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.

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 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.

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 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.

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 authors of this paper are the three General Lighthouse Authorities (GLAs) of the United Kingdom and the Republic of Ireland. It was presented on their behalf at the RIN-96 conference by Captain Turner. The paper gives a brief overview of the policy of the GLAs (i.e. the Corporation of Trinity House, the Northern Lighthouse Board and the Commissioners of Irish Lights) regarding the provision of an aids to navigation service with emphasis on the future prospects of traditional aids to navigation over the next 25 years. The three GLAs have recently carried out a consultation exercise on marine aids to navigation into the 21st century. The results of this consultation exercise are discussed. It should be noted that, for clarity, the General Lighthouse Authorities (GLAs) refer to the systems that they provide as ‘aids to navigation’ (AtoN), to differentiate their provision from the equipment carried on board ships for navigational purposes which are referred to by the GLAs as ‘navigational aids’. This paper therefore in the main deals with AtoN.

The coastlines within the GLAs' areas of responsibility rank with the most heavily trafficked and dangerous in the world. The coastlines vary from isolated rocks and the steep, Atlantic coastline, to the low-lying relatively featureless coastline of south-east England, off which are shifting sandbanks and channels. The tidal range in GLA waters is significant and tidal streams can reach 10 knots or more in a number of places.

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 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.

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

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.

Part I of this chapter was included in the January 1997 issue of the Journal, Vol. 50, p. 65.

The Smith Brothers, 1919. Captain Ross M. Smith, of the Australian Flying Corps based in Palestine, flew a Handley Page 0/400 late in 1918 on a special flight to Baghdad and beyond, carrying as passenger Major General W. G. H. Salmond, the RAF's Middle East Commander. Flying as co-pilot was Brigadier-General Borton, Commander of the Palestine Brigade. Smith had been flying, in support of Lawrence's forces, another 0/00 which Borton had brought from England.

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.

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.

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.

Most of the radar systems used in operating marine vessel traffic management services experience problems, such as track loss and track swap, which may cause confusion to the traffic regulators and lead to potential hazards in the harbour operation. The reason is mainly due to the limited adaptive capabilities of the algorithms used in the detection process. The decision on whether a target is present is usually based on the amplitude information of the returning echoes. Such method has a low efficiency in discriminating between the target and clutter, especially when the signal-to-noise ratio is low. With modern signal processing techniques more information can be extracted from the radar return signals and the tracking parameters of the previous scan. The objectives of this paper are to review the methods which are currently adopted in radar target identification, identify techniques for extracting additional information and consider means of data analysis for deciding the presence of a target. Instead of employing traditional two-state logic, it is suggested that the radar signal should be allocated in terms of threshold levels into fuzzy sets with its membership functions being related to the information extracted and the environment. Additional signal processing techniques are also suggested to explore pattern recognition aspects and discriminate features which are associated with a return signal from those of clutter.

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.

Navigation is a human activity with the aim being to arrive at a predetermined destination. In order to find the way to the destination, the use of current input from the actual environment while travelling is needed as well as stored and organized knowledge of the local geography. Although the knowledge requirement has been studied extensively in the form of cognitive maps or other spatial representation, few studies deal with how the knowledge is used together with the input from the actual environment while navigating.

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.

It is not possible from Captain Gyldeń's contribution to fully explain the phenomenon. It is, however, important to note his experience and to encourage other practical navigators to report similar events. It is essential to have the best possible picture of circumstances when GPS suffers problems, before it is decided to close down alternative systems, which might not be affected in the same way.