The following is the third and final 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. This final part deals almost exclusively with the development of the Omega Navigation System, which was the first truly ‘global’ navigation system to enter service. The editing principle used here has been to preserve Dr. Pierces' own wording while eliminating those parts of a purely personal nature. The entire original document without cuts may be found on www.internationalnavigation.org

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.

The following is the second 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 www.internationalnavigation.org.

The associate members of the North European LORAN-C System (NELS) will, before the end of the six-nation co-operation agreement in 2004, need to take a decision whether to prolong or decommission LORAN-C operation in Europe. The Minister of Fisheries in Norway has already indicated decommissioning of the Norwegian LORAN-C stations. Such a decision raises the fundamental debate about whether we can rely on GPS as a ‘sole-means’ system, or if we need a secondary backup system, such as LORAN-C. The purpose of this article is to highlight important aspects and conflicts related to an extension of LORAN-C in Europe. The focus will therefore be towards the limitations and vulnerability of GPS vs. the potential of LORAN-C improvements. The discussion will be based on a Norwegian nautical perspective.

This is the second of two papers on Quantitative Safety Assessment – vital to the successful introduction of future Air Traffic Management systems. The focus is en route European controlled commercial traffic, particularly the mid-air collision risk. Part 2 develops soundly based and practical methods for safety assessment. The objective is to determine the key questions and the best ways to answer them. Aspects covered include lessons from Hazard Analysis and Airproxes together with ‘realistic’ risk budgeting. Two abstract concepts are introduced: Position Integrity and Reasonable Intent (essentially the need to be on the ‘right’ flight path), and their implications for risk calculations are discussed.

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.

This paper deals with the modelling of airspace capacity in Europe by first considering the factors that affect controller workload and then using a model, aided by the appropriate analytical techniques, to make an estimate of airspace capacity. The results show that capacity can be estimated based on the combination of different types of air traffic movement in a sector. The model has been used to provide airspace capacity estimates and utilisation measures for ATC sectors in Europe.

This is the first of two papers on Quantitative Safety Assessment – vital to the successful introduction of future Air Traffic Management systems. The goal of the two papers is to identify key future questions and the best methods to deal with them. The focus is en route European commercial traffic in controlled airspace, particularly risks from mid-air collision. Part 1 is a critical sketch of the historical context, methods used, and the use of analytical ‘models’ for safety assessment. Aspects covered include safety philosophy principles, safety targets, procedural separation standards, the Reich model and its problems, and radar separation standards.

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 year marks a watershed in the design, production and operational use of Civil Marine Radar (CMR) as we know it. Tighter regulations for in-band spectral purity and out-of-band transmission, when coupled to a possible loss of S-band frequencies for both CMR and Air Traffic Control (ATC) radars, will seriously restrict the synergistic advantage of dual-band systems, as well as the form of new RF heads. There is a conflict of IMO requirements to still retain simple pulse radars to activate Racons and SARTS while also meeting these new stringent spectral regulations. Options are given for serious discussion amongst all concerned before it is too late.

This paper discusses issues relating to the practical application of the collision avoidance regulations (COLREGS) from the sociological viewpoint that rules are always contingent, defeasible and that no rule can exhaustively specify the conditions of its use. It is proposed that, due to the inherent nature of rules, the only way successfully to manage collision risks at sea, is physically to separate opposing traffic flows, so as to remove the interpretative and mutually co-ordinating factors from the COLREGS.

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.

It is 30 years since major changes were last made to the collision regulations. This paper identifies a number of shortcomings in the current Rules, including excessive verbiage, unnecessary duplications and complications, and the use of weasel words. It also examines the use that has been made of Rule 2 in broadening the interpretation of other Rules. Proposals are then put forward for rewriting The Rules so as to improve their clarity and hopefully their understanding. The paper is written from the viewpoint of a mariner.

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.

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.

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.

This paper, and that following, were first presented at NAV 2001 – Location and Navigation – held at Church House, Westminster, London, 6th to 8th November 2001. Full Proceedings of the Conference are available on CD-ROM from the Royal Institute of Navigation.

This paper covers the current status of wireless network location capabilities, including a view of each method describing the strengths and weaknesses of the various approaches. The paper will describe developments in network-assisted GPS to reveal the capabilities of the so-called high sensitivity receivers. The question of what has to be done to get GPS to work indoors will be answered, together with the impact of this capability on the positioning of mobile telephones fitted with GPS capability. The paper discusses the concepts of integrating terrestrial network-derived location with GPS/GNSS and very short range location systems such as Bluetooth. It will explain how Location-Based Services are operated, when they will become widely available, some of the key applications and the impact of this technology on some of the traditional sciences, in particular mapping. This area of navigation is developing extremely rapidly, with potentially a huge market for navigation on land.

One of the most controversial issues relating to marine navigation is the efficacy of ships' crews using VHF radio technology for bridge-to-bridge communications to agree manoeuvres. Through a re-evaluation of historic case studies, this paper provides background on the development of applying VHF technology in collision avoidance and the legislation, national and international, underpinning the practice; a practice that has found little or no support from the legal establishment. Finally the consequential development of a policy to require specific VHF technology to be installed on ships to facilitate agreements in relation to collision avoidance manoeuvres will be reviewed, that is the Automatic Identification System (AIS).

Integrity without knowledge is weak and useless, and knowledge without integrity is dangerous and dreadful. Samuel Johnson

Marine radiobeacons are widely used by the maritime community worldwide as an efficient means of broadcasting differential GPS data to users at sea. In Europe and North America, large numbers of these beacons now serve coastal regions, waterways, and some inland areas. Frequently there is overlapping coverage and a choice of stations. But users receive little guidance as to how to select the beacon that gives the highest quality service. Receivers that choose a beacon automatically generally select either the nearest station or the strongest signal. But the performance of the data-link is optimised by choosing the station received with the highest ratio of signal to either noise or interference. With Selective Availability set to zero, spatial dilution and time-to-alarm have become key factors. This paper compares four beacon selection strategies by means of a computer model based on well-established coverage analysis and system design techniques. We recommend a new ‘post-SA’ beacon selection method that chooses the nearest station that meets the time-to-alarm requirement. This strategy has been used to identify the ‘best beacon’ throughout the European Maritime Area, with stations operating in accordance with the new band-plan adopted last September. We also identify the alternate beacon to use if the preferred station should fail.

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.