5. User Interface Issues

5.1 USING TRADITIONAL MAPS

Though the position obtained from paper and electronic maps and charts have been known for some time to differ from WGS 84, unless that is they have been surveyed to WGS84. The difference between the WGS 84 datum and that of the maps and charts in use are known to usually be less than 200 metres but have been reported to be as much as 7 miles for Islands in the Pacific Ocean, and even larger undiscovered differences may exist. Most maps and charts are not yet referred to WGS84 Datum. This means that, in those cases, positions obtained from satellite navigation receivers will not be directly compatible with the chart and must not be used without adjustment. Cartographic offices are attempting to refer as many new charts as possible to WGS84, but there remain many areas of the world where information does not exist to enable the transformation to be performed.

In most European areas the difference between the chart datum and WGS 84 datum are known. However, the shift correction provided is an average for the area of coverage of the chart and therefore may not be consistent with the shift correction of another chart covering part of the same area. This may result in the position plotted being slightly different.

Though many "manufacturers of GPS receivers are now incorporating datum transformations into their software which enable users to (apparently) receive positions referred to datums other than WGS84 Datum. Unfortunately, many cases exist where a single transformation will not be accurate for a large regional datum. For example, the relationship between WGS84 Datum and European Datum (1950) is very different between the north and south of the region, despite the datum name being the same. In the light of the 100 metre accuracy of the Standard Positioning Service of GPS this may not be significant, but it is an additional source of error and is of major significance if differential GPS (DGPS) is being used to obtain accuracies of just a few meters or better.

It must not be assumed that all charts in a region are referred to the regional datum. For example, although most metric charts of mainland European and waters are referred to European Datum (1950), many charts are also referred to local datums. Additionally, as there are no international standards defining the conversion parameters between different horizontal datums; the parameters used by the GPS and future GALILEO devices may be different.

Current positioning with DGPS is, usually more accurate than position-fixing used for surveys conducted before 1980. The consequence is that, although a user may know its position to an accuracy of better than 10 metres, the positions of objects in his vicinity may only be known to an accuracy of 20 metres or much worse, depending on the age of the latest survey. Unfortunately, it will be many years before all areas are re-surveyed and all maps and charts revised.

A satellite navigation receiver may output a position to a precision of three decimal places of a minute, but that does not mean that all its positions are accurate to 2 metres or that the resulting position is compatible with the positions of objects shown on modern charts (paper or digital) which may have been established 100 years ago and not surveyed since.

Now users are relying on equipment that relies on the use of specific radio-navigation services and their corresponding datum. Others are still evolving but in the future will enable remote control and integrated vehicle / traffic management. The first stepping stones in this new direction is where navigation information is directly input and used in a decision support role. This is for the first time will providing information that both the driver and infrastructure operator will depend on for decision support or autonomous control / direction. However, unless the issue is tackled could be based on differing datums and from services of different accuracies. Though not so important for users in remote situations, differences could lead to dangerous situations within geographically challenging and / or traffic congested areas.

This problem is not just restricted to paper charts, but also further frustrated by the possibility that horizontal datums and map and chart projections may differ between differing 2 and 3 dimensional GIS electronic chart standards.

Due to the emergence of ever more applications where navigation, guidance or position information originating from GNSS is a major factor for the performance of safety critical decision support tools, we have to be aware and avoid the real risk to safety caused by differences in local maps and charts, WGS 84 and 2D & 3D Geographic Information Systems. Action will be required to ensure the provision of tools, services and policy direction:-

1. to provide the user with the information to reduce or negate altogether errors and discrepancies due to differences between the geodetic datum of the positioning system used for navigation and that provided by the radio-navigation service (including augmentation and datum selection) so that it corresponds to the actual maps and chart in use and informs others with information they require to plot the position with the datum in use by them;
2. to provide information that enables the user to plot the position of all other users within an envelope of interest by their position from any number of sources with those derived from Satellite according to the datum selected (may be the wrong datum), geographic o-ordinate, by the other users, and from third parties;
3. to quantify the scale and scope of the problem related to differing datums and out of date surveys and then seek a co-ordinated action by EU member states, to resolve the problem by a programme that will range from the provision of linear and non linear transformation formulae to the re-survey of all land and sea areas that are not compatible with WGS 84. Further co-operation will need to be sought from the united nations for the conduct of surveys in areas outside Europe, particularly where no organisation has responsibility, or have insufficient resources. Many of these area have not been surveyed for 100 years or more, and some never "largely unexplored".

5.2 HUMAN INTERACTION

The New Age brings new demands for radio-navigation where there is a radical change in the type of users and types of uses of the information, such as autonomous control or control guidance for a number of processes of a safety critical nature including vehicle velocity. For some of these new uses, rather than deciding whether or not to use the information to assist in their decision making processes, users will have to decide when to stop autonomous control, so to make decisions based on other information, such as sight and sound. The new users will utilise the information in a number of business and leisure land-based applications. These are as diverse as driving vehicles to navigating whilst walking and cycling. The number of users will explode from a few hundreds of thousand then to many tens/hundreds of millions.

With the arrival of this new age, there is a need to have a new perspective on the future outlook for radio-navigation. Because of the diverse nature of the users of radio-navigation ranging from positioning satellites in orbit to walking in the countryside, and because of the emerging socio-economic cultural changes requiring more and more dependence on decision support systems to enhance environmental protection, safety and efficiency, there is a great appetite for tools that can offer greater precision and integrity for all manner of processes. Fortunately, with the huge numbers of new age users, it is now far easier to contemplate research into the application of new and emerging technologies where previously costs would be prohibitive for potential number of exploitable products.

Rather as in the past, future development looked at application specific scenarios for a few tens of thousand or less users or for those having a military role, there is need to look to application generic scenarios serving tens of millions of normal citizens who are engaged in a multitude of professional and leisure pursuits. Rather than looking only at the capabilities of a system such as GPS or the future GALILEO and setting user requirements within the parameters that can be offered, now industry can realistically look to other technologies that can enhance the vertical and horizontal accuracies of terrestrial and satellite based services, and therefore set the user requirements to a level offering optimum performance of the process or operation that they need to accomplish.

5.3 ERNP (EUROPEAN RADIO-NAVIGATION PLAN)

During the latter part of 2001 the European Commission DG TREN assembled member state representatives and nominated experts to set out the aims of European Radio-navigation Planning. Many individual member states have either presented or are under way in producing their own plans that will contribute to the ERNP, however at this stage it is still in its infancy, has still to be shaped before a clear way forward can be published. Though the maritime and air sector are well represented through the European Maritime Radio-navigation Forum and Eurocontrol, the road, rail and mobile / E112 communities are not.

It is clear that the plan will seek to achieve interoperability and use of generic technology to enable maximum fulfilment of cross sector requirements. It is also clear that the plan will evolve and not just be applicable for today, but seeks to address requirements for many years to come.

It has become evident that safety critical application should not rely on one radio-navigation service, and because Galileo and GPS could be vulnerable to spoofing or jamming and are both in the control of NATO countries that might require them to be unavailable for national security purposes, we need to have a terrestrial services that will continue to serve the community. LORAN at present is the only medium / long range service, It is available widely in the northern hemisphere, but is at present blighted by poor political direction. We should ensure that the service is not shut off in 2004 but continues and is extended to complete the SELS (Southern European LORAN Service) until a viable alternative emerges. GPRS (mobile telephone network) techniques are emerging in conjunction with E112 service, these could be used where coverage exists, but need to be interoperable with all service providers.

In the past for GNSS and GALILEO, working groups and forum such as the European Radio-navigation forum have considered the accuracy and integrity requirements in relation to the proposed services. The main emphasis now should be to identify all operations / process, that have a need of horizontal / vertical or velocity accuracy, their typical area of coverage required (Local, Regional and Global), and any the other parameters such as of safety critical nature needing enhanced integrity. This should be conducted along with other "mobility groups" to enable the European Radio-navigation plan to derive baseline standards for services and technologies that may service applications of all groups.

The output will determine non-safety critical applications that can rely on one source of radio-navigation service, those of a safety critical nature or having serious financial or environmental consequence and therefore require a secondary service or increased integrity. It will also identify applications that require enhanced services that can-not be catered for by normal terrestrial or satellite services and may require high precision within a restricted locality and therefore require complementary (interoperable) services originating from for example blue-tooth or psuedolites technology.

5.4 ISSUES RELATED TO GALILEO SOL (SAFETY OF LIFE) AND LBS (LOCATION BASED SERVICES)

At the time of this report being drafted (June 2002) a number of experts from all modalities have been called to assist in re-defining the Galileo "High level document" to be available for December 2002. Among many issues the following are of particular interest.

The GALILEO SOL was intended for use by the Aviation and Maritime community and is different from the open service by the inclusion of Integrity information. The opinion of experts now however is that integrity is only needed in congested areas which will normally be supplemented by local integrity and augmentation services. The result is that neither the maritime or air community are likely to need this Galileo SOL service. Though not originally considered, experts advised that main users of Galileo satellite derived integrity information would be users whose receiver information would be used in a process that was subject to regulation or insurance risk. This for example could include tracking and tracing, tolling and charging, and any application regulated by a member state or at a European Union level that could require integrity to enable pursuit of wrong doers or non-payers through legal routes.

Receivers for the open service offered to all communities free of charge, where not envisaged to need an authentication signal (this was reserved for the SOL service receivers). However, the opinion of experts is that because spoofing or jamming (more likely) could lead a user into danger, all open service Galileo receivers must be capable of receiving and decrypting a authentication signal.

The High-level document had not considered Local element services. The experts advised that though these services might not be under the control of the Galileo support structure, they should be considered within the context of Galileo due to the timing elements that would need to be provided, the need for base line standards for interoperability requiring a single responsible body and the perception of user community that though other organisation might be responsible for some local elements, the user looks to added value from Galileo over GPS for the overall service provision. Local element services will improve accuracy and integrity for users in a limited area to a much higher level than that provided by the space segment alone.

The Galileo SAR (Search and Rescue) only of real interest to the maritime community, if given the go ahead, will complement the existing Cospas-Sarsat service by enabling a quicker response (especially in the southern Hemisphere) and enabling communication back to the casualty via the Galileo space element which is currently not possible.

The Galileo Commercial service will also provide for communication of a small amount of data to users. As yet there has been no work directed at determining the type of information that could be made available.