Back in 1914, an army surveyor who was carrying out an airborne reconnaissance of potential sites for a new military aerodrome to the west of London is alleged to have held his map upside down – and that, consequently, RAF Northolt was built to the south of what was then called the Great Central Railway Line instead of about a mile to the north-east near where South Ruislip is now. A short apocryphal story perhaps, undoubtedly distorted by the mists of history, but it serves to illustrate the need for aeronautical charts that are designed with the requirements of visual air navigation firmly in mind.

To both professional and amateur divers, navigation underwater in reduced visibility, or in a current or tideway, can be a daunting business. This paper explores some of the options that are available for extending or improving the diver's sensory envelope and navigational capability in such conditions, and presents some new equipment ideas that have evolved from the author's work in this field.

The North Sea is at the leading edge of offshore hydrocarbon technology due to its hostile environment and deep water. This paper gives an overview of the role of the offshore surveyor in the North Sea by discussing the survey aspects, tools and techniques used in the development of a contemporary oil/gas field. Particular attention is paid to some of the more unusual techniques being developed today.

The first part of the above title was used in the Journal in 1953 for a paper by Captain Carl V. Solver. His special interest was to discover how the Norse navigators of the Viking age found their way across the North Atlantic. He was the first person to interpret the small wooden disc shown in Fig. i as a fragment of an early bearing-dial and investigations since his paper was published provide considerable supportive evidence. At the time, there was some strong opposition to his views, but he persisted with his theory and wrote a book, Vestervejen. This formed a basis for other researchers to carry his work further and, as a result, there have been many international contributions over some 40 years. The archaeological find from southern Greenland seems to show that the Norse navigator used the path of the Sun's shadow during the day as the basis of a compass.

Approach and landing are the phases of flight most associated with accidents and near accidents, especially when external visual cues are sparse. At what is now Australia's DSTO Aeronautical Research Laboratory, research on ways of reducing the hazard incidence resulted in the development and testing of several ground-based visual approach slope indicators. The T-VASIS landing aid was an outcome of this work, T-VASIS, which has been in international use for over twenty years, is now under potential threat of displacement by PAPI which is a more recent UK development. The research which led to the implementation of T-VASIS is described here, along with subsequent events leading to the introduction of PAPI to Australia. A glossary of abbreviations is included at the end of the paper.

Orienteering is a navigational sport using large–scale maps (1: 15000) and a compass to locate, as quickly as possible, a series of control points in a pre–defined order. Orientation of self and map are fundamental skills in the sport of orienteering. The traditional teaching or coaching of this skill is based on a hierarchical model. This model introduces the concept of location of self by initial reference to landmarks, then routes linking individual landmarks followed by configurations of these landmarks and routes. This model quite clearly aligns with the hierarchical model of spatial reference systems suggested by Seigal & White (1975). However, it is proposed that the process-oriented model offered by Downs & Stea (1977) may be more appropriate to orienteering. The model is based on orientation and then develops through route choice, route monitoring and route recognition. Orienteering behaviour, which is based on using map and compass information to select and follow a novel route in a multi-choice route following task, appears to follow this model.

This paper, and the following 2 papers were presented at the 17th Annual Meeting of the International Omega Association held on 3—7 August at Amsterdam. Permission to reproduce these papers is gratefully acknowledged.

The US Coast Guard has a project to provide a differential global positioning system service for harbour and harbour approach (HHA) areas of the coastal United States. The Great Lakes, Puerto Rico and most of Alaska and Hawaii will also be covered by the service. The Coast Guard's DGPS system will fulfil the 8–20 metre navigation accuracy requirement for HHA with an availability of up to 999 percent. The Coast Guard intends to provide this service to the general public and other government agencies, as well as use the system for its own missions. This capability is expected to enhance maritime safety in keeping with the National Transportation Policy by providing an all-weather radionavigation service to supplement existing radar and visual techniques, as well as a highly accurate position sensor for future electronic chart displays. This paper describes the Coast Guard's programme. Background and historical information on the development of pseudorange differential GPS is presented first, followed by a description of currently available technology. Various aspects of the Coast Guard's plan for implementing DGPS are then described, concluding with a rough project time line and a statement concerning Federal DGPS policy.

Recently, integration of different radionavigation systems has become very popular, since it improves system integrity, availability, accuracy and reliability. This paper discusses a new, flexible and cost-effective approach to system integration, centred on a single-chip application specific processor (ASP). An overview of this integrated system is presented and the application of the ASP for the implementation of a six-channel GPS, OMEGA, Loran-C and MLS receiver is given. The ASP is currently being implemented on a 180000 transistor 1·6μ, m CMOS Sea of Gates chip, and is expected to run at 100 MHz clock speed.

Projected requirements for automatic dependent surveillance (ADS) include the downlinking of certain aircraft flight parameters periodically and upon command from the ground. This will require a primary source of the data such as a flight management system (FMS) and, of course, a radio datalink. This paper provides a description of an existing system that could fulfil much of the interim airborne ADS equipment requirements by using GPS/OMEGA/INS/ACARS for existing aircraft which are not equipped with, or envisioned to be equipped with, SATCOM, FMS or IRS.

A variety of different techniques has been developed for the weather routeing of sailboats. These have varied according to whether the technique is intended for yachts or for sail-assisted powered vessels, whether the routeing is for long or short time periods, and whether the routeing is used for navigation or design purposes.

The techniques that have been implemented to date are reviewed, comparing their strengths and weaknesses. Ways in which these problems may be overcome in future implementations of weather routeing are also discussed