Introduction to GPS and Other Global Navigation Satellite Systems

No abstract availabl

GNSS характеристики та вплив погоди на фінальному етапі заходу на посадку.

Робота публікується згідно наказу ректора від 21.01.2020 р. №008/од "Про перевірку кваліфікаційних робіт на академічний плагіат 2019-2020р.р. навчальному році" . Керівник проекту: професор, д.т.н. Авер’янова Юлія АнатоліївнаIn the Civil Aviation sphere, Research activities aim to improve efficiency and tightening safety targets by providing new strategies of operations, all this is achieved through the implementation of modern and new Communication, Navigation, Surveillance and Air Traffic Management process. In Air Navigation, these goals are met by improving the exiting services and introduce the new one applicable for navigation towards safety, more reliable approach in all weather conditions. The Global Navigation Satellite System (GNSS) has been identified as a key to technology by providing essential position and timing information supporting flight and ATM operations. GNSS can be observed in the fitting of new CA Aircraft, since a majority of them are now equipped with its receivers. GNSS contains numerous satellites, for instance GPS for The United State of America, Glonass for Russian Federation, Galileo for Europeans Unions, Beidou for Chinese, and more that are still under development. This Master’s has demonstrated the power and benefits of combining two satellites for better performance This thesis argues that atmospheric layers (Ionosphere, Troposphere) do play a vital role on the perturbation of signals from Satellites, in order to improve navigation regardless of the lost signals. Pseudo-range model is presented together with the performance of GNSS integrity with two constellations (GPS combined with Galileo). However, a significant number of reports have been received on different harmful interference to GNSS signals and some suggestions to correct those were mentioned. This thesis focuses on the final approach of an aircraft using combined signals for reliability and safety navigation in CAT I operation. Lastly an innovative algorithm is presented for better guidance at the final approach

Multiple reference consistency check for LAAS: a novel position domain approach

Since the traditional Maximum Likelihood-based range domain multiple reference consistency check (MRCC) has limitations in satisfying the integrity requirement of CAT II/III for civil aviation, a Kalman filter-based position domain method has been developed for fault detection and exclusion in the Local Area Augmentation System MRCC process. The position domain method developed in this paper seeks to address the limitations of range domain-based MRCC by focusing not only on improving the performance of the fault detection but also on the integrity risk requirement for MRCC. In addition, the issue of the stability of the Kalman filter in relation to the position domain approach is considered. GPS range corrections from multiple reference receivers are fused by the adaptive Kalman filter at the master station for detecting and excluding the single reference receiver’ failure. The performance of the developed Kalman filter-based MRCC has been compared with the traditional method using experimental data. The results reveal that the vertical protection level is slightly better in the traditional method compared with the developed Kalman filter-based approach under the fault-free case. However, the availability can be improved to over 97% in the proposed method relative to the traditional method under the single-fault case. Furthermore, the fault-tolerant positioning result with an accuracy improvement of more than 32% can be achieved even if different fault types are considered under the single-fault case. In particular, the algorithm can be a candidate option as an augmentable complement for the traditional MRCC and can be implemented in a master station element of the LAAS integrity monitoring architecture

Modes dégradés résultant de l'utilisation multi constellation du GNSS

Actuellement, on constate dans le domaine de la navigation, un besoin croissant de localisation par satellites. Apres une course a l'amelioration de la precision (maintenant proche de quelques centimetres grace a des techniques de lever d'ambiguite sur des mesures de phase), la releve du nouveau defi de l'amelioration de l'integrite du GNSS (GPS, Galileo) est a present engagee. L'integrite represente le degre de confiance que l'on peut placer dans l'exactitude des informations fournies par le systeme, ainsi que la capacite a avertir l'utilisateur d'un dysfonctionnement du GNSS dans un delai raisonnable. Le concept d'integrite du GNSS multi-constellation necessite une coordination au niveau de l'architecture des futurs recepteurs combines (GPS-Galileo). Le fonctionnement d'un tel recepteur dans le cas de passage du systeme multi-constellation en mode degrade est un probleme tres important pour l'integrite de navigation. Cette these se focalise sur les problemes lies a la navigation aeronautique multiconstellation et multi-systeme GNSS. En particulier, les conditions de fourniture de solution de navigation integre sont evaluees durant la phase d'approche APV I (avec guidage vertical). En disposant du GPS existant, du systeme Galileo et d'un systeme complementaire geostationnaire (SBAS), dont les satellites emettent sur des frequences aeronautiques en bande ARNS, la question fondamentale est comment tirer tous les benefices d'un tel systeme multi-constellation pour un recepteur embarque a bord d'un avion civil. En particulier, la question du maintien du niveau de performance durant cette phase de vol APV, en termes de precision, continuite, integrite et disponibilite, lorsque l'une des composantes du systeme est degradee ou perdu, doit etre resolue. L'objectif de ce travail de these est donc d'etudier la capacite d'un recepteur combine avionique d'effectuer la tache de reconfiguration de l'algorithme de traitement apres l'apparition de pannes ou d'interferences dans une partie du systeme GNSS multiconstellation et d'emettre un signal d'alarme dans le cas ou les performances de la partie du systeme non contaminee ne sont pas suffisantes pour continuer l'operation en cours en respectant les exigences de l'aviation civile. Egalement, l'objectif de ce travail est d'etudier les methodes associees a l'execution de cette reconfiguration pour garantir l'utilisation de la partie du systeme GNSS multi-constellation non contaminee dans les meilleures conditions. Cette etude a donc un interet pour les constructeurs des futurs recepteurs avioniques multiconstellation. ABSTRACT : The International Civil Aviation Organization (ICAO) has defined the concept of Global Navigation Satellite System (GNSS), which corresponds to the set of systems allowing to perform satellite-based navigation while fulfilling ICAO requirements. The US Global Positioning Sysem (GPS) is a satellite-based navigation system which constitutes one of the components of the GNSS. Currently, this system broadcasts a civil signal, called L1 C/A, within an Aeronautical Radio Navigation Services (ARNS) band. The GPS is being modernized and will broadcast two new civil signals: L2C (not in an ARNS band) and L5 in another ARNS band. Galileo is the European counterpart of GPS. It will broadcast three signals in an ARNS band: Galileo E1 OS (Open Service) will be transmitted in the GPS L1 frequency band and Galileo E5a and E5b will be broadcasted in the same 960-1215 MHz ARNS band than that of GPS L5. GPS L5 and Galileo E1, E5a, E5b components are expected to provide operational benefits for civil aviation use. However, civil aviation requirements are very stringent and up to now, the bare systems alone cannot be used as a means of navigation. For instance, the GPS standalone does not implement sufficient integrity monitoring. Therefore, in order to ensure the levels of performance required by civil aviation in terms of accuracy, integrity, continuity of service and availability, ICAO standards define different systems/algorithms to augment the basic constellations. GPS, Galileo and the augmentation systems could be combined to comply with the ICAO requirements and complete the lack of GPS or Galileo standalone performance. In order to take benefits of new GNSS signals, and to provide the service level required by the ICAO, the architecture of future combined GNSS receivers must be standardized. The European Organization for Civil Aviation Equipment (EUROCAE) Working Group 62, which is in charge of Galileo standardization for civil aviation in Europe, proposes new combined receivers architectures, in coordination with the Radio Technical Commission for Aeronautics (RTCA). The main objective of this thesis is to contribute to the efforts made by the WG 62 by providing inputs necessary to build future receivers architecture to take benefits of GPS, Galileo and augmentation systems. In this report, we propose some key elements of the combined receivers' architecture to comply with approach phases of flight requirements. In case of perturbation preventing one of the needed GNSS components to meet a phase of flight required performance, it is necessary to be able to switch to another available component in order to try to maintain if possible the level of performance in terms of continuity, integrity, availability and accuracy. That is why future combined receivers must be capable of detecting the impact of perturbations that may lead to the loss of one GNSS component, in order to be able to initiate a switch. These perturbations are mainly atmospheric disturbances, interferences and multipath. In this thesis we focus on the particular cases of interferences and ionosphere perturbations. The interferences are among the most feared events in civil aviation use of GNSS. Detection, estimation and removal of the effect of interference on GNSS signals remain open issues and may affect pseudorange measurements accuracy, as well as integrity, continuity and availability of these measurements. In literature, many different interference detection algorithms have been proposed, at the receiver antenna level, at the front-end level. Detection within tracking loops is not widely studied to our knowledge. That is why, in this thesis, we address the problem of interference detection at the correlators outputs. The particular case of CW interferences detection on the GPS L1 C/A and Galileo E1 OS signals processing is proposed. Nominal dual frequency measurements provide a good estimation of ionospheric delay. In addition, the combination of GPS or GALILEO navigation signals processing at the receiver level is expected to provide important improvements for civil aviation. It could, potentially with augmentations, provide better accuracy and availability of ionospheric correction measurements. Indeed, GPS users will be able to combine GPS L1 and L5 frequencies, and future GALILEO E1 and E5 signals will bring their contribution. However, if affected by a Radio Frequency Interference, a receiver can lose one or more frequencies leading to the use of only one frequency to estimate the ionospheric code delay. Therefore, it is felt by the authors as an important task to investigate techniques aimed at sustaining multi-frequency performance when a multi constellation receiver installed in an aircraft is suddenly affected by radiofrequency interference, during critical phases of flight. This problem is identified for instance in [NATS, 2003]. Consequently, in this thesis, we investigate techniques to maintain dual frequency performances when a frequency is lost (L1 C/A or E1 OS for instance) after an interference occurrence

Desarrollo de algoritmos para el tratamiento de datos GNSS : su aplicación a los escenarios GPS modernizado y Galileo

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Matemáticas, Sección Departamental de Física de la Tierra, Astronomía y Astrofísica I (Geofísica y Meteorología) (Astronomía y Geodesia), leída el 24-07-2012Nowadays, the major GNSS systems are the american GPS and the russian GLONASS, however, in a near future the european project Galileo and the chinesse system COMPASS will become part of the current GNSS scenario. These systems will transmit for the first time three different frequencies, giving place to a multi-system and multi-frequency scenario which will dramatically push the boundaries of the positioning techniques. Currently, one of the most studied positioning techniques is known as Precise Point Positioning (PPP), which is aimed at estimating precise receiver position from undifferenced GNSS code and carrier phase observations and precise satellite products. In this thesis, some new and original algorithms for static PPP have been developed, which are able to deal with the future multi-system and multifrequency GNSS observations. The new algorithms have been named MAP3. In the new approach, the least squares theory is applied twice to estimate the ionospheric delay, initial ambiguities and smoothed pseudodistances from undifferenced observations, which in turn are used to recover the receiver position and its clock offset. MAP3 provides position estimations with an accuracy of 2.5 cm after 2 hours observation and 7 mm in 1 day, being at the same level as other PPP programs and even better results are obtained with MAP3 in short observation periods. Moreover, MAP3 have provided some of the first results in positioning from GIOVE observations and GPC products. In addition, these algorithms have been applied in the analysis of the influence of ionospheric disturbances on the point positioning, concluding that the presence of a high ROT (Rate of TEC), observed at equatorial latitudes, reflects a significant degradation of the point positioning from dual-frequency observations.Actualmente, los únicos sistemas globales de navegación por satélites operativos son GPS y GLONASS, sin embargo, en un futuro cercano el proyecto europeo Galileo y el sistema chino COMPASS entrarán a formar parte del actual escenario GNSS. Estos sistemas emplearán por primera vez, tres frecuencias distintas, dando lugar a un escenario multi-frecuencia que revolucionará las técnicas de posicionamiento. Entre las técnicas actuales de posicionamiento con GNSS destaca el Posicionamiento Preciso Puntual (PPP), que consiste en determinar la posición de un receptor a partir de observaciones de código y fase no differenciadas y productos precisos. En este trabajo de tesis se han desarrollado unos nuevos y originales algoritmos para PPP estático, llamados MAP3, capaces de procesar observaciones GNSS multifrecuencia y multi-sistema del futuro escenario GNSS y determinar la posición de un receptor de forma precisa y exacta. Los algoritmos MAP3 se dividen en dos partes en las cuales se ha aplicado la teoría mínimos cuadrados y se han obtenido expresiones explícitas para estimar el retraso ionosférico, ambigüedades de fase inicial y pseudodistancias suavizadas, que se emplean para determinar la posición del receptor y el offset de su reloj. MAP3 proporciona una estimación de la posición con una exactitud de 2.5 cm tras 2 horas de observación y de 7 mm tras 24 h, resultados que mejoran los obtenidos hasta el momento con otros programas para PPP en periodos cortos de tiempo. Además, MAP3 han proporcionado los primeros resultados en el posicionamiento con observaciones GIOVE y productos del GPC. Por otro lado, estos algoritmos se han aplicado al análisis de los efectos de ciertas perturbaciones ionosféricas en el posicionamiento concluyendo que la presencia de un ROT (Rate of TEC) elevado, observado en latitudes ecuatoriales, refleja una degradación significativa del posicionamiento puntual con observaciones doble frecuencia.Unidad Deptal. de Astronomía y GeodesiaFac. de Ciencias MatemáticasTRUEunpu

Optimal GPS/GALILEO GBAS methodologies with an application to troposphere

In the Civil Aviation domain, research activities aim to improve airspace capacity and efficiency whilst meeting stringent safety targets. These goals are met by improving performance of existing services whilst also expanding the services provided through the development of new Navigation Aids. One such developmental axe is the provision of safer, more reliable approach and landing operations in all weather conditions. The Global Navigation Satellite System (GNSS) has been identified as a key technology in providing navigation services to civil aviation users [1] [2] thanks to its global coverage and accuracy. The GNSS concept includes the provision of an integrity monitoring function by an augmentation system to the core constellations. This is needed to meet the required performances which cannot be met by the stand-alone constellations. One of the three augmentation systems developed within civil aviation is the GBAS (Ground Based Augmentation System) and is currently standardized by the ICAO to provide precision approach navigation services down to Cat I using the GPS or GLONASS constellations [3]. Studies on-going with the objective to extend the GBAS concept to support Cat II/III precision approach operations with GPS L1 C/A, however some difficulties have arisen regarding ionospheric monitoring. With the deployment of Galileo and Beidou alongside the modernization of GPS and GLONASS, it is envisaged that the GNSS future will be multi-constellation (MC) and multi-frequency (MF). European research activities have focused on the use of GPS and Galileo. The MC/MF GBAS concept should lead to many improvements such as a better modelling of atmospheric effects but several challenges must be resolved before the potential benefits may be realized. Indeed, this PhD has addressed two key topics relating to GBAS, the provision of corrections data within the MC/MF GBAS concept and the impact of tropospheric biases on both the SC/SF and MC/MF GBAS concepts. Due to the tight constraints on GBAS ground to air communications link, the VDB unit, a novel approach is needed. One of the proposals discussed in the PhD project for an updated GBAS VDB message structure is to separate message types for corrections with different transmission rates. Then, this PhD argues that atmospheric modelling with regards to the troposphere has been neglected in light of the ionospheric monitoring difficulties and must be revisited for both nominal and anomalous scenarios. The thesis focuses on how to compute the worst case differential tropospheric delay offline in order to characterize the threat model before extending previous work on bounding this threat in order to protect the airborne GBAS user. In the scope of MC/MF GBAS development, an alternative approach was needed. Therefore, in this PhD project, Numerical Weather Models (NWMs) are used to assess fully the worst case horizontal component of the troposphere. An innovative worst case horizontal tropospheric gradient search methodology is used to determine the induced ranging biases impacting aircraft performing Cat II/III precision approaches with GBAS. This provides as an output a worst case bias as a function of elevation for two European regions.The vertical component is also modelled by statistical analysis by comparing the truth data to the GBAS standardized model for vertical tropospheric correction up to the height of the aircraft. A model of the total uncorrected differential bias is generated which must be incorporated within the nominal GBAS protection levels. In order to bound the impact of the troposphere on the positioning error and by maintaining the goal of low data transmission, different solutions have been developed which remain conservative by assuming that ranging biases conspire in the worst possible way. Through these techniques, it has been shown that a minimum of 3 parameters may be used to characterize a region’s model

Etude de la Performance du Contrôle Autonome d'Intégrité pour les Approches à Guidage Vertical

L'Organisation de l'Aviation Civile Internationale (OACI) a reconnu la navigation par satellite, Global Navigation Satellite System (GNSS), comme un élément clé des systèmes CNS/ATM (Communications, Navigation, and Surveillance / Air Traffic Management) et comme une base sur laquelle les Etats peuvent s'appuyer afin de délivrer des services de navigation aérienne performants. Mais l'utilisation des systèmes de navigation par satellites pour des applications de type aviation civile ne va pas sans répondre à des exigences en terme de précision, de continuité, d'intégrité et de disponibilité. Ces exigences opérationnelles liées aux différentes phases de vol requièrent pour les systèmes GNSS l'appui de moyens d'augmentation tels ceux utilisant des stations de surveillance sol pour vérifier la validité des signaux satellitaires et calculer des corrections ou ceux fonctionnant de manière autonome, tel le RAIM (Receiver Autonomous Integrity Monitoring). Ce dernier moyen est particulièrement intéressant car il engendre des coûts de mise en oeuvre réduits et il constitue à l'heure actuelle un moyen simple et efficace d'effectuer des approches de non précision. La prochaine mise en place du système de navigation européen Galileo ainsi que la modernisation du système historique américain GPS vont entrainer une nette amélioration, à la fois en terme de nombre et de qualité, des mesures satellitaires disponibles, laissant entrevoir la possible utilisation du RAIM pour des approches à guidage vertical, très intéressantes du point de vue opérationnel. Les différentes notions liées aux exigences de l'aviation civile sont définies dans le chapitre 2, notamment les différents critères de performance. Chaque phase de vol, et plus particulièrement chaque catégorie d'approche, y est également décrite ainsi que les niveaux de performance associés. Plusieurs types d'erreurs sont susceptibles d'affecter les mesures GNSS. Parmi elles il convient de distinguer les erreurs systématiques ou nominales des perturbations liées à une défaillance du système de navigation. Ces dernières peuvent être dues soit à un problème matériel survenant au niveau d'un des satellites ou du récepteur, soit d'une perturbation de l'environnement de propagation des signaux GNSS. Ces aspects sont adressés dans le chapitre 3 à l'issu duquel un modèle complet de mesure de pseudo distance GNSS est proposé. Les algorithmes de contrôle d'intégrité ont été développés pour détecter ces anomalies et exclure les mesures erronées de la solution de navigation. Il s'agit de méthodes uniquement basées sur la redondance des mesures satellite, éventuellement enrichies de celles d'autres capteurs, devant déterminer si les conditions sont réunies pour occasionner une erreur de position dépassant une limite spécifiée. Devant répondre à des exigences relatives aux performances décrites dans le chapitre 2, le choix du type d'algorithme de contrôle d'intégrité est laissé à l'utilisateur. Le chapitre 4 étudie plusieurs de ces méthodes et propose des innovations.l'algorithme de surveillance doivent être réexaminées. En effet, elles pourraient avoir une plus petite amplitude et des taux d'occurrence qui ne sont pas clairement définie pour le moment. C'est dans ce contexte que la Direction Générale de l'Aviation Civile a initié cette thèse dont l'objectif est d'évaluer le potentiel des algorithmes RAIM pour les approches à guidage vertical. On tachera de savoir dans quelle mesure l'augmentation du nombre de satellites et de l'amélioration de qualité de mesures de pseudodistance pourraient elles permettre l'utilisation de RAIM les approches à guidage vertical. Cette thèse est organisée de la manière suivante. Tout d'abord, le chapitre 2 présente les exigences de l'aviation civile quant à l'utilisation du GNSS. Cette section inclut une description des différentes phases de vol et plus particulièrement des phases d'approche. Elle introduit les concepts RNAV et RNP et définit également les critères de performance requis par l'OACI pour chaque les phases de vol. Finalement, les termes de détectionet d'exclusion de faute, plus spécifiques au contrôle autonome d'intégrité, sont définis. Le chapitre 3 a pour objectif de donner un modèle complet des mesures GNSS en adressant aussi bien le mode nominal et le mode défectueux, en tenant compte des pannes satellite et de l'effet des interférences. Le chapitre 4 a pour but d'étudier differents algorithmes RAIM mais certains aspects généraux comme l'estimation de la position d'utilisateur ou le calcul du plus petit biais sur une mesure de pseudo distance entrainant une erreur de positionnement sont d'abord présentés. La manière dont les exigences aviation civile et le modèle d'erreur sont interprétés afin de constituer les paramètres d'entrée des algorithmes RAIM est discutée au chapitre 5. Le chapitre 6 présente des résultats des simulations qui ont été effectuées pour évaluer la performance RAIM pour les approches à guidage vertical. Cette évaluation a été réalisée grâce à des simulations Matlab. Finalement, le chapitre 7 résume les principaux résultats de ce travail de doctorat et propose quelques pistes de reflexion quant à de futurs travaux. ABSTRACT : The International Civil Aviation Organization (ICAO) has recognized the Global Navigation Satellite System (GNSS) as a key element of the Communications, Navigation, and Surveillance / Air Traffic Management (CNS/ATM) systems as well as a foundation upon which States can deliver improved aeronautical navigation services. But civil aviation requirements can be very stringent and up to now, the bare systems cannot alone be used as a means of navigation. Therefore, in order to ensure the levels required in terms of accuracy, integrity, continuity of service and availability, ICAO standards define different architectures to augment the basic constellations. Some of them use control stations to monitor satellite signals and provide corrections, others only use measurement redundancy. This study focuses on this last type of augmentation system and more particularly on Receiver Autonomous Integrity Monitoring (RAIM) techniques and performance. RAIM is currently a simple and efficient solution to check the integrity of GNSS down to Non Precision Approaches. But the future introduction of new satellite constellations such as the European satellite navigation system Galileo or modernized Global Positioning System (GPS) will imply great improvements in the number as well as the quality of available measurements. Thus, more demanding phases of flight such as APproaches with Vertical guidance could be targeted using RAIM to provide integrity monitoring. This would result in some interesting safety, operational and environmental benefits. This Ph.D. evaluates the potential capacity of RAIM algorithms to support approach and landing phases of flight with vertical guidance. A thorough bibliographic study of civil aviation requirements is first presented; some candidate LPV200 signal in space performance requirements not yet included in the ICAO standards are also provided. To evaluate GNSS positioning performance, pseudorange measurements have to be modeled as precisely as possible and especially the different errors that affect them. The main sources of error are signal propagation delays caused by the ionosphere and the troposphere, space vehicle clock error, satellite position estimation error, multipath, receiver errors which main source is code tracking loop noise. Thus, these errors can be due to the space segment, the control segment or the user segment. Systematic errors are gathered in the fault free case measurement model; unusual errors, that may cause a dangerous positioning failure and that may have to be detected, are gathered in the faulty case measurement model. Finally, a complete model of pseudo range measurements, including interference effects and satellite failures, is given. A special attention is put on the User Equivalent Range Error (UERE) variance computation. Indeed, among all input parameters of RAIM availability simulator, UERE has, by far, the most significant impact on the estimated availability. Three distinct classes of RAIM algorithms are studied in this thesis. The Least Square Residual method in which the sum of the squares of the pseudorange residuals plays the rôle of the basic observable is first recalled. The Maximum Solution Separation method which is based on the observation of the separation between the position estimate generated by a fullset filter (using all the satellite measurements) and the position estimate generated by each one of the subset filters (each using all but one of the satellite measurements) is then discussed and an improved way of computing the associated protection level is proposed. Finally, a new promising method based on the Generalized Likelihood Ratio test is presented and several implementations are described. The way these different methods are implemented to take into account both civil aviation requirements and threat model is then detailed. In particular some methods to obtain the inner probability values that RAIM algorithms need to use are presented. Indeed, high level requirements interpretation for RAIM design is not clearly standardized. Finally simulations results are presented. They permit to evaluate RAIM ability to provide integrity monitoring for approaches with vertical guidance operations considering various scenarios. The main contributions of this thesis are a detailed computation of user equivalent range error variance, an analysis of the effect of interferences on pseudorange measurement, an adaptation of LSR RAIM algorithm to nominal biases, an improvement of MSS protection levels computation, the implementation of GLR algorithm as a RAIM including the computation of an analytical expression of the threshold that satisfies the false alarm probability and the prediction of the probability of missed detection, design of a sequential GLR algorithm to detect step plus ramp failure and an analysis of the amplitude of smallest single biases that lead to a positioning failure. Least Squared Residual, Maximum Solution Separation and constrained Generalized Likelihood Ratio RAIM availabilities have been computed for APVI and LPV200 approaches using both GPS L1/L5 and Galileo E1/E5b pseudorange measurements. It appears that both APV I and LPV200 (VAL=35m) operations are available using GPS/Galileo + RAIM to provide integrity as an availability of 100 % has been obtained for the detection function of the three studied algorithms. An availability of 100 % has also been obtained for the LSR exclusion function. On the contrary, LSR RAIM FDE availabilities seem not sufficient to have Galileo + RAIM or GPS +RAIM as a sole means of navigation for vertically guided approaches

International Competition for Satellite-Based Navigation System Services

The goal of this work is to review the current state of Global Navigation Satellite System (GNSS) development and its potential impact on the social, economic, and political dynamics of the various states fielding the systems. The most recognizable GNSS is the US GPS. It is the only operational system functioning at the time of this writing and has become part of the global commons. GPS, by virtue of its uniqueness, is considered the \u27gold standard\u27 of satellite based positioning, navigation, and timing systems. This uniqueness has also enabled the US to fully capitalize on the sizable economic dividends gained by the US technology sector from the development and sales of GPS user equipment and services. This work argues that the emergence of three global peer competitors to GPS is going to usher in a changed international relations environment for those new players. The economic implications go beyond a simple return on investment and could represent the continued space science and technical competitiveness of these states or not. The international political ramifications of the success or failure of the particular GNSSs could have a greater impact on the current international order than has been previously considered. The European Union, Russia, and China have become inexorably locked in a contest of domestic political will to field the next generation of GNSS in order to free themselves from US GPS domination and at the same time gain economic advantage over the other in space system technologies. Concurrently, the US is endeavoring to field the next generation of GPS and maintain its dominance in the associated technologies linked to GPS

Integration of ARAIM technique for integrity performance prediction, procedures development and pre-flight operations

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is a new Aircraft Based Augmentation System (ABAS) technique, firstly presented in the two reports of the GNSS Evolutionary Architecture Study (GEAS). The ARAIM technique offers the opportunity to enable GNSS receivers to serve as a primary means of navigation, worldwide, for precision approach down to LPV-200 operation, while at the same time potentially reducing the support which has to be provided by Ground and Satellite Based Augmented Systems (GBAS and SBAS). Previous work analysed ARAIM performance, clearly showing the potential of this new architectures to provide the Required Navigation Performance down to LPV 200 approach procedures. However, almost all of the studies have been performed with respect to fixed points on a grid on the Earth’s surface, with full view of the sky, evaluating ARAIM performance from a geometrical point of view and using nominal performance in simulated scenarios which last several days. Though, the operational configuration was not examined; attitude changes from manoeuvres, obscuration by the aircraft body and shadowing from the surrounding environment could all affect the incoming signal from the GNSS constellations, leading to configurations that could adversely affect the real performance. In this research, ARAIM performances in simulated operational configurations are presented. Four different algorithms were developed that integrate the ARAIM technique for performance prediction analysis. These algorithms could usefully be implemented: • In the design of instrument approach procedures. The algorithms could be used to improve the procedure of the development of new instrument approaches, reducing time, effort and costs. • In the aircraft Flight Management Systems. The algorithms could support the pilots in the pre-flight briefing, highlighting possible integrity outage in advance and allowing them to select a different approach or making them aware of the need to utilise additional positioning systems. Increased awareness and better pre-flight planning could ultimately improve the safety of flights and contribute to the safe introduction of GNSS as a viable positioning method for instrument approach. The results showed that the aircraft attitude and the surrounding environment affect the performance of the ARAIM algorithm; each satellite lost generates a peak in the performance parameters that depends on the total number of satellites in view, their relative geometry and on the number of satellites lost at the same time. The main outcome of this research is the identification that the ideal scenario would be to have a tri-constellation system that provides at the same time high redundancy, reliability and increased safety margin

Precise Point Positioning Augmentation for Various Grades of Global Navigation Satellite System Hardware

The next generation of low-cost, dual-frequency, multi-constellation GNSS receivers, boards, chips and antennas are now quickly entering the market, offering to disrupt portions of the precise GNSS positioning industry with much lower cost hardware and promising to provide precise positioning to a wide range of consumers. The presented work provides a timely, novel and thorough investigation into the positioning performance promise. A systematic and rigorous set of experiments has been carried-out, collecting measurements from a wide array of low-cost, dual-frequency, multi-constellation GNSS boards, chips and antennas introduced in late 2018 and early 2019. These sensors range from dual-frequency, multi-constellation chips in smartphones to stand-alone chips and boards. In order to be comprehensive and realistic, these experiments were conducted in a number of static and kinematic benign, typical, suburban and urban environments. In terms of processing raw measurements from these sensors, the Precise Point Positioning (PPP) GNSS measurement processing mode was used. PPP has become the defacto GNSS positioning and navigation technique for scientific and engineering applications that require dm- to cm-level positioning in remote areas with few obstructions and provides for very efficient worldwide, wide-array augmentation corrections. To enhance solution accuracy, novel contributions were made through atmospheric constraints and the use of dual- and triple-frequency measurements to significantly reduce PPP convergence period. Applying PPP correction augmentations to smartphones and recently released low-cost equipment, novel analyses were made with significantly improved solution accuracy. Significant customization to the York-PPP GNSS measurement processing engine was necessary, especially in the quality control and residual analysis functions, in order to successfully process these datasets. Results for new smartphone sensors show positioning performance is typically at the few dm-level with a convergence period of approximately 40 minutes, which is 1 to 2 orders of magnitude better than standard point positioning. The GNSS chips and boards combined with higher-quality antennas produce positioning performance approaching geodetic quality. Under ideal conditions, carrier-phase ambiguities are resolvable. The results presented show a novel perspective and are very promising for the use of PPP (as well as RTK) in next-generation GNSS sensors for various application in smartphones, autonomous vehicles, Internet of things (IoT), etc