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Reconstruction of geomagnetic event as observed in Northern Adriatic region and Its correlation with GPS single-frequency positioning deviations

Brčić D., Ćelić J., Valčić S.

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

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2020

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Vol. 14, no. 2

349--357

EN

Space weather effects are generally recognized as causes of degradation of satellite positioning, navigation and timing (PNT) services. We analyze GPS position estimation error during a geomagnetic storm, focusing on manifestations of geomagnetic processes. The position estimation error was analyzed in terms of GPS coordinates’ deviations (latitude, longitude and height) from their reference values. The storm’s impact was studied in the Northern Adriatic region where GPS observables from two Global Navigation Satellite System (GNSS) reference stations were analysed. Geomagnetic indices were elaborated, comprising readings from interplanetary, magnetospheric and geomagnetic observatories. Total Electron Content (TEC) on both stations was computed using dual frequency GPS pseudorange observables. The experiment was to reconstruct the movement of geomagnetic disturbances entering the geospace, reaching the earth’s surface. The aim was to correlate possible space weather manifestation on satellite positioning performance in terms of positioning error. Regularities in changes in positioning deviations were identified with relation to influential indices. The research offered a possibility of experimental positioning deviations assessment as well as forecasting. Evaluation of generated rudimentary Classification and Regression Trees (CART) models showed that the risk of satellite positioning errors could be assessed and predicted considering absolutes, as well as changes in values of geomagnetic indices. During the research process, several activities emerged as preferable continuation of the work, with the aim of further development of predictive models and the complement of space weather scenarios and their consequences on navigational systems. Along with summarized results, they are outlined in the conclusion section.

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A model of OFDM based maritime VHF communication system for data exchange

Valčić S., Pogány T., Mrak Z.

Polish Maritime Research

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2018

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nr 2

27--36

EN

In the maritime Very High Frequency (VHF) band, there are no systems for transmitting large amounts of data. Therefore, it is necessary to develop new systems that would modernize the Global Maritime Distress and Safety System (GMDSS), significantly relieve the Automatic Identification System’s (AIS) communication channels, and set guidelines for the development of communication infrastructure of the e-Navigation. In line with this, analytical and simulation models of the maritime VHF data transmission communication system using Orthogonal Frequency Division Multiplexing (OFDM) modulation are worked out in this paper. The achieved data rate, the spectral efficiency and the bit error rate (BER) represent validation parameters on which the results of the analytical and simulation models are evaluated. It is concluded that the application of the digital OFDM modulation in the maritime VHF band may improve the GMDSS system by achieving higher data rates compared to the current terrestrial mandatory systems for data exchange, i.e. Digital Selective Calling (DSC) and AIS.

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ECDIS possibilities for BWE adoption

Žuškin S., Brčić D., Valčić S.

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

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2017

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Vol. 11, no. 3

477--482

EN

The Electronic Chart Display and Information System (ECDIS) development and implementation have been linked primarily to the safety of navigation. Further development allows the implementation from other aspects of navigation. This primarily pertains to the Harmful Aquatic Organisms and Pathogens (HAOP) from Ballast Water Exchange (BWE) and the use of ECDIS system for improving environmental protection. The paper contains an overview of important legal aspects of sea environment protection related to the Ballast Water Management (BWM) Convention on global as well as on local scale. Apart from enhancing the safety of navigation, integration of the proposed tool for sea environment protection in the ECDIS with onboard ballast water system can significantly contribute to sea and sea environment protection from harmful substances. In this paper, the architecture of such system is suggested. This approach also ensures a reduction of possible consequences on ecological incidents and human errors.