Safe and efficient marine navigation in ice-infested waters requires comprehensive and timely information on the sea ice conditions. These include information on the ice concentration and type, ice edge location, icebergs and open leads. The Canadian Ice Service is responsible for providing ice information in Canadian waters, mainly through its daily ice charts. Unfortunately, due to the difference in time between the ice chart production and its use by mariners, the ice information is always out of date. This problem might be overcome by developing a neural network-based system for predicting the ice conditions over time. A supervised neural network is trained to predict the ice conditions at a given location and time using the current ice charts, which are provided by the Canadian Ice Service. The input ice data is mapped to an output vector that gives the predicted ice conditions. The traditional non-modular feed-forward neural network structure failed to map the required function, and hence, was modularized to give better prediction performance. Each neural module was responsible for the prediction of a 5×5 km area, while the ice characteristic of interest was the total concentration.

Connected-Element Interferometry (CEI) is a technique for measuring the phase delay of difference of Time Of Arrival (TOA) of a downlink radio signal to two antennae on a short baseline. This technique can use an atomic clock for time-frequency transmission and achieve intermediate accuracy angular tracking. Owing to the relatively short length of the baseline, the passive reception mode, and near real-time operation, CEI can be used to continuously monitor the orbit variations of both cooperative and non-cooperative satellites. In this paper, a small-scale CEI system of two orthogonal baselines (75 m × 35 m) is investigated to track a Geostationary Earth Orbit (GEO) Television (TV) satellite at 110·5°E. The phases are extracted from correlation results. The results show that the Root Mean Square (RMS) of the phase fitting residuals, if not calibrated, is within 2° at night and up to 10° in the daytime. After applying the calibration signal, the RMS of the phase fitting residuals in the daytime decreases to the same level at night. Comparing the phase delay with the a priori phase delay using Two-Line-Element (TLE) data, the integer ambiguity is successfully resolved. Finally, a batch algorithm is used to estimate the orbit of the GEO satellite, and the orbit determination accuracy is evaluated using the precise orbits provided by the China National Time Service Centre (NTSC). The results show that the accuracies in the radial direction and the cross-track direction are less than 1 km, and the Three-Dimensional (3D) position accuracy reaches the 2 km order of magnitude.

The positioning technique employing the ubiquitous signals of opportunity of non-cooperative satellites does not send special navigation signals, instead it passively receives satellite signals as noise, presenting advantages of concealment and difficulty for potential attackers. Thus, this study investigates the ranging principle and model using non-cooperative communication satellites and a time difference estimation algorithm. The technology of time difference measurement under non-cooperative observation mode was determined and simulated. A test platform for time difference measurement was built to receive the signal from an unknown geostationary Earth orbit communication satellite and verify the ranging feasibility and performance. The ranging accuracy was found to be smaller than 6 m, as demonstrated by experimental data, which shows the viability of the proposed positioning technique for ranging technology.

This article proposes a novel method to autonomously determine the relative orbits of a small spacecraft formation flying with a slowly rotating near-Earth asteroid for the asteroid mitigation mission. A combined model of spacecraft-to-asteroid measurements with inter-spacecraft communication is built up. The dynamic model accounting for the perturbations is derived to describe the state variables of the Unscented Kalman Filter (UKF). The Lyapunov function approach is used to design a control law to maintain the orbits of the spacecraft formation. Four navigation scenarios are presented based on the different combinations of multiple measurements: two of them are non-collaborative scenarios which only include the spacecraft-to-asteroid measurements in the measurement models, while the other two are collaborative scenarios with the inter-spacecraft communication added into the measurement models. Simulation results are analysed and compared with each other to show the improvements of the filter performance in the aspects of the convergence speed and the accuracy of the estimator.

Many countries have presented new requirements for in-orbit space services. Space autonomous rendezvous and docking technology could speed up the development of in-orbit spacecraft and reduce the threat of increasing amounts of space debris. The purpose of this paper is to provide real-time high-precision navigation data for high-orbit spacecraft, thus reducing the cost of ground monitoring for high-orbit spacecraft autonomous rendezvous operations, and to provide technical support for high-orbit spacecraft in-orbit services. This paper proposes a new high-orbit spacecraft autonomous navigation approach, based on a communication satellite transmitting ground navigation signals. It proposes an overall navigation system design, sets up the system information integration model and analyses the precision of the navigation system by simulation research. Through simulation of this navigation method, the positional precision of a spacecraft at an altitude of 40 000 km, can be within 2·6 m with a velocity precision of 0·0011 m/s. The transponding satellite navigation method greatly reduces the development costs by using communication satellites in high-orbit spacecraft navigation instead of launching special navigation satellites. Moreover, the signals of transponding satellite navigation are generated on the ground, which is very convenient and cost-effective for system maintenance. In addition, placing atomic clocks on the ground may also help improve the clock accuracy achieved. In this study, the satellite-based navigation method is for the first time applied in high-orbit spacecraft navigation. The study's data could improve the present lack of effective high-orbit spacecraft navigation methods and provide strong technical support for autonomous rendezvous and docking of high orbital spacecraft, as well as other application fields.

Human watch-keeping is necessary to prevent incidents at sea such as groundings and collisions. For many years, electronic aids to navigation have been utilised in watch-keeping but, with electronic marine systems becoming more sophisticated, the part they play in preventing collisions and groundings should become increasingly important. However, this article uses secondary data from the Safety Digest for 2008 compiled by the Marine Accident Investigation Bureau of the United Kingdom; eight case studies are used to show that electronic marine systems, whether integrated or not, are still playing a part in poor watch-keeping resulting in collisions, near misses and groundings. Primary data from fishing skippers of British based vessels have been used to confirm the findings from the secondary data that poor watch-keeping is often the cause of not keeping a proper lookout and that the watch-keeper has a too heavy reliance on the electronic aids. Brief suggestions are made as to how the electronic aids may be adapted to overcome these problems and thus to support the watch-keeper.

A novel robust scheme for Transfer Alignment (TA) is proposed for improving the accuracy of the navigation of a Hypersonic Cruise Vehicle (HCV). The main goal is to instil robustness in the safety and accuracy of the attitude determination, despite mode uncertainties. This article focuses on Robust Sparse-Grid Quadrature Filtering (R-SGQF) using two given robust factors for norm-bounded model uncertainties in non-linear systems. Missile dynamic and measurement model uncertainties are established to validate TA technologies. The nominal stability of the R-SGQF is defined by estimating error dynamics. The technique gives sufficient conditions for the R-SGQF in terms of two parameterised Riccati equations. Robust stability is analysed using Lyapunov theory and the accuracy level of the Sparse-Grid Quadrature (SGQ) algorithm. Embedding the SGQ technique into the robust filter structure, R-SGQF is not only of robust stability against uncertainty but also of higher accuracy. The simulation results of the TA algorithm demonstrate that attitude determinations validate the effectiveness of the R-SGQF algorithm.

The existence of Unexploded Ordnance (UXO) is a serious environmental hazard, especially in areas being converted from military to civilian use. The detection and discrimination performance of UXO detectors depends on the sensor technology as well as on the processing methodology that inverts the data to infer UXO. The detection systems, typically electro-magnetic induction (EMI) devices, require very accurate positioning (or geolocation) in order to discriminate candidate UXO from non-hazardous items. For this paper, a hand-held geolocation system based on a tactical-grade IMU, such as the HG1900, was tested in the laboratory over a small, metre-square area in sweep and swing modes. A camera position system was used to emulate GPS or alternative ground-based external ranging systems that control positioning errors. The proposed integration algorithm is a combination of linear filtering (Extended Kalman Filter) and nonlinear, also non-Gaussian filtering (Unscented Particle Filter) in the form of the Rao-Blackwellized Particle Filter (RBPF). The test results show that the position accuracy was improved by applying nonlinear filter-based smoothing techniques in both the straight and curved sections of the sweep and swing trajectories.

The tight combination model improves the positioning accuracy of the Global Navigation Satellite System (GNSS) in complex environments by increasing the redundancy of observation. However, the ambiguity cannot be calculated directly because of the correlation between it and the phase difference inter-system bias (DISB) in the model. This paper proposes a method of DISB estimation based on the principle of maximum ratio. From the data analysis, for the standard deviation of code DISB, the improvement of the method can up to 0·179 m with the poor quality data. In addition, compared to the parameter combination method, the standard deviation of all the phase DISB was deceased with the method in the paper. About the phase DISB of GPS L1/Galileo E1, the standard deviation decreased from 0·014/0·022/0·009/0·051 cycles to 0·006/0·015/0·004/0·029 cycles of four baselines, which represents the improvement of 57·14/31·82/55·56/43·14%. About the phase DISB of GPS L1/BDS B1, the standard deviation decreased from 0·014/0·061/0·010/0·052 cycles to 0·002/0·005/0·009/0·004 cycles of four baselines, which represents the improvement of 85·71/91·80/10·00/92·31%.

The instructor of a full mission marine simulator faces a daunting task, controlling several target ships under varying environmental conditions while responding to a variety of communications. This project applies computer agent technology to an instructor station. Each target ship is controlled by a collision avoidance agent which takes command of the ship and a track-keeping agent which acts as an assistant, sending the collision avoidance agent advisory messages. Experiments have been performed for a number of collision situations in varying environmental conditions. An analysis of the results demonstrates the potential of such a system for producing realistic target ship motion, including track-keeping and some collision avoidance manoeuvres, thus reducing the instructor’s immediate load.

An integrated GPS/INS navigation system can employ inertial velocity information to produce a more robust system. For a stand-alone GPS receiver, decreasing the receiver tracking loop bandwidth reduces the probability of losing lock in a jamming or interference environment if vehicle dynamics are low. However, reduced bandwidth increases tracking errors when dynamics are present. Beyond a certain limit, it causes a serious degradation in the dynamic tracking loop performance. Providing inertial velocity aiding to the receiver tracking loops is an effective and popular treatment to help resolve this problem. In this paper, performance of the GPS receiver tracking loops using inertial velocity aiding will be investigated. Different types of tracking loops, from 1st to 3rd order, are covered. Following the discussion of the system architecture and derivation of the related transfer functions for the tracking loops, both with and without aiding, the system performance, including transient response, steady-state error, and noise bandwidth is evaluated.

This study examines the way in which attention is allocated by watchkeepers on fishing vessels and identifies differences in the approach displayed by individuals with different levels of training and experience. A method of analysing the way in which attention is allocated on a sample of UK fishing vessels is described. It was found that both skippers and mates allocated disproportionate amounts of attention to fishfinding equipment at certain stages of the fishing trip, while crewmen were heavily reliant upon the track plotter both while fishing and on passage. Those with more training and experience appeared to treat the array of navigation and control components as an integrated system, while untrained crewmen dealt with each aspect in isolation.

Scouring and sedimentation effects on the seabed induced by ship propellers during ship manoeuvring near harbour structures affect both structure stability and ship manoeuvring capabilities. This contribution proposes solutions at an operational level using the automatic identification system (AIS) and a bridge simulator. Two new alternative manoeuvres were designed and tested on a bridge simulator to obtain expected maximum scour depth and the results were compared with that of real manoeuvres (i) using mooring lines, and (ii) with tug assistance. A total of 42 test scenarios combining several manoeuvres and meteorological conditions were reproduced. Results confirmed a clear reduction in erosion depth with the alternative manoeuvres, with total reduction when using the tugboat. The presented methodology can be very useful to port authorities to prevent the effects of ship erosion on harbour infrastructures.

The objective of this study was to design and evaluate new means of complying to time constraints by presenting aircraft target taxi speeds on a head-up display (HUD). Four different HUD presentations were iteratively developed from paper sketches into digital prototypes. Each HUD presentation reflected different levels of information presentation. A subsequent evaluation included 32 pilots, with varying flight experience, in usability tests. The participants subjectively assessed which information was most useful to comply with time constraints. The assessment was based on six themes including information, workload, situational awareness, stress, support and usability. The evaluation consisted of computer-simulated taxi-runs, self-assessments and statistical analysis. Information provided by a graphical vertical tape descriptive/predictive HUD presentation, including alpha-numerical information redundancy, was rated most useful. Differences between novice and expert pilots can be resolved by incorporating combinations of graphics and alpha-numeric presentations. The findings can be applied for further studies of combining navigational and time-keeping HUD support during taxi.

This paper reports on a new navigation algorithm for fixed-wing Unmanned Aerial Vehicles (UAVs) to bridge Global Position System (GPS) outages, based on a common navigation system configuration. The ground velocity is obtained from wind-compensated airspeed, and a centripetal force model is introduced to estimate the motion acceleration. Compensated by this acceleration, the gravity vector can be extracted from the accelerometer measurement. Finally, fusing the information of the ground velocity, magnetic heading, barometric height, and gravity vector, the Integrated Navigation System (INS) is reconstructed, and an Extended Kalman Filter (EKF) is used to estimate INS errors. Hardware-in-loop simulation results show that compared with INS-only solutions, the proposed method effectively resists long-term drift of INS errors and significantly improves the accuracy for dynamic navigation during GPS outages.

To track multiple ships and estimate the feature parameters of multiple emitters on board using electronic intelligence satellites under clutter interference, a long and random revisit time, and other complex conditions, a novel tracking algorithm using both kinematic (position and velocity) and feature information based on an improved Multiple Hypothesis Tracking (MHT) approach is proposed in this paper. Firstly, the characteristics of multi-ship tracking with multiple emitters using satellite electronic information are analysed, and a new model of an emitter is built as an extended target in geographical coordinates. Secondly, a pre-processing of measurements is utilised via hierarchical clustering using the location and feature information of emitters. Thirdly, feature information is incorporated into the MHT framework using Jensen-Shannon divergence distance and fuzzy C-means clustering to calculate track scores. Finally, we present the prediction and update of target states, especially the update of feature parameters, to realise joint kinematic and feature tracking of ships. The results of the simulation show that the proposed method has much better tracking performance than the standard MHT algorithm.

Using near miss data detected from non-accident information to analyse marine traffic risk can alleviate some of the limitations of accident-based methods. A model based on an arena for detecting scenes of near miss is proposed to detect comprehensively those ship encounters with potential collision risk. To eliminate the influence of data sampling frequency on the detection of scenes of near miss, a single near miss is defined as the whole progress of traffic state from the time the target ship sails into the arena of the subject ship to the time it leaves the arena of the subject ship. To research the geographical distribution characteristics of marine traffic risk, first, a statistical model for the scenes of near miss based on the water grid method is proposed, and then a macroscopic collision risk model based on near miss is developed. The geographical distribution characteristics of marine traffic risk in the Bohai Sea are analysed, and the water areas of high marine traffic risk are obtained. The findings can provide theoretical support for marine safety management.

Privacy is an increasingly important aspect surrounding the introduction of road pricing in the Netherlands. Different systems for monitoring vehicles result in different consequences for privacy. This contribution describes the privacy aspects in the different scenarios used by the Dutch government. It is often suggested that privacy is a hindrance for road pricing, but if smart choices are made, this does not necessarily have to be the case. In this contribution, we suggest several concrete technological, legal and organizational (partial) solutions, that could be useful in implementing privacy-friendly road pricing.

Historians of the mariner's compass (particularly those of the last century) have introduced into the literature of the subject a number of statements which can be shown to be incorrect, or at the least to be extremely doubtful. Unfortunately it is just these ‘facts’ which have been seized upon by later historians and appear in one authoritative book after another. I have myself fallen into one stock trap or another in the past.