François Peyret

A New Modeling Based on Urban Trenches to Improve GNSS Positioning Quality of Service in Cities

Digital maps with 3D data proved to make it possible the determination of Non-Line-Of-Sight (NLOS) satellites in real time, whilst moving, and obtain significant benefit in terms of navigation accuracy. However, such data are difficult to handle with Geographical Information System (GIS) embedded software in real time. The idea developed in this article consists is proposing a method, light in terms of information contents and computation throughput, for taking into account the knowledge of the 3D environment of a vehicle in a city, where multipath phenomena can cause severe errors in positioning solution. This method makes use of a digital map where homogeneous sections of streets have been identified, and classified among different types of urban trenches. This classification is so called: Urban Trench Model. Not only NLOS satellites can be detected, but also, if needed, the corresponding measurements can be corrected and further used in the positioning solver. The paper presents in details the method and its results on several real test sites, with a demonstration of the gain obtained on the final position accuracy. The benefit of the Urban Trench Model, i.e. the reduction of positioning errors as compared to conventional solver considering all satellites, gets up to an amount between 30% and as much as 70% e.g. in Paris.

Unscented Kalman filter for urban link travel time estimation with mid-link sinks and sources

To estimate link travel time, the classical analytical procedure uses vehicles counts at upstream and downstream locations. This procedure is vulnerable in urban networks mainly due to significant flow to and from mid-link sinks and sources. One of the important developments recently done on this topic has yielded to the CUPRITE methodology. This method is derived from the classical analytical procedure. It integrates probe vehicle data to correct deterministically the upstream cumulative plot to match the information of probe vehicles travel times, whilst the downstream cumulative plot is kept unchanged. The algorithm proposed and validated in this research estimates urban links travel times based on an unscented Kalman filter (UKF). This algorithm integrates stochastically the vehicle count data from underground loop detectors at the end of every link and the travel time from probe vehicles. The proposed methodology, which can be used for travel time estimation in real-time, is compared to the classical analytical procedure and to the CUPRITE method in case of mid-link perturbation. Along to its lower sensitivity than CUPRITE, the UKF algorithm makes it possible detection and exclusion of outliers from both data sources.

Assessment of end-to-end performances of a GNSS-based road user charging system based on IFSTTAR-GEOLOC and Q-Free cooperation

The paper deals with the issues that have to be faced when researching a Road User Charging (RUC) in Norway based upon GNSS and with an innovative methodology especially developed to address these issues proposed by CEN-CENELEC TC5/WG1 and supported by the SaPPART COST Action. The paper presents a case study applying the methodology to a specific RUC algorithm developed by the Norwegian company Q-Free. A dedicated GNSS position error model has been produced by Ifsttar GEOLOC for this purpose.

The SaPPART COST Action: Towards positioning integrity for road transport

Global Navigation Satellite Systems (GNSS) is becoming one of the main components supporting Intelligent Transport Systems (ITS) and value-added services in road transport and personal mobility. The use of GNSS is expected to grow significantly due to improvements in positioning performance, with positive impacts such as: finding the optimal route; improving traffic and travel efficiency as well as safety and security; reducing congestion and optimizing fuel consumption. The deployment of mission critical applications needs high reliability in the positioning information. However, the positioning reliability is not easy to achieve because of the heterogeneous quality of the GNSS signal, which is highly influenced by the road environment and the operational scenario of the application. It is important to understand the requirements and performance GNSS can achieve for various road transport applications. This paper is presenting the SaPPART COST Action on the Satellite Positioning Performance Assessment for Road Transport. It introduces the goal and the framework of the Action with the research programme and some related activities dedicated to dissemination and supporting standardisation working groups.

Les systèmes coopératifs dans les transports : une approche coordonnée qui nécessite une affirmation des champs de compétence

Les nouvelles technologies de l’information revolutionnent l’organisation de notre societe avec un impact sur le monde du travail, sur notre rapport avec les autres et sur notre mobilite. Le domaine des transports avec ses multiples challenges lies a la gestion du trafic et des infrastructures, a la diffusion d’information et au controle operationnel, a integre depuis de nombreuses annees les technologies de l’informatique et des telecommunications pour repondre aux besoins croissants des autorites, des gestionnaires, des societes de services et des usagers. Jusqu’a recemment, les canaux d’information etaient relativement bien identifies et s’appuyaient souvent sur une architecture centralisee, permettant une diffusion reglementee des messages aux differentes categories d’utilisateurs.