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due to the difference in time between the ice chart production and its use by mariners, the ice information is always out of date.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.

In 1972 an atomic time standard based on the fundamental properties of the caesium atom is being substituted for Greenwich Universal Time, based on the rotation of the Earth on its axis, as the ultimate control for international time signals. Greenwich Time and longitude are inseparable, so that any necessary correction to the time signals he receives will be of vital importance to the navigator.

This paper was presented at a meeting of the Institute in London on 27 January 1970 with the Hydrographer of the Navy, Rear-Admiral G. S. Ritchie, C.B., D.S.C., in the Chair. Mr. Humphry Smith, head of the Time Department at the Royal Greenwich Observatory and Chairman of the Directing Board of the Bureau International de l'Heure, reviews the relationship of uniform time systems to the precise astronomical observations that determine the irregularities of the Earth's rotation. He outlines the current proposals for time signals, their correction to Universal Time and the implications for the navigator.

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.

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.

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.

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.

As no internationally agreed-upon method for determining safe speed values currently exists, collecting vast amounts of information on conventional ship behaviour could be used to train autonomous ship intelligence in determining safe speeds in different conditions. This requires speed data collected from conventional ships to resemble what can be described as safe speeds. To test this, the Automatic Identification System (AIS) and environmental data – namely visibility, mean wind speed and significant wave height – were collected and merged for two study areas in Norway in the period between 27 March 2014 and 1 January 2021. Regression analyses based on 47,490 unique vessel transits were conducted and supplemented by two graphical methods for revealing relationships between variables. Contrary to the contemporary understanding of safe speed, reduced visibility did not lead to significantly reduced transit speeds. Wind and waves caused a reduction in speed in the open ocean, but not in coastal waters. Transit speeds were lower in coastal waters than in the open ocean.

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.

Remote monitoring and control systems are being used with more frequency, but the characteristics of situational awareness and decision-making from remote locations are largely unknown. Remote operators’ sources of information differ from on-board sources greatly in terms of perspective, field of view, and available data type (qualitative or quantitative). This study focused on clarifying the cognitive effects of first- and third-person perspectives on ship handling. A working hypothesis was formulated based on the findings of visual information processing and previous studies and tested using a developed ship handling simulator. The results revealed that: (1) the cognitive characteristics of the first-person perspective make it more effective in safely guiding ship handling than does the third-person perspective, and (2) the deviation in cognitive characteristics is prominent where collision can be easily avoided. The findings will aid the development of on-board and remotely piloted vessels and ensure the safety of their crews.

As every schoolboy learns, a point has position but no size, and a line has length but no breadth. Nevertheless, to a navigator concerned with fixing his ship, points and lines are represented on his chart as fine pencil marks.

The manner of representing the results of observations as pencil ‘points’ or ‘lines’, has undoubtedly led to the belief that a ship's position must be represented as lying at a point on a position line which is drawn on a chart. Nothing short of perfection in position lines is ever expected by most practical navigators, and two position lines crossing at a point are usually regarded by seamen as yielding a perfect position: and if three position lines meet at a point! … there is seldom even the slightest doubt in the mariner's mind about the reliability of such a fix. On the other hand, three position lines which do not meet at a point are usually regarded as being something not quite respectable.

The accuracy of speed prediction error to the next waypoint is a key factor in maintaining longitudinal separation on oceanic routes. This estimation is often used by air traffic control to estimate the future position of aircraft, and the estimation errors result in potential separation infringement. While most aircraft can calculate the estimated time at each future waypoint using the onboard Flight Management System, the factors affecting the inaccuracy of the estimation require more clarification. This paper investigates the accuracy of the speed prediction error on oceanic routes and examines the main factor of error using airline flight data. The results show that wind prediction error is a main source of speed prediction error, and significant differences of the speed prediction error among airlines and aircraft types were observed.

The frequency division multiple access (FDMA) strategy used in GLONASS causes inter-frequency phase bias (IFPB) and inter-frequency code bias (IFCB) between receivers from different manufacturers. The existence of IFPB and IFCB significantly increases the difficulties of fixing GLONASS ambiguity and limits the accuracy and reliability of GLONASS positioning. Moreover, the initial value of IFPB and IFCB may be unavailable or unreliable with the increasing number of receivers from different manufacturers in recent years. In this study, a real-time and reliable calibration algorithm of IFPB and IFCB based on multi-GNSS assistance is proposed by providing a fixed solution. Real-time IFPB rate and IFCB can be obtained using this algorithm without the initial IFPB and IFCB. The IFPB rate for all GLONASS satellites and IFCB for each GLONASS satellite are estimated due to different characteristics of IFPB and IFCB. IFPB calibration can be divided into constant and real-time IFPB calibrations to meet the different positioning requirements. Results show that constant IFPB rate has only 2 mm difference from the mean value of real-time IFPB rate. The IFPB rate and IFCB estimated by this algorithm have excellent stability, and the change in reference satellite cannot affect the results of IFPB rate and the stability of IFCB. The centimetre-level positioning results can be obtained using two calibration methods, and the positioning results with real-time calibration method are 10%–20% better than those with the constant calibration method. Under satellite-deprived environments, the improvements of multi-GNSS positioning accuracy with constant inter-frequency bias calibration gradually increase as the satellite cut-off elevation angle increases compared with GPS/BDS, which can reach up to 0·9 cm in the vertical direction.

Vessels are found frequently operating under the Automatic Identification System (AIS) ‘Not Under Command’ (NUC) option near ports and close to shores in order to report their manoeuvre status to nearby traffic. When asked if they are under any kind of restriction regarding their engines or steering, they often answer that they are just drifting or waiting for the pilot or shipowner's orders. The question that arises is this: “Are these vessels really under an NUC situation or can the AIS Navigational Status menu adapt to the different circumstances of navigation?”.

Accurate navigation systems are required for future pinpoint Mars landing missions. A radio ranging augmented Inertial Measurement Unit (IMU) integrated navigation system concept is considered for the Mars entry navigation. The uncertain system parameters associated with the Three Degree-Of-Freedom (3-DOF) dynamic model, and the measurement systematic errors are considered. In order to improve entry navigation accuracy, this paper presents the Multiple Model Adaptive Rank Estimation (MMARE) filter of radio beacons/IMU integrated navigation system. 3-DOF simulation results show that the performances of the proposed navigation filter method, 70·39 m estimated altitude error and 15·74 m/s estimated velocity error, fulfill the need of future pinpoint Mars landing missions.

Professor Kemp1 has revisited the circumstances in which the Princess Alice crossed ahead of, and was run down by, the oncoming Bywell Castle in 1878. This note focuses on the seamanship of the manoeuvre made by the Bywell Castle in the agony of the moment before collision. This manoeuvre was judged to be wrong at the time. The note concludes by considering how this manoeuvre would be judged today in the light of the seamanship required by Rule 17 of Colregs 1972 and draws attention to proposals made by Captain Phillip Colomb to the Thames Traffic Committee in 1879.

One of the major concerns in the operation of an air traffic system is the maintenance of adequate separation between aircraft. The assurance of an ‘acceptably low’ risk of collision is a crucial element in the system design. A number of factors need to be assessed in this process. What is the navigational performance of the aircraft in the system ? What are the possibilities for radar surveillance ? Are procedural arrangements together with position reporting a suitable mechanism? What difference would be made by collision avoidance or warning systems? Given that any combination of these or other factors has an implication on the minimum separation between aircraft, the level of safety ‘assured’ has to be balanced against the costs of the various alternatives which may present themselves.

In planning for change the implications of new operating practices or devices have to be assessed carefully. For most changes the process is one of evolution rather than revolution, although collision avoidance devices may have more of the latter's characteristics. Even for ‘revolutionary’ changes it may be possible to model the new system. Thus the existing situation is studied and its characteristics observed, then there are hypotheses of the ways in which the change alters the mechanisms in the system and finally the likely effects on system performance through mathematical and computer (often fast-time simulation) modelling.

The requirements of navigation entering or leaving harbour or in narrow waters are exacting, and a very accurate position is usually essential. For this reason it is believed that inertial techniques should be applied in the first instance only to ocean navigation as, although the system will give the ship's position continually, the accuracy will be of the order of one mile.

The latitude and vertical references are absolute, but the longitude reference is relative to a known starting point. Besides position, an inertial system can also provide course, sidereal time and roll and pitch and, by comparison of successive positions, course and speed made good, and leeway. Furthermore the system could be used to feed position into an automatic plotting table, with a chart of suitable scale superimposed, so that the vessel's geographical location would be visible at a glance.