Before the middle of the 19th Century, sailing vessels under way at night did not set a light. This paper investigates the reasons for this practice and explains the development of navigation lights which culminated in the requirement for both steamships and sailing vessels to display lights at night.

The European Geostationary Navigation Overlay Service (EGNOS) system is being developed in Europe to provide Global Positioning System (GPS) and GLONASS regional augmentation services to aviation, maritime and land users. The EGNOS system, as any other Wide Area Augmentation System (WAAS), relies on the broadcast of differential correction and integrity information in the pseudo-range domain, which are then used to provide a solution in the position domain. EGNOS is a major element of the European Satellite Navigation Program, which is jointly being implemented by the Commission of the European Union, the European Space Agency (ESA) and Eurocontrol (the European Organisation for the Safety of Air Navigation). It is also the first European step to the GALILEO system.

As part of the EGNOS validation activities, flight trials have been organised by ESA and the EGNOS Industrial Consortium at various locations in Europe during Spring 2005. To demonstrate the system capability in a challenging mountainous environment, tests have been conducted at Lugano airport in the Swiss Alps. Due to the difficult topography of the airport and its surroundings, the use of conventional ground based navigation aids present some limitations. For the trials, a new Satellite Based Augmentation System (SBAS) procedure has been designed to take advantage of the system flexibility. In particular, a reduction of the approach glide path angle has been achieved, potentially allowing more aircraft types to fly the approach than today. This article presents the operational benefits that could be obtained with the new test procedure. The very impressive EGNOS performance is also described in details, showing that it can support Approach Procedure with Vertical guidance (APV) operations even in a very challenging environment.

It is well known that GPS measurements are regularly obstructed in urban environments. Positioning accuracy in such environments is significantly degraded and in many areas, it is not possible to obtain a GPS position fix at all. There are currently two methods that can be used to improve availability in the urban environment. Firstly, GPS receivers can be augmented with dead reckoning sensors such as an INS. Alternatively, High Sensitivity GPS (HSGPS) receivers can be used which are able to acquire and track very weak signals. This paper assesses the performance obtained from a GPS and low cost INS integrated system and a HSGPS receiver in an urban environment in Nottingham, UK. The navigation systems are compared to a high accuracy integrated GPS/INS system which is used to provide a reference trajectory. It is demonstrated that the differential GPS and low cost INS system can provide horizontal positioning accuracy of better than 2·5 m RMS in real-time, and better than 1 m RMS in post-processing, whereas the non-differential HSGPS receiver provides a real-time performance of 5 m RMS. These results were obtained in an environment where, with conventional GPS receivers, a position solution is only available 48·4% of the time. Operational considerations such as initial alignment of the GPS and low cost INS are also discussed when comparing the two systems for urban positioning applications.

This paper proposes a computation method for the determination of the worst user location (WUL) instead of the current grid search-based methods. The WUL is a key parameter in the estimation of the Galileo integrity data. Since a satellite clock error is the same for all users whereas the orbital error is different depending on the location of users, the WUL depends on the satellite orbit errors which can be estimated using the measurements from the Galileo sensor stations. The proposed algorithm uses the resolved orbital errors to calculate an approximate WUL on a spherical model of the Earth. The next step is to determine the WUL on a specified ellipsoid model using an iterative transformation process. Results show that the proposed method is more accurate and computationally efficient than the current search-based methods. The computation time required is minimal making it valuable in meeting the real time requirements for the generation of the Galileo integrity flag.

Four arctic offshore loading concepts are selected, loading from the corner of a platform, loading in the wake of a loading tower, Submerged Turret Loading (STL) and Single Anchor Loading (SAL). The influence of variations in the ice drift direction on the performance of these concepts is discussed and critical drift events are determined. Ice drift measurements from eight ARGOS/GPS buoys deployed in the Pechora Sea in winters 1995 and 1998 are analysed to estimate downtime rates of these loading systems due to ice drift heading changes. Depending on the location in the Pechora Sea and the chosen concept, downtime rates range from 6 to 72%. A discussion on how these rates will vary with different assumptions, different ice conditions or different ice management is given. Finally the loading concepts are compared through a qualitative risk analysis.

During World War II women in the US and the UK were given the then unprecedented opportunity to fly military aircraft. Yet while the women flying in the UK soon gained the privileges and status enjoyed by their male colleagues, the American women pilots were expressly denied the same status, rank, pay, and benefits as USAAF pilots. In fact, after an ugly slander campaign against the women pilots' organisation, the US programme was discontinued and the women were sent home before their job was done. The American women pilots were not less dedicated or inherently less capable than the women flying in Britain. Rather, key environmental and organisational differences and above all a failure of leadership accounts for their fate. This paper summarises the differences and their impact. The complete findings of the comparative research on the experiences of women pilots in the US and the UK during WWII will be published by Pen & Sword Books Inc early in 2006 under the title Sisters in Arms.

The article introduces a method of finding optimal routes on raster planes. The method presented takes advantage of a new algorithm that tends to minimize a number of direction changes within a route, while steering clear of the obstacles. Two different schemes, suitable for restricted area Vessel Traffic Service (VTS) system and collision avoidance system located on the own ship are described. The VTS-oriented scheme supports VTS priority policy that may extend or override international give-way regulations. The own-ship routing scheme in a give-way situation is capable of determining the shortest safe path to the destination point. The method takes into account own ship dynamics. It has linear time and space complexities and therefore is sufficiently fast to perform real-time routing on the raster grids. Both the general method and the algorithm it uses are presented in detail in the paper. Implementation issues are also discussed.

Many researchers have studied vessel systems to enhance navigation safety at sea, or analysed the statistics of marine casualties of different flagged vessels as well as the fatalities and injuries in ferry accidents. However, little research has been devoted to port safety and especially navigation safety within Taiwanese territorial waters where over a 10-year period there have been 3428 marine accidents with 548 deaths and 524 vessels sunk. In this paper, we use the Grey Relational Analysis (GRA) to analyse the marine accident records of each of Taiwan's commercial ports from 1992–2003. Then, after interviewing the port authority managers and marine specialists, we discover the concerns felt by these professionals about Taiwanese commercial ports. We provide suggestions to strengthen port navigation safety.

Nowadays GPS is widely used to monitor the ionosphere. However, the current results from ground-based GPS observations only provide some information on the horizontal structure of the ionosphere, and are extremely restricted in mapping its vertical structure. In this paper, tomography reconstruction technique was used to image 3D ionospheric structure with ground-based GPS. The first result of the 3D images of the ionospheric electron density distribution in South Korea has been generated from the permanent Korean GPS Network (KGN) data. Compared with the profiles obtained by independent ionosondes at or near the GPS receiver stations, the electron density profiles obtained by the GPS tomographic construction method are in better agreement, showing the validity of the GPS ionospheric tomographic reconstruction. It has also indicated that GPS-based 3D ionospheric mapping has the potential to complement other expensive observing techniques in ionospheric mapping, such as ionosondes and radar.

The development of a seamless vertical reference surface is accompanied by a number of challenges pertinent to the availability, volume and uncertainty of bathymetric and topographic data. Data uncertainty, which is by far the most difficult to deal with, is attributed to various sources of errors including those of geodetic and hydrographic origin. The uncertainties in the geodetic measurements originate mainly from the limitations in the geodetic technique employed, i.e. terrestrial or space. Old nautical charts and topographic maps were based on terrestrial techniques, which are far less accurate than modern space techniques. In addition, the distribution of the positioning uncertainty is not expected to follow a consistent pattern across the chart (map). This is mainly due to the inconsistent datum distortion as well as the discrepancies in the measuring techniques in the subsequent chart (map) versions. The existing paper (and digitized) charts in many areas of the world were also based on old hydrographic surveying methods, for example the lead-line, which are far less accurate than modern techniques such as multibeam echo-sounding surveys. This creates inconsistent depth uncertainty across the chart. As uncertainties are propagated into the estimated transformation parameters, estimated positions and their covariance matrix, it is of utmost importance that they are properly modelled. This paper addresses the issue of uncertainty in hydrographic data and suggests ways to account for it.

Because GPS is a radio navigation system which has a very low power level, it is vulnerable to RFI. Excessive RFI could cause receiver performance degradation, such as degradation of position accuracy, loss of lock and increased acquisition time. After GPS modernization plans introduce dual-frequency civil signals to mitigate ionospheric errors, RFI will remain as one of the dominant threats for differential GPS navigation systems. Examples of safety-critical civil aviation and military missions threatened by RFI include the Local Area Augmentation System (LAAS) and the Joint Precision Approach and Landing System (JPALS). This paper focuses on RFI mitigation through integrity monitoring for a DGPS system like LAAS or JPALS. The mitigation strategy consists of two parts. First, the paper develops a new RFI detection method, using a raw divergence statistic. Second, the paper investigates strategies for maintaining integrity in the case that RFI is detected.

To validate the utility of the divergence-based RFI monitor, this paper takes an experimental approach. The experiments assess the performance of the divergence metric and compare it to existing alternatives for RFI detection, such as metrics for Automatic Gain Control (AGC) and carrier-to-noise ratio (C/N0). Generating a monitoring threshold for these statistics proves challenging, because the threshold depends both on the type of RFI threat (e.g. continuous wave, narrow band, wideband, pulsed) and on environmental conditions, such as temperature. As experiments illustrate, the divergence statistic resolves these limitations, as divergence directly estimates ranging source error, independent of the type of RFI threat or the environmental conditions.

We utilised precision Global Positioning System (GPS) tracking to examine the homing paths of pigeons (Columba livia) released 20 times consecutively 25 km from the loft. By the end of the training phase, birds had developed highly stereotyped yet individually distinct routes home, with detailed recapitulation evident at each stage of the journey. Following training, birds also participated in a series of releases from novel sites at perpendicular distances of up to 3 km from their established routes. Results showed that subjects were attracted back to their established routes and recapitulated them from the point of contact. Naïve conspecifics (yoked controls) released from the same off-route sites confirmed that the experienced birds' route choices were not influenced by constraints exerted by terrain features, but that increased experience with the general area conferred a homing advantage in the form of more efficient flight tracks, even from these novel sites. Patterns in the paths taken by experienced birds to rejoin their established routes are discussed with reference to navigational mechanisms employed by homing pigeons in their familiar area.

This paper describes the complexity of the Baltic archipelago, and the navigational and operational processes involved in piloting these waters. This four year ethnographic study shows how piloting is learned, performed, and passed on to the next generation of pilots. The blend of new technology and old methods is discussed, the indivisibility of working and learning, and the individuality of the mental constructs of the mariners/pilots.

This paper presents a collision risk model and operational concepts for longitudinal separated aircraft in the North Atlantic Region air traffic control track system, and indicates how it might be used to reduce separation minima safely, and hence deliver cost savings. It is an event-based model: it is easy to see what is being assumed, to understand the role of the main parameters, and to incorporate collision detection and hazard analysis. A potential future operation, with a 7-minute separation and a strategic lateral offset system, is sketched using the model.

Marine accidents have many causes but a recurring theme is poor watch-keeping often caused by weak bridge management. Information overload is sometimes blamed for accidents and attempts to reduce information overload may include electronic systems which have been produced for integrating information from various electronic sources so that information is concentrated on fewer screens. This article explores some of the issues facing the designers of such systems. While acknowledgement is given to some of the technical problems, the article concentrates on those issues associated with the user of such systems, in particular, domain knowledge, screen design and user control. Available Marine Accident Investigation Reports for 2004 are used to highlight that, in that year, only one passenger vessel incident was attributed in part to poor data from electronic aids. However, it is accepted that a much wider study of such reports is needed before any firm conclusions can be drawn.

The benefits of integrated INS/GPS systems are well known. However, the knowledge required to jam GPS is becoming public and the hardware to achieve this is basic. When GPS data are unavailable and a low grade INS is used, navigation accuracy quickly degrades to an unacceptable level. The addition of one or more terrain referenced navigation (TRN) systems to an integrated INS/GPS navigation system enables the INS to be calibrated during GPS outages, increasing the robustness of the overall navigation solution. TRN techniques are compared and integration architectures are reviewed. For the initial studies of INS/GPS/TRN integration, radar altimeter based terrain contour navigation (TCN) with a batch processing algorithm is used in conjunction with a centralised integration filter. Four different approaches for using these TCN fixes to calibrate the INS are compared. These are a best fix method, a weighted fix method using a probabilistic data association filter (PDAF) and single and multi-hypothesis versions of the Iterative Gaussian Mixture Approximation of the Posterior (IGMAP) method. Simulation results are presented showing that the single hypothesis IGMAP technique offers the best balance between accuracy, robustness and processing efficiency.

Synesius’ letter to his brother, describing his passage from Alexandria to Cyrene, is a fruitful source of information on seafaring at the turn of the 4th century CE. The present article is an experiment to discover maritime information, based on this source and geographic and climatic facts. The distance from Alexandria to Azarium, the final landfall, is 360 nautical miles, although the distance actually sailed was 400 miles. The sailing, generally against the prevailing wind, lasted seven days, of which two were spent on shore. A log and a chart of the complete passage are suggested. Concentrating on the maritime details reveals the skill of the professional skipper, Amarantus, experienced in navigating these waters.

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.

Recently new location technologies have emerged that can be employed in modern advanced navigation systems. They can be employed to augment Global Navigation Satellite System (GNSS) positioning techniques and dead reckoning as they offer different levels of positioning accuracies and performance. An integration of other technologies is especially required in indoor and outdoor-to-indoor environments. The paper gives an overview of the newly developed ubiquitous positioning technologies and their integration in navigation systems. Furthermore two case studies are presented, i.e., the improvement of land vehicle safety using Augmented Reality (AR) technologies and pedestrian navigation services for the guidance of users to certain University offices. In the first case study the integration of map matching into a Kalman filter approach is performed (referred to as “Intelligent Vehicle Navigation”) and its principle is briefly described. This approach can also be adapted for the pedestrian navigation service described in the second case study.

This paper presents a practical application of the probabilistic-fuzzy method for assessment of the safety of a ship manoeuvring in waterways. The method, based on probabilistic risk analysis and elements of fuzzy logic, takes into account situations of threatened navigational safety and situations when a navigator intuitively thinks that the safety of manoeuvring ship is threatened. The probability of grounding a ship manoeuvring in a waterway bend is determined by means of simulation method. Then, with the use of experts' knowledge and tools of fuzzy logic the probability of a dangerous situation is determined. Two different approaches are applied for the determination of that probability. The results are compared.