bluuebunny/crossref_metadata_2025 huggingface dataset:
Sailing Directions of the North Atlantic Viking Age (from about the year 860 to 1400)
Authors: Thirslund Søren
Published: November 2009

As long as man has ventured to go to sea, sailing directions have existed. Man's survival depended upon knowing the best fishing and hunting places and how to find these were secrets, told only to family or friends.

Later, sailing directions covered areas in the world where trade or new settlements had begun and, as early as 500 years B.C., some of these sailing directions were written down. They covered the Mediterranean Sea and part of western Europe and they were called PERIPLUS meaning ‘sailing around’. They contained almost the same information as sailing directions today, namely: harbours, anchorages, currents, possibilities for fresh water, provisions and other supplies.
Pedro Nunes' Discovery of the Loxodromic Curve (1537). How Portuguese Sailors in the Early Sixteenth Century, Navigating with Globes, had Failed to Solve the Difficulties Encountered with the Plane Chart
Authors: Randles W. G. L.
Published: November 2009

In the early sixteenth century, Portuguese navigators on voyages outside the tropics ran into an unexpected problem in navigating with the plane chart since the latter took no account of the convergence of the meridians. Voyages between Brazil and the Cape of Good Hope were accomplished much faster than the chart led them to forsee. To overcome this problem, were Portuguese pilots of the first half of the sixteenth century using globes to set their courses with on great circle courses? The general opinion is that they were not. Yet the mathematician Pedro Nunes (1502–78) describes in a short treatise entitled Tratado que ho Doutor Pedro Nunez fez sobre certas duvidas na navigação (published in 1537, but probably written in 1534) how the navigator Martim Afonso de Sousa, on his return from the east coast of Brazil in 1530–2, had asked him to solve several problems of navigation encountered on the voyage.
A New High Precision Wide Area DGPS System
Authors: Ashkenazi V. , Chao C. H. J. , Chen W. , Hill C. J. , Moore T.
Published: November 2009

This paper describes an advanced method, and the corresponding algorithms, which could provide a high precision Wide Area Differential GPS (WADGPS). The service would be suitable for single or dual frequency users, and could be introduced with very few reference stations. The two main components of the service are a precise, near real-time orbit determination of the GPS satellites, and an accurate estimation and modelling of ionospheric and tropospheric effects. Broad principles of the processing algorithms and results of both simulation and real data tests are described. User positioning accuracies of better than 2·5 m (r.m.s.) in plan and 3·0 m (r.m.s.) in height are achieved by both single and dual frequency scenarios.

Wide Area Differential GPS (WADGPS) is being developed to overcome the main drawbacks of conventional or Local Area Differential GPS (LADGPS), where positional accuracy of a user degrades as the reference-to-user separation increases. The spatial decorrelation of the error sources, notably the atmospheric propagation and satellite orbital errors inherent in GPS, are the main causes of this accuracy degradation. Several organizations are involved in WADGPS research, and different conceptual approaches have been suggested. The proposed methods all share a common basic assumption: that the error sources which affect the system are broken down into individual error components and are modelled separately. The variance between the different techniques comes from the way in which the different error components are modelled.
A Fuzzy Autopilot Optimized Using a Genetic Algorithm
Authors: Sutton Robert , Marsden Gareth D.
Published: November 2009

The feasibility of using a genetic algorithm to optimize a fuzzy fixed rule based autopilot is considered in this paper. Simulation results are presented to show the applicability of the approach. It is concluded such a procedure gives more credence to the resulting design than can be achieved by totally heuristic methods.

As a result of the general recognition given to the robustness qualities of fuzzy control algorithms, studies have been undertaken in the marine field to develop autopilots based on this approach. Indeed, a fuzzy autopilot was recently installed in a small leisure vessel and very successful fullscale sea trials were undertaken. In the past, the main problem in designing a fuzzy autopilot, or any other fuzzy controller, has been the reliance on purely heuristic methods to obtain an optimum solution. To compensate for such shortcomings in the design cycle analytical approaches are now being proposed.
‘Requirements for Coordination and the Application of an Automatic Collision Avoidance System’
Authors: Vendrell John
Published: November 2009

May I congratulate Chris Perkins and Tony Redfern for their excellent paper in the May issue of the Journal. For many years I have read in the Journal, and on occasions listened to, learned ladies and gentlemen discoursing on the subjects of safe navigation and collision avoidance. Also to what I believe are their misguided wanderings into ‘ship domains’ and assumptions that ships behave as atomic particles. Thus it was very refreshing to read the latest and practical contribution by Chris and Tony. Well done chaps!
‘Requirements for an Automatic Collision Avoidance System’
Authors: Cooper R. W.
Published: November 2009

I am disturbed by Perkins and Redfern's paper in the May 1996 Journal.

The COLREGS have been developed over many years of tinkering and tuning. They are not designed only for educated European masters driving big merchant ships. The users; fishermen, yachtsmen, oarsmen, tugmasters, Rhine bargemasters, and Yangtse junkmen, etc, are from all educational standards and from all the world's cultures. The COLREGS are now well-known. There is such a huge investment of time and effort, of learning by millions of different people, that the prospect of tampering with their fundamentals is horrific, even if it would suit a small class of user belonging to the more advanced countries. Change is painful, and too much change, too fast, kills. Compare the practical decision not to change the side of the road on which we British drive: it might be convenient, but it would cost too much. The same applies to the COLREGS.
Presidential Address: Radio-Navigation's Transition from Sail to Steam
Authors: Blanchard Walter F.
Published: November 2009

My title is deliberately rather similar to that of Jed Williams' book because it was from his erudite and comprehensive work that I drew my inspiration. There are many volumes dealing with radio navaid engineering development but few, if any, about the very real and practical problems faced by navigators of interpreting, sometimes under very difficult circumstances, what they presented. Very few navigators of the 40s and 50s were expert draughtsman or academicians with degrees in mathematics or electronics, yet they were expected to comprehend and apply concepts that a few years earlier would have earned them such degrees. These fundamental problems of interpretation also seem to have been rather lost on some of those who were responsible for choosing which radio navaids to install. I have terminated my survey at the ‘steam’ era, rather than going all the way to ‘satellites’, not only because we have heard so much of satellites lately that it is time to give them a rest, but also because it was computers — the ‘ steam’ of navaids — that got us into the modern age of automated navaids when interpretation became far easier and the need for specialists doing little else vanished. My own experience is that of an aerial navigator so I hope our marine and land-based members will not object if I confine my remarks to aviation.
Reliability Performance in GPS Receivers and the Nature of Their Failures: Planning to Live with Realistic Failure Rates in Satellite Navigation System Receivers
Authors: Sharkey Sarah , Johannessen Rolf
Published: November 2009

This paper and the following three papers were presented at the Institute's NAV-96 Conference, “Global Navigation — Where are we now?” The Conference was held in London In November 1996. Copies of the full proceedings may be obtained on application to the Director, price £35 for members and £50 for non-members.

The National Air Traffic Services (NATS) in London require data on the performance likely to be achieved by the navigation system on board aircraft flying in UK airspace. To that end the performance of three different GPS receiver types (all designed for aviation use) have been examined. This paper details the result of that work. The achieved Mean Time Between Failures (referred to here as ‘Outages’) MTBO is presented along with the nature of some of the failures that have been encountered. The paper concludes with the operational implication of the findings.
The FAA's Local Area Augmentation System (LAAS)
Authors: Swider Raymond , Braff Ronald , Wullschleger Victor
Published: November 2009

The Federal Aviation Administration (FAA) is developing the Local Area Augmentation System (LAAS) as a public use local area differential GPS system. The LAAS is required to support all categories of precision approach navigation. The purpose of this paper is to summarize the FAA's LAAS technical activities and programme plans. First, the complementary roles of the Wide Area Augmentation System (WAAS) and LAAS are summarized. Then technical activities are discussed, including requirements, system architecture, and flight tests. The paper concludes with a summary of the FAA's plans for LAAS, including the planned schedule of major programme activities.
Real-time differential GPS/GLONASS trials in Europe using all-in-view 20-channel receivers
Authors: Capaccio S. , Lowe D. , Walsh D. M. A. , Daly P.
Published: November 2009

Following the initial development of 20-channel, all-in-view Global Navigation Satellite System (GNSS), GPS/GLONASS/Inmarsat-3, receivers at the Institute of Satellite Navigation (ISN), University of Leeds, a modification programme has been undertaken to allow real-time differential corrections to be sent from one 20-channel receiver to another identical receiver using a serial link between them. The differential correction software incorporates the RTCM SC-104 and RTCA DO-217 format developed specifically for GPS and adjusted by the ISN to allow simultaneous GLONASS operation.

After successful laboratory testing, real-time differential GNSS tests were successfully completed in static mode between Aberdeen and Leeds via the SkyFix differential data-link, and in dynamic mode at DTEO Boscombe Down using a C-band data-link between the ground and a receiver on board the DRA BAC 1–11 aircraft. The aims of the tests were, (i) to demonstrate real-time differential GNSS position-fixing, (ii) to establish the accuracy improvements brought about, and (iii) to examine the effects of data-link latency and satellite PDOP on the solution accuracy.
Eurofix: Test Results of a Cost-Effective DGNSS Augmentation System
Authors: Offermans G. W. A. , Helwig A. W. S. , van Willigen D.
Published: November 2009

Eurofix is an integrated navigation system, which combines Differential GNSS and Loran-C. The Loran-C system is used to provide differential corrections for the GNSS pseudo-range measurements and integrity information by additionally modulating the transmitted signals. This modulation, however, is not allowed to degrade normal Loran-C operations. As data transmission is hindered by the aggressive Loran-C signal environment, special modulation patterns and Forward Error Correcting codes are designed to fulfil the requirements. Compared to other DGNSS services, Eurofix has a number of advantages: It covers a large area, its implementation in an already existing infrastructure is basically low-cost, it offers enhanced datalink availability in urban and mountainous environment, it has wide-area capabilities and, finally, it provides a free backup navigation system in case either Loran-C or GPS fails.

The paper describes the Eurofix system, focusing on the Loran-C data channel. A modified RTCM type-9 message format is used with special Forward Error Correction. At Delft University a real-life test set-up has been built to evaluate the Eurofix performance for different scenarios. The results on datalink and DGNSS performance are presented. It is shown that metre-level DGNSS performance is achievable with low bit rate data channels, using Loran-C stations at up to 1000 km distance.
Radionavigation at a Time of Decision
Authors: Last David
Published: November 2009

This paper and the following 5 papers were presented at the Institute's RIN-96 Conference, held at the University of Southampton, in September 1996. Copies of the complete Proceedings may be obtained from the Director. Price £6 members, £8.50 non-members.

This is a time of unprecedented change in radio-navigation systems and practices. The rapid development of satellite technology is challenging navigation authorities in every country to question the future of terrestrial navigation systems. The technical adequacy of the new techniques is being demonstrated in many applications but there remain serious questions concerning the reliability, integrity and political control of the current satellite systems and their long-term future.

The paper describes the operational principles of the present satellite Global Positioning System (GPS) and GLONASS. It compares them with terrestrial aids, identifying their advantages and drawbacks. Accuracy, availability and integrity are considered. The reasons for the development of differential operation are examined.

Finally, the paper looks at the future of satellite systems and addresses some of the difficult institutional issues concerning satellite navigation with which navigation authorities worldwide are having to grapple. It reviews the development of the future Global Navigation Satellite System (GNSS) and identifies the economic benefits it could bring.
The Future of Radar Beacons
Authors: Ward N.
Published: November 2009

The principles of radar beacons (racons) are described and their significance for navigation discussed. Developments in radars which may affect the operation of racons are considered and ways of meeting the requirement to locate and identify aids to navigation on a radar display are considered. The developments in non-radar band transponders are reviewed to determine whether they might present an alternative to racons in the future.
The Future of Radar Target Enhancers
Authors: Ward N.
Published: November 2009

The development, present status and likely application of Radar Target Enhancers are discussed. Their role in improving the effectiveness of aids to navigation and enhancing the safety of small craft is considered and their likely further development assessed.

The Radar Target Enhancer (RTE) is a device which automatically transmits a signal in response to an interrogating signal received. The response from an RTE has no identifying code. The RTE only amplifies and retransmits the radar signal received, so that it has the same appearance on a display as a passive return, but is more consistent. The purpose is to improve the radar returns from navigation marks and to improve radar detection of small craft, to reduce the risk of collision.
Digital Charting, Now and in the Future
Authors: Dawson John
Published: November 2009

The views expressed in this paper are personal to the author, and not intended to represent official policy of the UK Hydrographic Office.

With the ever increasing use of electronic charts in the small craft sector, this paper is designed to give some background to developments at the United Kingdom Hydrographic Office. Included is a short review of the state of the market, with the author's view of possible future progression. The various formats of data are discussed, with a summary of the legislative background within the commercial market. This discussion is relevant, as it will ultimately shape the future market for small craft users
Fast Craft and the COLREGS
Authors: Pike R. D.
Published: November 2009

The past 10 years have seen an explosion in the use of high speed marine craft. This explosion has been in most sectors of operation, leisure, passenger carrying and military, and is now poised to expand into the cargo carrying sector. The sizes of the new generation of fast craft can range from small 60 knot, 7 metre leisure craft up to fast ferries which are 140 metres long with speeds of 40 knots. Future developments encompass 40 knot large cargo ships, 100 knot passenger and cargo vessels and very high speed military craft. Added to this galaxy of high speed concepts is the 200 knot wing-in-ground (WIG) craft, which, because it flies close to the sea surface, will interact with other marine traffic.
A History of Navigation in The Royal Air Force from the 60s to the 80s: ‘The Last Days of Airborne Analogue Computing’
Authors: Bonnor Norman
Published: November 2009

This paper is based on a presentation at a seminar on the History of Navigation in the Royal Air Force, held at The Royal Air Force Museum, Hendon, on 21 October 1996. The seminar was organized by the Royal Air Force Historical Society in Association with the Guild of Air Pilots and Air Navigators and the Royal Institute of Navigation. The complete proceedings of the seminar are being published in 1997.
Quality Surveillance on a Commercial Marine Survey Vessel
Authors: Green Bob
Published: November 2009

There is a recent trend amongst oil companies or oil field construction companies to leave Quality Control (QC) to the survey subcontractor. Increasingly they do not put their own survey QC representative on survey vessels they hire. This may be a mistake, although at this point the author, being himself an offshore QC representative, must confess to a vested interest.

Quality assurance is a term which is often misunderstood. Even people who use the expression are vague about what it actually means in any given industry or how it should be applied in any particular situation. The confusion is compounded because the quality assurance ‘bible’ (BS5750/lSO 9001 documentation), was written primarily for the manufacturing industry, and needs expert translation to apply to a service industry such as the commercial marine survey business.
A Neural Auto-depth Controller for an Unmanned Underwater Vehicle
Authors: Sutton R. , Johnson C. , Roberts G. N.
Published: November 2009

Artificial neural networks offer an alternative strategy for the nonlinear control of unmanned underwater vehicles (UUVS). This paper investigates the use of a multi-layered perceptron (MLP) network in controlling an UUV over a sea-bed profile and compares the use of applying chemotaxis learning to that of the more commonly employed back propagation algorithm. The results show that, for differing sized MLPs, the chemotaxis algorithm produces a successful controller over the sea-bed profile in an improved training time. Also it will be shown that, in the presence of noise and change in vehicle mass, the neural controller out-performed a classical proportional-integral-derivative controller.
Gnomonic Projection of the Surface of an Ellipsoid
Authors: Williams Roy
Published: November 2009

When a surface is mapped onto a plane so that the image of a geodesic arc is a straight line on the plane then the mapping is known as a geodesic mapping. It is only possible to perform a geodesic mapping of a surface onto a plane when the surface has constant normal curvature. The normal curvature of a sphere of radius r at all points on the surface is I/r hence it is possible to map the surface of a sphere onto a plane using a geodesic mapping. The geodesic mapping of the surface of a sphere onto a plane is achieved by a gnomonic projection which is the projection of the surface of the sphere from its centre onto a tangent plane. There is no geodesic mapping of the ellipsoid of revolution or the spheroid onto a plane because the ellipsoid of revolution or the spheroid are not surfaces whose curvature is constant at all points. We can, however, still construct a projection of the surface of the ellipsoid from the centre of the body onto a tangent plane and we call this projection a gnomonic projection also.
Interference to GPS in the Marine Environment
Authors: Gyldeń Sven
Published: November 2009

In a paper in the May 1996 issue of this Journal, Ward and Johannessen gave an excellent summary of the work carried our for the General Lighthouse Authorities on the significance of potential interference to GPS. They identified three possible types of interference for their study:

(i) Interference from other systems on board the ship using GPS.

(ii) Interference from emissions generated onboard other ships or at structures in the vicinity of the ship using GPS.

(iii) Deliberate interference from malicious persons.
‘Conflicts in Offshore Waters’
Authors: Cullen Donald K.
Published: November 2009

The September 1996 issue of the Journal has an article by J. C. Hines which, as a RYA instructor and former maritime lawyer, I found very confusing.

I agree with him that there are many yachtsmen and some professionals who I would not let out in a pram dinghy, let alone in the vessels they are commanding.

It is significant that many commercial ships will have one watchkeeping officer on the bridge, no other lookout, and a helmsman on call. The ship will be on autopilot and, upon a target being seen, it will take two minutes or so before the helm is manned.
Arctic Navigation Past, Present and Future
Authors: Maybourn R.
Published: November 2009

Any comment on arctic navigation must be broadly based since the ability to conduct voyages in ice-infested waters is influenced by many factors. The traditional technique of exploiting open channels in the ice is now no longer adequate and there is an increasing need for vessels to force ice in order to reach places and to carry out activities well inside the boundaries of the permanent ice cover during parts of the year when the sea ice is at its maximum extent.
The Programmed Traverse Light
Authors: Spottiswoode N. L. , Richardson R. B.
Published: November 2009

Due to the very low power-to-weight ratio found in large deadweight ships, their high inertial values and the very long reaction time to manoeuvring commands, difficulties often arise in achieving entry to the berthing area at an exactly pre-determined speed over the ground.

This paper describes a dynamically programmed optical aid to help the navigator achieve exactly the prescribed speed over the ground as he decelerates along his traverse or intended track when approaching his terminal or swinging area. The authors are consultants to AGA Navigation Aids Ltd who have developed this device.

Over the last decade or more, some very significant changes have occurred in the general requirements relating to the handling and manoeuvring of certain classes of modern vessel in the approach to their terminal berth – whether jetty, single-buoy mooring or even when coming to anchor. The economy of size in the bulk trades has probably had the most profound effect. This often reduces the power/weight ratio of the vessel itself to a very low order. In turn this has led to radical adjustments in techniques of ship handling in the final approach phases, due to the long response time between command instructions and reactions to these by the vessel itself. When considering the inertia of a vessel of 220000 tons deadweight or more – where the feasible deceleration or rate of change of speed is also of a low order – we can see the difficulties met with when endeavouring to enter the berthing area at an exactly required pre-determined speed over the ground (as opposed to speed through the water) often as low as one tenth of a knot or less.
Airline Navigation Planning
Authors: Page D. M.
Published: November 2009

This paper was presented at a meeting of the Institute in London on 25 May 1980 with Captain S. S. D. Jones in the chair. Mr Page assesses the role of air navigation as one factor in coordinated flight planning, through the application of modern techniques, to secure maximum efficiency in airline operation and in the conservation of fuel.

This paper presents an airline view of developments in aircraft navigation and planning. It considers aircraft navigation in the widest sense together with the current change in emphasis in navigational requirements. Present technology can produce navigational systems of almost any desired accuracy – at a price. The cost of such systems, together with the requirements of ATC, will dictate the choice.
The Evaluation of Aircraft Collision Probabilities at Intersecting Air Routes
Authors: Hsu D. A.
Published: November 2009

In this article formulas useful for the calculation of aircraft mid-air collision probabilities at intersecting air routes are developed. The aircraft overlap density, a key parameter in the calculation, is expressed as a function of the intersection angle of air routes, aircraft speeds, the nominal separation, and parameters in the position-error distribution. Two representative probability models for position errors are used to illustrate the computational procedures suggested. A method of approximation over large navigation systems is also proposed.

The calculation of aircraft mid-air collision probabilities is an important step in the design of air-route structure and is a key element in the specification of separation standards and minimum requirements of facilities reliability and accuracy. A thorough analysis of collision probabilities for long-range parallel air routes over oceanic areas was reported by P. G. Reich in three research documents and in a series of papers published in this Journal in 1966. Analysis of collision probabilities at intersecting air routes typical in off-shore and continental areas, however, has not been fully explored to date. The only direct reference available on this subject appears to be the work by Bellantoni,7 in which a collision problem was formulated in the three-dimensional space and was apt to deal with airport terminal landing or take-off situations. For circumstances where horizontal linear air routes intersect one another at preassigned positions, the analysis provided by Bellantoni needs to be simplified and refashioned for use in extensive applications.
Characterizing Cross-track Error Distributions for Continental Jet Routes
Authors: Polhemus Neil W. , Livingston Dale
Published: November 2009

The establishment of standards for lateral separation between adjacent jet routes depends in large part on an adequate description of aircraft path-keeping ability. While it has been accepted for many years that deviations from route centreline follow a distribution which is more peaked in the core and longer tailed than the gaussian distribution which was initially assumed, the selection of an alternative distribution is still moot. Early studies of oceanic data suggested that a double exponential distribution gave a much better description of the core data. However, this distribution still appeared to underestimate the frequency of occurrence of very large errors, so that a double-double exponential distribution was proposed and is currently used for establishment of MNPS (Minimum Navigational Performance Specification) criteria for the North Atlantic organized track system. A physical rationale for the occurrence of the double-double exponential distribution has recently been derived, with suggestions for consideration of alternative formulations.
Banded Contour Charts
Authors: Wright A. J.
Published: November 2009

A chart is the data base to which other navigational information is related and yet has to serve ships of widely different draughts. A possible alternative providing more draught-specific information based largely on currently available hardware, would be the creation of ‘banded contour charts’ on microfilm. Produced directly from a computer data bank by a fast flying light-spot microfilm plotter, the master charts would be single frames of 35 mm microfilm mounted in cards 183 by 83 mm. A set of micro-charts would be produced covering the same sea area and differing only in that each has a different, limited band of depth contours of critical importance to ships in a limited draught range: for example, the first going from 0 to 5 metres by 1-metre intervals, the second from 3 to 8, the third from 5 to 10 and so on. All other data, including spot depths outside the contours, would be the same on all charts in the series.
The Analysis of Great-circle Tracks
Authors: Jofeh M. L.
Published: November 2009

It is the common practice to draw great-circle tracks on gnomonic charts, on which they appear as straight lines, to pick off the latitudes of intermediate points where the track is intersected by the charted meridians, and finally to transfer the pairs of coordinates thus measured to a Mercator chart. The purpose of this note is to present the derivation of some formulae by means of which the coordinates of points along the track may be calculated very easily.
Navigational Safety in European Waters
Authors: De Bièvre Aline
Published: November 2009

This paper, which was presented at a seminar sponsored jointly by the Institute with the Nautical Institute in London on 9 December 1982, seeks to identify the environmental and political pressures behind the international and regional efforts to regulate the safety of shipping in European waters. It examines the role of Port State control and vessel traffic management in safety and the prevention of pollution.
Designing a North Sea Shipping Route
Authors: Van Riet J. A. , Tresfon R. , Pollen R. A. W. , Valstar A. P.
Published: November 2009

This paper describes the process of developing a safe access route to the Hook of Holland. The traffic situation in the Roads was tested by means of simulation. Van Riet, Pollen and Valstar are with the Directorate General of Shipping and Maritime Affairs in the Netherlands, Tresfon with the Maritime Research Institute in the Netherlands.
The Channel Navigation Information Service
Authors: Emden R. K. N.
Published: November 2009

Since its inception in 1972 progress of the Channel Navigation Information Service (CNIS) has twice been described in the Journal. The tenth anniversary of the first broadcast bulletin of information occurred on 31 July 1982, and it is perhaps appropriate to review and bring up to date the major milestones in the history of the Service and to review the safety of navigation in the Dover Strait.

It will be recalled that, following the multiple collision off the Varne in 1971 and bearing in mind previous major disasters – Torrey Canyon, Pacific Glory, etc. – the Department of Trade concluded that a voluntary Traffic Separation Scheme (TSS), without surveillance and without a coordinating information service, was inadequate for the dense and complex maritime traffic problems of the Dover Strait. Thus was born the Dover Strait Information Service, now CNIS, under the aegis of HM Coastguard, and located on the upper floor of an old Port War Signal Station at Leathercote Point, St Margaret's Bay. The Decca Marine Radar Company installed a simple harbour radar and its associated display towards the end of 1971 and Coastguard evolved the essential elements of what remains to this day a half-hourly bulletin, broadcast on vhf/rt Channel 10. In low visibility intermediate broadcasts are given, based on actual visibilities reported from sea.

In August 1973 the French authorities installed a similar system at Cap Gris Nez and a very close co-ordination, vital from the mariner's point of view, developed.
Measurements used in Experiments to Evaluate the Performance of Watch Officers
Authors: Cook J. F. , Crawshaw C. M.
Published: November 2009

This paper reviews the measures commonly used in experiments to evaluate collision avoidance systems. The use of Closest Point of Approach, Time to Closest Point of Approach, and Manoeuvre Magnitude was criticized particularly for multi-ship encounters. However, the data do suggest that two measures, Entropy and the use of experienced judges to give rank scores of performance, seem to be good measures even in multi-ship encounters. The use of a composite measure is not experimentally evaluated in this paper, but it is suggested that if one were used, it would have to be very complicated. Mr Cook is with the Department of Applied Psychology at UWIST, Dr Crawshaw in the Department of Psychology at the University of Hull.
A Return to the Sumner Line?
Authors: Sadler D. H.
Published: November 2009

In spite of, or perhaps because of, the almost universal use of some ftym of electronic calculator for the reduction of astronomical sights, there is a growing demand for a simple back-up method for emergency use when a calculator is not available. Presumably the need arises because of the disinclination to carry the material for a standard method in order to provide cover for the small chance of calculator failure. It is a surprising development, enhancing the continued interest in, and use of, astronomical navigation in a field increasingly dominated by instant and continuous position-fixing systems of high precision and universal applicability.

Similar considerations may apply to the ephemeris data, which are being increasingly generated by calculator or computer. However, to a precision adequate for emergency use, near-permanent data for the Sun and stars can be given in a few pages in tables similar to those for G.H. A. Aries (Vol. I) and the Sun (Vols. 2 and 3) in Table 4 of AP 3270 Sight Reduction Tablesfor Air Navigation. In fact the simplest conceptual solution might well be to carry the appropriate latitude pages extracted from the loose-leaf US edition, HO 249.

In 1948 I had occasion to review the existing tables for the reduction of astronomical sights (this Journal, Vol. 1, p. 298, 1948); the review was limited to intercept methods and, mainly, to those based on the use of the DR position.
On the Use of Height Rules in Off-route Airspace
Authors: Ford R. L.
Published: November 2009

The standard height rules applied in off-route airspace are examined to assess the degree of intrinsic safety they provide, i.e. the reduction of conflicts without action being taken by pilots or ATC. The yardstick used is the conflict rate which would obtain if the aircraft were uniformly randomly distributed in the height dimension and flying straight and level on uniformly randomly distributed tracks. It is shown that the application of the standard rules can lead to a reduction in intrinsic safety unless significant height-keeping errors are present. An alternative height rule apparently having more desirable characteristics is examined on the same basis.
Manoeuvring Times, Domains and Arenas
Authors: Colley B. A. , Curtis R. G. , Stockel C. T.
Published: November 2009

Two main concepts in mathematical modelling of ship encounters have been proposed by Davis. The first, the ‘domain’, was an adaptation of a concept originally introduced by Goodwin, who defined the domain as the ‘area about own-ship that a navigator wished to keep free with respect to ships and other stationary objects’. The second, the ‘arena’, conceived by Davis, is the area around the domain which when infringed causes the mariner to consider whether to make a collision-avoidance manoeuvre. Thus, in a computer model, when a vessel enters the arena the computer analyses the situation and, depending on the severity of the threat, makes a collision-avoidance manoeuvre.

Goodwin's domain was divided into three sectors corresponding to the ‘giveway’, the ‘stand-on’ and the ‘overtaking’ regions as defined by the relative velocity of approach. The domain was derived from radar films of ship tracks and records of radar simulator experiments. Davis smoothed the sectored domain to a circle with own-ship off-centred astern and to port, and the weighting of each of the sectors retained. Davis's domain had a solid theoretical grounding; the arena, however, was simply a larger version of the smoothed domain. Its size and position were obtained by means of a well-distributed questionnaire. It served its purpose in the model, but lacked any real validation.

One problem with the Davis arena was its inability automatically to take into account different velocities, both of own-ship and of targets.
The Automation of Air Traffic Control
Authors: Villiers Jacques
Published: November 2009

Experience gained in the automation of air traffic control is of interest from more than one point of view, and not only because of the range and diversity of new and delicate problems to which this application of automation has given rise, and for which it is necessary to find simultaneous solutions. It has been necessary to design and develop new methods for the acquisition, processing and display of information and to link them with digital computers, for which a complex and voluminous ‘real-time’ software has had to be compiled and brought up to date without interrupting the procedure. But it is when it comes to visualizing the total pattern that the most difficult problems arise because the major decisions determining the success or failure of the operation have had to be taken without the possibility of acquiring any preliminary experience.

Man and the computer have to work together in real time as harmoniously as possible to obtain the best results from the modern data processing systems that it was proposed to employ; it was therefore essential to consider very deeply the complementary roles which each was intended to play.

To describe this research in detail or the solutions arrived at would not be of great interest to those other than specialists.
I.—The Severn Estuary
Authors: Cotter Charles H.
Published: November 2009

F. J. North reminds us that the well defined geographical entity now called the Bristol Channel should, on historical grounds, be called the Severn Sea. This was the name used by Giraldus Cambrensis (1146?–1223) in his Topographic Hibernica of 1188 and by Roger Barlow in his A Brief Summe of Geographic of 1540, among other early writers. But with Bristol's rise to fame as a great seaport the name Bristol Channel came to be used and, as early as 1693 we find the name ‘Canal de Bristol’ on a French sea chart by H. Jaillot.

An unknown writer of 1578, whose Discourse was published in John Stow's Survey of London of 1598, in explaining why a site on the Thames instead of one on the Severn was chosen for the metropolitan city, stated that:

‘… the Thames both for the straight course in length and reacheth furthest into the belly of the land, and for the breadth and stillness of the water is most navigable up and down the stream…. The river openeth indifferently upon France and Flaunders, our mightiest neighbours, on whose doings we ought to have a bent eye and special regard…

… For the Prince of this Realm to rest and dwell upon Severn were to be shut up in a cumbersome corner, which openeth but upon Ireland only, a place of much less importance…’
The Craft of the Navigator
Authors: Anderson E. W.
Published: November 2009

Sir George Deacon, F.R.S., a past president, has recently written a most persuasive case for founding a Chair in Navigation. He mentions Sir Isaac Newton's insistence that Christ's Hospital should teach ‘not only what is necessary to make a mariner skilful in his ordinary road, but also what would assist him to invent new things and practices and to judge what comes before him’. It was in this spirit that a basic analysis of navigation was begun some years ago although it was not expected that Sir Isaac Newton's great conception would be realized. Indeed, the object was only to try to suggest to educators the potential of navigation as a scientific discipline.

Elements of the work dealing with probability and with information theory have already appeared in the Journal and certain ideas have been crystallised into patents taken out by Smiths Industries Limited. Other results are presented here in a condensed form starting with a definition which leads on to a pattern of equipments by using a particular development of dimensions and which highlights the special difficulty of collision avoidance. Linkages between gimballing error, precession and coriolis effect are suggested, and the significance of frames of reference is emphasized, suggesting a unified approach to the trigonometry needed by the navigator. If these crude tools can be tempered by the fire of criticism or replaced by finer cutting edges, the effort will not have been wasted.
Early Portuguese Navigation
Authors: Cortesão Armando
Published: November 2009

Professor Cortesão sent the following message to the Annual General Meeting of the Institute on 23 October which he had been unable to attend to receive personally his Honorary Membership. An account of the meeting appears at page 111.

The Honorary Membership which the Royal Institute of Navigation bestows upon me, when I have reached the eighty-fourth year of my laborious life, the last forty years of which have been largely dedicated to the study of the history of early cartography and navigation, impresses me deeply and I am very sorry that, due only to my advanced age, I cannot be present at this ceremony to thank you personally for such a great distinction.
‘K's and F's’
Authors: May W. E. , Cotter Charles H.
Published: November 2009

I am indebted to Captain Duncan M. Henderson (Journal27, 536) for causing me to seek further than I had done previously to enable me to prove that ‘F’ in old log-books stood for fathoms and not fractions.

I would quote the following authorities who all state definitely that the ‘F’ meant fathoms and that there were usually eight fathoms to a knot, at any rate in the eighteenth and early nineteenth centuries. They are:
V.H.F. Interference
Authors: Downer Ivan
Published: November 2009

Having read Professor Hugon's informative paper on ‘Navigation in the French merchant navy’ and in particular his remarks regarding the cluttering of the 182 kHz band, I would hazard a guess that he has not listened to the v.h.f. channel 16 band in recent years, when clear of the U.K. and continental areas.

In the open sea well away from land this channel is not often abused, but off the West African coast between about 13° N. and 22° N. the air at night is, more often than not, cluttered with noises like animal and bird calls for long periods on channel 16, and during the day with lengthy chitchat, possibly between foreign fishermen, on this and other channels.
A Geometrical Construction for Horizontal Angle Fixes
Authors: Meaden T. R.
Published: November 2009

The method here described for finding the position of an observer from horizontal angles to fixed marks, without the use of a station pointer and without the necessity of drawing position circles, was devised by the author and although it may not be original it may be of interest to other navigators.
The Optimal Speed of Ships
Authors: Goodwin Elisabeth M. , Kemp J. F.
Published: November 2009

The following paper was presented at a meeting of the Institute held in London on 21 February 1979 with the President, Captain R. Maybourn, in the Chair. It considers some of the factors which apply in the context of overall safety and the weightings which they should be assigned in estimating the optimal speed for ships in given circumstances and conditions.

In air traffic control the speed of individual aircraft cannot be significantly varied without unacceptable economic penalties, or the aircraft falling out of the sky. In the case of ships the speed is a useful variable for traffic management and individual ships can choose, or be assigned, any value between zero and their normal service speed. The following discussion concerns the choice of a suitable speed for marine traffic in terms of safety criteria.
A Stranding in the Magellan Strait
Authors: Burger W. , Corbet A. G.
Published: November 2009

The paper by Captain Burger and Captain Corbet was presented by Captain Corbet at a meeting of the Arab Institute of Navigation held in Alexandria on 9 April 1979. Before the meeting M. W. Richey, as Director of the Royal Institute of Navigation, gave a short talk to the Arab Institute.

On the 9 August 1974 the steam tanker Metula grounded in the First Narrows of the Magellan Strait. The grounding of this deeply laden VLCC provoked very little publicity either on television or in the press, probably because of the remoteness of the area. The Metula was a first-class, well-found vessel manned by properly qualified and experienced personnel, and had two Chilean pilots on board to assist with the navigation through the Strait. How could such an accident happen?
GPS Navstar: A Review
Authors: Jones S. S. D.
Published: November 2009

The Global Positioning System, Navstar, is an advanced satellite-based navigation system which is currently under development and evaluation in the United States of America. Progress has been very fully reported in the open literature and a definitive paper on the concept has in fact been published in this Journal. The concept has now been experimentally validated and much of the evidence which supports this validation has in turn been published.

The impact of Navstar on navigation in the period beyond 1985 is potentially very great indeed in that it offers, worldwide, a navigation capability to surface and aerospace users of a standard of accuracy combined with continuous availability which is currently associated only with short-range aids.

This paper has the objective of presenting (a) a general introduction to the physical principles on which Navstar is based, followed by (b) a survey of its potential relevance to the operational needs of various classes of user. Finally there is some more speculative matter in the form of (c) a discussion of the potential impact of successful implementation of Navstar on current and projected future navigation systems.
Radar Estimation of the Height of a Cruising Aircraft
Authors: Nagaoka S. , Yoshioka E. , Muto P. T.
Published: November 2009

Separation standards are used for assuring the safe and effective operation of aircraft in a traffic control environment and as aircraft operations increase in number the need to reconsider separation standards is strongly voiced both by operators and controllers. A panel, the Review of the General Concept of Separation Panel (RGCSP), has been organized by ICAO and the possibility of reducing conventional separation standards has been discussed. Mathematical models for estimating collision risk due to loss of separation between aircraft require data on navigation accuracy. In general, three-dimensional radars are used for height finding but these are complicated and expensive.

The altitude of the cruising aircraft is required within about 100 ft. In the simplified radar here described a rotating antenna produces a fan beam for scanning aircraft flying overhead. The data obtained from several scans are processed by a mini-computer and the height of the aircraft estimated by a least-square method and sequential approximation. Between the items of information obtained for each scan (the distance, the elevation angle and the data acquisition time) a theoretical relationship is established as an observation equation, one of the coefficients of which includes the height information. The coefficient is determined by a curve-fitting method. The paper first describes the method of analysis for height estimation and then an evaluation of the accuracy of the method by a computer simulation.