Inside GNSS Media & Research

MAR-APR 2018

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40 Inside GNSS M A R C H / A P R I L 2 0 1 8 www.insidegnss.com I n the rail sector, the state-of-the-art localization of trains is determined by track-side equipment, which is expensive and a general cost driver for rail transportation. In order to reduce infrastructural costs and to enable new safety critical applications and non-safe- ty critical business cases, a reliable but infrastructure-independent positioning system is required. Challenges of such a system include achieving high accu- racy, robustness, and availability of train localization even under harsh environ- mental conditions. For these purposes, the use of satellite-based navigation systems is a viable option, especially the parallel use of both GPS and Galileo signals. For GNSS data integration, a pre- processing is required, which corrects e.g. signal delays caused by passing the ionosphere. For satellite measure- ments the positioning error caused by ionospheric path delay at daytime is in average up to 45 meters (See BDStar Navigation BeiDou Application the Omni-Directional Service Business, Additional Resources). In the case of using GPS with one single frequency, the well-known Klobuchar correction model provides corrections of approxi- mately 50 % in average (Kaplan and Hegarty, Additional Resources). How- ever, Klobuchar is not suitable for high- ly precise localization, especially not for satellites with low elevation angles. In turn, very accurate corrections can be performed by means of differential correction distributed by surrounding ground stations. ese corrections can be received via mobile communication and are only provided for a fee in most cases. To cover situations even without local reference stations available, with poor mobile connectivity, or to avoid the use of expensive correction data, the present work investigates the use of multi-constellation with dual-frequency as a viable alternative. Therefore, this article introduces dual-constellation and dual-frequency GNSS-navigation using both GPS and Galileo signals. is article reviews the work within the GO! project in developing a naviga- tion filter, which is capable of processing dual-constellation – the parallel usage of GPS and Galileo signals – in combina- tion with dual-frequency signals. e fil- This article focuses on the research project Galileo Online: GO! – which with support from the Federal Ministry for Economic Affairs and Energy (grant number 50NA1510) designs and develops a reliable and high-precision receiver for multi-constellation and dual-frequency GNSS whose suitability and capabilities are tested in railway applications. Project results showcase the advantages of GPS and Galileo if used simultaneously in railway applications. How the Parallel Use of GPS and Galileo Benefits Railway Applications JAN-JÖRAN GEHRT INSTITUTE OF AUTOMATIC CONTROL AT RWTH AACHEN UNIVERSITY, GERMANY RENÉ ZWEIGEL INSTITUTE OF AUTOMATIC CONTROL AT RWTH AACHEN UNIVERSITY, GERMANY THOMAS KONRAD INSTITUTE OF AUTOMATIC CONTROL AT RWTH AACHEN UNIVERSITY, GERMANY DIRK ABEL INSTITUTE OF AUTOMATIC CONTROL AT RWTH AACHEN UNIVERSITY, GERMANY © iStockphoto.com/den-beiltsky

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