Four on-road studies were conducted in the Clifton area of Nottingham, UK, aiming to explore the relationships between driver workload and environmental engagement associated with ‘active’ and ‘passive’ navigation systems. In a between-subjects design, a total of 61 experienced drivers completed two experimental drives comprising the same three routes (with overlapping sections), staged one week apart. Drivers were provided with the navigational support of a commercially-available navigation device (‘satnav’), an informed passenger (a stranger with expert route knowledge), a collaborative passenger (an individual with whom they had a close, personal relationship) or a novel interface employing a conversational natural language ‘NAV-NLI’ (Navigation Natural Language Interface). The NAV-NLI was created by curating linguistic intercourse extracted from the earlier conditions and delivering this using a ‘Wizard-of-Oz’ technique. This term describes a research experiment in which subjects interact with a computer system that they believe to be autonomous, but which is actually being operated or partially operated by an unseen human being. The different navigational methods were notable for their varying interactivity and the preponderance of environmental landmark information within route directions. Participants experienced the same guidance on each of the two drives to explore changes in reported and observed behaviour. Results show that participants who were more active in the navigation task (collaborative passenger or NAV-NLI) demonstrated enhanced environmental engagement (landmark recognition, route-learning and survey knowledge) allowing them to reconstruct the route more accurately post-drive, compared to drivers using more passive forms of navigational support (SatNav or informed passenger). Workload measures (the Tactile Detection Task (TDT) and the National Aeronautical and Space Administration Task Load Index (NASA-TLX)) indicated no differences between conditions, although SatNav users and collaborative passenger drivers reported lower workload during their second drive. The research demonstrates clear benefits and potential for a navigation system employing two-way conversational language to deliver instructions. This could help support a long-term perspective in the development of spatial knowledge, enabling drivers to become less reliant on the technology and begin to re-establish associations between viewing an environmental feature and the related navigational manoeuvre.

In recent years, navigation by stellar refraction has received considerable attention, having advantages of high accuracy, simple construction, and low cost. Nevertheless, there are many limitations to the precision and application of this method using a traditional measurement model. This article studies the changing pattern of atmospheric density, the disturbed atmospheric density model and measurement model of stellar refraction ranging from 20 km to 50 km. Furthermore, a control algorithm of multiple mode switching and an adaptive measurement model are proposed. With this method, any refracted starlight from the scope of between 20 km and 50 km can be captured and the measurement model at the appropriate height can be automatically established. Due to this, the reliability and practicality of navigation have been raised considerably. Accuracy of navigation using the adaptive measurement method is observed to improve by about 14%, using computer simulation based on an Unscented Kalman Filter (UKF).

The increasing availability of small, low-cost GPS receivers has established a firm growth in the production of Location-Based Services (LBS). LBS, such as in-car navigation systems, are not necessarily reliant on high accuracy but a continuous positioning service. When available, the accuracy provided by the standard positioning service (SPS) of 30 metres, 95% of the time is often acceptable. The reality is, however, that GPS does not work in all situations, and it is therefore common to integrate GPS with additional sensors. The use of low-cost inertial sensors alone during GPS signal outage is severely restricted due to the accumulation of errors that is inherent with such dead reckoning (DR) systems. Through the integration of spatial information with real-time positioning sensors, intelligence can be added to the land mobile navigation solution. The information contained within a Geographical Information System (GIS) provides additional observations that can be used to improve the navigation result. With this approach, the solution is not dependent on the performance capabilities of the navigation sensors alone. This enables the use of lower accuracy navigation devices, allowing low-cost systems to provide a sustained, viable navigation solution despite long-term GPS outages. Practical results are presented comparing solutions obtained from a hand-held GPS receiver to a gyroscope and odometer.

The roll motion of a ship on waves is one of the six degrees of freedom and is the most difficult to predict since it deals with a motion similar to a spring-mass damper system, poorly damped by ship generated waves, in addition to the action of waves from the high seas. This problem increased from the second half of the 19th century when sailing propulsion was replaced by steam machines and iron replaced wood, which led to design modifications in ships affecting transversal stability, with the result of an increment in the ship's roll motion. As a consequence, it has been necessary to develop different systems which, on the one hand, increase the natural period of this motion in order to decrease its amplitude and reduce the risks that the wave encounter frequency would resonate with the natural frequency of the ship's motion; and on the other hand, to generate a damping effect to this motion. Bilge keels, passive stabilisers with no moving parts, form the simplest and cheapest element that may be incorporated on a ship to reduce this motion. This paper studies roll motion in general and then analyses bilge keels from different points of view.

With the widespread use of mobile devices and increased demand for mobile services, Location-Based Services (LBS) represent a promising addition to service offerings of network operators as well as third-party service providers. Based on long-term research in LBS, our group has proposed a generic Enhanced LBS Reference Model (ELRM), which describes the concept, the architecture and the functionalities of the LBS. In addition, an evolutionary information process has been identified within the LBS, that represents knowledge maturity from position awareness to situation awareness. Both the ELRM and the information evolution process in LBS are presented in this article and illustrated by a case study within the framework of the 3GPP-standardised IP Multimedia Subsystem (IMS). This case-study emphasises the opportunities for navigation- and LBS-related solutions development provided by modern telecommunication technologies.

It has hitherto been generally presumed that the division of the horizon into thirty-two points was a development of the late medieval period. Such a division, it has been said, was impossible in the pre-compass era. ‘It is questionable whether even so many as sixteen directions could have been picked out and followed at sea so long as Sun and star, however intimately known, were the only guides’, one eminent authority has declared; ‘Even the sailors in the north-western waters had only four names until a comparatively late date.’ Chaucer's reference in his Treatise on the Astrolabe to the thirty-two ‘partiez’ of the ‘orisonte’ has for long been quoted as the earliest evidence on the subject. The Konungs Skuggsjà, a thirteenth-century Norwegian work, however, refers to the Sun revolving through eight œttir; and the fourteenthcentury Icelandic Rímbegla talks of sixteen points or directions. An important discovery by the distinguished Danish archaeologist, Dr. C. L. Vebæk, in the summer of 1951, brings a new light to the whole problem and makes the earlier held view scarcely tenable. Vebæk was then working on the site of the Benedictine nunnery (mentioned by Îvar Bárdarson in the mid-fourteenth century) which stands on the site of a still older Norse homestead on the Siglufjörd, in southern Greenland. Buried in a heap of rubbish under the floor in one of the living-rooms, together with a number of broken tools of wood and iron (some of them with the owner's name inscribed on them in runes) was a remarkable fragment of carved oak which evidently once formed part of a bearingdial. This was a damaged oaken disk which, according to the archaeologists, dates back to about the year 1200.

Early in 1976 the Navigation Research Centre of the Netherlands Maritime Institute started research to develop a ‘maritime risk criterion number’ for a specific sea area. The need was urgent as the Navigation Research Centre (NRC) became more involved in marine traffic studies in the North Sea and the approaches to Dutch harbours. The main purpose is to calculate the criteria for traffic patterns in a given area as an element in the information needed to find the best regulatory solution for the overall traffic situation. The criterion should give due recognition to such elements as the traffic density, the course and speed distribution of the traffic, and the danger classes of the ships participating in the traffic.

This paper was presented at the West German-Soviet Workshop on Scientific and Industrial Cooperation in the use of GLONASS, held in Leningrad, USSR, September 1990. At this meeting, the author represented the Inter-Union Commission on the Allocation of Frequencies for radioastronomy and space research (IUCAF).

This paper derives a fast satellite selection algorithm; that is, an algorithm to select the best subset of satellites to use for positioning in circumstances whereby a satellite navigation receiver is not capable of using all satellites in view. The algorithm adopts the weighting factor concept to determine the contribution of each satellite to the overall positioning accuracy. Selection by this algorithm is shown to be especially efficient when the number of available satellites is large, so it is likely to be particularly useful for receivers capable of making combined measurements to GPS and GLONASS satellites.

A practical traffic control system can be envisaged as a hierarchy of control loops, each serving to convert a traffic demand into a potential traffic flow. Each loop is concerned with problems that can be foreseen to arise at some time in the future and the distinctive characteristic of any loop is the distance ahead, in time, to which it prognosticates. Although this model is probably applicable to most traffic systems the present note will apply it in the context of air traffic control.

Figure 1 shows a whole family of possible control loops. (Not all of these are present in all A.T.C. systems.) In each loop there is a mechanism for the prediction of future traffic. This prediction is compared with certain internal criteria and, if these are not satisfied, some control action is taken to coerce the traffic pattern into some more acceptable form. It is characteristic of most of these loops that they cannot be proved to be capable of safely handling all conceivable traffic demands; there is an implicit assumption that the superior elements of the control system will not tolerate a traffic demand which is beyond the handling capability of the inferior loops, but that a residue of unsolved problems can generally be left to be handled further down the chain.

Code phase Global Navigation Satellite System (GNSS) positioning performance is often described by the Geometric or Position Dilution of Precision (GDOP or PDOP), functions of the number of satellites employed in the solution and their geometry. This paper develops lower bounds to both metrics solely as functions of the number of satellites, effectively removing the added complexity caused by their locations in the sky, to allow users to assess how well their receivers are performing with respect to the best possible performance. Such bounds will be useful as receivers sub-select from the plethora of satellites available with multiple GNSS constellations. The bounds are initially developed for one constellation assuming that the satellites are at or above the horizon. Satellite constellations that essentially achieve the bounds are discussed, again with value toward the problem of satellite selection. The bounds are then extended to a non-zero mask angle and to multiple constellations.

Knowing what information, and from which sensory cues, is available to an animal regarding its position and direction of movement is vital for unravelling the mechanisms underlying animal navigation. Although considerable progress has been made with traditional field and laboratory techniques, these approaches generally do not provide direct control over the animal's motivation to display its sensory abilities. In contrast, psychologists have for many decades used conditioning as a reliable tool to study sensory perception as well as the mechanisms underlying learning. There has been growing interest in the use of conditioning techniques to investigate responses to stimuli that might be used in guiding movement over long distances. This review seeks to facilitate that development by providing a general introduction to conditioning and the considerations involved in designing robust conditioning experiments together with a perspective for its future use in studying sensory systems in migratory and homing species.

A ship's grounding appears to be a significant threat to the safety of its crew, marine environment and the local ports economy. The risk of such incidents is higher in rivers since weather conditions can significantly alter the depths of channels from those shown on navigation charts. By means of a fuzzy analytic hierarchy process, a new methodology is proposed, capable of evaluating the hazards of a ship's grounding in a river. The proposed method contributes to safe navigation in rivers. Navigators are able to assess grounding risk in a river passage based on local information of past incidents. The proposed methodology is used to evaluate commercial risks from groundings in the Parana River. A case study was carried out using data from 118 cases, as provided by local agencies for the period 2008–2017.

Although there have been improvements to the interface design of marine systems, there are still calls for increased usability as designers are blamed for systems that users find difficult to operate. This paper examines some of the issues and constraints that the designer faces when attempting to design a usable interface. The approach to designing that the developer may take is considered as well as more practical issues such as the limitations of using design principles. The importance of domain and context knowledge is stressed as well as other issues such as safety and culture. The paper concludes that design is a complex compromise but user involvement throughout the lifecycle can improve the ease of using marine systems.

Collective detection is a promising approach to positioning in a weak signal environment, in which the navigation solution is directly obtained by acquisition search in a multi-dimensional position and common clock bias uncertainty space. By combining the correlation values from multiple satellites and fully utilizing the coherence between them, the detectable C/N0 of individual satellites can be lowered. However, the lack of a computationally efficient optimization algorithm due to high dimensionality and complexity has hindered its application. A multi-resolution collective detection is therefore proposed to be a coarse-to-fine searching approach to solve for the position and common clock bias estimation. Although it reduces the computation time of collective detection, there is a gap in the efficiency study, which is the contribution of this research. The features of different levels of search in a multi-resolution algorithm are investigated. For a coarse search with large horizontal position step size, a smaller common clock bias step size is proposed instead of an averaging correlogram to reduce computation complexity as well as to obtain high time resolution. For the fine search with small horizontal space step size, a 3-D Dichotomous searching scheme is designed and applied to reduce the number of searching grids. Computer simulation results using experimental raw data are provided, to demonstrate the performance improvement against the conventional methods.

The presence of code Doppler and navigation bit sign transitions means that the acquisition of global positioning system (GPS) signals is difficult in weak signal environments where the output signal-to-noise ratio (SNR) is significantly reduced. Post-correlation techniques are typically utilised to solve these problems. Despite the advantages of these techniques, the post-correlation techniques suffer from problems caused by the code Doppler and the navigation bit sign transitions. We present an improved semi-bit differential acquisition method which can improve the code Doppler and the bit sign transition issues in the post-correlation techniques. In order to overcome the phenomenon of navigation bit sign transitions, the proposed method utilises the properties of the navigation bit. Since each navigation bit takes as long as 20 ms, there would be 10 ms correlations duration integration time between the received signal and the local coarse/acquisition (C/A) code in which the navigation bit sign transitions will not occur. Consequently, this problem can be cancelled by performing 10 ms correlations in even and odd units separately. Compensation of the code Doppler is also accomplished by shifting the code phase of the correlation results. To validate the performance of our suggested method, simulations are performed based on three data sets. The results show that the quantity of required input SNR to detect at least four satellites in the proposed method is − 48·3 dB, compared with − 20 dB and − 9 dB, respectively, in traditional differential and non-coherent methods.

Human fatigue is a major risk factor in transportation that contributes, directly or indirectly, to a large number of traffic accidents. Though many studies have investigated fatigue-inducing factors in transportation to manage human fatigue more efficiently, there are limited studies related to vessel traffic service (VTS). To fill this gap, this work aims to determine the key causal factors and symptoms of human fatigue with a focus on VTS operations. Achieving this aim is hindered by the problems of no standard definition of task-related fatigue and limited data sources. To solve these problems, this paper proposes a novel definition of task-related human fatigue, a task-driven approach for identifying causal factors and a causal network-based approach for selecting key causal factors. Twelve key causal factors of human fatigue in VTS were identified and analysed. In addition, it was found that VTS operators suffered from multidimensional fatigue, especially physical fatigue. The results provide a foundation and future directions for designing interventions to manage human fatigue.

The use of single-receiver single-satellite data validation parameters for numerical and graphical diagnostics of the multi-frequency observations is presented. This method validates Global Navigation Satellite System (GNSS) measurements of a single receiver where data from each satellite are independently processed using a geometry-free observation model with a reparameterised form of the unknowns. The method is applicable to any GNSS with any number of frequencies. The diagnostic tools are based on checking agreement of characteristics of the validation test statistics against theory. The use of these diagnostics in static and kinematic modes is demonstrated using multiple-frequency data from three GNSS constellations; Global Positioning System (GPS), Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) and Galileo.

This critical review addresses 26 studies of Wayfinding conducted in a real-world setting (large-scale), and with subjects using a map or an aerial photograph in their navigation. The purpose of the review is to summarise how previous surveys have been conducted and to provide some methodological advice for future research. Research design has consequently been the main priority, emphasising methods, measures, participants, context and types of map. Both qualitative and quantitative studies should be initiated, but the lack of research is significant within quantitative studies, the link between laboratory-based and real-world studies, studies where the subjects have been children with map experience and adult novices, and studies conducted in complex settings. Type of map appears to be an important determinant of performance and should be varied according to age and level of skills. Alignment of a map could be a possible source of error.

This paper proposes the novel use of a weighted Interval Kalman Filter (wIKF) in a robust navigational approach for integration with the guidance and control systems of an uninhabited surface vehicle named Springer. The waypoint tracking capability of this technique is compared with that of one that uses a conventional Kalman Filter (KF) navigational design, when the model of the sensing equipment used by the filter is incorrect. In this case, the KF fails to predict correctly the vehicle's heading, which consequently impacts negatively on the performance of its integrated navigation, guidance and control (NGC). However, the use of a wIKF technique that is immune to this kind of erroneous modelling endows the integrated NGC system with better accuracy and efficiency in completing a mission.