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

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AIS R-mode trilateration for GPS positioning and timing insurance

100%

Shyshkin O. V. , Konovets V. I. , Koshevyy V. M.

2024

tom Vol. 18 No. 2

369--374

Satellite navigation is the backbone of maritime navigation today. However, the technical vulnerability of on-board Global Navigation Satellite System (GNSS) receivers the satellite system greatly destabilizes maritime security due to the loss of ship’s position and accurate time. This article devoted to study an alternative method for obtaining coordinates and accurate time based on the use of automatic identification system (AIS) radio channels, so-called range mode (R-Mode). We use other AIS ship stations with reliable position data as reference stations and determine time of arrival for received AIS transmissions. To improve the accuracy of measuring signal arrival instance in the time difference of arrival (TDOA), that we utilize for trilateration, it is proposed signal oversampling and applying the fast Fourier transform (FFT) to the product of quadrature components of the baseband Gaussian minimum shift keying (GMSK) signal in the window of AIS time slot. To take into account the movement of other ships, appropriate coordinate corrections are foreseen, which can be calculated by dead reckoning or by the inertial navigation system of our ship. The proposed method is fully compatible with the existing AIS signals and may be employed in critical situations of locally limited (jamming, spoofing) GNSS abilities. It can be implemented as a separate unit, working for receiving in parallel with the mandatory AIS transponder.

Evolution of SBAS/EGNOS enabled devices in maritime

100%

López M. , Antón V.

tom Vol. 15 No. 3

543--549

The maritime sector was one of the first communities that recognized and exploited the opportunities and advantages provided by Global Navigation Satellite Systems (GNSS). In fact, 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. GPS provides the fastest and most accurate method for mariners to navigate, measure speed, and determine location. However, its performance can be enhanced by taking advantage of augmentation systems such as differential GNSS or Satellite-Based Augmentation Systems (SBAS/EGNOS), especially in terms of accuracy. Direct access to EGNOS in vessels can be achieved through EGNOS-enabled navigation receivers and EGNOS-enabled AIS transponders. This paper provides an analysis of the number of onboard devices, mainly devoted to navigation purposes, and AIS transponders which are SBAS compatible. In addition, other equipment using GNSS positioning in the maritime and inland waterways domains are also considered for the analysis of SBAS compatibility, including inland AIS, Portable Pilot Units (PPUs) and Dynamic Positioning (DP) equipment. A first survey was done in 2017 to have an overview of the percentage of SBAS enabled devices available in the maritime market [8]. Since then, the analysis has been yearly updated to understand the market evolution in terms of SBAS compatibility and its main results are summarised in this paper.