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1
Content available remote Assessing the Limits of eLoran Positioning Accuracy
Safar J., Vejrazka F., Williams P.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2011
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Vol. 5, no. 1
93--101
EN
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.
2
Content available remote Galileo AltBOC E5 Signal Characteristics for Optimal Tracking Algorithms
Vejrazka F., Kovar P., Kacmarik P.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2010
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Vol. 4, no. 1
37--40
EN
The paper deals with an optimal processing of a Galileo E5 signal. A proposed correlator struc-ture was developed on a base of a deep study of an E5 signal cross correlation function. Due to the non linear-ity of the E5 AltBOC modulation the proposed correlator calculates the cross correlation function between a received signal and a signal replica for all possible hypotheses of the navigation message bits. A correct peak tracking verification is realized by implementation of a single side band correlator, which also serves for course signal acquisition and secondary ranging code synchronization. The signal processing was verified on the Galileo Giove A and Giove B satellites with very positive preliminary results.
3
Content available remote Software navigation receivers for GNSS and DVB
Vejrazka F., Kovar P., Eska M., Puricer P.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2007
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Vol. 1, no. 2
137--141
EN
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.
4
Content available remote Experimental GNSS receiver
Seidl L., Kovar P., Vican M., Kacmarik P., Vejrazka F.
Zeszyty Naukowe. Transport / Politechnika Śląska
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2004
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z. 55
381-385
EN
At the Czech Technical University in Prague the Experimental GNSS Receiver based on Software Defined Radio Architecture has been developed. The receiver is determined for research and development of new GNSS signal processing algorithms including massive parallel processing for navigation in urban area with low quality signal coverage and for the study of new forms of the GNSS signals during the early phase of the GALILEO mission. As a first step the ability of weak signal processing in indoor environment was tested.
PL
Na Politechnice Czeskiej w Pradze opracowano Doświadczalny Odbiornik GNSS oparty na Zdefiniowanej Komputerowo Architekturze Radiowej. Odbiornik jest przeznaczony do badania i opracowania nowych algorytmów przetwarzania sygnałów GNSS, włącznie z masowym przetwarzaniem równoległym do nawigacji w obszarach miejskich, w zasięgu sygnału niskiej jakości oraz do opracowania nowych form sygnałów GNSS w czasie wczesnych etapów prac nad GALILEO. Jako pierwszy krok przetestowano możliwość przetwarzania słabego sygnału w zamkniętych pomieszczeniach.
5
Content available remote Radio Systems for Real Time GNSS - experimental GMSS Receiver
Vejrazka F., Seidl L., Kovar P., Kacmarik P.
Reports on Geodesy
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2002
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z. 3/63
29-38
EN
This paper deals with the radio systems for real time satellite navigation and position determination GPS, GLONASS and GALILEO. The AGPS, DGPS and RTK modes of GPS including requirements for data channel are analyzed here. The CTU experiments with the RDS DGPS, LW DGPS, DGPS reference station and ExperimentalGNSS receiver are presented in this paper.
6
Content available remote Activity of CEI WG SNS in the field of satellite positioning and navigation
Doeller H., Manzoni G., Oszczak S., Vejrazka F.
Reports on Geodesy
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2000
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z. 8/54
33-40
EN
This paper joins two presentations at the 2nd International Workshop on Satellite Navigation in CEI Area, Olsztyn, 3-5 July, 2000, which show an experimental activtty in the frame of the WG on Satellite Navigation Systems. This WG acts in the frame of the Central Europe lnitiative WG on Science and Technology, section C "Geodesy". This activity includes a very close scientific cooperation between four CEI countries also in view of involving as many as possible CEI countries in the definition of a unified real time accurate satellite positioning. Several tests have been carried on mainly in Austria and one of them has used both the corrections for DGPS diffused by the transmitter Low Frequency Prague and the ones diffused by the Austrian DGPS service, performed by dGPS Datenverbreitungsgesllshaft mbH, on the Frequency Modulation Network of ORF, Oesterraichische Rundfunk. The WG has begun also tests on the GPS without SA positioning, as well as on the EGNOS WAAS positioning which is under experimentation with the Inmarsat AOR-E.
7
Content available remote Low frequency DGPS correction dissemination system and EGNOS
Vejrazka F.
Reports on Geodesy
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1999
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z. 3/44
297-300
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