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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.

2

Availability of maritime radio beacon signals for R-Mode in the Southern Baltic Sea

Gewies S., Grundhöfer L., Hehenkamp N.

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

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2020

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Vol. 14, no. 1

170--163

EN

This paper presents an overview of the development of a terrestrial positioning system called Ranging Mode (R-Mode) in the Southern Baltic Sea region which utilizes already existing maritime radio infrastructure. Here, an R-Mode testbed is planned to be set up until 2020 that meets maritime user needs for resilient PNT. First measurements of radio beacon signals on-board a vessel sailing in the Southern Baltic Sea show the good availability of beacon signals in this region. A comparison of received signals with a coverage prediction based on the nominal range of radio beacons shows the shortcoming of this approach and emphasizes the need for more elaborated coverage predictions which consider all effects of medium frequency wave propagation at day and night. In the measurements results the skywave has a major impact on the beacon signal stability in the night. The time stability of the signal amplitude seems to be a good indicator for disturbed reception conditions.

3

Analysis of tropospheric contribution to GPS positioning error during tropospheric cyclone Marcus in 2018

Sikirica N., Horvat M., Špoljar D., Rumora I.

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

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2020

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Vol. 14, no. 2

343--348

EN

GNSS positioning performance assessment is essential for sustainable development of a growing number of GNSS-based technology and socio-economic applications. Case-studies of GNSS positioning performance in critical environments and applications scenarios reveals vulnerabilities of the GNSS Positioning, Navigation, and Timing (PNT) services, and suggest mitigation techniques and GNSS application risk containment. Here we address the case of GPS positioning performance during a devastating tropical cyclone Marcus that hit the greater area of the city of Darwin, Australia in 2018. We identified specific statistical properties of time series of tropospheric contribution to GPS northing, easting, and vertical positioning error that may contribute to understanding of tropospheric effects on GPS positioning performance during a massive weather deterioration in maritime and coastal areas, and analysed their adversarial effects on GNSS-based maritime applications.

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GNSS positioning error change-point detection in GNSS Positioning Performance Modelling

Filić M., Filjar R.

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

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2019

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Vol. 13, no. 3

575--579

EN

Provision of uninterrupted and robust Positioning, Navigation, and Timing (PNT) services is essential task of Global Navigation Satellite Systems (GNSS) as an enabling technology for numerous technology and socio-economic applications, a cornerstone of the modern civilisation, a public goods, and an essential component of a national infrastructure. GNSS resilience may be accomplished only with complete understanding of the causes of GNSS positioning performance disruptions and degradations, presented in a form of applications- and scenarios-related models. Here the application of change-point detection methods is proposed and demonstrated in a selected scenario of a fast-developing ionospheric storm’s impact on GNSS positioning performance, as a novel contribution to forecasting GNSS positioning performance model development and GNSS utilisation risk mitigation.

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SBAS/EGNOS enabled devices in maritime

López M., Anton V.

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

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2018

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Vol. 12, no. 1

23--27

EN

Nowadays, it is a fact that Global Navigation Satellite Systems (GNSS) have become the primary means of obtaining Position, Navigation and Timing (PNT) information at sea. Most of the ships in the world are equipped with GNSS receivers. And currently these users take advantage of different augmentation systems such as DGNSS or SBAS/EGNOS, as they provide an adequate answer, especially in terms of accuracy and integrity. To take advantage of this improved accuracy, direct access to EGNOS in vessels can be achieved through EGNOS-enabled navigation receivers and EGNOS-enabled AIS transponders. Therefore, the natural question is: Are those GNSS receivers SBAS (EGNOS) enabled? In most cases they are; SBAS is being used. This paper provides an analysis of the number of onboard devices, mainly devoted to navigation purposes and AIS transponders, which are SBAS compatible.

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Foundations of GNSS spoofing detection and mitigation with distributed GNSS SDR receiver

Filić M.

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

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2018

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Vol. 12, no. 4

649--656

EN

GNSS spoofing is an intentional and malicious action aimed at degrading and suppressing GNSS Positioning, Navigation, and Timing (PNT) services. Since it affects data and information segment of GNSS, it is considered a GNSS information (cyber‐) security attack. Considering a significant and powerful threat, GNSS spoofing should be treated seriously to avoid damage and liabilities resulting from disruptions of GNSS PNT services. Here the GNSS position estimation procedure is examined for potential vulnerabilities, and the nature of and motivation for GNSS spoofing attacks exloiting the vulnerabilities assessed. A novel GNSS Spoofing Detection and Mitigation (GNSS SDM) method is proposed within the established computational and communication infrastructure, that allows for successful overcoming and classification of GNSS spoofing attacks. Proposed method is applicable without requirements for core GNSS modification, and leaves majority of user equipment easily transferable to the GNSS spoofing‐free environment. Potential GNSS spoofing effects and GNSS anti‐spoofing opportunities in maritime sector were given a particular attention.

7

The concept of time in navigation

Weintrit A.

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

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2017

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Vol. 11, no. 2

209--219

EN

The article discusses the concept of time in navigation, especially in marine navigation, as well as selected time measures, among others: Greenwich Mean Time (GMT), Universal Time Coordinated (UTC), International Atomic Time TAI (Temps Atomique International), GPST (Global Positioning System Time) eLoran Time and interrelation between these measures. Understanding how time is involved in navigation, and using it, is one of the navigator's most important duties. Nowadays we have satellite navigation to help us know where we are. These satellites contain several very precise and accurate clocks, because time and location are completely and totally inter-related in satellite navigation. There is growing interest internationally concerning the vulnerability Global Navigation Satellite Systems (GNSS) to natural and man-made interference, plus the jamming and spoofing of their transmissions. These vulnerabilities have led to a demand for sources of resilient PNT (Positioning, Navigation and Timing) [16], including a robust means of distributing precise time nationally and internationally.

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Global Positioning System: Political Support, Directions of Development, and Expectations

Czaplewski K.

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

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2015

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Vol. 9, no. 2

229--232

EN

Over the last decade the Global Positioning System has become a global, multifunctional tool which provides services that are an integral part of U.S. national security as well as the security of other highly developed countries. Economic development, transport security as well as homeland security are important elements of the global economic infrastructure. In 2000 the United States acknowledged the growing significance of GPS for civilian users and stopped intentionally degrading accuracy for non-military signals that are known as “Selective Availability”. Since then, commercial applications of satellite systems have been proliferating even more rapidly, and therefore, their importance in everyday life has greatly increased. Currently, services that depend on information obtained from the Global Positioning System are the driving force behind economic growth, economic development and the improvement in life safety. This economic development would not be possible without the financial and political support of the US government to maintain the operation of the GPS system. Therefore it is important to have knowledge about the intentions of the US government how system GPS will be developed in the future. Decisions taken in the last 3 months are the subject of this article.