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ION GNSS + 2022, Denver, ETATS-UNIS, 21-/09/2022 - 23/09/2022; In safety-critical applications, the vulnerability of the Global Navigation Satellite System (GNSS) to radio frequency interferences (RFIs) is a major concern. The development of a fail-safe and robust localization system now necessarily requires detection and mitigation of such interferences, which has increased with the proliferation of wireless systems and easy access to personal privacy devices (PPD) also known as jammers. Moreover, the advent of software-defined radio (SDR) permitting the transmission of customized and more complex signals has further complicated this problem. This paper provides an in-depth comparison of interference mitigation techniques at multiple levels primarily focusing on the safety perspective at the position level. For this purpose, the classical adaptive notch filter (ANF) and the wavelet packet decomposition method are applied to mitigate the effects of interference. This comparative study aims to assess the performance of these mitigation techniques at multiple levels (frequency estimation, acquisition, tracking and position). However, the main goal for the final user is to study the impact on key performance indicators (KPIs) such as accuracy, availability, and safety. Furthermore, two cases are considered: 1): interference in the absence of any mitigation strategy and after applying interference mitigation technique at the pre-correlation level. The complete study is presented for two different types of time-varying continuous wave (CW) interferenc.e signals namely frequency hopping and the chirp signal.

ION ITM 2022 - International Technical Meeting of Institute of Navigation, Long Beach, CA, ETATS-UNIS, 25-/01/2022 - 27/01/2022; Localization function for an advanced intelligent transport system, such as an autonomous vehicle, must ensure various operational requirements such as safety, accuracy, availability and continuity of service, anytime, anywhere, at a reasonable cost. Global Navigation Satellite System (GNSS) have many advantages insofar as they present the most accessible technology to the user to determine its position with a certain accuracy without prior knowledge. However, in an environment where signal reception may not be optimal especially due to phenomena such as satellite blockage, multipath, intentional or unintentional interferences and spoofing, it becomes very challenging to meet all these requirements, especially those related to operational safety. The latter is measured by evaluating the integrity of the localization function. It can be evaluated through a Protection Level, which is calculated by the receiver to self-monitor its integrity, also called RAIM (Receiver Autonomous Integrity Monitoring). In the literature, integrity in presence of multipath and NLOS has been extensively investigated [1] as well interference detection and mitigation solutions [2]. However, the impact of interference presence and mitigation on integrity monitoring is not deeply addressed yet. In this study, we evaluate some key performance indicators (KPI's) for GNSS users. These indicators will be evaluated for three different cases; 1) when no interference is applied and clean GNSS signals are processed. 2) In the presence of interference but without any mitigation technique. 3) After applying a mitigation technique at the pre-correlation level to filter the interference signal. The mitigation technique relies on state-of-the-art Notch filters provided by a Septentrio receiver. The interference signals are generated in the laboratory to produce disturbances in the GNSS band. Thus, and thanks to the a priori knowledge of the true position, it is possible to establish the Stanford diagrams for these cases. A deep analysis of performance in the presence and absence of interferences and in the presence and absence of a mitigation technique allows the first conclusions to be drawn on the evolution of accuracy, availability and operational safety indicators. The preliminary results reveal the importance of considering, from the design phase of the localization function, the possibility of dealing with this phenomenon, in particular in the measurement weighting model to use for enhanced performance.

L'utilisation des GNSS (Global Navigation Satellite System) dans le milieu ferroviaire est d'ores et déjà une réalité sur le terrain. Mais les défis pour l'intégration des technologies de positionnement par satellites dans des systèmes complexes de contrôle-commande et de gestion du trafic ferroviaire restent nombreux.

The ERSAT-Galileo Game Changer research project, which concluded last November, has laid the foundations for GNSS satellite location technology to support train positioning on secondary railways, potentially reducing the cost of ERTMS deployment.This paper summarizes the main contributions of the project and the perspectives.

WCRR 2019, 12th World Congress on Railway Research, Tokyo, JAPON, 28-/10/2019 - 01/11/2019; The use of GNSS positioning into the ERTMS/ETCS has been identified as the technology for supporting the detection of Virtual Balises (VB). However, the presence of local GNSS threats (e.g. multipath, non-line-of-sight (NLOS) or interference) that may not be detectable by a local or wide area augmentation network, can potentially lead to unbounded errors in the pseudorange measurement and ultimately to an error in the VB position that cannot be bounded with the required integrity. In order to prevent a priori the risk of this hazardous situation, VB must be located in areas there are no local threats that may lead a Virtual Balise Reader (VBR) on board the train to dynamically estimate unbounded virtual balise position errors. The ERSAT-GGC project has been funded to tackle with this challenge. This paper aims to present the techniques and methods developed to characterize track areas to know a priori which track portions are suitable for placing VBs. They will rely on basic equipment that every stakeholder shall be able to install and use, composed of a COTS GNSS receiver providing raw data and, when necessary, a spectrum analyzer. The paper describes and illustrates the selected techniques.

WCRR 2019, 12th World Congress on Railway Research, Railway Research to Enhance the Customer Experience, Tokyo, JAPON, 28-/10/2019 - 01/11/2019; Innovative technologies enable new approaches for train control, command and signaling systems. E.g. digitalization and automation lead to completely new concepts. The partner RAILENIUM, NSL, CEIT and DLR have founded the consortium Smart Rail Control (SmartRaCon) to develop new concepts, approachs and technologies for the train control, command and signaling systems of the future. In this contribution the developments in the areas of communication, localization and train integrity will be discussed. For the communication the next generation of mobile radio 5G is in the focus with the capability to support software defined networks and radio as well as virtualization potentials. For localization and train integrity supervision algorithms for the fusion of sensor data and digital maps are the key elements. E.g. Global Navigation Satellite Systems (GNSS) together with complementary sensors can be used to achieve a safe and reliable localization. This concept again can serve as a core of a end-of-train device for train integrity monitoring. Further elements like the traffic management or moving block as well as procedural aspects like simulation-based testing are subject of the SmartRaCon concepts and are related to the issues discussed here. The architectural concept to integrate all those elements is based on the idea to use components and software common-off-the-shelf (COTS) and to integrate them into a railway network in a modular way.

WCRR 2019, 12th World Congress on Railway Research, Tokyo, JAPON, 28-/10/2019 - 01/11/2019; New technologies such as GNSS-based positioning solutions will contribute to the modernization and efficiency enhancement of the railway system. Its capacity to provide a global absolute position without any infrastructure to be supported by the user at reasonable cost makes GNSS a game changer for rail. However, in order to reach the high-level performance requirements needed to apply these technologies to safety-critical applications, and in particular, for the use of virtual balises, some solutions need to ensure their accuracy, robustness and safety. Coming from aeronautics experience, the RAIM (Receiver Autonomous Integrity Monitoring) can help reducing inaccuracy by detecting and excluding faulty measurements and bounding residual errors. In this paper, we intend to demonstrate how the combination of weighting schemes and FDE (Fault Detection and Exclusion) can help the system to enhance GNSS performance in a railway environment where multipath, non-line of sight signals and interferences can occur. Some results based on real data are presented in order to quantify the benefit. Application of such techniques will help designing future on-board location units by evaluating their potential performance before deciding the level of hybridization that will be mandatory to ensure continuity of service and compensate the drawbacks of GNSS in harsh environments.

This is the deliverable D4.5 Process Execution Report of the ERSAT GGC project. This document reports the execution of the track area classification process developed during the work package WP4 Track Survey and Track Classification along with the main outcomes and results obtained during this process. The goal of WP4 is to set up a standard measurement and classification system that is able to provide a prediction of the expected presence of GNSS hazard causes and degraded performance to be expected at a given track area, in order to enable the evaluation if the specific environment is suitable or not to place virtual balises or on the contrary should be discarded beforehand. In this document, we detail the results of applying the classification standard process, by means of the developed software Toolset to the measurement data collected in the three measurements campaigns during ERSAT GGC project. This execution report addressed the main important aspects that need to be carried out for the correct application of the classification process and the results obtained with the data collected.

IEEE RTSI 2018, 4th International Forum on Research and Technologies for Society and Industry, Palerme, ITALIE, 10-/09/2018 - 13/09/2018; Global Navigation Satellite Systems (GNSS) have continually involved in our daily life in the past decades. Among all these GNSS-based applications, there is an increasing number of GNSS-based urban transport applications, especially the critical liability ones, such as the Electronic Toll Collection (ETC) and the Intelligent Transport System (ITS). For these GNSS-based applications, not only positioning accuracy but also its reliability is required. Latter has attracted more and more attention from urban GNSS users. Yet urban environments present great challenges for common commercial GNSS receivers since the existence of local effects such as multipath and the Non-Line-of-Sight (NLOS) receptions. The main objective of this paper is to investigate the integrity performance one can expect from a lowcost common GNSS receiver. Under this framework, this paper proposes an innovation-based integrity monitoring scheme by using an Extended Kalman Filter (EKF) with the help of carrierpower-to-noise ratio (C/N0) weighting. The derivations of the Horizontal Protection Level (HPL) for the EKF innovation-based integrity monitoring is also presented in detail. The accuracy and integrity performances are evaluated with real GPS data collected in urban environments. Compared to the classic residual-based snapshot Receiver Autonomous Integrity Monitoring (RAIM), the innovation-based EKF integrity monitoring scheme presents more advantages in terms of accuracy and integrity. With the real dataset collected in urban canyon of Nantes center, the results show that the average size of horizontal position error has been reduced by 1.15 meter with the proposed approach compared to the classic weighted RAIM, the median size of HPL has been reduced by 7.5 meters and the algorithm availability is 100% instead of 98.57%.

Fourth International Conference on Railway Technology: Research, Development and Maintenance, Sitges, ESPAGNE, 03-/09/2018 - 07/09/2018; Présentation de l'architecture développée pour le projet ERSAT GGC utilisant l'image pour la caractérisation de la réception des signaux GNSS le long d'une voie.

TRA 2018, 7th Transport Research Arena, Vienne, AUTRICHE, 16-/04/2018 - 19/04/2018; Cet article présente un résumé de l'état de l'art réalisé pour le projet EU STARS sur l'utilisation d'EGNOS dans le domine ferroviaire. GNSS is expected to help the railway system to be modernized. However, such localization applications requires a high level of accuracy and safety that deserve to use the best potential of satellite-based technologies. The augmentation systems, as the satellite-based augmentation system EGNOS (European Geostationary Navigation Overlay Service), helps to increase the nominal performance. One of the tasks of the EU STARS project deals with the study of the usability of EGNOS in railway environments. EGNOS has indeed been developed driven by the requirements of civil aviation safety procedures in conditions for signal reception that differ from the railway ones. In this paper, after introducing the needs and the basic principles of these systems, we describe the limitations caused by the specificities of railways and some solutions perspectives proposed by the project.

Au cours des dernières décennies, de plus en plus d'applications de transport urbain basées sur les systèmes de positionnement par satellites (GNSS) ont vu le jour. Des applications exigent une fiabilité critique comme le télépéage basé sur l'utilisation du GNSS, pour lesquelles des erreurs de positionnement peuvent entraîner de graves conséquences. Pourtant, les environnements urbains présentent de grands défis pour le positionnement GNSS en raison de l'existence des trajets multiples et de signaux NLOS (None-Line-of-Sight). Cet article présente un système complet de surveillance de l'intégrité pour les applications de transport urbain. Tout d'abord, les erreurs de mesure sont mieux caractérisées en utilisant des modèles de pondération tirant parti d'un modèle de multi-trajet urbain (UMM). Deuxièmement, différentes méthodes de détection et d'exclusion de défauts (FDE) sont appliquées afin de détecter et d'exclure des mesures erronées. Enfin, les niveaux de protection horizontale (HPL) sont calculés et la probabilité d'événements redoutés (MI) est analysée., In the past decades, more and more Global Navigation Satellite Systems (GNSS)-based urban transport applications emerged. Among these applications, the liability critical ones, such as Electronic Toll Collection (ETC) and Pay as you Drive insurance, have high requirements for positioning accuracy as well as integrity since large errors can lead to serious consequences. Yet urban environments present great challenges for GNSS positioning due to the existence of multipath effects and None-Line-of-Sight (NLOS) receptions. This article presents a complete integrity monitoring scheme for urban transport applications. This scheme is realized in several levels. Firstly, measurement errors are better characterized by using weighting models with the help of an Urban Multipath Modeling (UMM). Secondly, several Fault Detection and Exclusion (FDE) methods are applied in order to detect and exclude erroneous measurements. Finally, Horizontal Protection Levels (HPLs) are computed and the probability of Misleading Information (MI) is analyzed.

RAIL Live 2018, Bilbao, ESPAGNE, 18-/04/2018 - 19/04/2018; Présentation de l'état de l'art des applications GNSS pour le ferroviaire, des enjeux et des verrous. Industry update: the state of GNSS-based solutions and projects for rail. Understanding the implications of GNSS for the rail industry: optimising operations and reducing costs. Remaining issues and next short term steps: developing tools and methodology to enhance and prove both the reliability and safety of GNSS-based positioning solutions

International Congress on High-speed Rail: technologies and long term impacts, Madrid, ESPAGNE, 04-/10/2017 - 06/10/2017; High Speed Railway services have shown that Railways are a competitive and, at the same time, an environmentally friendly transport system. The next level of improvement will be a higher degree of automation, with partial or complete automatic train operation up to fully automatic unattended driverless operation to reduce energy consumption and noise, as well as improving punctuality and comfort. Based on extensive experience in separated railway systems such as Metros, VAL (Véhicule automatique léger) and subways, today's discussion focuses on the fully automatic train operation on regular railway lines. This introduces some questions that are more complex than in today's systems: the performance, length and weight of the trains spreads in a wider range; there are other and more complex operations; components such as level crossings in different equipment variants are added; requirements are higher and the technological equipment point is more heterogeneous. Many evolutionary or innovative approaches for railway automation rely on precise and reliable localization. Especially for higher levels of automation it is essential. Starting from existing technologies such as the European Train Control System (ETCS), moving on to advanced driver assistance systems for local automatic operation up to full automatic train operation (ATO), all of these solutions depend on knowledge of the position of the train on the network. Improved concepts for railway operation e.g. using moving block, on-board integrity supervision or virtual train sets will result in even higher requirements for accuracy and reliability of the localization. The contribution shows an approach based on Global Navigation Satellite Systems (GNSS) as a priority source of information used in combination with sensor data fusion. Elements such as trackside augmentation as well as the use of digital maps will be discussed. Different approaches are considered, e.g. those currently under development by projects in the innovation program in the joint undertaking Shift2Rail.

Les applications des systèmes de positionnement par satellites (ou GNSS - Global Navigation Satellite System) ont progressivement envahi les systèmes de transport et les applications mobiles. Les applications déployées sont peu exigeantes en termes de performance : elles tolèrent une certaine imprécision et ne requièrent pas nécessairement une grande confiance dans l'information délivrée. Avec l'arrivée des véhicules autonomes ou les évolutions des systèmes de signalisation ferroviaire, de nouveaux besoins sont exprimés : une plus grande précision assortie d'un indicateur de confiance dans l'information fournie, en particulier pour des applications qui mettent en jeu la sécurité des biens et des personnes. Un récepteur GNSS utilise la mesure simultanée de 4 (au moins) temps de propagation des signaux issus de 4 satellites différents pour estimer sa position. Dans les environnements traversés par les systèmes de transports, la réception de ces signaux est fréquemment sujette à des conditions de réception difficiles liées à la présence d'obstacles proches de l'antenne de réception (blocage, réflexion, diffraction) qui engendrent indisponibilité, retards de propagation et donc, erreurs sur le calcul de la position. Pour comprendre les causes et les conséquences des erreurs introduites par le canal de propagation radio sur les performances de localisation, les travaux présentés dans ce mémoire de HDR rassemblent les travaux menés selon 3 axes principaux. Dans ces travaux, nous avons ainsi analysé les effets du canal de propagation radio sur le signal reçu par l'antenne du récepteur GNSS, caractérisé et quantifié la qualité du signal reçu en sortie du récepteur, proposé des méthodes originales permettant de modéliser et pallier les erreurs de localisation et enfin nous avons contribué au développement d'une méthodologie d'analyse de la sûreté de fonctionnement du système de localisation dans le domaine ferroviaire. L'erreur que nous cherchons à réduire en particulier est l'erreur engendrée par les phénomènes de propagation locaux et en particulier par l'utilisation des signaux reçus après réflexions et en l'absence de signal direct, encore appelés NLOS (Non-Line-Of-Sight). Parmi les résultats, nous avons mis en oeuvre des techniques de traitement d'images pour une détection déterministe associée à des techniques d'exclusion et de pondération des signaux reçus. Avec des techniques de traitement du signal, nous avons proposé des méthodes d'estimation dynamique des retards de propagation qui ont montré leur efficacité dans la réduction des imprécisions sur les calculs de la position en milieux urbains. Enfin, nous abordons le concept d'intégrité de la position. Les processus de surveillance de l'intégrité sont aujourd'hui issus de l'aéronautique et s'adaptent mal aux conditions de réception en milieu urbain. Notre connaissance des conditions de propagation des signaux nous a conduits à étudier et à proposer de nouveaux processus pour borner les erreurs de position introduites par l'environnement urbain. Enfin, nous présentons les axes de recherche mis en oeuvre afin de contribuer à l'introduction des solutions GNSS pour des applications de signalisation ferroviaire : nos travaux portent sur l'adaptation des méthodologies classiques ferroviaires au système GNSS et à ses sources de dégradation.

Les applications des systèmes de positionnement par satellites (ou GNSS - Global Navigation Satellite System) ont progressivement envahi les systèmes de transport et les applications mobiles. Les applications déployées sont peu exigeantes en termes de performance : elles tolèrent une certaine imprécision et ne requièrent pas nécessairement une grande confiance dans l'information délivrée. Avec l'arrivée des véhicules autonomes ou les évolutions des systèmes de signalisation ferroviaire, de nouveaux besoins sont exprimés : une plus grande précision assortie d'un indicateur de confiance dans l'information fournie, en particulier pour des applications qui mettent en jeu la sécurité des biens et des personnes. Un récepteur GNSS utilise la mesure simultanée de 4 (au moins) temps de propagation des signaux issus de 4 satellites différents pour estimer sa position. Dans les environnements traversés par les systèmes de transports, la réception de ces signaux est fréquemment sujette à des conditions de réception difficiles liées à la présence d'obstacles proches de l'antenne de réception (blocage, réflexion, diffraction) qui engendrent indisponibilité, retards de propagation et donc, erreurs sur le calcul de la position. Pour comprendre les causes et les conséquences des erreurs introduites par le canal de propagation radio sur les performances de localisation, les travaux présentés dans ce mémoire de HDR rassemblent les travaux menés selon 3 axes principaux. Dans ces travaux, nous avons ainsi analysé les effets du canal de propagation radio sur le signal reçu par l'antenne du récepteur GNSS, caractérisé et quantifié la qualité du signal reçu en sortie du récepteur, proposé des méthodes originales permettant de modéliser et pallier les erreurs de localisation et enfin nous avons contribué au développement d'une méthodologie d'analyse de la sûreté de fonctionnement du système de localisation dans le domaine ferroviaire. L'erreur que nous cherchons à réduire en particulier est l'erreur engendrée par les phénomènes de propagation locaux et en particulier par l'utilisation des signaux reçus après réflexions et en l'absence de signal direct, encore appelés NLOS (Non-Line-Of-Sight). Parmi les résultats, nous avons mis en oeuvre des techniques de traitement d'images pour une détection déterministe associée à des techniques d'exclusion et de pondération des signaux reçus. Avec des techniques de traitement du signal, nous avons proposé des méthodes d'estimation dynamique des retards de propagation qui ont montré leur efficacité dans la réduction des imprécisions sur les calculs de la position en milieux urbains. Enfin, nous abordons le concept d'intégrité de la position. Les processus de surveillance de l'intégrité sont aujourd'hui issus de l'aéronautique et s'adaptent mal aux conditions de réception en milieu urbain. Notre connaissance des conditions de propagation des signaux nous a conduits à étudier et à proposer de nouveaux processus pour borner les erreurs de position introduites par l'environnement urbain. Enfin, nous présentons les axes de recherche mis en oeuvre afin de contribuer à l'introduction des solutions GNSS pour des applications de signalisation ferroviaire : nos travaux portent sur l'adaptation des méthodologies classiques ferroviaires au système GNSS et à ses sources de dégradation.

The objective of STARS task 5.1 is to review the existing navigation augmentation systems and services in terms of performances achieved and application environments, and to analyse the experimentations and projects already performed in railway applications related to the use of these systems and services.This report aims to draw the state of the art of existing monitoring system (as used in aeronautics) and past experiences of railways when using such concepts. The focus only concerns GNSS-based positioning systems and do not pretend to present the global systems developed to insure the complete safety level of railway signalling.

Institute of navigation - International Technical Meetings - ION ITM 2017, Monterey, Etats-Unis, 30-/01/2017 - 02/02/2017; Integrity is one of the most important parameters characterizing the Global Navigation Satellite Systems (GNSS) performance for safety-related applications. It is defined as a measure of trust to be placed in the correctness of the information supplied by the total system. This concept is more and more important, especially for applications in urban environment with standalone GNSS system, where GNSS performance is strongly degraded by the signal propagation conditions. Non line of Sight (NLOS) signals, caused by the surrounding obstacles, are of particular interest, as the error they induced remains a large cause of inaccuracy. In order to get rid of these constraints and to guarantee a better performance of positioning accuracy as well as integrity, several approaches can be used, such as positioning weighting models, 3D city models, Fault Detection and Exclusion (FDE) techniques etc. Since the concepts of integrity and accuracy are strongly related to each other, a better accuracy can help to improve the integrity performance. Thus, to reduce and to bound position errors are our two main objectives. In the work presented here, we will introduce 2 classes of methods which contribute to the NLOS signal mitigation as well as integrity performance. The first class concerns the use of different weighting models in order to reduce the influence of the NLOS on the overall measurements. The second class consists of Fault Detection and Exclusion (FDE) algorithms which allow users to identify and remove the outliers.

Séminaire Ferroviaire et Applications GNSS, Toulouse, FRANCE, 24-/03/2016 - 24/03/2016; Cette présentation fait l'état des lieux des projets passés visant l'introduction du GNSS dans le ferroviaire : enjeux, bilan et verrous restant.

22nd ITS World Congress, Bordeaux, France, 05-/10/2015 - 09/10/2015; Most of the Intelligent Transport Systems rely on GNSS positioning information. Unfortunately, most of the vehicles circulate in dense urban areas where the GNSS signals are affected by multipath caused by the buildings surrounding the antenna. The CAPLOC project deals with inaccuracy by associating image processing techniques and signal propagation knowledge to understand and reduce GNSS inaccuracy. Our solution embeds fisheye cameras located on the roof of a vehicle and oriented upwards to capture images of the sky. Our approach consists in processing the images to 1/ determine whether satellites are located in a sky or non-sky region and 2/ construct a 3D model around the camera/antenna in order to estimate the pseudo-range delays caused by the close propagation effects. This knowledge allows us to propose several strategies of exclusion/weighting or correction of these pseudoranges for a better accuracy.

European Navigation Conference 2015, Bordeaux, France, 07-/04/2015 - 10/04/2015; GNSS accuracy still remains a challenge in dense urban areas where, unfortunately, most of the localization users travel. Propagation effects and, in particular reflections of the signals, induce major inaccuracy measurements of the pseudoranges. For most of the Intelligent Transport Systems (ITS), there is a need to face this source of in accuracy in order to offer new services in a low cost solution. The work presented in this paper has been performed in the context of a French project named CAPLOC that aims to propose accurate localization in dense urban areas in this context .The solutions explored in the projects propose to use only available GNSS signals, and chose some of them or weight some of them in order to increase performances. CAPLOC intends to use the knowledge of the propagation environment close to the antenna to enhance GNSS positioning accuracy.

Les nouveaux services de transport intelligent foisonnent. La plupart d'entre eux reposent de façon plus ou moins directe sur une information de localisation, parmi lesquelles les services de navigation bien sûr, mais aussi de l'aide à l'éco-conduite, des assurances « pay as you drive », la limitation de vitesse variable... Techniquement, la solution la plus répandue aujourd'hui repose sur l'installation de puces GPS à bord des véhicules, agrémentée des équipements logiciels et matériels capables d'exploiter l'information de position pour délivrer un service (calcul d'itinéraire, recalage sur la carte, système de communication etc). Le système de radionavigation par satellites GPS offre en effet le meilleur compromis coût/simplicité/performance aujourd'hui. Il peut être complété par l'utilisation de signaux EGNOS, améliorant ainsi sa précision et sera bientôt compatible avec Galileo. Certains services, tels que la navigation automobile, s'accommodent aujourd'hui assez bien des performances obtenues. Malheureusement, alors que l'utilisateur urbain d'un système de localisation par satellites est le plus demandeur de précision, il dispose d'un service dégradé en raison des conditions de propagation des signaux, fortement liées à la densité des obstacles, qui limitent les performances optimales atteignables. Pour améliorer les performances, en termes de précision, disponibilité et d'intégrité (c'est-à-dire de garantie de service), les travaux menés dans les laboratoires Leost et Geoloc de l'Ifsttar exploitent la connaissance de l'environnement de réception proche afin de réduire les perturbations sur la localisation GNSS. Dans le projet CAPLOC, cette connaissance est extraite d'une analyse d'images de l'environnement au-dessus du véhicule ; dans INTURB d'une carte numérique 3D. Ces deux approches innovantes s'inscrivent dans la suite d'un brevet déposé en 2006 pour CAPLOC et dans un courant de propositions utilisant les modèles 3D de plus en plus disponibles et complets. Le rapport proposé en livrable synthétisera l'ensemble des travaux publiés et décrira en particulier les approches suivies dans ces deux projets, illustrées chacune par des résultats expérimentaux.

The chapter 3 is organized in three main sections. The first section is devoted to wireless communications for public transport applications. We first recall some challenges for sustainable mobility and the difficulties encountered to implement on the shelf wireless systems for public transport. Then, we will give a brief overview and some examples of the wireless technologies deployed today: beacons, bifilar communications, radio systems, etc. After this, we present the future trends in the domain of wireless systems for public transport applications and the ongoing research in the railway domain as well as the metro and tramway domains. Particularly, we emphasis the railway applications of Internet of Things. The second section of the chapter is focused on the localization function for public transport applications. The position is the core of every intelligent transportation system, for non-safe as well as safe systems. After a brief description of the principles and the advantages and drawbacks of the systems, we describe the main existing applications and the one foreseen in the future. We then extend to the case where satellites are not available, particularly in the case of tunnels. We describe the more solutions deployed or planned for the future. In the last section, we highlight the problems set up by the specific context of electromagnetic and propagation environments for railways. We show the necessity to develop electromagnetic modeling of some environments, to set up ad'hoc channel models as well as noise distribution. It is also important to cope with non-metallic material of the trains and to find solution for the implementation of multiple antennas at various locations and at very different frequencies (from several kHz to several GHz). Finally we conclude this chapter.

IC-ARE'15, International Congress on Advanced Railway Engineering, Istanbul, TURQUIE, 02-/03/2015 - 04/03/2015; In this paper the results of the EU-funded project GaLoROI (Galileo Localization for Railway Operation Innovation) are presented. The satellite based localization unit for railways developed within GaLoROI serves as a basis for modern train control systems allowing a safe and precise continuous localization of trains increasing the capacity and operational performance of railways in comparison to current discrete train localization methods.GaLoROI started with the specifications of the localization unit which represent the state of the art of both railway and GNSS technology. Based on these specifications, the product development including system integration, verification and validation has been carried out with the target to reach the high safety level of SIL 3 specified in railway standardisation. The development was followed by tests and demonstration runs. It was accompanied by a RAMS performance analysis and an economical assessment. The results from the safety perspective have been summarized and reflected in the safety case and the assessment of the safety case.These results of GaLoROI are presented in this paper. They are a unique step in the field of satellite based localization for railways. Prior to GaLoROI, only the viability of satellite based localization in railways could be demonstrated. In GaLoROI it has been shown that satellite based localization is able to provide a precise and safe localization following the demonstration processes required by the railway safety standards.

This report is the deliverable corresponding to task 4.2 "demonstration of SATLOC concept exportation capability based on performance assessment of GNSS in any railway intended environment.

The SATLOC project aims at demonstrating an innovative concept of applying the GNSS to railway safety and advanced operation on low traffic lines. One of the issues is to determine if GPS, Galileo and EGNOS are available along the track and can answer to the railway requirements even in the presence of masking obstacles along the track. This paper presents the simulation approach developed by Spirent and Ifsttar in order to simulate GNSS signals in a realistic masking environment known by image acquisition and processing. The paper illustrates the concept with results obtained at a tunnel output near to Brasov, Romania, and concludes with perspectives that could enrich the results, in particular by including multipath effects and not only line-of-sight satellites.

Une introduction réussie de la technologie de navigation par satellite dans la sécurité ferroviaire nécessite une accréditation d’une nouvelle façon de penser, de l’innovation, une démonstration convaincante, de lever les barrières techniques et changer les mentalités. Cet article montre l’état d’avancement du projet SATLOC, et ses objectifs en lien avec les termes du FP7, item Galileo.2011.1.4-1 Use of EGNOS and GALILEO for safety-of-life applications for all transport modes. L’article résume les réalisations notables de l’équipe projet, l’avancée des tests sur la ligne pilote Brasov-Zarnesti en Roumanie ainsi que la validation de concepts en laboratoire qui les a précédés.

Evaluating dependability of complex systems requires the evolution of the system states over time to be analysed. The problem is to develop modelling approaches that take adequately the evolution of the different operating and failed states of the system components into account. The Fault Tree (FT) is a well-known method that efficiently analyse the failure causes of a system and serves for reliability and availability evaluations. As FT are not adapted to dynamic systems with repairable multi-state components, extensions of FT (eFT) have been developed. However efficient quantitative evaluation processes of eFT are missing. Petri nets have the advantage of allowing such evaluation but their construction is difficult to manage and their simulation performances are unsatisfactory. Therefore, we propose in this paper a new powerful process to analyse quantitatively eFT. This is based on the use of PN method, which relies on the failed states highlighted by the eFT, combined with a new analytical modelling approach for critical events that depend on time duration. The performances of the new process are demonstrated through a theoretical example of eFT and the practical use of the method is shown on a satellite-based railway system.

Cette communication est le second volet de la présentation des résultats obtenus dans le cadre du projet CAPLOC dont les objectifs sont : de développer un système capable d'extraire et de modéliser des connaissances sur l'environnement traversé par le mobile à partir d'une perception vidéo afin d'inférer les caractéristiques du canal de propagation entre les satellites et l'antenne du récepteur ; - de proposer des techniques d'estimation plus précise de la position du mobile à partir de ces nouvelles connaissances.

The new information technologies are revolutionising the order of our society with impacts on business and the professions, on our interaction with other people, and on our mobility. The transport sector faces many challenges, relating to traffic and infrastructure management, to the provision of information and to operations; in order to meet the growing needs of authorities, traffic managers, service providers, and users, it has embraced IT technology for many years. Up until recently, the information channels used have been relatively wellidentified and have often been based on a centralised architecture, which has allowed controlling the transfer of messages to the various user categories.; Les nouvelles technologies de l'information révolutionnent l'organisation de notre société avec un impact sur le monde du travail, sur notre rapport avec les autres et sur notre mobilité. Le domaine des transports avec ses multiples challenges liés à la gestion du trafic et des infrastructures, à la diffusion d'information et au contrôle opérationnel, a intégré depuis de nombreuses années les technologies de l'informatique et des télécommunications pour répondre aux besoins croissants des autorités, des gestionnaires, des sociétés de services et des usagers. Jusqu'à récemment, les canaux d'information étaient relativement bien identifiés et s'appuyaient souvent sur une architecture centralisée, permettant une diffusion réglementée des messages aux différentes catégories d'utilisateurs.

On présente ici des travaux du LEOST visant à améliorer la précision d’une localisation utilisant les signaux GNSS disponibles en environnement contraint.

This paper describes the development and use of a simulation tool, called QualiSIM. This tool simulates GNSS-based position accuracy under various operational and environmental conditions, in particular in environments with large amounts of signal reflections. The signal reflections are implemented using the geometric path length the signal travels when it gets reflected from the surrounding buildings. Environmental influences on GNSS-based positioning are obstacles, such as buildings along streets which can lead to blocking and reflection of satellite signals. Examples of operational conditions are atmospheric effects and changes in the satellite geometry. The tool has been developed to work either with Galileo or GPS or with both satellite constellations. Since Galileo is only preoperational, the simulator is based on the nominal 27 satellite Galileo constellation. Further, the simulator uses: atmospheric models to simulate the effect on satellite signals through Earth’s atmosphere, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the close environment of the GNSS (Global Navigation Satellite System) antenna. The simulator thus models: the signal path from satellite to receiver, satellite availability, the extended pseudoranges caused by signal reflection, and the position accuracy based on a least squares adjustment of the extended pseudoranges. In order to handle temporal and spatial variations of the different errors sources in GNSSbased positioning, the simulator has been developed for observing variations in position accuracy over time, along a given test trajectory, at different latitudes, and with different azimuths of the environment around the receiver. The environments used by the simulator could be typical representative scenarios such as, a narrow city street, a t-cross or mountain landscape. The choice of not using specific streets or cities has been made in order to keep the simulator open for every kind of environment. In this paper a simulation example is illustrated and shows the possibilities for visualisation of a narrow street with buildings on each side over a simulation time period of 24 hours. The impact of using reflected satellites in the position domain is significant. The DOP values are in general lower, but the error ellipses can be up to 8 times larger and furthermore deviate in shape.

La communication présente l'avancée des travaux à mi parcours du projet CAPLOC. Le projet CAPLOC vise l’amélioration des performances des systèmes de localisation par satellites en environnement contraint, typiquement les centres urbains. Pour ce faire, un système d’acquisition vidéo est utilisé pour apporter au calcul de position, la connaissance des conditions de propagation des signaux. Deux approches sont étudiées : la première consiste à détecter, grâce à l’image, les satellites reçus en NLOS, et donc vecteur d’erreurs de calcul ; la deuxième, via l’appréhension de la position des obstacles en 3D, vise l’estimation de la valeur du biais induit par ces NLOS.

L'article présente le projet CAPLOC, ses objectifs et les premiers résultats obtenus à mi-projet. L’objectif du projet CAPLOC est, avant de combler les lacunes du GNSS avec d’autres capteurs, d’explorer les performances du GNSS et de les enrichir à l’aide de la connaissance de l’environnement de propagation. Cette connaissance est apportée par un système d'acquisition vidéo et différents procédés de traitement d'images.

Introduction du dossier "les systèmes coopératifs dans les transports : une approche coordonnée qui nécessite une affirmation des champs de compétence. Les nouvelles technologies de l’information révolutionnent l’organisation de notre société avec un impact sur le monde du travail, sur notre rapport avec les autres et sur notre mobilité. Le domaine des transports avec ses multiples challenges liés à la gestion du trafic et des infrastructures, à la diffusion d’information et au contrôle opérationnel, a intégré depuis de nombreuses années les technologies de l’informatique et des télécommunications pour répondre aux besoins croissants des autorités, des gestionnaires, des sociétés de services et des usagers. Jusqu’à récemment, les canaux d’information étaient relativement bien identifiés et s’appuyaient souvent sur une architecture centralisée, permettant une diffusion réglementée des messages aux différentes catégories d’utilisateurs.

Most of the Intelligent Transport Systems rely on GNSS positioning information. Unfortunately, most of their uses occur in dense urban areas where signal propagation is degraded by surrounding obstacles because of the reception of NLOS (Non Line-Of-Sight) signals. Since the end of the 90’s, as a research institute concerned by transport applications, the LEOST team of IFSTTAR pursues research on the impact of the surroundings of a GNSS antenna on the receiver’s performances and in particular on NLOS cases when the direct path is not present or it is undetectable due to its low power compared to the rest of path. NLOS detection and mitigation remains an open research problem that can be studied from different angles: at signal processing level, at observable level and at PVT level. First works of LEOST have dealt to the development of a satellite availability prediction tool based on image processing already (PREDISSAT) for guided transport modes. Then, in collaboration with the Ecole Centrale of Lille, signal processing techniques have been developed to model the evolution of the satellite states of reception versus time and propose pseudo-range error models linked to the different states and in particular the NLOS case where reflected signal can be received without a direct ray. Recent activities are performed in the context of the CAPLOC research project. The main objective of CAPLOC, in collaboration with the Technical University of Belfort Montbéliard, is to provide an innovative tool for the positioning function, relying on satellite-based technologies, GPS and EGNOS, and mitigating the difficulties linked to the constricted environment of reception. In the same way than users of 3D models, our goal is to compare satellite positions to obstacles in order to detect satellite states of reception. Our approach relies on video records of the environments. This paper presents how the images sequences provided by several cameras installed on the roof of the vehicle allow characterizing GNSS performance and gives a quick overview of how they are used for accuracy enhancement in the CAPLOC project.

This paper adresses the problem of position computation in an urban canyon, using signals transmitted by Global Navigation Satellite Systems (GNSS) satellites. Due to the high masking level of buildings in a dense urban environment, the signals arrive at the receiver antenna often by more than one path (multipath). Multipath is a source of positioning error, since the receiver solutions for position fail to converge, because of the travel time of the received signal and the moving vehicle. In this paper, we are presenting a post-processing treatments based on observations variances modelling, in order to solve for vehicle position in an urban canyon.

Cet article se penche sur l’évaluation de propriétés de sûreté de fonctionnement de systèmes embarqués ferroviaires capables de se localiser à l’aide de signaux satellitaires. Plusieurs projets de recherche ont déjà montré l’intérêt et la faisabilité d’utiliser les GNSS (Global Navigation Satellite Systems) dans des applications ferroviaires. Pour le moment, les erreurs de position dans ces applications n’ont pas d’impact sur la sécurité. Aujourd’hui, l’emploi des technologies satellitaires est envisagé dans un cadre sécuritaire. En effet, ces technologies peuvent répondre aux besoins d’interopérabilité et de compétitivité des transports ferroviaires, en particulier pour la gestion du trafic. Cependant, l’usage des GNSS en sécurité dans les systèmes de localisation développés requiert l’analyse des attributs FDMS de ces systèmes afin de respecter les normes ferroviaires. Aucune technique d’évaluation n’existe pour l’analyse des signaux utilisés par ces systèmes, notamment les dégradations qu’ils subissent en environnement d’exploitation. Dans cet article, nous proposons une approche fondée sur la simulation d’un modèle en réseau de Petri. Nous appliquons la méthode à différentes données de positions obtenues dans plusieurs environnements ferroviaires types. Les résultats obtenus sont présentés et discutés.

This paper is focused on real time detection of satellite reception state. In constrained environment, such as urban areas, GNSS signals can be received directly, reflected or blocked by obstacles (building, vegetation, etc) and can lead to an error or a lack of positioning. This paper proposes to characterize the GNSS signals reception environment using image analysis. The proposed approach consists of detecting the visible sky part in the images thanks to a k-means based classification algorithm applied in segmented/simplified images. In this paper, two images segmentation/simplification techniques are proposed and compared in terms of robustness, reliability and processing rate. The first one is based on a combination of color and texture information. The second technique uses a geodesic reconstruction by dilatation with an optimal constrast parameter. The main aim of this work consists of determining how many satellites are positioning in the area of visible sky and have a direct reception state. Experimental classification and positioning results, using real data and an evaluation methodology are presented to demonstrate the effectiveness and the reliability of the proposed approach.

Les techniques de localisation par satellites ont aujourd'hui montré leur intérêt dans diverses applications de transport terrestre. Le rôle du GNSS dans le service de positionnement est déterminé par les performances que le GNSS peut fournir aux utilisateurs. Les performances actuellement délivrées ne permettent pas d'utiliser l'information de position dans les applications à caractère sécuritaire, en particulier dans les systèmes de contrôle-commande des circulations ferroviaires. En effet, l'environnement de transport a un impact dégradant sur la qualité du positionnement. Ceci est dû aux phénomènes de propagation locaux qu'il génère. Cet article montre, dans une première partie, la dégradation des performances du système de localisation utilisé dans différents environnements urbains contraints. Dans le cadre spécifique des applications ferroviaires de sécurité, les normes préconisent d'évaluer la qualité du service au travers d'une analyse de sûreté de fonctionnement (SdF). La deuxième partie de cet article présente une méthode originale permettant de quantifier les attributs de SdF associés à un récepteur GNSS soumis aux contraintes de l'environnement ferroviaire.

International audience; The reception state of a satellite is an unavailable information for Global Navigation Satellite System receivers. His knowledge or estimation can be used to evaluate the pseudorange. This article deals with the problem using three reception states: direct reception, alternate reception and blocked situation. This parameter, estimated using a Dirichlet distribution, is included in a particle filtering algorithm to improve the GNSS position in urban area. The algorithm takes into account two observation noise models depending on the reception of each satellite. Gaussian probability distribution is used with a direct path whereas a Gaussian mixture model is used in the alternate case.

http://www.ciren.org/ciren/laboratoires/Paysage_Technologique/index.html; À travers différents concepts et dispositifs comme le parcours ou la machine, de nombreux artistes interrogent et expérimentent depuis une trentaine d'années ce "paysage technologique". En l'utilisant comme un moyen capable de capter des mobilités, de représenter le paysage et d'agir avec lui, le GPS, au delà de ses usages technologiques et de sa signification pour les transformations actuelles du paysage est en train de se transformer en un véritable instrument artistique. Il s'agit d'expliquer la technologie GPS, son fonctionnement et ses évolutions futures, de savoir comment le paysage se transforme, devient technologique puis finalement comment ces pratiques artistiques peuvent produire des représentations et des usages qui s'inscrivent dans ce contexte dynamique.

TRA 2022, Transport Research Arena, Lisbonne, PORTUGAL, 14-/11/2022 - 17/11/2022; GNSS are now in everybody's pocket, embedded in our smartphones and is widely used for informative uses (navigation, leisure...). In future transportation modes, and in particular autonomous vehicles or for safety related railways applications, localisation needs to be accurate and/or safe and trustful. In many of the environments crossed by users, satellite signal propagation is disturbed by buildings, trees or other obstacles that degrade performance. To contribute to the development of safe and accurate localisation solutions in these environments, the LOCSP project intends to evaluate and compare past algorithms on a new shared database but also focuses on the development of two research proposals: through cooperative vehicle localisation using artificial intelligence and with interference mitigation. This paper aims to introduce the project and the first results on these two axes