS-based systems even when operating in a well-protected urban environment, in a short range and under low-power sources of radiation. Graphs are presented with the range of effectiveness for different power levels of jammer in different situations. Evaluations are performed not only for the acquisition but also for the tracking processes of the GPS receivers, therefore being possible to establish a safe operation range for having a trustful GPS signal and mitigate malicious actions. The comparisons allow, as well, highlighting the importance of using the correct propagation model, in order to achieve consistent results, depending on the desired situation.

In the age of continually developing satellite navigation practically every ship is equipped with GPS receivers, providing the coordinates of her position. However, relying solely on the navigational data from one autonomous receiver the navigator may expect that a given position is burdened with significant errors or that the position data will be lost. This results from the shortcoming of GPS systems which are susceptible to disturbances affecting their operation. One method to substantially reduce such risk is a navigational system that makes use of a number of sources for accurate position determination. The obtained data are processed, which involves data integration and filtration in order to further diminish measurement errors. One possible solution is the application of a system based on an algorithm of multi-sensor navigational data fusion using a Kalman filter. After a brief description of the algorithm, this article presents some results of the fusion of data from parallel position measurements, where the data come from two mobile GPS receivers. The said solution is intended to be implemented in a navigational decision support system on board a sea-going vessel.

The ionosphere is commonly divided into the portion below (bottomside) and above (topside) the region at which peak values of electron density occur. Topside ionospheric modeling is a challenging problem because of the limited data available. Indeed, the more intense peak ionization region, or bottomside ionosphere, dominates the effects observable from ground stations. High-altitude ionosondes, such as sounding rockets, have been traditionally used for direct sounding only of the higher ionospheric layers. Nowadays, signals of opportunity exist for sounding the ionosphere with no dedicated ionosondes. With the continuous deployment of GPS receivers on board spacecraft for positioning, indirect sounding of the topside ionosphere using navigation signals can be performed. This paper reviews geometric-based models allowing to infer the total electron content of the topside ionosphere from spacecraft GPS measurements.

Consumer-grade single-frequency GPS receivers with their known limitations are the predominant means of localization for small Unmanned Aircraft Systems (UAS). More intricate maneuvers such as automatic landings require a level of accuracy this class of receivers does not provide. As a contribution to improve the positioning accuracy without sacrificing the low-cost approach of this class of vehicles, a Local Area Augmentation System (LAAS) has been developed, based on consumer-grade single-frequency miniature GPS receivers both for the base station and airborne positioning. On the part of the airborne receiver, the conventional approach of carrier phase smoothing has been extended by incorporating Doppler measurements to propagate the position during carrier phase signal outages or in the event of cycle slips. Pseudoranges and the augmented carrier phase observations are merged by means of an indirect linear Kalman filter in the position domain. The characteristics of the error state allow for some simplifications that reduce the computing effort of the filter. To evaluate the system’s performance under dynamic conditions, raw GPS data have been collected on a ground based moving platform and processed with Simulink. The results show a significantly improved 3D position accuracy compared to the standalone receiver solution.

This final degree project is divided in two differentiated blocks. In the first one, an analysis of the actual landing systems is made, explaining how they work, their requirements and the advantages and disadvantages of each one. Those systems can be classified into two different groups; on one side the systems that we will call as "classic systems", which are the Instrument Landing System (ILS) and the Microwave Landing System. On the other side, the new approach systems which use global navigation satellite systems, with the support of augmentation systems in order to ensure the definite levels of precision and integrity. Those systems are the Satellite Based Augmentation System (SBAS) and the Ground Based Augmentation System (GBAS). Next, the project focuses in the GBAS system and analyses how it works and the subsystems that form it. Also the GNSS error sources are commented and whether them can be corrected or not. Finally how the corrections which will be send to the aircraft are generated is explained. The second block focuses on the analysis of the on board VHF Data Broadcast (VDB) receiver, which gets the corrections generated by the GBAS system. This receptor follows the scheme of a superheterodyne receiver and in the project it is explained how each of the blocks that form it work. These blocks are the different filters, amplifier, mixer and frequency synthesizer and their characteristics and requirements are exposed. Also the calculus to check that the requirements of transmitted power fixed by the International Civil Aviation Organization (ICAO) are made to test out the suitability of the receiver. In the last chapter of the project, a simulation of the blocks of the receiver is made using the software Advance Design System (ADS) and the obtained results are compared with the values of the calculus made before. Català: Aquest treball final de carrera es divideix en dos blocs diferenciats. En el primer d’ells, es farà un anàlisi del sistemes d’aproximació actuals, explicant el seu funcionament, requisits i els avantatges i inconvenients que cada un d’ells aporta. Aquests sistemes es poden classificar alhora en dos grups diferents; per una banda els sistemes que anomenarem clàssics, com són l’Instrument Landing Systems (ILS) i el Microwave Landing System (MLS). Per l’altra, els nous sistemes d’aproximació que utilitzen sistemes de posicionament global per satèl·lit, sempre amb l’ajuda de sistemes d’augment per garantir requeriments de precisió i integritat. Aquests últims són el Satellite Based Augmentation System (SBAS) i el Ground Based Augmentation System (GBAS). A continuació el treball es centra en el sistema GBAS i hi analitza el seu funcionament i els subsistemes en que es divideix. Es comenten també les diferents font d’error del sistemes GNSS, quines d’aquestes podran ser corregides, i finalment com es generen les correccions que seran enviades a l’aeronau. El segon bloc se centra en l’anàlisi del receptor VHF Data Broadcast (VDB) embarcat, el qual rep les correccions que crea el sistema GBAS. Aquest receptor segueix el model d’un receptor superheterodí i en el treball s’explica el funcionament de cada un dels blocs que el formen; com són els diferents filtres, amplificadors, mescladors i sintetitzadors de freqüència; així com les seves característiques i requisits. També es realitzen els càlculs per comprovar que es compleixen els requisits implantats per l’Organització d’Aviació Civil Internacional (OACI) en quant a potencies de transmissió i que, per tant, el receptor es apte. En l’últim capítol del treball es realitza la simulació de tots els blocs del receptor mitjançant el software AdvanceDesign System (ADS) i es comparen els resultats obtinguts amb els càlculs realitzats anteriorment.

Automated localization is an important functionality for Mobile Mapping Systems (MMS). This thesis presents complimentary solutions to the current localization methods used in a terrestrial MMS, using GPS receivers and Inertial Measurement Units (IMU). A smoothing-based post-mission processing improves the 3D maps generated by MMS. However, this approach is still insufficient, when exposed to slowly varying input sensor errors. The thesis proposes an alternative localization method using 2D laser scanners. The proposed laser odometry approach uses planar landmarks in manmade environments, to detect and compute the transformation of the mobile platform. Unlike Simultaneous Localization and Mapping (SLAM) technique, used in indoor robotic navigation, the relative 3D transformation is computed without using a map, but by exploiting the time invariant properties of the extracted features. A new Divide & Conquer (D&C) approach is proposed to simplify the computation, involving both transformation and Data Association.; La localisation automatique est une fonctionnalité importante des systèmes de cartographie mobiles (Mobile Mapping Systems, MMS). La présente thèse présente des solutions complémentaires aux méthodes de localisation utilisées actuellement dans un système MMS terrestre, qui utilise des récepteurs GPS et des centrales à inertie (Inertial Measurement Units, IMU). Un post-traitement, par lissage des données, permet d'améliorer les cartes 3D générées par un MMS. Cette approche est cependant insuffisante pour corriger les erreurs à variations lentes des capteurs. La présente thèse propose une technique de localisation alternative, fondée sur des scanners 2D à lasers. La méthode présentée ici, d'odométrie par laser, utilise des repères plans, qui sont fréquents dans les environnements créés par l'Homme : ces repères fixes permettent de déterminer le déplacement opéré par la plateforme mobile. Contrairement à la technique du SLAM (Simultaneous Localization and Mapping), utilisée pour la navigation des robots à l'intérieur d'un bâtiment, la transformation 3D est calculée sans avoir recours à une carte préétablie, mais en exploitant des propriétés invariantes des caractéristiques extraites de l'environnement. Nous proposons une approche par "division pour régner" (divide and conquer, D&C) qui simplifie les tâches d'association des repères (data association, DA) et de reconstruction du mouvement.

Automated localization is an important functionality for Mobile Mapping Systems (MMS). This thesis presents complimentary solutions to the current localization methods used in a terrestrial MMS, using GPS receivers and Inertial Measurement Units (IMU). A smoothing-based post-mission processing improves the 3D maps generated by MMS. However, this approach is still insufficient, when exposed to slowly varying input sensor errors. The thesis proposes an alternative localization method using 2D laser scanners. The proposed laser odometry approach uses planar landmarks in manmade environments, to detect and compute the transformation of the mobile platform. Unlike Simultaneous Localization and Mapping (SLAM) technique, used in indoor robotic navigation, the relative 3D transformation is computed without using a map, but by exploiting the time invariant properties of the extracted features. A new Divide & Conquer (D&C) approach is proposed to simplify the computation, involving both transformation and Data Association.; La localisation automatique est une fonctionnalité importante des systèmes de cartographie mobiles (Mobile Mapping Systems, MMS). La présente thèse présente des solutions complémentaires aux méthodes de localisation utilisées actuellement dans un système MMS terrestre, qui utilise des récepteurs GPS et des centrales à inertie (Inertial Measurement Units, IMU). Un post-traitement, par lissage des données, permet d'améliorer les cartes 3D générées par un MMS. Cette approche est cependant insuffisante pour corriger les erreurs à variations lentes des capteurs. La présente thèse propose une technique de localisation alternative, fondée sur des scanners 2D à lasers. La méthode présentée ici, d'odométrie par laser, utilise des repères plans, qui sont fréquents dans les environnements créés par l'Homme : ces repères fixes permettent de déterminer le déplacement opéré par la plateforme mobile. Contrairement à la technique du SLAM (Simultaneous Localization and Mapping), utilisée pour la navigation des robots à l'intérieur d'un bâtiment, la transformation 3D est calculée sans avoir recours à une carte préétablie, mais en exploitant des propriétés invariantes des caractéristiques extraites de l'environnement. Nous proposons une approche par "division pour régner" (divide and conquer, D&C) qui simplifie les tâches d'association des repères (data association, DA) et de reconstruction du mouvement.

Date of Conference: 20-22 April 2011 Conference name: IEEE 19th Signal Processing and Communications Applications Conference (SIU), 2011 GPS sinyalleri iyonosferdeki elektron yoğunluğunun kestirilmesi için önemli bir bilgi kaynağıdır. Ancak, GPS alıcılarında sinyallerin kaydedilemediği durumlar olmaktadır. Bu kesinti sırasında iyonosfer elektron içeriğinin kestiriminin yapılabilmesi için kesinti sureleri içinde kalan verilerin aradeğerleme ile kestirimi gereklidir. Bu çalışmada, bir GPS ağındaki ölçümlerin uzay-zamansal ilintileri kullanılarak yeni bir aradeğerleme tekniği geliştirilmiştir. Gerçek veriye dayalı sonuçlar, geliştirilen tekniğin yüksek başarımlı kestirimler ürettiğini göstermiştir. GPS signals are crucial, because they are used to estimate the electron density in the ionosphere. However, sometimes GPS receivers can not receive signals. In order to estimate ionospheric electron density during this cutoff, the interpolation of the data is necessary. In this paper, a new interpolation scheme that uses spatio-temporal correlation in the GPS network is proposed. The simulation results on real data show that the proposed technique produces promising results. © 2011 IEEE.

Variations in solar, geomagnetic, and seismic activity can cause deviations in the ionospheric plasma that can be detected as disturbances in both natural and man-made signals. Total electron content (TEC) is an efficient means for investigating the structure of the ionosphere by making use of GPS receivers. In this study, TEC data obtained for eight GPS stations are compared with each other using the cross-correlation coefficient (CC), symmetric Kullback-Leibler distance (KLD), and L2 norm (L2N) for quiet days of the ionosphere, during severe geomagnetic storms and strong earthquakes. It is observed that only KLD and L2N can differentiate the seismic activity from the geomagnetic disturbance and quiet ionosphere if the stations are in a radius of 340 km. When TEC for each station is compared with an average quiet day TEC for all periods using CC, KLD, and L2N, it is observed that, again, only KLD and L2N can distinguish the approaching seismicity for stations that are within 150 km radius to the epicenter. When the TEC of consecutive days for each station and for all periods are compared, it is observed that CC, KLD, and L2N methods are all successful in distinguishing the geomagnetic disturbances. Using sliding-window statistical analysis, moving averages of daily TEC with estimated variance bounds are also obtained for all stations and for all days of interest. When these bounds are compared with each other for all periods, it is observed that CC, KLD, and L2N are successful tools for detecting ionospheric disturbances.

This work introduces, implements and evaluates different adaptive Kalman filtering techniques based on the innovation autocorrelation function. The reason of considering these adaptive techniques is the effect of a wrong noise statistics initialization in a Kalman filter and the resulting estimation errors. Of course, different noise statistics than the actual for the stochastic process under estimation would lead to significant errors. For that reason, it is interesting to have a meaning of the effect of wrong noise statistics and to adapt these quantities when necessary. The adaptive techniques considered within this work are the innovation autocorrelation based methods. The particularity of these methods is that the innovation sequence, defined as the new information introduced by the measurements, is a stationary Gaussian white noise sequence for an optimum filter. Moreover, an estimate of the autocorrelation function of that innovation sequence is obtained easily by using the ergodic property of a stationary sequence. Finally, the Kalman filter is applied to the problem of carrier-phase tracking in a GNSS receiver. Some of the algorithms are evaluated for the case of carrierphase tracking. Different scenarios from different measurement campaigns are used in this later implementation. The results demonstrate the estimated values of the noise variances for a carrier-phase tracking loop.

International audience; The main scientific objectives of the International Heliophysical Year are to discover and study all the physical processes coupling the Earth to the Sun. During the IHY a number of scientific instruments are being deployed all over the world. This brief report presents the scientific objectives, the GPS receiver network over Africa and the long lasting research planned for the next decades in Africa

Este documento presenta un resumen del proyecto de desarrollo de una aplicación de seguimiento vehicular por GPS realizado para la empresa IROX IT S.A de C.V. Se hace una presentación a grandes rasgos de todo el proceso llevado a cabo para dar solución a un problema de costes de subcontratación de servicios de posicionamiento que termina con el desarrollo de un componente de hardware basado en un módulo de comunicaciones integrado, el GE863-GPS de la empresa Italiana Telit. Se incluyen diseños eléctricos y procedimientos de modo muy resumido, y finalmente las características del módulo desarrollado. El proyecto se realiza en el marco de un convenio de colaboración entre el Instituto Tecnológico de Monterrey y la Universidad Politécnica de Cataluña.

Since its introduction in the early 1980 s, the Global Positioning System (GPS) has become an important worldwide resource. Although the primary use of GPS is for position location, the inherent timing accuracy built into the system has allowed it become an important synchronisation resource for other systems. In most cases the GPS end user only requires a position estimate without awareness of the timing and synchronisation aspects of the system. A low accuracy position (at the several-metre level) with a low update rate of about 1Hz is often acceptable. However, obtaining more accurate position estimates (at the sub-metre level) at higher update rates requires the use of differential correction signals (DGPS) and greater processing power in the receiver. Furthermore, some extra challenges arise when simultaneously gathering information from a group of independently moving remote GPS receivers (rovers) at increased sampling rates (10Hz). This creates the need for a high bandwidth telemetry system and techniques to synchronise the position measurements for tracking each rover. This thesis investigates and develops an overall solution to these problems using GPS for both position location and synchronisation. A system is designed to generate relative position information from 30 or more rovers in real-time. The important contributions of this research are as follows: a) A GPS synchronised telemetry system is developed to transport GPS data from each rover. Proof of concept experiments show why a conventional RF Local Area Network (LAN) is not suitable for this application. The new telemetry system is developed using Field Programmable Gate Array (FPGA) devices to embed both the synchronising logic and the central processor. b) A new system architecture is developed to reduce the processing load of the GPS receiver. Furthermore, the need to transfer the DGPS correction data to the rover is eliminated. Instead, the receiver raw data is processed in a centralised Kalman filter to produce multiple position estimates in real-time. c) Steps are taken to optimise the telemetry data stream by using only the bare essential data from each rover. A custom protocol is developed to deliver the GPS receiver raw data to the central point with minimal latency. The central software is designed to extract and manage common elements such as satellite ephemeris data from the central reference receiver only. d) Methods are developed to make the overall system more robust by identifying and understanding the points of failure, providing fallback options to allow recovery with minimal impact. Based on the above a system is designed and integrated using a mixture of custom hardware, custom software and off-the-shelf hardware. Overall tests show that efforts to minimise latency, minimise power requirements and improve reliability have delivered good results.

The atmosphere in low latitude regions is of particular interest to GPS researchers because the propagation of GPS signals becomes significantly delayed compared with other regions of the world. Hence this limits GPS positioning accuracy in equatorial regions. Although the atmospheric delay can be modelled, a residual component will still remain. Reducing, or mitigating the effect of residual atmospheric delay is of great interest, and remains a challenge, especially in equatorial regions. Analysis of relative positioning accuracy of GPS baselines has confirmed that the residual atmospheric delay is distance-dependent, even in low latitude areas. Residual ionospheric delay is the largest component in terms of both absolute magnitude and variability. However it can be largely eliminated by forming the ionosphere-free combination of measurements made on two frequencies. The residual tropospheric delay is smaller in magnitude but rather problematic due to strong spatio-temporal variations of its wet component. Introducing additional troposphere scale factors in the least squares estimation of relative position can reduce the effect of the residual. In a local GPS network, the distance-dependent errors can be spatially modelled by network-based positioning. The network-based technique generates a network correction for user positioning. The strategy is to partition this network correction into dispersive and non-dispersive components. The latter can be smoothed in order to enhance the ionosphere-free combination, and can be of benefit to ambiguity resolution. After this step, both the dispersive and non-dispersive correction components can be used in the final positioning step. Additional investigations are conducted for stochastic modelling of network-based positioning. Based on the least squares residuals, the variance-covariance estimation technique can be adapted to static network-based positioning. Moreover, a two-step procedure can be employed to deal with the temporal correlation in the measurements. Test results on GPS networks in low latitude and mid-latitude areas have demonstrated that the proposed network-based positioning strategy works reasonably well in resolving the ambiguities, assisting the ambiguity validation process and in computing the user s position. Furthermore, test results of stochastic modelling in various GPS networks suggests that there are improvements in validating the ambiguity resolution results and handling the temporal correlation, although the positioning result do not differ compared to using the simple stochastic model typically used in standard baseline processing.

This thesis provides a comprehensive analysis of the acquisition performance of the mobile-embedded Global Positioning System (GPS) receiver. Particular emphasis is given to the analysis of differentially coherent processing techniques and parallel acquisition strategies. New analytical expressions for the distribution of the decision variable of differentially coherent detectors are derived. In addition, new Gaussian approximations are derived and shown to be more accurate than existing approximations. Using these Gaussian approximations it is demonstrated that the traditional noncoherent combining detector is the best choice when the signal to noise ratio is large, but that differentially coherent combining is a superior choice at low signal to noise ratios. An analysis of the effects of carrier Doppler, code Doppler and data modulation on detector performance is also conducted. For the noncoherent combining detector, new expressions are obtained for the mean and worst case power attenuation due to the combined effects of carrier Doppler and data modulation. Approximate expressions are also derived for the differentially coherent combining detector. New expressions are also obtained for the mean and variance of the time to first hit using a Markov chain model and matrix methods. These models permit the use of numerical techniques to determine the optimal choice of receiver parameters for a given performance requirement. Finally the effect of unknown power levels and multi-access interference (MAI) are considered. A novel technique for detecting MAI, referred to as the power level detector, is introduced and its performance analysed. All results are verified by Monte Carlo computer simulation using a simplified signal model. The simulations were implemented on a 100 processor computer cluster.

During January and February 1990, 1991 and 1992 an important collaboration took place between the Rio Grande Astronomical Station (Estación Astronómica de Río Grande - EARG) and the Royal Institute and Observatory of the Spanish Navy (Real Instituto y Observatorio de la Armada de España - RIOA). Using RIOA GPS receivers a single base between one point in EARG (Rio Grande) and another point located at the Centro Austral de Investigaciones Científicas (CADIC, Ushuaia) was measured several times. Measured distances repetitivity is about 0.7 ppm (9 cm) and in components, 1 ppm. These results will permit the planning of an appropriate network to be measured with GPS which will contribute to the determination of crustal movements in the Tierra del Fuego region., En los meses de enero y febrero de los años 1990, 1991 y 1992 se realizó un trabajo de colaboración entre la Estación Astronómica Río Grande (EARG) y el Real Instituto y Observatorio de la Armada de España (RIOA). Con posicionadores GPS pertenecientes al grupo español se midió reiteradamente una misma base entre un punto situado en la EARG (Río Grande) y otro situado en el Centro Austral de Investigaciones Científicas (CADIC, Ushuaia). La repetitividad de las distancias medidas es del orden de 0.7 ppm (unos 9 cm) y en componentes, de 1 ppm. Esto permitirá planificar una red apropiada en la región fueguina para la determinación de movimientos tectónicos utilizando GPS., Material digitalizado en SEDICI gracias a la colaboración de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP)., Asociación Argentina de Geofísicos y Geodestas

Objetivos de este TFC: 1.- Aprender a utilizar la herramienta gLAB para realizar el posicionamiento preciso de receptores GPS. 2.- Analizar los efectos en la precision del sistema GPS de las diferentes fuentes de error. 3.- Llevar a cabo procesamientos del tipo "Standard Positioning Service" (SPS) y "Precise Point Positioning" (PPP). 4.- Utilizar diferentes estrategias para el posicionamiento cinematico de dos vehiculos con receptores GPS embarcados: Una aeronave ligera y un satelite en orbita baja. 5.- Discutir las ventajas y desventajas relativas de utilizar diferentes estrategias de posicionamiento cinematico GPS. The main aim of this project is to use the gLAB program to analize the data generated by some GNSS receivers. The program gLAB was created by the GAGE/UPC research group, with the purpose of offering an easy to use tool to the students who want to get more deep knowledge on GPS, as well as to professionals who need precise positioning. In this project we will explain the program’s main characteristics in a theoretical way and through examples where it is explained how to get a precise positioning of GPS receivers. In this document we can also find the analysis of the different sources of error that make the GPS system not so precise to be used in aeronautical fields, such as to know the correct positioning of an airplane or to take off and landing guidance. Along the project I have carrier out a series of experiments with the SPS and PPP processing strategies to localize a ground station with a static strategy, and the route of a light aircraft with a GPS receiver has been followed. For the latter case a kinematic positioning strategy was used. To end up we explain how to plot these routes using Google-Earth