Assessment of positioning accuracy of vehicle trajectories for different road applications

Global navigation satellite systems (GNSS) has become a kind of positioning standard due to the high penetration rate of this technology on mass market intelligent transportation systems (ITS) applications. However, this positioning technique remains a real challenge for very demanding ITS services which require continuity and a specific accuracy of the data. This study reports on a practical and methodological approach for the evaluation of the GNSS and multi-sensors positioning and attitude of vehicles in real life conditions. Test scenarios have been set up with several positioning sensors mounted on a vehicle for the collection of raw data on different road sections. The measurement of a high quality reference trajectory with an accuracy of several centimetres allows to estimate position accuracy under different environmental conditions. The authors will show in detail the results and identify some typical situations (e.g. sub-urban environment) where the quality of positioning parameters is reduced to several metres instead of dm and may impact the level of ITS services, e.g. road user charging or safety applications. This study results from the methodology developed in the satellite positioning performance assessment for road applications COST Action on the performance assessment of positioning terminals for ITS.

Positioning Accuracy of Vehicle Trajectories for Road Applications

Philipp Clausen, Pierre-Yves Gilliéron

Global Navigation Satellite Systems (GNSS) has become a kind of positioning standard due to the high penetration rate of this technology on mass market ITS applications. However, this positioning technique remains a real challenge for very demanding services. This paper reports on a practical and methodological approach for the evaluation of the GNSS positioning and attitude of vehicles in real life conditions. Test scenarios have been set up with several positioning sensors mounted on a vehicle for the collection of raw data on different road sections. The measurement of a high quality reference trajectory allowed to estimate position accuracy under different environmental conditions. We will show in detail the results and identify some typical situations where the quality of GNSS-only positioning is reduced and may impact the level of ITS services, e.g. road user charging or safety applications.

2015

Position Accuracy with Redundant MEMS IMU for Road Applications

Philipp Clausen, Pierre-Yves Gilliéron, Bertrand Merminod, Jan Skaloud

The diversity of road applications and intelligent transportation systems (ITS) makes the definition of positioning integrity a real challenge because the requirements are changing from one application to another. Even within liability or safety critical applications, the role of positioning may vary if the application layer requires a position at specific location (e.g. emergency call) or a series of positions along a vehicle’s trajectory (e.g. transport of dangerous goods). -- This paper is focusing on the positioning assessment of vehicle trajectories collected by different navigation sensors (GNSS and redundant MEMS Inertial Measurement Units (R-IMU)) in real test scenarios. Single GNSS, integrated GNSS and R-IMU are compared to a high quality ground truth solution based on a high-end navigation system. The low cost equipment is based on a single frequency GNSS receiver combined with four IMUs (triad of accelerometers and gyroscopes) of the same type. The architecture and the algorithms for the sensors integration have been developed at EPFL and are used on several mobile platforms (land vehicles, ultra-light planes, micro-drones). A series of measurements of different kind and thus dynamics have been conducted by EPFL and NTUA during a scientific mission form the COST Action TU1302 on Satellite Positioning Performance Assessment for Road Transport (SaPPART). Several test scenarios were performed in different traffic and environmental conditions in order to face with challenging GNSS signal reception. Road sections have been selected ranging from open sky condition (e.g. rural roads) down to poor GNSS reception (e.g. urban road network). The evaluation of the positioning quality is done by comparing the position-output from several solutions: single GNSS, D-GNSS, integrated GNSS/R-IMU. The comparison to a reference trajectory of precisely time-stamped positions allows to calculate and to plot along-track as well as cross-track differences. This visualisation of the results make sense for many road applications like road user charging (RUC), pay as you drive and some advanced driver assistance systems (ADAS). Finally, this quality assessment of vehicle positioning in real conditions will be a valuable material for future simulations of navigation systems in severe conditions. This contribution is fully adequate to the goals of the COST Action SaPPART, especially for the definition of the performance assessment methodology.

2015

Calibration Aspects of INS Navigation

Philipp Clausen

The use of a Bayesian filter (e.g., Kalman filter) for the fusion of information from satellite positioning and inertial navigation is a common approach in many applications, where the knowledge of position, velocity, and attitude in space are of great interest. The correctness of these estimates depends on many factors, among others the quality of the sensor measurements and the errors within, which are directly reflected in the filter design. A calibration process allows compensating for deterministic influences (which in return improve for instance qualitatively the attitude initialization) and their inherent stochastic error signals required for filtering. This thesis presents in the first part the development of methods to perform a thorough calibration of different sensors in-lab under controlled conditions and in-field for a simplified calibration with limited resources and equipment. The stochastic properties of error signals are analyzed in the second part. A novel approach called Generalized Method of Wavelet Moments (GMWM) allows investigating the error structure using wavelets, which is similar to the Allan variance. An intuitive online tool is presented, which grants simplified access to the GMWM framework that provides a consistent, identifiable, and computationally efficient estimation of stochastic model parameters. The parameters of these error models are then made dependent on an external covariate such as temperature or motion. Indeed, it is experimentally confirmed that these properties shape the stochastic behavior of the measurements and how the stochastic parameters relate functionally to the influence of the covariate. Later, such knowledge is included in the filter for the correct estimation of confidence levels. The successful implementation of these proposed concepts is validated in a fully functional drone-system for mapping purposes. A real-time calibration scheme is applied first in-lab, later in-field to initialize the navigation processor. Apart from the benefit of achieving considerably better estimates of the attitude, and in case of satellite signal outage also of the position, the calibration allows for a simplified fusion of redundant inertial sensors. The improved performances through calibration and sensor redundancy are attractive to drone mapping applications relying on an accurate direct or integrated orientation such as lightweight airborne laser scanning systems or frame-cameras, which are utilized in the experiments.

EPFL2019

Position Accuracy with Redundant MEMS IMU for Road Applications

Philipp Clausen, Pierre-Yves Gilliéron, Bertrand Merminod, Jan Skaloud

2015

Calibration Aspects of INS Navigation

Philipp Clausen

EPFL2019