This paper is intended to provide an operator's view of the impact of GPS on the air transport industry. The discussion centres on use of GPS for the en-route, oceanic, terminal area and precision approach phases of flight. In summary the author suggests the following:

(i) Inefficient use of airspace is costing the airlines a huge amount of money. However, GPS is not a pre-requisite of a move towards more efficient use of that airspace, although it will be required as part of the eventual CNS/ATM package. In the near term, better usage of current equipment such as IRS and DME, together with the introduction of ADS can provide the required level of accuracy for reduced separation in en-route and oceanic airspace.

(ii) There is a real need to provide navigation for non-precision approach worldwide, independent of ground-based infrastructure. This is the area in which GPS can provide the most immediate improvement to safety.

(iii) There are still a large number of questions hanging over GPS for precision approach. This leads the author to believe that it will not be capable of replacing ILS for the more critical Cat 2 and 3 applications quickly enough to avoid the loss of these capabilities in some critical locations. For this reason, it is postulated that MLS will be required in Europe, at least. Even if MLS is not required, there will still need to be a means of dealing with the transition away from ILS and for this reason the concept of a multi-mode receiver has been developed.

Reduced manning levels, the lack of skilled maritime labour and new satellite navigation systems have created a need for electronic charts in merchant ships. Developments in information technology have made it possible to design and produce these charts and the equipment to display them. It is essential that shipowners and others understand the issues which affect the use of these charts and equipment. It is also important for users to understand the effects that the revolution in satellite technology is having on all types of charts, paper and electronic. Only with this knowledge can shipowners appreciate the economic and operational benefits of using electronic charts, and IMO complete its work on the safety rules for the carriage and operation of all types of electronic charts and equipment for merchant ships.

During the summer months of 1994 the yacht Jester undertook a seagoing investigation into some of the navigational problems that would have confronted the Portuguese discoverers of the thirteenth and fourteenth centuries returning to mainland Portugal from the coasts of Africa and the Atlantic archipelagos. The investigation was made at the suggestion of the maritime historian D. W. Waters to illuminate one aspect of how astronomical navigation was first introduced at sea in the west.

The availability of an aeronautical mobile satellite service and the emergence of a global navigation satellite system should enable CNS services to be established for civil aviation, virtually worldwide. This paper discusses how the development of a low-cost ADS system, employing these satellite services, might be used to the advantage of European air traffic management (ATM). It indicates that the earlier action is taken, the greater will be the potential benefits. This paper is an updated version of that presented at the NAV94 Conference in November 1994.

Captain George Vancouver's survey of the North Pacific coast of America has been characterized as being among the most distinguished work of its kind ever done. For three summers, he and his men worked from dawn to dusk, exploring the many inlets of the coastal mountains, any one of which, according to the theoretical geographers of the time, might have provided a long-sought-for passage to the Atlantic Ocean. Vancouver returned to England in poor health but, with the help of his brother John, he managed to complete his charts and most of the book describing his voyage before he died in 1798. He was not popular with the British Establishment and, after his death, all of his notes and personal papers were lost, as were the logs and journals of several of his officers.

Vessel traffic service systems (VTS systems) have been established, throughout the world, in areas of high traffic density. These systems, operating with such tools as VHF radiotelephony, land-based radar installations and ship's data processing, gather information to respond to collision and grounding danger, to organize traffic flow and assist allied activities. It is expected that VTS systems should effectively reduce the number of collisions in the VTS area. But efforts for collision avoidance can only be successful if the VTS operator in front of the shoreside radar screen is precisely instructed as to which measurements he has to make to identify a risk-of-collision situation. Uncertainties about the direction in which ships must take evasive action arise in VTS areas, where ships are free to engage in encounters.

Radar transponders and radar target enhancers have been in use in a variety of applications for many years. Perhaps the most widely-known applications of radar transponders are in Identification Friend or Foe (IFF) and its civilian counterpart, secondary surveillance radar for air traffic control, and as racons in marine navigation and, most recently, as Search And Rescue Transponders (SART) in the Global Marine Distress and Safety System (GMDSS).

Marine accident frequencies reported in 20 different sources have been studied and compared. Further than this, comparisons were made with an analysis done by the present authors. There seems to be consistency within the sources in the use of the terms total loss, casualty and accident/incident. The rates were observed to decrease by an order of magnitude going from accident/incident to casualty and likewise from casualty to total loss. The overall frequencies were found to be in the range of 0·0009 to 0·07 total losses per 106 ship miles, 0·03 to 1 casualties per 106 ship miles, and 0·5 to 13 accidents/incidents per 106 ship miles. It was found that the frequency depends on visibility, brightness, geographical environment, age of vessel and size of vessel. Collision and grounding frequencies were found to increase with decreasing visibility, brightness and more restricted waters. Collision frequencies were found to increase with increasing size of vessel. Fire/explosion and structural damage frequencies were found to increase with increasing age, and collisions to decrease with increasing age. No firm trend was found from the effect of flag state or type of vessel.

It is well known that many collisions occur because one ship turns right whilst the other turns left when in close proximity to one another. Little is known as to why this occurs and, although some simulation models have been established using entropy theory, the problem remains unsolved.

In this paper, an assessment model for uncertainty is reviewed briefly. The concepts of uncertainty and uncoordination of mariners' behaviour in collision avoidance are discussed. A simulation model in conjunction with a DCPA (distance to the closest point of approach) decision-making model using fuzzy programming is introduced to discuss coordination.