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

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

100%

Filić M. , Filjar R.

tom Vol. 13, no. 3

575--579

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.

A South Pacific Cyclone-caused GPS positioning errorand Its impact on remote oceanic island communities

100%

Filić M. , Filjar R.

tom Vol. 12, no. 4

663--670

Satellite navigation gains importance in sustainable development of modern civilisation. With the increasing number of GNSS-based technology and socio-economic systems and services, satellite navigation has become an essential component of national infrastructure. This calls for novel requirements on GNSS positioning perfomance, and increasing need for resilient GNSS development. Here we examined the impact of rapidly developing tropical cyclone on GPS positioning performance degradation, and the resulting impact on oceanic non-navigation and navigation GPS applications. We presented the methodology for indirect simulation-based GPS positioning performance evaluation through utilisation of experimental GPS observations, GNSS Software-Defined Radio (SDR) receiver, and a statistical analysis and framework we developed in the R environment for scientific computing. We identified alteration of GPS positioning error components time series statistical properties, and discuss the potential impact on GPS-based services essential for remote oceanic island communities. Manuscript concludes with the summary of findings, proposal for recommendations on improved GNSS resilience, and an outline for future research.

Modelling GPS positioning performance in Northwest Passage during extreme space weather conditions

70%

Špoljar D. , Jukić O. , Sikirica N. , Lenac K. , Filjar R.

tom Vol. 15 No. 1

165--169

New shipping routes are emerging as a result of iceberg melting in polar regions, allowing for more efficient transport of people and goods. Opening of the Northwest Passage, the maritime route connecting Pacific Ocean with Atlantic Ocean through Arctic region, is considered such a development. The increasing transport exploitation of the Northwest Passage requires the quality assessment of maritime navigation aids for compliance with the established requirements. Here we contribute to the subject with addressing the polar commercial-grade GPS positioning performance in the Northwest Passage in the extreme positioning environment conditions during the massive 2003 space weather storm, a space weather event similar to the Carrington Storm of 1859, the largest space weather event recorded. The GPS positioning environment in the Northwest Passage during the Carrington-like storm in 2003 was reconstructed through the GNSS SDR receiver-post processing of the experimental GPS observations. The raw GPS dual-frequency pseudoranges and navigation messages were collected at the International GNSS Service (IGS) reference station at Ulukhaktok, Victoria Island, Canada. Pseudorange processing and GPS position estimation were performed in three scenarios of pre-mitigation of the ionospheric effects, known as the single major contributor GPS positioning error: (i) no corrections applied, (ii) Klobuchar-based corrected GPS positioning, and (iii) dual-frequency corrected GPS positioning. Resulting GPS positioning error vectors were derived as positioning error residuals from the known reference station position. Statistical properties of the northing, easting, and vertical components of the GPS positioning error vector were analyzed with a software developed in the R environment for statistical computing to select suitable methods for the GPS positioning error prediction model development. The analysis also identified the most suitable theoretical fit for experimental statistical distributions to assist the model development. Finally, two competitive GPS positioning error prediction models were developed, based on the exponential smoothing (reference) and the generalized regression neural networks (GRNN) (alternative) methods. Their properties were assessed to recommend their use as mitigation methods for adverse massive space weather effects in polar regions.