Abstract
Location referencing is a traffic telematics technology to reference real-world objects (locations) between different systems (provider, end user) in a machine-readable way. Conventional location referencing as applied in RDS-TMC uses pre-coding of locations, and storage of the location codes and related information in so-called location tables. Disadvantages are the costs of creation, maintenance and dissemination of these tables, and the limited number of locations that can be addressed. In addition, for navigation systems (that actually brought the success for TMC) the codes need to be incorporated in the map database, which further increases creation and maintenance costs.
An alternative for map-based systems (on both ends of the service chain) that overcomes the disadvantages of pre-coding, is so-called on-the-fly location referencing. On-the-fly means that a location reference (a code) is created, when needed, in the map database of the sending system, incorporated in a message, decoded by the receiving system using its local map database, and discarded. Key is that the map databases of the sending and receiving systems may be of different origin and specification, but should be of comparable detail. A further key requirement yet difficult to achieve is that the method should be robust.
On-the-fly location referencing will be a key technology for many future applications in the fast developing world of telematics and multimedia, in the first place for traffic information services and traffic management applications (on both the data collection and distribution sides), but also for the emergency and other position dependent services that are a centre of current attention.
The paper describes the AGORA method for on-the-fly location referencing. It is based on a fusion of the best of three different underlying approaches, and combines matching of geometry, the comparison of name information and other attributes, and the topology of the network. AGORA provides a flexible coding scheme, based on a high level data model, and its translation into a more operational set of mandatory encoding rules and optional guidelines. Although focussed on the construction of an algorithm for encoding, these also provide the basis for a decoding algorithm, which however may be tailored to the specific application for which it is designed.
The EU funded AGORA project is currently implementing the method for testing and demonstration in applications on both sides of the service chain (encoding and decoding). Especially the implementation at the navigation system side is, due to the special physical storage format of the map database on the CD, and the limitations in computational power in the navigation system, a major challenge for the project.