A mainly theoretical study has been undertaken to demonstrate how the extent of cover from a hyperbolic navigation system chain can be evaluated. The impetus for the study was the need to assess how Loran-C could be extended over Western Europe, particularly in the South western Approaches, North Sea, English Channel and Bay of Biscay sea areas.

The technique described in this article leads to an accurate determination of the electric field strength at a distance from each transmitting site and takes into account the complexities of the ground-wave propagation path. This field-strength contour is combined with the geometric effects of station siting (expansion factors) to yield a constant S/N contour (–10 dB) which defines the ¼n.m. error and hence the limit of cover for the hyperbolic chain under study.

In order to exercise the analytical methods a hypothetical Loran-C chain was studied comprising a master station at Lessay (France), with secondary stations at Soustons (also in France), at Sylt (dual rated; off the North Sea coast of Germany, near the Danish border) and at a fourth station located in north-west Britain on the Hebridean island of Barra. The study indicated that such a hypothetical chain would significantly improve Loran-C cover over much of western Europe.

In mid-1985 the 20 metre outrigger canoe Sarimanok, built in the Southern Philippines from tropical forest materials, sailed out of Bali, Indonesia, to follow the direct east-west Indian Ocean track which the first Austronesian settlers of Madagascar may have taken.

Global satellite navigation systems have been under development by the United States and the Soviet Union for many years. The US Navstar GPS system saw its first launch in 1978 and the USSR's Glonass system followed 4 years later. The US space shuttle, which was foreseen as the launch vehicle for Navstar spacecraft, received an enormous setback in 1986 as a result of the Challenger accident. In the meantime, Glonass launches, which carry three spacecraft at once into orbit, have proceeded without incident (until the failure on 24 April 1987). Both systems are currently still in test phase and can be expected to reach operational status in 3 or 4 years' time. In the meantime, the idea of combining Navstar and Glonass into a single civil programme has many attractions for all concerned. Some aspects of Glonass orbital characteristics and signal structure are discussed with this end in view. In addition, features of the data message content of Navstar and Glonass are also compared, to gain a better understanding of the feasibility of a dual satellite navigation system.

This paper was originally presented at a meeting of the International Omega Association in October 1987. It describes the operational use of the Omega system for daytime air-pollution monitoring and control, and for night-time low-level pest-spraying operations in South Africa.

The ability of visually impaired individuals, especially when blind, to locate themselves in an urban or rural environment with respect to road intersections, prominent landmarks, etc. has always been a serious problem. In addition, and of equal importance, is the inability to communicate their location to a central control facility in the event of their needing any additional assistance.

With the advent of high accuracy global positioning many applications, which heretofore had been considered highly futuristic and discussed only in the most tentative terms, are now being researched. One such application is the use of differential Navstar GPS and its capability as an aid to the visually impaired. The concept envisions a small device that can be worn by the user. This device will have the means for providing Navstar GPS phase information accurate enough to be converted to a specific street location. Inherent in the concept is means by which the users can be instantly apprised of their location and/or can communicate with a central location for other purposes.

To establish feasibility of such an application, it was necessary to understand the limitations of Navstar GPS. In particular those that may result from its use in an urban environment. Accuracies of the Navstar GPS system tend to depend on the sophistication of the receiver to be used. At the time there was some question as to future developments of a small enough package for the intended use. Along with this was the question of the suitability of differential positioning for increased accuracy. This article deals with the initial field tests that were run and the conclusions drawn from this work.

Similar work was previously accomplished in 1985 by the US Department of Transportation, Transportation Systems Center. The referenced effort included both the use of Navstar GPS as well as Loran-C which our effort did not but did confirm a number of our findings relating to the limitations of Navstar GPS in an urban environment and attenuation in the presence of foliage, it did not centre on differential Navstar GPS as did our work.

This paper describes a computer aided method which has been developed for assessing impending platform contacts (Impact). Some preliminary results are presented.

The 1987 Conference of the Institute was held at the Penta Hotel, London, in the autumn. A selection of nine papers from the Conference is reprinted here, following an introductory summary.

The complete proceedings, comprising some 40 papers, may be obtained from the Institute price £25 to Members (£50 to non-Members).

The need for maritime navigation is obvious and the subject has a long history, indeed the science of navigation was mainly developed for maritime purposes. The areonautical requirement is nowhere near as old as the maritime, in the early days it was sufficient to follow roads or railways, the need for navigation came when crossing seas or not being able to see the ground for a large part of the journey. Space navigation requirements are even younger.

The Central Forecast Office Headquarters (CFO) in Bracknell has a number of national and international functions including a co-located World Area and Regional Area Forecast Centre in support of the International Civil Aviation Organization (ICAO). The CFO is also a Regional Meteorological Centre within the World Meteorological Organization (WMO) and a National Meteorological Centre for the United Kingdom. The CFO receives considerable support from an operational numerical prediction model. There are two versions of the model: a global version has a horizontal resolution of about 150 km and is used to produce forecasts up to 6 days ahead twice daily from 0500 GMT and 1200 GMT starting conditions with results available by 0500 GMT and 1700 GMT, respectively. A regional version of the model has a horizontal resolution double that of the global version and is limited to the area bounded by 80° W –40° E, 30° N – 80° N, with the lateral boundaries updated by interpolations from the global model. The regional model is used to compute forecasts up to 36 hours ahead twice daily, with results available by 0300 GMT and 1500 GMT. The fine-mesh model is used mainly to provide detailed forecasts of precipitation, cloud, surface winds and temperatures, which are better specified on relatively small horizontal grids. Physical and sub-grid scale processes are parametrized in the numerical model.

Marine Safety Information is defined as the coordinated service of navigational and meteorological warnings, meteorological forecasts and distress alerts.

It represents the core information which the Master of a ship is required to receive under the provisions of chapters IV and V of the Safety of Life at Sea Convention (SOLAS).

In essence these cover the responsibilities of nations to broadcast messages relating to marine hazards, the obligation placed upon Masters to report such hazards, and to receive messages broadcast about them.

Three separate kinds of information are dealt with in the SOLAS Convention. First, Meteorological Services: these are the business of the World Meteorological Organization (WMO), which seeks to coordinate the work of various national meteorological administrations. Unfortunately a multitude of overlapping services and areas have grown up out of an expanding practical requirement and capability. This has resulted in overlap of services and consequent multiplication of effort.

The data base has become the heart of many of our businesses. This discussion will begin with an overview of the many aspects of how the data base is used and manipulated at Jeppesen Sanderson. The core of NavData has been named the Flight Information Master Data Base.

Marine radars, introduced generally for merchant ships immediately after World War 2, play a vital role in ship navigation and collision avoidance. They are now considered to be essential to a ship's safe operation and internationally agreed carriage rules and performance specifications exist for most classes of vessels.

Electro-optic sensors – forward-looking infra-red and night vision goggles – are today providing a dramatic enhancement of low-level operational capability, but causing increased demands for precision navigation, situation awareness and advanced displays. Digital map displays, also available today, offer the flexibility of map presentation that is needed. In the future, terrain-referenced systems incorporating digital data bases hold the promise of the integrated flying aid and mission displays that are required for ‘all-weather’ operations. This paper describes first the fit and usage of the EO systems likely in a future combat aircraft and goes on to review the status of data-base systems. It establishes the baseline against which digital map systems and later terrain-referenced displays that exploit an elevation data base might be integrated into the aircraft.

Although the Royal Navy has used various bridge designs during the past 20 years it has chosen a readily recognizable layout for its Type 23 frigate. This conservatism is not the result of a wilful disregard for changes being made elsewhere in the marine world but arises from the particular requirements of a warship's bridge and considerable differences in manning. The most significant changes to layout, in recent years, have been the siting of the quartermaster on the bridge, the introduction of the versatile console system (vcs) of instrument display, the provision of engine controls at the quartermaster's console and the siting of a radar display at the bridge front.

One of the main motives for establishing the International Hydrographic Bureau (1921) was: ‘To bring about … the greatest possible uniformity in nautical charts and documents’.

Among recent trends in the development of automatic navigation aids is the designing of integrated navigation systems with navigational data being presented on electronic displays. The integrated system concept seems promising, in particular due to possible improvements which may be achieved in areas of vital importance such as navigational safety, seafarers ' labour consumption and the efficiency of a ship's operation as a transport unit.