Challenges for Integrity in Navigation of High Precision

M.J. Pasnikowski, E. Domínguez, E. Aguado, D. Lowe, M. Pattinson, M. Hutchinson, G. Seco-Granados, J. Salcedo, D. Egea, UAB, Spain; D. Naberezhnykh, F. Dovis, J.P. Boyero, I. Fernandez

Peer Reviewed

Abstract:	Providing integrity to precise positioning navigation techniques utilizing carrier-phase measurements, like Precise Point Positioning (PPP) and Real-Time Kinematic (RTK), is still a challenge. Whereas these methods can provide centimetre-level positioning accuracy, their use has been limited mainly for static and kinematic positioning solutions, with less employment for general navigation purposes. Both techniques are dependent on external information which has to be considered in the integrity monitoring process. For RTK, a differential method, the external information could be the distance to a reference station, its coordinates, or the atmospheric effects, for which the associated reliability needs to be considered. The nature of PPP as an absolute technique demands considering a reference frame, estimating several parameters and eliminating others - estimated in a different process- which requires the convergence of the solution. As it was mentioned in [Laínez and Romay, 2013], all of these factors influence the integrity and reliability in PPP methods. The use of carrier-phase in both techniques allows higher achievable accuracy, but also causes their vulnerability on cycle slips and loss of lock of satellite signal. These problems occur extensively in harsh environments, especially in urban scenarios. High precision navigation techniques were not intended for road or urban environments, but their performance in these scenarios in aspects of navigation and integrity can be analysed and improved. In this article different road scenarios will be analysed, both in motorway and urban scenarios, in terms of navigation and integrity performance of precise positioning techniques. The data utilised in the paper were collected for the IGNSSRX project purposes. The analysed scenarios were challenging for the evaluated techniques, with a significant number of elements obstructing the sky view, causing cycle slips both in motorway and urban conditions. Performances of navigation and integrity of high accuracy algorithms will be assessed in relation to the characterization of pseudorange, Doppler, C/N0, and carrier-phase observables, in motorway and urban environments. The discontinuities and gaps in the observables, especially in carrier-phase measurements, impact not only the navigation convergence and accuracy but also the integrity of the solution. To identify integrity threats, the distribution of the errors of the observables will be analysed. Subsequently, the identified outliers will be examined in terms of their magnitude, frequency of occurrence, ambiguity resolution, and clock errors. In the carrier-phase measurements, the analysis will be focused on the L1 frequency as raw signal samples in this band have been recorded exhaustively in all the scenarios of interest.
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:	2983 - 2994
Cite this article:	Pasnikowski, M.J., Domínguez, E., Aguado, E., Lowe, D., Pattinson, M., Hutchinson, M., Seco-Granados, G., Salcedo, J., Egea, D., UAB,, Naberezhnykh, Spain; D., Dovis, F., Boyero, J.P., Fernandez, I., "Challenges for Integrity in Navigation of High Precision," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 2983-2994.
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