This, and the following three papers, were first presented at GNSS 2000, the Third European Symposium on Global Navigation Satellite Systems held in Edinburgh, Scotland from 1st to 4th May 2000.

This paper presents the methodology and a practical implementation approach to perform GNSS Safety Assessment and Certification with due consideration of the satellite navigation system users. It places Galileo GNSS in a total system that includes vehicles, on-board equipment, crews and traffic controllers and defines the necessary organisation for implementing safety analyses right from the early design phases of navigation systems. Civil aviation has very demanding requirements based on objectives for air navigation safety. It is much better organised on a worldwide basis than other GNSS users and is considered in this paper as the leading study case. Some methods are then proposed to build a bridge between all user organisations and to set up a common approach to certification.

This paper argues for the use of landmarks (for example, traffic lights, churches, petrol stations) within the turn-by-turn visual and voice directions given by in-vehicle navigation systems. Such prominent features of the driving environment are consistent with basic human navigational strategies, are valued by drivers, and have been shown significantly to improve the usability of electronic in-car navigational aids. For future systems actively to include such information, it is critical that (a) only ‘good’ landmarks are used, (b) such landmarks are presented to the driver in the most appropriate way, and (c) the practical needs of industry are fully accounted for.

One approach to increasing the area coverage of small-screen map displays is to exploit the ‘elasticity’ of the electronic display through use of non-linear scaling. Although resolution is necessarily lost in areas of smaller scale, bitmap images lose important information when re- scaled. This can render features unrecognisable and text unreadable. Vector maps are more tolerant to non-linear scaling because critical position information found in vertices of lines is distorted without being lost. Examples of non-linear scaling are presented to demonstrate the effect on bitmap and vector images. Ongoing research examining the user performance benefits of non-linear displays is also described.

Conventional cruise control systems fulfil the function of automatic speed control. A desired speed is selected by the driver, and a control system operates on the throttle to maintain this desired speed. When traffic density is moderate or high, the driver is faced with having to adjust the set speed regularly in order to maintain a comfortable distance from preceding vehicles and will frequently have to brake, disengaging the cruise control. Thus conventional cruise control can become a source of irritation when used in moderate or heavy traffic. If a distance sensor is added to a conventional cruise control system, then it is possible to add distance keeping to the basic speed control function. This forms the basis for adaptive cruise control, which can be further improved if a limited authority braking system is incorporated. Use can then be made of both throttle and brake actuators to control the distance and relative velocities between a vehicle and a preceding target vehicle.

This paper presents a novel approach to computing minimum-time paths based on a technique originally developed for use in geophysics. The technique is based on a finite difference scheme and is quite efficient in terms of both computing effort and storage. A particular strength of the technique is that it provides optimal paths to all locations in the field, thus being useful in situations where the goal is not known at the outset of the search. Details are presented on the basic technique and extensions are derived to include the integrations of resources (such as fuel store), and to provide flexibility in the objective. Two examples are given: minimum-time planning for vehicles under the influence of drift, and planning to minimise the risk of detection for a stealthy vehicle in the presence of threats.

This paper is based on the results of the ‘GNSS Support Task’ study for the European Commission, DGXIII. It summarises the results of the cost benefit analysis in terms of coverage, accuracy and safety requirements for different types of user and describes the most cost-effective GNSS 2 architecture. These analyses also assume that the overall system is layered into wide area, regional and local systems. The future planning of satellite navigation is essentially driven by the wide area requirements and ensuring that these are global and seamless. There is some flexibility in coverage and accuracy for a wide area system in that it can be augmented regionally or locally if required, but it must provide the highest level of safety required. The paper approaches the architecture for a future navigation system from this safety aspect. An analysis of the chosen architecture shows that the required safety performance can be met. An implementation plan is described which allows a gradual evolution from the first system to be realized for safety critical operations to a fully civilian owned and operated system.