Device and method for determining the position of another road user

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and device for determining the position of another road user.

[0003] 2. Description of Related Art

[0004] Driver assistance systems make it easier for the driver of a motor vehicle to detect hazardous situations, among other things. Assessing a threat based on other oncoming, passing vehicles appearing on the side requires a reliable determination of the distance to the particular other vehicle.

[0005] A method for determining the distance to other vehicles with the aid of two cameras and triangulation is known from published German patent document DE 102 19 788 C1. Accuracy in determining a distance by triangulation decreases hyperbolically as the distance increases.

[0006] The method according to the present invention is used to determine the position of another road user. The following steps are carried out for this purpose: The position of a road user is determined with the aid of a position detection unit. A distance of the road user to the other road user is estimated with the aid of a distance sensor. The position of the other road user is determined on the basis of the position of the road user, the estimated distance, and a road map, the other road user being assumed to be located in a road area predefined by the road map.

[0007] The information from the road map is used for adjusting the information from the distance estimate. This may increase the accuracy of the distance determination.

[0008] For the purpose of this application, the road area is not understood to be limited to an ordinary road. Instead, a road area includes the usual locations where one can expect to find a moving or stopped road user, in particular a motor vehicle.

[0009] According to the present invention, a device for determining the position includes a position detection unit for determining the position of a road user; a distance sensor for estimating a distance of the road user to another road user; and an evaluation unit for determining the position of the other road user on the basis of the position of the road user, the estimated distance, and a road map, the other road user being assumed to be located in a road area.

[0013] Optical camera-based methods for determining a distance record a traffic situation from two different directions. In a simple configuration, two cameras 1, 2 are provided for this purpose (FIG. 1). The two cameras 1, 2 record two different images of a road user. The distance of the road user to the cameras establishes the relative displacement of the road user's representation in the two different images. The distance may be determined from the displacement according to the principles of triangulation.

[0014] The greater the distance of the road user from the cameras, the smaller the relative displacement in the images. The distance is approximately in reverse proportion to the distance in the images. It can be inferred therefrom that an error in determining the distance increases as the distance increases.

[0015] The cameras have a limited spatial resolution. This may be caused, among other things, by the grid pattern of a CCD sensor. The distance to two road users may no longer be discerned if the road users undergo the same displacement in the particular images in the grid pattern of the sensor. By way of illustration, areas 3 for distances 4, which are not distinguishable by a stereoscopic camera system, are drawn in FIG. 1.

[0016] FIG. 2 shows a device for determining the position of another road user according to am example embodiment in the form of a block diagram. The device includes two cameras 10, 11, a triangulation evaluation unit 12, a position detection unit 13, a data memory 14 having stored road maps, and an evaluation unit 15.

[0017] The two cameras 10, 11 and triangulation evaluation unit 12 estimate the distance to another road user. According to the example embodiment, more than two cameras may be used to increase the resolution. Individual example embodiments use a single camera, which records images from two different directions simultaneously or delayed.

[0018] Other optical distance sensors may also be used instead of cameras. Among other things, this includes radar sensors, which may enable a distance to be determined by measuring the propagation time as well as by using an angle-resolved distance measurement.

[0019] In addition to the distance, triangulation evaluation unit 12 may also determine the direction or only the direction in relation to another road user. The angle-resolved measurement may also be determined by triangulation.

[0020] Position detection unit 13 may be a navigation device of a vehicle. The navigation device may determine the position of the vehicle by using the GPS signal of the global positioning system.

[0021] Other position detection units record the route distance covered and changes in direction. For example, acceleration sensors are used for this purpose.

[0022] Further position detection units determine the position of the vehicle on the basis of route markings provided in the surrounding area. An example embodiment compares the determined position of the vehicle with road maps for plausibility.

[0023] The road maps provided in data memory 14 contain information about locations and the position alongside or on a road. They may also have information about road shoulders, entrances/on-ramps, exits/off-ramps, parking areas, pedestrian zones, bicycle paths, etc. The map material should contain position information for all locations where motor vehicles or other road users may be situated.

[0024] The map material may contain additional information which indicates the likelihood of a vehicle being present in the corresponding locations. Thus, the likelihood of encountering a motor vehicle is high on a road open to traffic, such as a highway, while the likelihood thereof is low on the shoulder or a sidewalk.

[0025] Evaluation unit 15 ascertains a possible position of the other road user from the estimated distance to the other road user and/or the estimated direction in relation to the other road user and the unit's own position.

[0026] On the basis of the stored road map, evaluation unit 15 determines the location which is closest to the possible position of the other road user and, at the same time, is on a road. A maximum likelihood estimate, a minimum value search of a distance vector, etc., may be used to establish locations of this type. The established location is output as a specific position of the other road user.

[0027] Evaluation unit 15 may be configured to take into account only specific locations where a vehicle is likely to be found. The configuration may be carried out, for example, automatically on the basis of the traffic situation. When driving on the highway, only the lane being traveled and the corresponding shoulder need to be taken into account, but not sidewalks, bicycle paths, or unpaved roads.

[0028] In a further embodiment, the type of the other road user is first ascertained. Based on the type of road user, only certain locations are taken into account. For a motor vehicle, the selection of location may be limited to roads open to traffic, shoulders, entrances/on-ramps, etc.

[0029] Another example embodiment takes into account the velocity of the other road user. Stopped vehicles are first expected only in the area in front of traffic lights, in parking areas and on shoulders, and these locations may therefore be excluded from the selection to be taken into account.

[0030] FIG. 3 shows an exemplary traffic situation. Vehicle 20 is located on a road 21. Another vehicle 22 is located on a side street 23.

[0031] Area 24 indicates the uncertainty with which the position of other vehicle 22 is determined solely on the basis of a triangulation measurement. The additional comparison using the map material in data memory 14 may reduce the uncertainty to area 25.