Real-Time Single-Frequency Precise Point Positioning on the Road, and on Track

Peter de Bakker and Christian Tiberius

Abstract:	The Single-Frequency Precise Point Positioning (SF-PPP) method, developed at Delft University of Technology, was previously demonstrated to provide lane-level position accuracy, in post-processing, in automative application on a freeway. Important applications of SF-PPP are lane-level traffic state estimation for future traffic management and lane-level specific driver advice for next generation car navigation. For a functional system, as well as for advanced experiments in these fields, the computed positions have to be available in real-time. Therefore, a new real-time implementation of the SF-PPP method was developed as part of the Dynamic Lane Guidance project carried out for Dutch authorities. An efficient implementation of the algorithm in software has been developed and it is anticipated to run – after porting – on relatively light platforms. Real-time satellite clock corrections, and predicted satellite orbit and ionosphere corrections are obtained from a global tracking network, while a-priori models are used to correct for the troposphere delay, solid Earth tide displacement, and carrier phase wind-up at both satellite and receiver side. In this contribution we present the newly developed real-time implementation and we present experimental results, collected on a number of freeways in the Netherlands. A test vehicle was equipped with a low-cost single-frequency u-blox receiver with a patch antenna to collect raw GPS observations. A mobile link (3G) was used to obtain precise correction streams via Ntrip. The SF-PPP processing was performed on a laptop onboard the vehicle, in real-time, and position solutions were provided live in the vehicle at a 5 Hz update rate, while driving. Our test vehicle was also equipped with two high-end antennas and receivers to provide a ground truth (in post-processing). The position accuracy obtained with the SF-PPP algorithm could thus be determined by comparison to the network solution with the high-end data. Additional validation was performed by means of 5 cm accurate road-infrastructure maps from Rijkswaterstaat, the Dutch ministry of infrastructure and the environment. The new real-time SF-PPP software was tested successfully, during many hours of road-tests, with performance comparable to our previous post-processing software (95% position error around 1.5 meters), and meeting the required accuracy for lane identification. Statistics on the performance will be provided, as well as their dependence on a number of external parameters including the number of available satellites. Precise corrections from the German Aerospace Organization (DLR) and International GNSS Service (IGS) were tested and are compared. Delays in the correction streams vary considerably between these providers and can increase further in the event of a time-out. The influence of these delays is considered, and an optimal approach to deal with outages will be presented.
Published in:	Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015) September 14 - 18, 2015 Tampa Convention Center Tampa, Florida
Pages:	1096 - 1114
Cite this article:	de Bakker, Peter, Tiberius, Christian, "Real-Time Single-Frequency Precise Point Positioning on the Road, and on Track," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 1096-1114.
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