In this paper, some improvements in feature extraction for geomagnetic matching are made. Geomagnetic entropy is extracted from the total intensity of the geomagnetic field and its performance for navigation is tested with real geomagnetic data. The matching progress is divided into two phrases: rough matching and precise matching. In the rough matching phase, a sub-region that includes the real position is obtained by using the total intensity of the geomagnetic field as the matching feature. The entropy is applied to precise matching in the sub-region to obtain the final result. Simulations show that the navigation effect is significantly improved with the entropy as an assistant feature. The combined match probability is much better than the results derived from those using only total intensity as the matching feature. This is especially true when the flight vehicle passes through an area without abundant magnetic information.

The problem of analysing a single vessel's behaviour from real but incomplete Automatic Identification System (AIS) data received by satellite has been investigated. The main objective was to infer the route of any single vessel of interest, utilising the dynamic information decoded from AIS messages. A complete process of route inference using position, speed, course over ground and time stamp information is proposed in this paper. Due to the incompleteness of satellite AIS messages, an algorithm incorporating random deviations is also presented to account for the missing sections of obtained vessel routes. Analysis results from a set of real AIS data have demonstrated the applicability of the proposed algorithms in various scenarios.

From the Surface Velocity Program (SVP) drifter current data, a detailed and complete track of strong ocean currents in the north-western Pacific is provided using the bin average method. The focus of this study is on the Kuroshio, the strong western boundary current of the North Pacific flowing northward along the east coast of Taiwan and then turning eastward off southern Japan. With its average flow speed of about 2 knots, the Kuroshio can significantly increase the ship's speed for a “super-slow-steaming” container ship travelling at speeds of 12 knots between the ports of Southeast Asia and Japan. By properly utilizing knowledge of strong ocean currents to follow the Kuroshio on the northbound runs and avoid it on the return trip, considerable fuel can be saved and the transit time can be reduced. In the future, the detailed Kuroshio saving-energy route could be built into electronic chart systems for all navigators and shipping routers.

This paper has made a comprehensive investigation of the contribution of inertial measurement unit (IMU) signal denoising in terms of navigation accuracy, through theoretical analysis, simulations and real tests. Analysis shows that the integral step in the inertial navigation system (INS) algorithm is essentially equivalent to a super low-pass filter (LPF), whose filtering strength is related to the integral time of the INS. Therefore the contribution of the IMU denoising filter is almost completely overshadowed by the effect of the integral step for normal navigation cases. The theoretical analysis result was further verified by the simulations with an example of inertial angle estimation and by real tests of INS and GPS/INS systems. Results showed that the IMU signal denoising cannot bring observable improvement to INS or GPS/INS systems. This conclusion is strictly valid in the condition that the equivalent cut-off frequency of the integral step (which equals the reciprocal of the INS working alone time) is lower than the cut-off frequency of the denoising filter, which is the usual case for INS applications (except for some static data processing such as the stationary alignment of INS).

This paper aims to introduce a novel approach named IMM-UKF-TFS (Interacting Multiple Model-Unscented Kalman Filter-Two Filter Smoother) to attain positional accuracy in the intelligent navigation of a manoeuvring vehicle. Here, the navigation filter is designed with an Unscented Kalman Filter (UKF), together with an Interacting Multiple Model algorithm (IMM), which estimates the state variables and handles the noise uncertainty of the manoeuvring vehicle. A model-based estimator named Two Filter Smoothing (TFS) is implemented along with the UKF-based IMM to improve positional accuracy. The performance of the proposed IMM-UKF-TFS method is verified by modelling the vehicle motion into Constant Velocity-Coordinated Turn (CV-CT), Constant Velocity – Constant Acceleration (CV-CA) and Constant Acceleration-Coordinated Turn (CA-CT) models. The simulation results proved that the proposed IMM-UKF-TFS gives better positional accuracy than the existing conventional estimators such as UKF and IMM-UKF.

This paper studies the risk of ship collision off the coast of Portugal based on Automatic Identification System (AIS) data, which is recorded and maintained by the Portuguese coastal Vessel Traffic Service (VTS) control centre (CCTMC). Computer programs for decoding, visualization and analysis of the AIS data have been developed. From analysis of the AIS data available, maritime traffic off the coast of Portugal is characterized and a statistical analysis of traffic in the Traffic Separation Schemes is provided. An algorithm has been developed to assess the risk profile and the relative importance of routes associated with ports. A method is proposed to calculate the collision risk from the assessment of the number of collision candidates by estimating future distances between ships based on their previous positions, courses and speeds, and comparing those distances with a defined collision diameter. Values of causation probability suggested in several studies are used to calculate the expected number of collisions in the period of time under investigation based on the number of collision candidates. The results of this study are then compared with the number of collisions that have occurred between 1997–2006, registered and maintained by the Portuguese Maritime Authority.

In order to enhance the independent viability of high-orbit satellites, an X-ray pulsar-based navigation (XNAV)/celestial navigation system (CNS) integrated navigation method is proposed. An improved kinematic and static filter is derived to fulfil data fusion that can obtain an optimal estimation for global use. In the filter, unscented transformation is used to reduce linearization error, and the technique of separate-bias is used to reduce the impacts of systematic errors in XNAV measurements. The results of simulations have shown that the proposed navigation system can reach a positioning accuracy of less than 100 m, an improved performance over separate XNAV and CNS.

The liquefaction of nickel ore is widely considered to account for the capsizing and sinking of bulk carriers, but the mechanisms that lead to the incidents still remain uncertain. In this paper, the sloshing motion of fluid with high viscosity in a rectangular tank has been studied; the Level Set Method has been employed to predict the behaviours of fluid sloshing motion under the circumstances of beam seas. In a bid to evaluate the consistency of the numerical solution, a full validation has been performed. The results obtained from the simulations are in good agreement with that from the experiment. The conclusions have also been made that the collapse of the shear resistance of the fluid or increasing heeling moment acquired from the fluid sloshing after liquefaction of the nickel ore may be responsible for the capsizing and sinking of the ships. Hopefully, our conclusions can help ship owners better understand how to take precautions to prevent the ships from capsizing while carrying nickel ore or similar cargos; the results could provide the IMO with the theoretical basis for stipulating new international safe standards for bulk carriers; the numerical methodology can also help engineers to predict sloshing motion of viscous fluids.

In this paper the minimum ship domain in which a navigator feels comfortable is estimated. That is, we estimate the free space surrounding a ship into which no other ship or object should enter. This is very useful when estimating the maximum flow through a channel or a bridge span. The paper benefits from the introduction of Automatic Identification System (AIS) data as it is now much easier to conduct studies involving a large number of observations. Our observations are based on ships sailing in southern Danish waters during a four year period, and from the observations we estimate how closely ships pass each other and fixed objects in open sea navigation. The main result is the establishment of an empirical minimum ship domain related to a comfortable navigational distance.

Ships navigate freely when in the open sea, but their freedom of movement is reduced in areas with intense traffic, restricted draught or obstacles. In such cases, a traffic separation scheme (TSS) can be established to guide the ship traffic. This paper is based on work performed in connection with a proposed bridge across Fehmarnbelt between Denmark and Germany, and the purpose is to estimate the efficiency of a TSS guiding traffic through the main bridge openings. The efficiency in terms of getting the traffic through the traffic lanes without the TSS hindering traffic flow is an important decision parameter in the bridge design process. In this paper, we present a new “free flow” paradigm based on an innovative, dynamic application of the ship domain theory.