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2 TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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Assessing the Limits of eLoran Positioning Accuracy

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Safar J. , Vejrazka F. , Williams P.

tom Vol. 5, no. 1

93--101

Enhanced Loran (eLoran) is the latest in the longstanding and proven series of low frequency, LOng-RAnge Navigation systems. eLoran evolved from Loran-C in response to the 2001 Volpe Report on GPS vulnerability. The next generation of the Loran systems, eLoran, improves upon Loran-C through en-hancements in equipment, transmitted signal, and operating procedures. The improvements allow eLoran to provide better performance and additional services when compared to Loran-C, and enable eLoran to serve as a backup to satellite navigation in many important applications. The Czech Technical University in Prague (CTU) participates in the eLoran research activities coordinated by the General Lighthouse Authorities of the United Kingdom and Ireland (GLAs). In our work we have focused on questions that arise when considering introducing new eLoran stations into an existing network. In particular, this paper explores the issue of Cross-Rate Interference (CRI) among eLoran transmissions and possible ways of its mitigation at the receiver end. An eLoran receiver performance model is presented and validated using an experimental eLoran signal simu-lator developed by a joint effort of CTU and GLAs. The resulting model is used to evaluate the achievable positioning accuracy of eLoran over the British Isles.

Software navigation receivers for GNSS and DVB

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Vejrazka F. , Kovar P. , Eska M. , Puricer P.

tom Vol. 1, no. 2

137--141

We describe the software GNSS receiver, its schema, implementation into a computer, results of tests and application for railway, municipal transportation and for shipping of dangerous matters. The receiver, originally for the Galileo system, is on a printed board which is the size of a Euro Card (160?100 mm). Because the Galileo signal is not in the air, it was modified for the GPS and GLONASS systems. Experimental GNSS receiver (EGR) was used as a tool for its development and it is also described. Even if we use the receiver which is able to process signals of all three systems, it is impossible to ensure reception of GNSS signals in adverse conditions (under leaves canopy, in urban canyons, in hollow tracks, etc.). Therefore we have studied the possibilities of communication systems which will use modern signals known from satellite navigation and we have obtained very interesting results when we used DVB-T transmitters as beacons.