Ricerca CERCA

Analysis of the contribution of new GNSS constellations, new signals, and advanced 3D maps, in urban geolocation

azienda Thesis in external company    estero Thesis abroad

Reference persons FABIO DOVIS

Research Groups Navigation Signal Analysis and Simulation group (NavSAS)


Applications of GNSS satellite positioning systems are becoming more common in land transport systems, whether road or rail. Future applications, however, require increasingly demanding performance in terms of accuracy as well as integrity. This is particularly the case in the development of autonomous vehicles (cars or trains) or highly critical systems for safety such as railway signaling.
These systems are also used in complex environments for the reception of GNSS signals such as urban environments or railway trenches, in which local phenomena present a significant source of error.
The work of [Zhu 2018] has shown that the combination of error models adapted to local phenomena and fault detection and exclusion techniques (FDE) can both reduce the inaccuracy of the estimated positions but also improve the integrity of the GPS solution by ensuring the exclusion of unacceptable residual errors.
With the deployment of new constellations (especially Galileo) and new signals (those more robust to multipath with Galileo in particular), and in the following of the aforementioned doctoral thesis, it is necessary to explore the potential of these solutions for multi-channel and multi-constellation systems. The thesis work proposed here consists, first of all, in adapting the algorithms to these new configurations and in evaluating their performance after having carried out a measurement campaign and constituted a test database.
In a second step, we propose to address the contribution of the map to these solutions. In the works of [Zhu, 2018] a 3D map was used to detect the reception state of the received signals on the one hand and to estimate the delay caused by NLOS reception by ray tracing on the other hand in order to correct it. These detection and correction were made based on the knowledge of the true position in the map, that is to say provided by the reference trajectometry system (an inertial unit coupled to GNSS PPK), which is not available a priori. These calculations (ray tracing) must be done from an approximate position, which can be inferred in real time by Kalman filtering. This position can also be projected (map-matched at lane level) on different assumptions of taxiways [Bétaille, 2017].
In this new thesis, we want to explore the potential of a map-matched solution to improve and simplify the use of the map for the ray tracing stage.
Finally, we will set the framework for a concept of monitoring the integrity of a map-matched position in order to provide the user with a set of information {Id_route; Id_lane; ATPL}, ie: identifiers of the road and taxiway on multi-lane road, associated with a longitudinal protection level (along track) characterizing the location error bounds on this road.

Keywords : Geopositioning, GNSS, Quality of Service, integrity, sensor data fusion, Bayesian estimation, digital maps, map-matching, lane-level positioning

See also  fiche_stage_emap_ifsttar_nantes_2019.pdf 

Required skills Satellite Navigation Systems, signal processing

Notes Interested students can ask more information to dr. David Bétaille david.betaille@ifsttar.fr of IFSTTAR.

For information regarding the activation of a curricular stage refer to prof. Roberto Garello (roberto.garello@polito.it)

Deadline 07/12/2019      PROPONI LA TUA CANDIDATURA

© Politecnico di Torino
Corso Duca degli Abruzzi, 24 - 10129 Torino, ITALY