Abstract:
In an automotive vehicle a road map is displayed that features an indicator of the actual vehicle orientation and position. Such orientation and position are on a long term basis maintained steady with respect to a display field. In particular, a geographical window is set up regarding actual movements of the vehicle. It is checked whether the vehicle remains inside or outside of the window. If inside, the movements are displayed while at least partially suppressing the maintaining. If outside, the movements are displayed while substantially upholding such maintaining.

Description:
CLAIM FOR PRIORITY A 1   
     This application claims priority to Application No. EP 01103318.0 which was published in the English language on Feb. 13, 2001. 
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a method for an automotive vehicle to display a road map, and in particular, to display a road map that features an instantaneous signal of the actual vehicle orientation and position while maintaining the orientation and position on a long term basis steady with respect to a display field. 
     BACKGROUND OF THE INVENTION 
     Standard vehicle navigation systems typically include an arrangement for a map that will display various aspects of a planned route, such as a complete or partial road network in a region around the actual position of the vehicle. These same systems typically highlight the route that is to be followed according to the planning by the system. An elementary display system will display the map in a stationary manner, for example, indication north in the “up” direction. A more advanced system may include a dynamic display, wherein the direction instantaneously followed by the vehicle will always be in the “up” direction. 
     Under normal driving conditions the display of the vehicle in the “up” direction will cause far too many rotations of the map. This will even apply when a certain averaging is effected of the instantaneous curves that are being followed. In the case of the vehicle following a route that is partially curved, but on the whole more or less straight, many of the rotations are superfluous and distracting to the driver. The above problem will likewise occur when the route being followed is displayed, without a route planning feature being present or active. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to restrict the amount and/or number of rotations in displaying a map to prevent distracting the driver and or detracting his attention from other incidents that could warrant immediate action. 
     According to one embodiment of the invention, there is a method for setting up a geographical window regarding actual movements of the vehicle, and checking whether the vehicle remains inside or outside the window. If the vehicle remains inside the window, displaying the movements while at least partially suppressing the orientation. If outside the window, displaying the movements while substantially upholding the orientation. Such will allow for a more pleasant display mode that will nevertheless present a user with adequate and easy-to-understand information regarding the vehicle position, and as such will improve the ergonomic performance of the display subsystem. 
     In a preferred embodiment of the invention, the window has a first angular size. Small changes in the orientation or heading of the vehicle will cause little necessity for changing the display. 
     In another preferred embodiment of the invention, the window has a first smaller angular size wherein maintaining the orientation is fully suppressed, and a second larger angular size wherein maintaining the orientation is temporarily attenuated. Such temporarily attenuating may imply a low-pass filtering of the changes, or generally, various operations to be executed in the time domain. 
     Alternatively, the temporarily attenuating may imply a full suppressing of the angular change during a predetermined period of time, but thereafter allowing a filtered change of the map orientation. 
     Advantageously, such window has a first linear size. Small movements in the position of the vehicle will cause little necessity for changing the display. 
     Preferably, such window has a first smaller linear size wherein maintaining the position is fully suppressed, and a second larger angular size wherein maintaining the position is temporarily attenuated. Such temporarily attenuating may again imply a low-pass filtering of the changes, or generally, various operations to be executed in the time domain. Again, the temporary attenuating may alternatively imply a full suppressing of the linear change during a predetermined period of time, but thereafter allowing a filtered change of the map position. 
     In another preferred embodiment of the invention, the method includes determining long-term values for shift and rotation of the vehicle position with respect to a geography, effecting such maintaining with respect to such long-term values, while suppressing the maintaining with respect to discrepancies between actual vehicle position and orientation with respect to such long-term values. This invention will under various circumstances produce a computationally and/or ergonomically superior solution. 
     Another embodiment of the invention relates to a vehicle route display system arranged for implementing a method for displaying, in an automotive vehicle, a road map including actual vehicle orientation and position which on a long term basis are maintained steady and on a short time basis selectively maintained under control of checking vehicle movements versus a window, and to a vehicle provided with such route display system. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     These and further aspects and advantages of the invention will be discussed more in detail hereinafter with reference to the disclosure of preferred embodiments, and in particular with reference to the appended Figures that show: 
     FIG. 1 is an exemplary functional block diagram of a navigation system. 
     FIG. 2 is an exemplary block diagram linking the navigation system to the map display. 
     FIG. 3 is a detailed map display with travelling display of the vehicle position. 
     FIG. 4 is an embodiment of the angular control limits. 
     FIG. 5 is an embodiment of the spatial control limits. 
     FIG. 6 is a flow chart of the control operation. 
     FIG. 7 is another exemplary flow chart of the control operation. 
     FIG. 8 is an exemplary diagram of a vehicle route subjected to an averaging operation. 
     FIG. 9 is an exemplary diagram of the vehicle angular position subjected to an averaging operation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a functional block diagram of a vehicle navigation system. Item  20  represents various absolute or relative position sensors, that may be based on roadside beacons, wheel sensors, GPS, etc. The input signals received will allow subsystem  24  to calculate an actual position and orientation of the vehicle. Block  22  has a map database that is accessed by microcontroller  26  which also receives the actual vehicle position data from subsystem  24 . 
     Through matching the position with the map, an on-map position with regard to a road will result, together with an actual direction of the vehicle in one of the two directions along that road. In principle, off-road positions are feasible, but such will be ignored hereinafter as not being fundamental to the present invention. Optionally, block  26  may include a vehicle guidance organization, through providing a calculated route to a destination, or including suggestions such as regarding instantaneous adversities connected with certain routes or parts thereof. The road map together with the instantaneous position of the vehicle will now be displayed on display  28 . 
     FIG. 2 illustrates a block diagram linking the navigation system to the map display. External data  20  will yield an actual position in block  24  (same numerals as in FIG.  1 ). User request input  30  together with actual position will allow navigation control in block  32  to calculate a target route. This will provide information to display controller  34  that also receives actual position and orientation from block  24 . Display field  36  is generally rectangular, although this is not a restriction, and displays the target route as an uninterrupted line  42 , together with a representation of the instantaneous position and orientation of the vehicle  38 . Generally, this will have some orientation indicator in the form of an arrow or the like. 
     Additionally, relevant roads have been indicated in the form of interrupted lines  40 , but other types of relative highlighting of certain roads with respect to others are equally feasible. The whole system is arranged within a motor vehicle that has been succinctly indicated by the corners  44  of a rectangle. 
     Prior art systems will typically display the vehicle position and orientation always in the same manner. Without express or implied limitation, the display has an upward orientation, and the position is at some 40% from the bottom, although other values are feasible. It should be clear, in particular when considering FIG. 3 hereinafter, that maintaining the vehicle in the same screen position often leads to many large and instantaneous jumps in the display, which can be distracting to the viewer. This also applies when the vehicle motion id subjected to time-based filtering for suppressing high-frequency components thereof. 
     FIG. 3 illustrates a detailed map display with a travelling representation of the vehicle position, according to the target route displayed in FIG. 2, but maintains the display field in a fully stationary position. Doing such would on a small scale be acceptable, but on a large scale is not. Moreover, there are two aspects of the maintaining: firstly, keeping the map position stationary, and secondly, keeping the map orientation stationary, but shifting the map position. In many cases map shifting is allowable, but maintaining the map orientation is not necessary. In fact, in most cases the coordinates of the vehicle on the map scale would change quite slowly, whereas the orientation may readily change by 90° within a second. Accordingly, the preferred embodiment of the present invention is to let the map shift more or less exactly according to the position of the vehicle, while partially suppressing the rotations. 
     FIG. 4 illustrates an embodiment of the angular control limits for use with effecting such suppressing. The actual instantaneous direction of motion of the vehicle has been indicated by line  54 . There is a first range of small changes in the orientation of the vehicle given by angle  50 , which in this case is +/−30°. Furthermore, there is a second range of larger changes in the orientation of the vehicle given by angle  52 , which in this case is +/−45°. 
     FIG. 5 likewise illustrates an embodiment of the spatial control limits. The actual instantaneous direction of motion has again been indicated by line  54 . There is a first range of small changes in the position of the vehicle given by circle  56 . The size of this circle may correspond to an average distance covered by the vehicle in ½ minute, such as 800 meters on a highway. The size of the circular window may even be controlled by the average vehicle speed during the last few minutes. Furthermore, there is a second range of larger changes in the position of the vehicle given by circle  58 , which in this embodiment is twice as large as circle  56 . Another possible shape for these windows may be square instead of circular. 
     FIG. 6 illustrates a first flow chart of the display control operation. In block  60 , the operation starts and necessary hardware and software facilities are assigned. In block  62 , the actual position and heading of the vehicle are determined. In block  64 , the system checks whether the vehicle is outside region  56  of FIG. 5, as relative to the last time when such had been determined. Of course, initially the answer is no, whereupon the system goes to block  74 , wherein the map display is shifted so as to represent the changing position of the vehicle. If yes, in block  68 , the system determines whether the vehicle heading has only changed within small angle  50  in FIG.  5 . If no, in block  68 , the system in block  66  determines whether the vehicle has been in region  58  long enough, such as for longer than one minute. If yes, however, the system still goes to block  74 . If yes, the system goes to block  70 . In block  70 , the system determines whether the vehicle has been within angle  52  long enough, such as for longer than one half minute. If no, the system still goes to block  74 . If yes, however, the system goes to block  72 , wherein, next to the shifting of the map, also the rotating of the map will be in principle allowed. This will also set new boundaries for the windows regarding angles and position. After updating of the map display, the system will return to block  62  for executing a next turn of the loop. If necessary, a certain waiting time may be implemented for each turn of the loop. 
     The logic of the decisions in FIG. 6 may be amended to some extent. For example, blocks  66  and  68  may be arranged in an OR-fashion, so that one of the two give an output to the left for controlling a transition to block  72 . The same may be valid for the two blocks  64  and  68 , so that one of the two give an “outside” answer for controlling a transition to the associated block  66 ,  70 , respectively. 
     The arrangement in FIG. 6 has been simplified, such as by not showing terminating of the operation, such as when the vehicle power is shut off. Furthermore, the arrangement of FIG. 6 has been set up with the understanding that an excess of the vehicle movement outside angle  52  or outside region  58  will immediately control a transition to block  72 . 
     FIG. 7 illustrates another flow chart of the control operation. Herein, the abbreviation CCP means Current Car Position indicator. In block  80 , the procedure ergonomically optimum map/CCP movement and rotation is started. In block  82 , the local positional average of the route is calculated. In a more sophisticated embodiment, this will also include the anticipated route. Next, in block  84 , the local heading average of the route is calculated. In a more sophisticated embodiment, this will also include the anticipated route. The anticipation may be extrapolated from actual position of the vehicle. 
     Another implementation would include such anticipation on the basis of the planned route that has been presented to the driver based on the driver&#39;s request for route planning and/or other data. Next, in block  86 , the map is moved and rotated according to the positional average S and the heading average 0(s), wherein s is the instantaneous position. Finally, in block  88 , the indicator CCP is moved and rotated according to the difference between the actual position s and positional average S, and also, according to the difference between the actual heading (p(s) and the heading average (D(s). Subsequently, the system returns to block  82 . 
     FIG. 8 illustrates a diagram of a vehicle route subjected to an averaging operation. This usually implies that a more smooth curve (interrupted line) is derived from a route that is built up from often straight sections. 
     FIG. 9 illustrates a diagram of the vehicle angular position subjected to an averaging operation. This may again imply that a smoother curve (interrupted line) is derived from a route which is built up from often straight sections. 
     Various further advantageous features of the invention and its embodiments would include the following. Long-term shifts and rotations of the vehicle position that have similar character, such as those that are more or less in the same direction, will be represented by moving the map, whereas differential shifts and rotations will be represented by moving the symbol used for the vehicle. This may be implemented by calculating a running average of position and orientation of the vehicle. The average is represented by the movements of the map. The discrepancy between actual values and average is represented by differences between the vehicle symbol position and orientation and the map representation. 
     The intervals for determining the average position may be set, either by the user, or by the system. An example for the setting by the system may be relative to the size of the actual map which itself may depend on the type of route that is being followed and/or the remaining distance to the destination. The average may for example be 20% of the map height. The interval for calculating the average value may be based both on the route that will be followed, as well as on the route that has been followed already. If there is no planned route available, the averaging goes until the next route point where a splitting is present. In the above cases the route axis has developed to a fixed average curve. 
     The map orientation may be changed smoothly or seamless. On the other hand, the rotation may be executed in a step-wise manner as well. In that case, the steps will be subjected to an upper bound. If a larger step were necessary, it will be executed in successive smaller steps that are separated in time, such as by a fixed time interval of e.g., 3 seconds. The result of the invention will generally be a quieter overall image, wherein the map will execute smooth motions, whereas the vehicle symbol will execute differential movements and rotations. 
     A further advantage is to maintain the vehicle symbol in a restricted region of the display, such as in the lower third of the display field, thereby keeping the main part of the map display in front of the vehicle. 
     While the above described embodiments of the invention are the preferred ones, it is apparent to those skilled in the art that many other changes and modifications may be made, without departing from the invention in its broader aspects. Therefore the intentions of the claims is to cover such changes and modifications, falling within the true spirit and scope of the invention.