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.

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.

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.

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 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.

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.

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.

Receiver Autonomous Integrity Monitoring (RAIM) is a method implemented within the receiver to protect users against satellite navigation system failures. For a receiver to execute a RAIM calculation, two conditions must be met: a minimum number of satellites and adequate satellite geometry. The non-existence of the minimum number of satellites (five) is referred to as a RAIM hole. Current regional and global RAIM availability studies use spatial (grid-based) and temporal sampling intervals driven by a trade-off between accuracy and computation workload. The implication of minimising computational load is that accuracy is compromised and potential RAIM holes remain un-sampled, with potential risk to safety. This paper proposes a direct and computationally efficient method (as opposed to the grid-based search approach) to predict RAIM holes. The method is based on the precise computation of satellite coverage (footprint) boundaries, the intersection points and analysis of the topology of the regions of intersection. Test results show that the proposed method is highly accurate and requires minimal computational load compared to the current approach.

Small Unmanned Aerial Vehicles (UAVs) or inexpensive airplanes, such as a Cessna single engine aircraft, require a navigation system with a cheap, compact and precise sensor. Over the past ten years, GPS receivers have begun to be used as primary or alternative navigation sensors, because their use can significantly reduce the overall system cost. This paper describes a navigation system incorporating a velocity-based attitude estimation system with an attitude determination system using multiple antennae, which was implemented and tested using a UAV. The main objective was to obtain precise attitude information using low cost GPS OEM boards and antennae. Attitude boundaries are derived from the relationship between the body frame and the wind coordinates, which are used to validate the resolved cycle ambiguity in an Euler angle domain. Angular rate based on Doppler measurements was used to exclude the degenerate pseudo-roll angle information during severe uncoordinated flight. Searching for cycle ambiguity at every epoch of the flight showed that the developed system gave reliable cycle integer solutions, although the carrier phase measurement was subject to additional errors, such as multipath, external interference, and phase centre variation. A flight test was performed using a 1/4-scale Piper J3 Cub model, CMC Allstar OEM boards, OEM AT575-70 antennae, and 700 MHz PC104 board.

In this paper we present a micro-electrical mechanical system (MEMS) based pedestrian navigation system (PNS) for seamless positioning. The sub-algorithms for the PNS are developed and the positioning performance is enhanced using the modified receding horizon Kalman finite impulse response filter (MRHKF). The PNS consists of a biaxial accelerometer and a biaxial magnetic compass mounted on a shoe. The PNS detects a step using a novel technique during the stance phase and simultaneously calculates walking information. Step length is estimated using a neural network whose inputs are the walking information. The azimuth is calculated using the magnetic compass, the walking information and the tilt compensation algorithm. Using the proposed sub-algorithms, seamless positioning can be accomplished. However, the magnetic compass based azimuth may have an error that varies according to the surrounding magnetic field. In this paper, the varying error is compensated using the MRHKF filter. Finally, the performance enhanced seamless positioning is achieved, and the performance is verified by experiment.

The sight-run-sight case involves a series of two or more sights in which each sight is ‘run on’ to the time of the last sight. There are several known techniques to account for the run, which is for convenience assumed to be at a constant course. It is argued that only the GHA-Dec updating technique (GD-UT) will give a correct position solution, whereas the pre-electronic Intercept Method (IM)-based technique and its modern least-squares variant (LSQ) and the Altitude updating technique (A-UT), are proxy techniques that may yield significant deviations in position solution. GD-UT can be used in combination with a double-sight solution method for two sights and with LSQ for two or more sights. IM, LSQ and a geometric or algebraic double sight solution method applied to simultaneous double sights give identical results but the simultaneous sights case is generally an abstraction and strictly not applicable on a moving vessel.

There is a significant error in the equation referring to the rule of thumb for ‘line-of-sight’ analogue transmissions given in the paper by William Cairns, in the May 2005 issue (Cairns, 2005). This incorrect formula has previously been quoted in other sources, and possibly the author obtained it from one of these. In addition, the term ‘line-of-sight’ implies geometrical optics, whereas use of the term ‘radio horizon’ would be more appropriate since this takes account of the extension of radio wave transmission distance over the earth's surface caused by the normal water vapour content of the lower atmosphere over sea.

Edmund Hadnett writing in his article AIS at the Front Line in the May 2005 issue of the Journal, attributes to me the argument that ‘the automatic radar plotting aid (ARPA) should remain the principal means of assessing a risk of collision’. ARPA has never been the principal means of assessing a risk of collision and I have never argued that it has been and should remain so. My argument concerns the merits respectively of ARPA and AIS as navaids or a fusion of data from both.

Past President of the Royal Institute of Navigation, Brian Calvert, was born in 1933 at Hankow on the Yangste in China (where his family was later interned by the Japanese during the Second World War) and educated at Stowe School, Buckinghamshire. He joined BOAC (now part of British Airways) in 1957, after National Service in the Fleet Air Arm. For his first two years with the airline he flew as a navigator, and this led to a lifelong interest in the subject.