Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2001-02-28
2002-07-09
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S210000, C701S213000
Reexamination Certificate
active
06418375
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of routing using a motor vehicle navigation system.
Navigation systems are increasingly being supplied for new vehicles or as retrofitted systems. In this context, a distinction is drawn between so-called onboard and offboard navigation systems. Onboard navigation systems are largely autonomous systems in which digital road map data are carried in the vehicle for route calculation, and the route calculation itself is also carried out by the control unit in the navigation system. In contrast to this, offboard navigation systems have no memory element for extensive road map data. Instead, in these systems, the route planning request is transmitted to a central station which stores the digital road map. Parts of the digital road map can then be transmitted to the motor vehicle and routing can be effected there, or the route calculation is performed in the central station and road points are transmitted to the vehicle with routing instructions. In this context, transmission usually takes place over a mobile radio link, but beacon systems are also known.
DE 195 44 157 C2 discloses a method of reliable routing for a vehicle, in which a route in the form of successive road points is determined and is indicated to the driver of the vehicle in the form of driving instructions. In this method, the position is ascertained in the vehicle using signals from a satellite navigation system (e.g., GPS system), and a comparison is continually made between the distance from the current position to the road point which the vehicle will pass next on its route and a prescribed minimum value. Detection of the position by a satellite navigation system is currently possible only with a limited degree of accuracy, however. This means that uncertainties arise with regard to the approach to the next road point. Although determination of the position by means of GPS navigation can be improved using DGPS systems, this is a complex method. In addition, in the method disclosed in DE 195 44 157 C2, comparison of the distance as the crow flies between the current position of the vehicle and the next road point on the basis of the specific route is sometimes very inaccurate, e.g., on mountain roads with many bends.
EP 0 674 007 B1 discloses a vehicle navigation system in which the digital road map data is carried in the vehicle itself. The road map data is stored in simplified form as nodes, with nodes which are connected to one another by real roads additionally having the distance between these nodes stored for them. The exact road shape, as is otherwise usually available in the road map data in onboard navigation systems, cannot be reconstructed in this case, but the memory requirement is significantly reduced.
SUMMARY OF THE INVENTION
It is an object of the invention to specify a method of routing using a motor vehicle navigation system which both requires only a small volume of data to be transmitted to the motor vehicle and at the same time ensures that driving instructions are output accurately for the position.
The object is achieved by a method of routing using a navigation system which contains, in the vehicle, a control unit and also an input unit and output unit which are connected to the control unit, an odometer and also a communication appliance for communicating with a central station which is located outside the vehicle and contains a digital road map, where
a starting point and a destination are used to calculate a route using the data of the digital road map,
characteristic road points, at which there is a road junction, and also the road distance between adjacent characteristic road points on the route are stored in a memory element in the vehicle,
on reaching a characteristic road point, a distance comparison between the distance from the road point reached to the next road point and the distance traveled from the road point reached is started, and then
the distance from the last road point reached is continually ascertained by the odometer in the vehicle, and the distance ascertained in this manner is compared with the stored distance between the last road point reached and the next road point on the route, and also
if a minimum value for the distance from the next road point has not been reached, a driving instruction is output.
The method according to the invention is thus based on a navigation system in which no digital road map is required in the vehicle itself. A digital road map is located in a central station, and the central station may be one which can be accessed by a multiplicity of motor vehicle drivers or may be a home PC (personal computer) with a route planning program. In the central station, the starting point and the destination are used to calculate a route using the data of the digital road map. The result of this route calculation is a list containing characteristic road points, at which there is a road junction, and the respective road distance between adjacent characteristic road points on the calculated route. Information about the exact shape of the road between the characteristic road points is not required. The characteristic road points are stored, together with the associated road distances, in a memory element in the navigation system in the vehicle. To determine the distance from the next characteristic road point, the distance covered since the last characteristic road point is compared with the stored distance between the last road point and the next road point. If this establishes that the distance of the vehicle from a next road point has reached a prescribed minimum value, then the next driving instruction is output.
The method according to the invention thus firstly requires only a very small volume of data needing to be transmitted to the vehicle and, for position finding during the journey, can do without a satellite navigation system. Instead, the position of the vehicle in relation to the next road point is determined preferably merely using the values from the odometer and from the comparison with the stored road distance.
The volume of data to be transmitted to the vehicle can be reduced still further if not all the road points on the route at which there is a road junction are transmitted to the vehicle, but only those road points which are turnoff points on the calculated route. Hence, in this embodiment, those road points at which, although there is a road junction, the calculated route carries straight on are not transmitted to the vehicle. In this case, the volume of data can be significantly reduced particularly in urban areas with a very large number of minor roads branching off from a main road.
In a further preferred embodiment, the distance from the next turnoff point is output in the vehicle. This information can actually be output immediately after a turnoff maneuver has been completed and can thus actually indicate the distance from the next turnoff point in good time. Such a method is advantageous particularly if the individual turnoff points are relatively far apart. In this case, the indication of the distance can signal to the driver that another turnoff point is not to be expected in the near future. This is conducive to more relaxed driving.
The route may, for example, be calculated on the home PC, and data are simply transmitted to the vehicle.
In one specific embodiment, the starting point and the destination are transmitted from the vehicle to the central station, the route is calculated outside the vehicle and the characteristic road points are subsequently transmitted to the vehicle. A particular preference in this context is an inherently known mobile radio link to a central station. In this case, the starting point as well as the destination can be selected from a list by the vehicle driver directly in the vehicle.
In an alternative embodiment to this, the starting point is determined by satellite navigation. This also allows the method to be used whenever the driver does not know his exact starting position. Although satellite navigation can also be used in a
Leimbach Jürgen
Tiede Lutz
Camby Richard M.
Mannesmann VDO AG
Mayer Brown Rowe & Maw
Thimmig David M.
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