Vehicle Navigation Systems (VNS)

In connection with navigation in general and with respect to Vehicle Navigation Systems (VNS) in particular two components are to be mentioned: positioning on the one hand and route guidance on the other hand. In this respect it hardly makes a difference from the geodetic point of view, whether one is treating a vehicle navigation system as an autonomous on-board system, as a dispatching system for fleet management, as a routing system in the sense of a traffic information system, or as a so-called inventory system for GIS data acquisition. With respect to the interrelation between a VNS and a GIS, the digital road map (DRM), which is modelled on the basis of graph theory, plays an essential role. It is not only used as a tool for the visualization of the road network, but also plays an active part within a VNS: as far as location is concerned, the DRM is used for projecting the vehicle's trajectory, which is enabled by in-vehicle sensors and/or GPS, to the graph model through map matching or any other kind of geometric approach; regarding route guidance, the DRM serves as a basis for route planning and path description.