Process for selecting the traffic information transmitted by a traffic information center which concerns a route of a vehicle equipped with a terminal in a road network

A suitable selection of information sent by a central traffic station with respect to its relevance for a route of a vehicle with a terminal unit through the traffic network is made possible by a terminal unit and by a process for the selection of traffic information which is relevant to a route of a vehicle in a traffic network, which vehicle has a terminal unit, and which is transmitted by a central station. The route is determined in the form of path points between a starting point and a destination in the traffic network. A zone is defined for the selection of relevant traffic information between two path points. Traffic information concerning a location in the zone is selected as relevant, while traffic information concerning a location outside of the zone is defined as irrelevant.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention is directed to a process for selecting traffic information
 which concerns a route of a vehicle with a terminal unit in a traffic
 network and which is transmitted by a central station and further is
 directed to a terminal unit and a central station for carrying out the
 process.
 2. Discussion of the Prior Art
 A route through the traffic network from a desired starting location to a
 desired target location can be determined for a vehicle with a terminal
 unit in a central traffic station based on distances and current traffic
 information such as traffic backups, etc. and transmitted to the terminal
 unit. It is also possible to determine in the terminal unit a route
 between a desired starting point and an end point in the traffic network.
 In particular, traffic information concerning a location at a great
 distance from the current location is of secondary importance for the
 decision about updating a route. When a complete map of the traveled
 traffic network is contained in the terminal unit, it is possible for
 traffic information sent from the central traffic station and received in
 the terminal unit to be allocated to determined roads or cities, etc. In
 the absence of a complete digital map of the traveled traffic network, it
 is not possible for roads to which traffic information relates to be
 identified in the terminal unit for a relevance check for the current
 route.
 SUMMARY OF THE INVENTION
 It is the object of the present invention to enable the simplest and most
 efficient possible relevance check of traffic information taking into
 account a route through the traffic network which is traveled by the
 vehicle with a terminal unit.
 The process according to the invention for selecting traffic information
 (such as information regarding backed-up traffic, traffic volume, travel
 times) which concerns a route of a vehicle with a terminal unit in a
 traffic network and which is transmitted by a central station enables a
 simple, efficient and error-proof allocation of received traffic
 information, including a relevance check with respect to the traveled
 route, even in the absence of a digital map of the traffic network or when
 the digital map is incomplete. The definition of a zone, especially a
 corridor, between two path points of a route defined by path points
 enables a continuously suitable selection of traffic information along the
 route. Selected traffic information can be displayed particularly to the
 user of the terminal unit optically and/or acoustically so that the user
 is spared insignificant traffic information. Further, traffic information
 which is selected as important for the route can be used to judge the need
 for a recalculation of the route, which is substantially more favorable
 with respect to telecommunications costs than continuous interactive
 communication between the terminal unit and the central traffic station as
 regards route recalculation. A route recalculation can be carried out in a
 central traffic station, which has the advantage that current traffic
 information is locally allocated and incorporated in an optimum manner in
 the central traffic station with extensive calculating effort and that a
 very detailed map of the traffic network is required only in the central
 traffic station. A route recalculation can also be carried out in the
 terminal unit, which enables greater autarky.
 One zone is advisably defined between every two successive path points of
 the entire route.
 Zones, especially corridors, are advisably defined in the terminal unit
 based on the path points of the suggested route which are transmitted with
 their geographic positions (especially geographic longitude and latitude
 rounded off in a predetermined manner).
 The zone between two path points is advisably defined as a corridor between
 two straight lines which extend parallel to a connection line (especially
 a straight line) between every two path points at a predetermined or
 predeterminable distance from the connection line. A zone of this kind can
 easily be calculated in particular in the terminal unit and makes it
 possible to check in a simple manner whether or not transmitted traffic
 information is in this zone. There is accordingly a roughly rectangular
 partial corridor between two path points.
 According to one embodiment of the invention, the spacing of the two
 parallel lines relative to the connection line between every two path
 points remains unchanged. This enables a simple calculation. Further, it
 is possible to increase the spacing as the distance from the current
 location increases in order to take into account the fact that, at a great
 distance, traffic information about locations at a greater distance from
 the route can be significant up to the point that the vehicle has moved
 ahead to these locations because backups, etc. can propagate up to the
 route during the travel period.
 The transmission of traffic information such as traffic backup reports,
 average speeds, travel times, accidents, etc. from the central traffic
 station to the terminal unit is advisably carried out with a designation
 of the road, roads, road sections, cities, etc. to which the traffic
 information relates. Alternatively, or in addition, it is advantageous to
 indicate location for traffic information in particular as geographic
 longitude and latitude of the location or locations to which the traffic
 information relates.
 The transmission of traffic information and/or route data and/or an inquiry
 from the terminal unit to the central traffic station concerning a new
 calculation of the route is advisably carried out by radio, especially
 mobile radio.
 The route information defining path points of a route is advisably
 transmitted from the central station to the terminal unit by radio,
 especially by mobile radio, in the case of route calculation in the
 central station. Traffic information for the traffic situation can be
 transmitted by radio; it can also be transmitted in particular by mobile
 radio, especially as a mobile radio short message (GSM SMS). Traffic
 information can also be sent in a locally limited manner in particular,
 for example, in locally defined GSM SMS pages.
 Further features and advantages of the invention follow from the
 description of an embodiment example with reference to the drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 A user of a terminal unit in a vehicle enters the starting point and the
 destination of his trip into the terminal unit. The terminal unit
 transmits the starting point and end point to a central traffic station,
 not shown. The central traffic station determines a route for the vehicle
 through the traffic network for the starting point and destination (i.e.,
 end point), wherein traffic information concerning backups, accident
 scenes, detours, travel speeds, traffic volume, etc. are taken into
 account in the central traffic station. The calculated route is
 transmitted from the central traffic station to the vehicle through route
 information which defines path points along the route. In particular, path
 points can be defined where a road along a route changes its name because
 of a turn-off, renamed road, etc. This is especially advantageous for a
 terminal unit without a digital map of the traffic network. A route is
 accordingly given as a chain of path points between the starting point and
 the destination of the desired journey through the traffic network. In
 particular, the name of the road to be traveled between two path points
 can be transmitted from the central station to the terminal unit for route
 information defining the path points of the route. Alternatively, or in
 addition, geographic information on a respective path point, especially
 its geographic longitude and latitude rounded off to a given length can be
 transmitted. While traveling along the route, a driver receives traffic
 information by radio and/or mobile radio from the central traffic station,
 especially regarding backups, etc. This traffic information can be
 displayed to the driver and/or used as a basis for a decision about a
 recalculation of a route due to backed-up traffic, etc. The traffic
 information sent by the central station is selected in the terminal unit
 in order to prevent the driver from being unnecessarily burdened with
 traffic information which is definitely irrelevant based on the driver's
 route.
 FIG. 1 shows two path points W and W' which define a partial segment of the
 route of the vehicle through the traffic network. A straight line G is
 drawn between these two path points W and W'. Traffic information
 concerning a point P whose distance from the straight line G lies above a
 predetermined or predeterminable limit is selected as irrelevant; traffic
 information about a location P whose distance from the straight line G
 lies below a predetermined limit is selected as relevant, whereupon it is
 displayed to the user or can form the basis for a decision about a route
 recalculation, for example.
 FIG. 1 shows traffic information (about a location P) whose distance from
 the straight line G lies above a limit of x/2 meter so that the traffic
 information relating to point P is selected as irrelevant. In the example
 shown in FIG. 2, the traffic information relates to a location P whose
 distance from the straight line G lies below a limit, that is, is at a
 distance below x/2 meters, so that the traffic information is selected as
 relevant.
 The distance of point P from the straight line G can be determined in
 particular based on geographic coordinates of W, W', P.
 Since, in the example shown in FIGS. 1 and 2, the criterion for the
 decision about the relevance of traffic information for the route is the
 distance from a straight line between two path points W and W', the zone
 in which traffic information is relevant is, this case, roughly a
 rectangle which is defined by two parallel lines Z1 and Z2 relative to the
 straight line G between the two path points W, W' (and by lines orthogonal
 to G through path points W, W'). Since additional path points for the
 suggested route are located to the left and to the right of W and W' in
 FIGS. 1, 2, there results for the route as a whole a corridor along the
 suggested route as a zone within which traffic information is relevant.
 The suggested route extends between path points W and W' along line R in
 FIGS. 1 and 2; the curvature of the partial route R is caused by the
 curves of a road, etc.
 The invention can be implemented in a terminal unit and/or in a central
 station especially as a program. In particular, program parts for the
 selection of traffic information which relates to a zone between two path
 points are to be implemented in the terminal unit. An arrangement as
 electronic circuit is also possible.