The fish-eye star sensor with a field of view (FOV) of 180° is an important piece of equipment for attitude determination, which improves the visibility of stars significantly. However, it also brings the star identification (star-ID) difficulties because of imprecise calibrations. Thus, a fish-eye star-ID algorithm supported by the integration of the precise point positioning/inertial navigation system (PPP/INS) is proposed. At first, a reference star map is generated in combination with the distortion model of the fish-eye camera based on the position and attitude information from the PPP/INS. Then the star points are extracted in a specific neighbourhood of the reference star points. Subsequently, the extracted star points are individually tested and identified according to angular distance error. Finally, the real-time precise attitude is determined based on the star-ID results. Experimental results show that, 270–310 stars can be identified in a fish-eye star map with an average time of 0.03 s if the initial attitude error is smaller than 1.5° and an attitude determination accuracy better than 10″ can be achieved by support from PPP/INS.

If you ask the average Briton, he will tell you that Robert Watson-Watt invented radar in 1935. A German, asked the same question, would reply Christian Hulsmeyer in 1904. Strictly speaking, neither reply would be correct. It is generally accepted that the acronym RADAR stands for “Radio Direction and Ranging”, thus a practical radar system requires that both direction and range be determined. For this, the development of high power pulse transmission, and techniques for direction finding and timing of very short time intervals were needed. Over a period of years, these were individually developed for other purposes, but radar arrived only when all were combined into a single system. By 1939 radar development was also proceeding in a number of countries including France, Holland, Russia and the USA, but only the United Kingdom and Germany had brought it to an operational state.

Vision navigation using environmental features has been widely applied when satellite signals are not available. However, the matching performance of traditional environmental features such as keypoints degrades significantly in weakly textured areas, deteriorating navigation performance. Further, the user needs to evaluate and assure feature matching quality. In this paper, a new feature, named Line Segment Intersection Feature (LSIF), is proposed to solve the availability problem in weakly textured regions. Then a combined descriptor involving global structure and local gradient is designed for similarity comparison. To achieve reliable point-to-point matching, a coarse-to-fine matching algorithm is developed, which improves the performance of the point set matching algorithm. Finally, a framework of matching quality evaluation is proposed to assure matching performance. Through the comparison, it is demonstrated that the proposed new feature has superior overall performance especially on correctly matched numbers of keypoints and matching correctness. Also, using real image sets with weak texture, it is shown that the proposed LSIF can achieve improved navigation solutions with high continuity and accuracy.

Earlier papers, based on a computer model of European air traffic, deal with the probability of conflicts arising between pairs of aircraft operating under free-flight rules. This paper discusses the problems of resolving these conflicts. When a potential collision takes place in the neighbourhood of other intruding aircraft, these must be taken into account when choosing an escape manoeuvre. A suggestion is made that may ease the problem.

This paper reports a diary study of rendezvousing as performed by university students. The study compares students' performance when meeting at familiar and unfamiliar rendezvous points. It reports various findings that help to set goals for the development of personal navigation and related services at appropriate levels. For example, when meeting at novel rendezvous points, students: (i) fail to meet as initially agreed more frequently; (ii) report more stress and lost opportunity as a result of rendezvousing problems; (iii) change plan during the rendezvous more often; (iv) communicate more about the rendezvous, particularly using text messaging; (v) attribute rendezvousing problems to lack of geographic and travel information more often, and to additional, spontaneous tasks such as ‘popping to the bank’ less often. Meetings at novel rendezvous points are also more likely to include acquaintances and strangers.

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.

At present, the whole shipping industry is concerned about safety of navigation. In particular, attention is focused on High Speed Craft. There has been a sharp increase in numbers of this kind of vessel, which primarily carries passengers but is also known to carry goods. Some units can reach speeds of over 45 knots with capacity for 900 passengers. These passengers have a basic right to life and their means of transport should obviously follow all safety codes, regulations and IMO resolutions. This paper describes the development of a monitoring system that could automatically transmit safety parameters and position from the ship to a management control centre. Digital and analogical alarms, ship condition readings and other safety-related parameters may be recorded and transmitted in near real- time using the latest communications and positioning technologies.

This paper was first presented at GNSS 2002 – European Navigation Conference – held in Copenhagen, 28th to 30th May, 2002.

At the 5th GNSS Symposium, held in Seville in 2001, the authors presented a paper entitled ‘The Portuguese DGPS network’, which began by addressing the current need for a DGPS service, given the removal of Selective Availability (Moore et al., 2001). In that paper, the benefits of DGPS for mariners, namely in terms of accuracy and integrity, were discussed and presented, in order to show that the option to embrace DGPS was, and is, still valid because it can provide the best accuracy and integrity at sea. However, the accuracy advantage afforded and the integrity check performed by DGPS are only useful if the DGPS service reaches very high standards of availability and continuity. It would be almost useless to have a DGPS service with low availability and continuity, because it could mean a ship losing the differential corrections in restricted waters, where the service is most needed. In summary, the level of benefit gained from DGPS is directly proportional to the user availability of the service and to its continuity. Having discussed accuracy and integrity last year, this paper covers issues related to availability and continuity (continuity replaced the previously used concept of reliability). The availability and continuity requirements recently adopted by the International Maritime Organization (IMO) and the International Association of Lighthouse Authorities (IALA) are presented, as well as the ways by which DGPS services can meet the very high requirements for the harbour entrance and approach phase of navigation. The concepts used in the Portuguese DGPS network to minimize downtime and ensure the highest reliability and availability, are presented as an example.

The 11-year solar sunspot cycle is approaching a maximum in 2000. The sunspot activity causes an increase in the solar flux, charged particles and electromagnetic rays emitted from the Sun. This solar flux affects the ionosphere, thus influencing the transmission of radio waves through the ionosphere. The GPS satellite navigation system is affected in that the transit time of the signals varies, introducing position errors. Also GPS equipment may experience degraded performance in tracking of the GPS satellites due to scintillations, rapidly varying amplitude and phase of the GPS signal. The equatorial and high latitude regions are most severely affected by this increased ionospheric activity. Experience has shown that, in equatorial regions, errors of 10–20 m may be introduced in Differential GPS services, even on distances down to a few hundred kilometres from the reference station. During the peak of the solar cycle, for the next 3–4 years, this situation will rather be the rule than the exception in the affected areas. Fugro has introduced an enhanced real-time DGPS service utilising dual frequency GPS called Starfix-Plus in selected areas. This service removes ionospheric delay errors by calculating the delay using dual frequency GPS receivers on the reference stations and the mobiles. The resulting accuracy is down to a few metres, even using reference stations up to 2000 km away. This increases the availability and redundancy of usable reference stations in a region, increasing the probability that the required accuracy is available, even if individual stations are not available due to scintillations or for other reasons.

This paper presents an approach for outdoor navigation of an autonomously guided canine using an embedded command module with vibration and tone generation capabilities and an embedded control suite comprised of a microprocessor, wireless radio, GPS receiver, and an Attitude and Heading Reference System. In order to determine the canine's motions, which inherently contain non-conventional noise characteristics, the sensor measurements were integrated using a specialized Extended Kalman Filter (EKF), equipped with a Fuzzy Logic controller for adaptive tuning of the Process Noise Covariance Matrix. This allowed for rejection of un-modelled canine motion characteristics which tend to corrupt accelerometer bias tracking in a standard EKF. The EKF solution provided an optimized estimate of the canine position and velocity and also proved to be effective in tracking the canine's position (within 7·5 m) and velocity (within 1·2 m/s) during simulated 10 second GPS outages.

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.

An assessment of the navigational accuracy of the Mercator world map of 1569 is made, aimed at better understanding how the information was adapted from the contemporary cartography. At the time the map was engraved, navigational charts were constructed on the basis of astronomically-observed latitudes, magnetic courses and estimated distances between places. Before this information could be incorporated into the new world map it should be first transformed in such a way that the longitudinal spacings between places were restored to their correct values, as defined on the surface of the Earth. The question of whether Mercator performed such transformations or just considered that the positions were approximately correct has hitherto never been addressed in the literature. It is demonstrated in this article that Mercator was not fully aware of the complexity of the contemporary charts – which he considered to implicitly comprise a square grid of meridians and parallels – and that all planimetric information was directly imported to the novel world map without correction. It is further shown that the Mercator projection was not compatible with the navigational methods of the time.

In this paper, we consider the joint estimation of the position of a spacecraft and debris in Earth orbit to achieve spacecraft localisation based on angular measurements and precise measurements of the debris relative to the spacecraft. The dynamic model of the spacecraft caters for several perturbing effects, such as Earth and Moon gravitational field asymmetry and the Earth's oblateness effect. The Moon's position is assumed to be accurately known for the purposes of simulation from published Jet Propulsion Laboratory (JPL) ephemerides. The measurement process is based on the elevation and azimuth of the Moon and the Sun with respect to the spacecraft reference system. Range measurements are not assumed to be available. Position and velocity of the spacecraft are estimated by using the Unscented Kalman Filter (UKF). The performance of the filters are evaluated on an example of an Earth-orbiting satellite at an altitude over 1200 km with measurements of the directions of the Moon and the Sun only. It is shown that the estimates of position and velocity components track the corresponding simulated position and velocity components.

This article proposes a batch-mode algorithm to handle the large databases generated from experimentations using probe vehicles. This algorithm can locate raw Global Positioning System (GPS) positions on a map, but can also be used to correct map-matching errors introduced by real time map-matching algorithms. For each journey, the algorithm globally searches for the closest path to the GPS positions, and so is inspired from the “path to path” algorithm's family. It uses the Multiple Hypothesis Technique (MHT) and relies on an innovative weighting system based on the area between the GPS points and the arcs making up the path. For high performance, the algorithm uses an iterative program and the data is stored in tree form.

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.

The BeiDou navigation satellite system (BDS) has been providing a regional service in the Asia–Pacific area since 27 December 2012, and a new Inclined Geosynchronous Satellite Orbit (IGSO) satellite IGSO-6 joined the 14-satellite constellation in operation on 29 March 2016. In this paper, the signal and positioning performance of IGSO-6 are assessed. Compared with other IGSOs, the carrier-to-noise-density ratios of IGSO-6 show comparable performance for the B3 signal and a lower power level for the B2 signal, while the B1 signal is more powerful and has the lowest noise and multipath errors. The satellite-induced code bias of IGSO-6 was investigated and indicates that IGSO-6 has similar characteristics to other IGSOs. The different inter-frequency bias variations among IGSOs with daily periodicity are demonstrated. The BDS positioning performances with IGSO-6 were investigated in Single Point Positioning (SPP) and Precise Point Positioning (PPP) modes at the 95% confidence level. For SPP, there was an improvement of about 4·9% and 3·6% in the horizontal and vertical components, respectively. The convergence time was improved by about 18·3% and 17·8% in the horizontal and vertical components for positioning accuracy to be better than 50 cm, respectively.

The purpose of this paper is to present data and draw conclusions on the chances of collision in different areas of the waters around the UK. The subject of risk analysis has recently grown in importance, and it is often necessary for an operator to demonstrate that a proposed operation is acceptably safe before he will be given permission to begin. Risk estimates are generally of two basic types, backward and forward. Backward estimates are based upon the number of accidents that have occurred in a particular situation, and if there have been many there will be a fair degree of confidence that the risk has been accurately estimated. Forward estimates have to be made where there are so few actual accidents that no backward estimates are possible: they are based upon an analysis of the situation into a sequence of events, the probability of each being known by comparison with data obtained from other situations. Although these data may themselves be reliable, the final risk estimates will depend upon the comparability of the situations and also upon whether the sequence of events has been correctly identified.