|Abstract:||For several years now, various market studies have highlighted the importance of the delivery of positioning or navigation information with a high level of integrity for a wide range of use cases, the first of which being land and air vehicles. This feature is, for instance, a key enabler for the highly anticipated autonomous vehicle application. Although aviation has succeeded in reaching significant levels of GNSS-based integrity performance when the aircraft is in the air, the challenges to do so for vehicles mostly operating in or near urban areas are still considerable and include: - Lack of well-defined performance requirements - The GNSS propagation channel being considerably degraded compared to an open environment, for example, due to the presence of signal blockage, strong multipath, NLOS situation, interference, etc - The potential difficulty to use civil aviation ground or satellite augmentation systems including: no worldwide system, blocked geostationary satellites in cities, systems tuned for aviation requirements, etc - Use of GNSS carrier phase measurements and complementary navigation sensors to maintain a high availability and accuracy. Problems include the addition of new failure modes and the complex measurement characterization for various sensors - Use of fusion filters that rely on strong input assumptions, approximate propagation models and are sensitive to the influence of time-correlated measurement errors - Constraints on the computational and memory resources as well as on the platform price for mass market solutions - The complexity of verifying and certifying the performance of a navigation platform in all targeted environments u-blox has dedicated a significant amount of effort in the recent years to be able to respond to these challenges. The paper will introduce some of u-blox’s activities towards tackling the issue of providing navigation information with high integrity in degraded environments. This paper will specifically focus on the automotive case and will be centered on the following elements: - Platform overview: this section will briefly introduce the current u-blox platform for Lane Accurate Positioning and its general accuracy and availability performance -Fault characterization and integrity performance requirements providing: a) an overview of the different sensors and sensor faults characteristics b) the performance requirements that are targeted for Lane Accurate Positioning as well as elements of the Fault Tree Analysis - Accurate modeling of GNSS measurements: this section will discuss the methodology used to accurately model tracking errors impacting GNSS measurements in urban and sub-urban environments. This effort is currently based on a massive data collection effort associated with advanced modeling mechanisms: a) strategy to collect a representative and statistically meaningful set of data b) ability to evaluate the true measurement errors c) ability to classify the reception conditions based on multiple quality indicators d) building of measurement models fit for integrity monitoring - Pre-processing mechanisms: With the fine knowledge of the measurement models, various pre-processing (or measurement selections) mechanisms can be put in place. This has the great advantage of limiting the amount of non-nominal/faulty measurements entering the PVT filter. This selection process can be done very efficiently in a multi-GNSS and multi-sensor context and can have a significant impact on the design of the integrity monitoring mechanism that will protect the PVT solution. - Multi-sensor integrity monitoring considerations: this section will provide an overview of the integrity monitoring mechanisms that are promising, including in a multi-sensor context. The constraints related to the platform computational and memory resources will also be discussed. - Example of integrity performances in challenging environments: the last section will provide first promising results based on real data collected in various environments, cities and countries. Innovation: The significance of the presented work lies in the demonstration of the concrete and promising steps taken by a leading mass market chip manufacturer towards the design of an integrity receiver for the automotive market.|
Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019)
September 16 - 20, 2019
Hyatt Regency Miami
|Pages:||573 - 593|
|Cite this article:||
Bryant, Rod, Julien, Olivier, Hide, Chris, Schuerch, C., Sheret, Ian, "Mass Market Lane Accurate Positioning with High Integrity," Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019), Miami, Florida, September 2019, pp. 573-593.
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