The following is the first part of an extract from the memoirs of Dr. J. A. Pierce who was deeply involved in the development of radionavigation aids in the USA between 1941 and 1973. These are, of course, personal reminiscences, and some issues might be challenged by others working in the same field at the time. However, they give a remarkable insight into the problems faced by the scientists of the day and how they were overcome. The editing principle used here has been to rigorously preserve Dr. Pierce's own wording while eliminating those parts of a purely personal nature. The entire original document without cuts may be found on the Institute's website.

This paper considers the need for better detectability of small targets at sea using marine radars in the 3 and 9 GHz bands. The problems of using radar reflectors and radar target enhancers to improve radar cross section, particularly when clutter is present, are discussed in detail. The IMO carriage requirement and the lack of suitably robust specifications are highlighted, and a proposal is made for a standard family of radar reflectors to meet the requirement. Radar target enhancers are also considered together with how these and radar reflectors should be mounted for best effect.

ICAO safety standards require low probabilities of collision of the order of 5×10−9 per hour. Such low probabilities are virtually impossible to confirm through simulations, implying the need for alternative and related safety metrics, which are easier to use. Several such alternative safety metrics are discussed in this paper. For example, it is shown that if the r.m.s. position error σ is less than about one-tenth L/σ ∼ 10 of the minimum separation distance L, then the probabilities of collision will be less than the ICAO standard, in the case of aircraft flying in opposite directions on parallel tracks. This result is derived from an analytical formula based on the statistical application of a Gaussian probability distribution to a worst-case collision scenario and a rather different result L/σ ∼ 20 arises for a Laplace probability distribution. The implication is that the ICAO standard of low probability of collision can be satisfied, by checking that the r.m.s. position error does not exceed a given value, though that value is dependent on the shape of the ‘tail’ of the probability distribution. Whether the condition is met can be checked in simulations, by measuring the drift between the intended and actual trajectory, due to all factors (navigation inaccuracy, atmospheric disturbances, trajectory drift between position updates, etc.). Thus the r.m.s. deviation from the intended trajectory can be used as a safety metric, as an alternative to the probability of collision, using the formulas and tables provided. The formulas concern a variety of possible safety metrics, including the maximum and cumulative probabilities of coincidence, probabilities of overlap, collision rates and collision probabilities; the tables apply to horizontal and vertical separation in controlled and transoceanic airspace. The sensitivity of the results to the probability distribution assumed (Gaussian or Laplace) suggests the introduction of a parametric family exponential of probability distributions, of which these are particular cases. A choice of the parameter is given that could lead to a probability distribution with a ‘tail’ shape more suited to typical Air Traffic Management (ATM) scenarios than the Gaussian and Laplace distributions, while being simpler than multi-parameter distributions.

This paper summarizes the current situation on maritime navigation transponders, including those used in the Global Maritime Distress and Safety System (GMDSS) and those installed in Rescue Co-ordination Centres (RCCs) and on board Search and Rescue boats, and discusses the possible future trends. The paper then describes the methods used and conclusions reached during a variety of tests carried out in Tenerife Roads, RCC Tenerife and on board Sociedad Estatal de Salvamento vessels, in order to determine the accuracy and efficiency of various ships' identification, positioning, location, tracking and homing systems in normal and distress situations. The systems tested included Radar/Automatic Radar Plotting Aids (ARPAs), Search and Rescue Transponders (SARTs), Target Enhancers and Radar Reflectors.

In this paper, the operability of the GMDSS is studied to identify those aspects that are hindering its successful use. Particular emphasis is placed upon the operator-equipment interface within the working environment of the ship's bridge. The results of a relevant survey, based on the opinion of recently G.O. certified navigation officers, indicate that – despite the automation in GMDSS and the resulting reduction of the human factor – there is a definite need to improve the knowledge-based proficiency of the operator. The current design of the system, and the increasing workload on the ship's bridge, constitute the main drawbacks to operability and dictate the requirement for improved knowledge and hence improved certification and refresher training for operators.

In this paper, we discuss the grounding of the Royal Majesty, reconstructed from the perspective of the crew. The aim is particularly to understand the role of automation in shaping crew assessments and actions. Automation is often introduced because of quantitative promises that: it will reduce human error; reduce workload; and increase efficiency. But as demonstrated by the Royal Majesty, as well as by numerous research results, automation has qualitative consequences for human work and safety, and does not simply replace human work with machine work. Automation changes the task it was meant to support; it creates new error pathways, shifts consequences of error further into the future and delays opportunities for error detection and recovery. By going through the sequence of events that preceded the grounding of the Royal Majesty, we highlight the role that automation plays in the success and failure of navigation today. We then point to future directions on how to make automated systems into better team players.

In this paper, back-propagation (BP) neural networks (NN) are applied to the GPS satellite Geometric Dilution of Precision (GDOP) approximation. The methods using BPNN are general enough to be applicable regardless of the number of satellite signals being processed by the receiver. BPNN is employed to learn the functional relationships firstly, between the entries of a measurement matrix and the eigenvalues and thus generate GDOP, and secondly, between the entries of a measurement matrix and the GDOP, both without inverting a matrix. Consequently, two sets of entries and two sets of output variables, respectively, are used that in total yield four types of mapping architectures. Simulation results from these four architectures are presented. The performance and computational benefit of neural network-based GDOP approximation are explored.

The navigational feats of the Vikings and Norse in the Middle Ages have excited much interest and admiration, and we are fortunate that actual sailing directions for their various North Atlantic routes have been passed down to us in the Icelandic sagas. Using statistical data of modern wind conditions, this paper examines the sailing directions to determine whether the sailing times quoted are reasonable for a type of ship that was making these voyages in the Middle Ages. The findings show very good correlation between the calculated times and those of the sagas. The paper goes on to study an apparent anomaly for a particular route quoted in the sagas and concludes that the departure and destination points have probably been misinterpreted in the past.

Collision avoidance remains the most important concern for ships at sea. Despite the electronic equipment now fitted on ships to support the mariner, expert experience is still essential when a ship is in danger of colliding with the others. To include these experts' experiences to resolve the problems of collision, we have designed a fuzzy collision-avoidance expert system that includes a knowledge base to store facts and rules, an inference engine to simulate experts' decisions and a fuzzy interface device. Either a quartermaster or an autopilot system can then implement the avoidance action proposed in the research. To perform the task of collision-avoidance effectively, a robust autopilot system using the state space H∞ control methodology has been designed to steer a ship safely for various conditions at sea in performing course keeping, course-changing and route-tracking more robustly. The integration of fuzzy collision-avoidance and H∞autopilot systems is then proposed in this paper.

Safe and efficient marine navigation in ice-infested waters requires comprehensive and timely information on the sea ice conditions. These include information on the ice concentration and type, ice edge location, icebergs and open leads. The Canadian Ice Service is responsible for providing ice information in Canadian waters, mainly through its daily ice charts. Unfortunately, due to the difference in time between the ice chart production and its use by mariners, the ice information is always out of date. This problem might be overcome by developing a neural network-based system for predicting the ice conditions over time. A supervised neural network is trained to predict the ice conditions at a given location and time using the current ice charts, which are provided by the Canadian Ice Service. The input ice data is mapped to an output vector that gives the predicted ice conditions. The traditional non-modular feed-forward neural network structure failed to map the required function, and hence, was modularized to give better prediction performance. Each neural module was responsible for the prediction of a 5×5 km area, while the ice characteristic of interest was the total concentration.

It is good to see the COLREGS reappearing in Forum as a subject for discussion. R. W. Cooper (2001) is right to point out the problem inherent in rule 10(j) that one of the vessels in an encounter to which the rule applies cannot be sure whether the length criterion is met or not. Clearly some amendment is desirable.

I read the Forum article ‘Removal of an Ambiguity from the Maritime Collision Regulations’ (Cooper, 2001) and make the following comments. As a Royal Yachting Association Yachtmaster Instructor, I find that many people quote Rule 10 of the COLREGS only in part and thus are misled by its intentions.

Finding the distance has always been a challenge to the mariner. What is the distance to the lighthouse at the mouth of the harbour? Am I far enough off the rocks and shoals? My assigned station in the formation is bearing 300°, range 1500 yards from the guide ship, am I on station? What is the range for gunfire to the enemy flagship?

In coastal navigation, if two horizontal angles between three fixed objects above the sea surface can be determined from a point of observation, two circular position lines are determined that cut at two points. One point of intersection is located in the central object and the other in the observation point itself. The coordinates of the observation point can be determined in various ways; for example, by calculating the radius of the circle – position line, or by graphical construction etc. All of these mehods are sufficiently elaborated in nautical literature.