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L'article présente le projet ERSAT GGC et les techniques de détection des effets locaux sur les GNSS développées pour l'introduction du GNSS dans le système ERTMS/ETCS

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.

This document is the deliverable D4.2-Technical Specification of the Survey Toolset where the outcome of the work performed in WP4.2 of the ERSAT GGC project is described. This document follows up the work performed in WP4.1 and reported in the deliverable D4.1, extending the ongoing general definition of the track area classification process. The goal of WP4.2 is the specification and development of the toolset for the survey and classification of track areas, giving the system overview and providing the different interacting blocks as the measurement hardware system, the processing software toolbox and the final classification data. Regarding this D4.2, the functional and technical specifications of the toolset are here provided with the description of the interfaces between the different detection techniques and decision logic blocks. Outcome of D4.3 will be the prototype implementation and installation. The document also includes the specification of the measurement system and hardware to be used in the survey process so that the necessary data for the classification techniques can be collected in the railway scenario. Finally, the specification of the output data - the track area classification results - is also analysed and provided. The specification of the survey measurement system and software toolset addressed in the current document will support the next project activities related to the development of the software tools for the classification of track areas in WP4.2 and the execution of measurement campaigns in WP4.3.

ITST 2018, 16th International Conference on Intelligent Transport Systems Telecommunications, Lisbonne, PORTUGAL, 15-/10/2018 - 17/10/2018; The introduction of the GNSS positioning technology into the evolution of ERTMS/ETCS is based on the concept of virtual balise to minimize the impact onto existing ERTMS solutions. The detection of virtual balises is foreseen by using GNSS in combination with odometry information. However, the presence of local GNSS threats (e.g, multipath, NLOS or interference) may lead to unbounded errors in the pseudorange measurement that cannot be corrected by local or wide-area augmentation systems, and will lead ultimately to an error in the virtual balise position that cannot be bounded with the required integrity. In order to a priori prevent the risk of this hazardous situation, virtual balises must be logically located in areas where there are not local threats that may lead a Virtual Balise Transmission System on board the train to dynamically estimate unbounded virtual balise position errors. This paper summarizes the initial work performed in the H2020 GSA Project ERSAT-GGC with respect to the different techniques that can be used to detect local GNSS threats and that can support a later classification of railway areas as suitable or not suitable for placing virtual balises.

The deliverable D4.1 Procedure Specification Document of the ERSAT-GGC project is related to the work performed in Task 4.1. The aim of WP4 is to set up a standard measured system that is able to provide a forecast method for the GNSS service performance to be expected at a given track point, in order to enable evaluation whether the specific scenario is favourable to place virtual balises or on the contrary should be discarded beforehand. The results of this assessment can be included in a database map where geo-referenced GNSS quality data is stored. Users may access the information via specified interfaces using standardized communication channels. In order to set up the system, at first a standardized process has to be defined and specified that will determine what has to be measured under which conditions and what has to be simulated for GNSS characterizing along the line. This is the scope of Task 4.1. In order to set the context of the work, a description of the need and importance of a standard process to classify the track areas for virtual balise placement is given in the introduction. Later, a first version of the high level requirements to the classification process is provided. Based on these requirements a preliminary study of the different techniques, measurements and parameters that are relevant to define a safe track area classification standard process has been performed. The document then focus on a detail description on the GNSS detection techniques that are relevant for the standard process and the track area classification criteria. Further works related to the detection and classification criteria are required, and they will be included in the next deliverable D4.2, which specifies the dedicated requirements for the toolset.The standard process will undergo reviews until the execution and test: all these improvements and the related links to the toolset development will be covered by the next deliverables of WP4.