Many animals have some kind of ‘home’ –a nest, a burrow, etc. This applies to insects that build nests and provide their larvae with food just as much as to numerous species of vertebrates. Rodents and moles are known to dig burrows; most other mammals, reptiles, amphibians and even many fresh-water fish do not roam around randomly either, but have well-defined home ranges with favourite resting places in particular cavities, under rocks or in dense thickets. Birds build nests for their young and fly out searching for food. All these animals permanently face orientation problems: they have to move swiftly and efficiently within their home range, and they must be capable of returning home when they have left their familiar area while exploring, fleeing, etc.

Navigation and manoeuvring simulators are increasingly being used in research centres to conduct complex navigation experiments and analyses. The structure and capabilities of simulation software make it possible to reproduce any conditions, including weather conditions. The complex mathematical models of marine environmental conditions that are being implemented nowadays take into account various sea wave models, which makes simulation tests more realistic. This paper deals with issues related to evaluating and verifying vessel simulation models based on real-world studies. As a result of the present research project, a methodology for comparing vessel simulation models with their real-life counterparts was developed. A measurement platform was created for the purpose of carrying out real-world studies; it is available at the Institute of Marine Navigation and Hydrography of the Polish Naval Academy. One important research step involved developing a procedural algorithm for making real-world measurements. This paper presents the results of using this platform in comparative tests of the manoeuvring elements of real and simulated vessels.

This paper discusses human error from two perspectives: errors made by operators on the one hand and errors made by designers and manufacturers of technological aids on the other. The question of operators' reliance on technological aids is discussed, as well as the concept of “overreliance” in connection with technologically aided presentation of navigational information. The accident investigation report following the grounding of the M/V Royal Majesty in 1995 is taken as an example. In that and many reports, designers and technology were not investigated as carefully as the operators on site. In that report, total responsibility for the accident was attributed to the mariners, while unreliable, incorrectly designed or incorrectly mounted technological aids, as well as the constructors, manufacturers and technical expertise behind it, were not investigated. This biased praxis when investigating human error is questioned and another investigative approach is suggested, in which operators and technology are treated equally and where the people behind the technologies can also be scrutinised. Such an approach would have a great beneficial impact on safety at sea.

Indoor/Outdoor (IO) detection (IOD) using Wi-Fi- and smartphone-based technologies is in high demand and interest in both the industrial and research fields. This paper proposes a novel and effective hybrid IOD (HIOD) approach for detecting a smartphone user's IO location. The HIOD approach uses signals received from both Wi-Fi and GPS as well as the latest positioning technologies such as multilateration, fingerprinting and machine learning. This paper proposes and implements two-level signal-to-noise ratio (SNR) threshold parameters for the first time, which are specifically derived from GPS signals through 42 empirical tests at seven test sites with adequate environmental factors considered. Using the newly derived IOD threshold parameters and a set of IO detection rules, the HIOD approach is then tested at 20 test points (TPs) in a city canyon area, where most of the TPs are under semi-indoor or semi-outdoor conditions. The final test results show that a 100% IOD rate is achieved.

In the July number of the Journal Captain C. V. Sølver described the discovery, by the Danish archaeologist Dr. C. L. Vebæk, in Greenland in the summer of 1951, of what was believed to have been part of an early bearing-dial. The object, which was dated by the archaeologists at about the year 1200, was one-half of an oak disk the outer rim of which was carved in such a way as to lead Captain Sølver to the conclusion that the complete disk was divided into thirty-two points or directions. Captain Sølver's paper was illustrated by a photograph of the fragment discovered and of his reconstruction of a similar bearing-dial.

Professor Taylor comments below on Captain Sølver's paper, and on the more general question of a Norse bearing-dial which it raised. Comment on the problem invited from a number of members and others is also given.

The aim of this study is to develop a simulation model which is capable of mimicking actual vessel arrival patterns and vessel entrance decisions (which are made based on expert opinions generally) on congested, narrow waterways. The model is tested on the transit traffic pattern in the Strait of Istanbul. Based on a heuristic scheduling algorithm, this model decides entrance times and vessel types on the strait. The model, with different policies for day and night traffic, is run for a period of seven years with 20 replications for each year. The performance measures of the model are: average interarrival times, number of vessels passed and entrance times for each successive vessel pair in both traffic directions. The model results are congruent with the actual results of performance measures. Therefore, it may be deduced that the proposed algorithm can be a guide for operators regarding scheduling decisions in congested, narrow waterways.

The strapdown inertial navigation system (SINS) with integrated Doppler velocity log (DVL) is widely utilised in underwater navigation. In the complex underwater environment, however, the DVL information may be corrupted, and as a result the accuracy of the Kalman filter in the SINS/DVL integrated system degrades. To solve this, an adaptive Kalman filter (AKF) with measurement noise estimator to provide noise statistical characteristics is generally applied. However, existing methods like moving windows (MW) and exponential weighted moving average (EWMA) cannot adapt to a dynamic environment, which results in unsatisfactory noise estimation performance. Moreover, the forgetting factor has to be determined empirically. Therefore, this paper proposes an improved EWMA (IEWMA) method with adaptive forgetting factor for measurement noise estimation. First, the model for a SINS/DVL integrated system is established, then the MW and EWMA based measurement noise estimators are illustrated. Subsequently, the proposed IEWMA method which is adaptive to the various environments without experience is introduced. Finally, simulation and vehicle tests are conducted to evaluate the effectiveness of the proposed method. Results show that the proposed method outperforms the MW and EWMA methods in terms of measurement noise estimation and navigation accuracy.

In 1991 Trimble Navigation introduced a Global Positioning System (Gps)-based attitude determination receiver capable of 3-axis solutions with accuracy to several milliradians for airborne, sea and land platforms. This paper discusses the physical, architectural, and operational features of this receiver system. Analysis of system performance will also be reviewed for various configurations and user applications. The Trimble Navigation attitude determination receiver uses differential carrier phase techniques to determine azimuth, pitch and roll angles of a 3-antenna array. This product is designed to operate in a variety of user applications and to withstand rugged operating environments. Trimble Navigation has expanded its proven GPS sensor architecture to incorporate three independent RF sections and additional processing channels to measure and process the differential phase between antennas on two orthogonal baselines. Direct measurement of differential phase utilizing a common local oscillator provides highly accurate relative phase data. The navigation and attitude processor computes azimuth, pitch, and roll angles as well as position, velocity and time. The solution accuracy and stability statistics are sensitive to various parameters. Antenna baseline length, signal multipath, platform dynamics and filtering are investigated. Test data from static and various dynamic platforms are also presented.

In the development of instrument systems for the purpose of flight control, traditional designs have consistently failed to solve three particular operational problems:

• (a) The difficulty of transition from instrument to visual flight conditions at the final stages of an instrument approach to land in bad weather.

• (b) The preservation of instrument control when the pilot±s attention is, for any reason, directed away from the appropriate instruments. Preoccupation with other duties, lack of concentration due to fatigue, keeping a look-out for other aircraft, &c, are examples of situations when the maintenance of accurate flight control may be lost.

• (c) The effective monitoring of the accuracy and precision with which an automatic pilot is achieving its selected function. Admittedly this can be achieved by the pilot continuously watching his appropriate primary instruments, but this tends to be extremely monotonous, and to a considerable extent reduces the advantages to be derived from effective automatic control. This particular problem reaches its peak under high altitude, high-speed, conditions of cruise of a jet transport, and in the final stages of an automatic approach, automatic flare, or automatic landing, on any type of aircraft.

It has been said that the mathematician accepts the gaussian distribution because he believes it to be supported in practice, and the practical man accepts it because he believes it has a sound mathematical foundation. Presumably it is for such reasons that the gaussian distribution is known as the ‘normal’ distribution and ‘probability paper’ has scales specially distorted so that a gaussian distribution will appear as a straight line.

In 1948, the port of Liverpool was probably the pioneer of European VTS, when they set up a radar station, in order to facilitate the boarding of pilots from the cutter. In 1951, Long Beach in California established a radar and VHF to facilitate port operations. Le Havre established another system and so, gradually, other ports followed. At this time commercial radar was comparatively new, and made it possible for the first time, under almost all weather conditions, to observe vessel traffic from the shore. In combination with VHF radio, a traffic surveillance system was achieved and real- time information exchange between the shore and ships became possible. Nevertheless, it was not until 1985 that the role of VTS in connection with navigation safety, traffic efficiency and environmental protection gained international recognition. This recognition is contained in an IMO resolution, which constitutes the VTS guidelines.

This paper was presented at the World Congress of the International Association of Institutes of Navigation (IAIN) held in Amsterdam, The Netherlands, 17–21 November 1997.

Remote, or shore-based, pilotage means different things to different people, despite a definition being produced by the European and International Maritime Pilots Associations. The debate about it is set in the context of increasing public awareness of the environment and a downward pressure on costs; these in themselves make for uncomfortable bedfellows. However, this sets the scene for the current aspirations within the European Union for vessel traffic management and the ongoing research into Vessel Traffic Services (VTS) and Vessel Traffic Management and Information Services (VTMIS). The technology to implement navigational assistance of a fairly high order is already in place, but there are still problems to be overcome before the concept can be taken further. Commonly recurring concerns over remote pilotage are the inadequacies of radar, difficulties with language, lack of ‘feel’ for the ship, which includes the on-board pilot's assessment of the quality of the vessel's crew, and the lack of ship motion data. Differential GPS is now capable of aiding automatic docking of some specialized vessels, but it has emerged, most recently at the IALA VTS Committee meeting, that ECDIS has shortcomings when being considered as the geographic information system of a VTS. Transponders are the subject of yet another debate, but will the data that they can convey be able to replace an on-board pilot?

The rapid development of positioning technology, wireless communication and mobile devices has given rise to the exciting Location Based Services (LBS) thus significantly influencing existing navigational procedures. Motivated by the increasing need to search efficiently through a huge number of service locations (e.g. restaurants, hotels, shops, and more), this paper presents an efficient spatial index QR-tree, a hybrid index structure of Quadtree and R-tree, instead of the exhaustive search to improve the performance in response to user queries. QR-tree consists of two levels: the upper level is a Quadtree residing in the main memory which partitions the data space and the lower level is disk-resident R-trees assigned to the subspaces resulting from the partitioning process. Computational experiments show that the hybrid index structure is able to reduce query response time by up to 30% and achieve significant improvement on data update over the conventional indexing methods, thereby providing an effective option for efficient navigation services.

The status of the tropopause has impact on weather phenomena and climate change occurring in the atmosphere of the Earth. The investigation of structure and variation of the tropopause plays a significant role in an in-depth understanding of water vapour exchange, mass and chemical materials across the tropopause, and their impacts on climate change and ecological environment. With the advantages of high vertical resolution, global coverage, unbiased instrumentation, and long-term stability, GPS Radio Occultation (RO) data is ideal for the monitoring of tropopause structure. In this research, GPS RO data from the two missions, CHAMP and COSMIC, were used to assess and analyse the temporal and spatial variations in tropopause heights and temperature over China. The consistency of the precision of the GPS temperature profiles derived from the two missions were also statistically validated. The two types of tropopause, i.e. the Lapse Rate Tropopause (LRT) and the Cold Point Tropopause (CPT), were determined from the GPS RO temperature profiles, and the trend of the variations in tropopause heights and temperatures of the two types of tropopause were compared and analysed.

Under some circumstances, dependent on a ship's velocity, the wave period and wave direction, certain courses induce heavy rolling and must be avoided. This paper proposes a computational method for the solution of optimal control problems in ship routing for ships with such limited manoeuvrability. Known results for the control problem of Bolza with additional constraints are interpreted in terms of this new problem. This approach is equivalent to the application of Pontryagin's maximum principle. The method is an extension of an earlier method dealing with the meteorological navigation of ships with unrestricted manoeuvrability and gives a more realistic picture of what really could happen in practice.

Colour is widely utilised as a visual coding system in visual search, but its application under vibration conditions (e.g., in various vehicles) has not been fully explored. This study was designed to examine the effect of colour combinations on performance of visual search tasks conducted in vibration conditions. Forty-eight university students participated in an experiment where they were required to identify target type and location under 24 colour combinations (half in negative polarity and half in positive polarity) and three vibration conditions (static, low, and high). The findings showed that vibration did not significantly affect performance, perceptions, or physiological aspects. Colour combination significantly affected response time, and the participants preferred colour combinations that had the potential to produce better performance. Colour combinations with negative polarity (e.g., yellow on black and white on black) are recommended for presenting search interfaces. These findings are of importance in human–computer interface designs for information display under vibration conditions.

In the effort to quantify Automatic Dependent Surveillance Broadcast (ADS-B) system safety, the authors have identified potential ADS-B failure modes in Syd Ali et al. (2014). Based on the findings, six potential hazards of ADS-B are identified in this paper. The authors then applied the Probabilistic Safety Assessment approach which includes Fault Tree Analysis (FTA) and Importance Analysis methods to quantify the system safety. FTA is applied to measure ADS-B system availability for each identified hazard while Importance Analysis is conducted to identify the most significant failure modes that may lead to the occurrence of the hazards. In addition, risk significance and safety significance of each failure mode are also identified. The result shows that the availability for the ADS-B system as a sole surveillance means is low at 0·898 in comparison to the availability of ADS-B system as supplemental or as primary means of surveillance at 0·95 and 0·999 respectively. The latter availability values are obtained from Minimum Aviation System Performance Standards (MASPS) for Automatic Dependent Surveillance-Broadcast (DO-242A).

One of the major topics of discussion at the moment is the subject of control in marine traffic systems. For many years the principle of the freedom of the sea and in particular the freedom of navigation was recognized universally, but recent advances in many directions have led people to question it closely. The increasing size of ships, and especially those used to transport cargoes such as oil, chemicals and liquid natural gas, is one factor, since various incidents have led to a growing awareness of the human and ecological consequences of even a minor incident at sea. Another factor has been the expansion of oildrilling operations and explorations for other resources, usually in areas such as the North Sea where the available navigable sea room was already restricted, especially for the modern deeper-draught ships. Purely economic factors have also been contributory; modern ships spend less and less time in port with more time at sea and the commercial world demands that the sea voyages should be completed as efficiently as possible, usually with respect to time. For these and other local reasons there is a growing demand for some form of marine traffic control system. Most of the world's major ports have traffic control to some extent and attention is now being paid to restricted seaways such as the Dover Strait.

Air traffic controllers use a radar separation minimum when keeping aircraft safely apart. The choice of minimum needs to ensure, to a very high degree of confidence, that radar inaccuracies are not putting the aircraft into a risk of collision – controllers can of course be required to use larger minima for operational reasons. A particular separation minimum necessarily feeds back into requirements on radar design criteria, data processing and performance. The estimation of the radar separation minimum is significantly improved by the use of a new methodology. Previous derivations were a major step forward, but were ‘static’, in that they did not attempt to take properly into account how controllers use separation minima dynamically. An analysis on the use of separation minima in en route airspace by controllers concludes that they are generally likely to use the radar minimum to pass aircraft, rather than to use the minimum in a ‘strategic’ sense (e.g. ‘in trail’ separation). The new ‘Event Model’ methodology recognises that collisions cannot happen instantly: the aircraft pair concerned must move from a safe configuration to a hazardous one. Collisions are therefore events caused by flawed flight paths, dependent on both the initial positions of aircraft and their subsequent movements and velocities.

In the Venus capture period, it is difficult for celestial autonomous navigation to satisfy the requirement of high precision. To improve autonomous navigation performance, a Direction, Distance and Velocity (DDV) measurements deeply integrated navigation method is proposed. The “deeply” integrated navigation reflects the fact that the direction and velocity measurements suppress the Doppler effects in the pulsar signals. In the pulsar observation period, the direction and velocity measurements are utilised to compensate for Doppler effects in the pulsar signals. By these means, the residual effects can be ignored. When the direction, distance or velocity measurements are obtained, they are fused to improve the navigation performance. Simulation results demonstrate that the DDV measurements deeply integrated navigation filter converges very well, and provides highly accurate position estimation without a high quality requirement on navigation sensors.