CA1337825C - Vehicle location system on a map display - Google Patents
Vehicle location system on a map displayInfo
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- CA1337825C CA1337825C CA000616568A CA616568A CA1337825C CA 1337825 C CA1337825 C CA 1337825C CA 000616568 A CA000616568 A CA 000616568A CA 616568 A CA616568 A CA 616568A CA 1337825 C CA1337825 C CA 1337825C
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Abstract
There is disclosed an apparatus for displaying the constantly changing current location of a vehicle on a two-dimensional coordinate system while detecting the distance travelled by the vehicle and its direction of travel. The current location is displayed on a map on a display screen on the basis of computed data. The apparatus extracts a linear travel segment from the current location of the vehicle by storing data of the current location, extracts a linear road segment from adjoining roads on the map, which corresponds to the linear travel segment extracted from the current location, matches the extracted travel segment and linear road segment depending on their positional relationship, and puts the current location onto the road for which matching has occurred.
Description
1 337~25 This is a divisional application of copending application 590,761, filed February 10, 1989.
The present invention relates to a current location ~ displaying apparatus in which a path of travel of a vehicle, such as an automobile, is displayed on a display screen with a map displayed thereon.
In an attempt to provide guidance to a driver of an automobile to prevent the driver from loosing his way while driving, for example in a strange place, a current location display apparatus has been developed. In this apparatus the distance travelled and direction of travel of the vehicle are detected from time to time, and the current location of the vehicle on a two-dimensional coordinate system is successively computed from the results of the detection, whereby the current location of the vehicle is successively displayed on a map, which is previously displayed on the screen.
In such an apparatus, it is difficult to avoid the occurrence of a positional error owing to accuracy of detection at the time of detecting the distance and the direction during running of the vehicle, and such positional error is progressively integrated, as the vehicle continues on its ~`
'~
1 337~2J
course with the result the current location on the map appears to run off the road and the driver becomes unable to see where he is driving.
It has been usual practice to correct this positional error by matching the road pattern with the trajectory of the vehicle, which is obtained by storing and holding data of the successively changing current locations as the vehicle continues its course, thereby enabling correction of the current location which has gone off the road. According to this method a plurality of roads, which are considered to be the roads through which the vehicle has passed are selected from a complicated road network, and adaptability of the pattern of each of the extracted roads and the trajectory is examined. Then the road having highest matching rate is - la -133~825 assumed to be the road where the vehicle is actually travelling and the correction in position is effected to bring the current location of the vehicle comes onto the road to which the matching has been effected.
In such a method, if the map includes complicated roads, a considerable number of road patterns must be matched to the actual trajectory. It is, therefore, necessary to effect matching of the pattern of the travel path to each of the road patterns, and so the processing becomes very complicated and requires considerable time. This method has the further disadvantage that if the vehicle passes through a road which does not exist on the map, the pattern matching cannot be effected, with the result that the correction of the current location becomes impossible.
In view of the disadvantages of the prior art, the present invention provides a current location display apparatus in which a current location of the vehicle which has come off its course is corrected by effecting matching of the pattern of a road on a map and the pattern of a travel path of the vehicle, which permits processing to continue even if the vehicle temporarily passes through a road which does not exist on the map, and to effectively and precisely effect matching between a road pattern and a travel path pattern.
According to an aspect of the present invention there is provided an apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen having a map previously displayed thereon, comprising: means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; means for bringing the current location into line with the road to which the matching has been effected; means for effecting coordinates transformation to transform the linear running portion extracted from the travel path and the linear road portion extracted from the road on the map in correspondence with said linear running portion on a first coordinate system into points on a second coordinate system; and means for effecting the matching between the linear running portion and the linear road portion on said second coordinate system, wherein the coordinates transformation is effected by using Hough Transformation.
According to a further aspect of the invention there is provided an apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen having a map previously displayed thereon, comprising: means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a 1 337~25 travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; and means for bringing the current location into line with the road to which the matching has been effected; wherein the means for extracting the linear running portion includes (a) means for ascertaining if a change in running direction is substantially zero at the time when the running body has moved for a predetermined distance from an initial position, (b) means for imposing an imaginary straight line in a running direction of the running body from the initial position, (c) means for determining a distance between the current location of the running body and the imaginary straight line, and (d) means for deciding that the running body is running on a straight line on the basis that as long as the distance between the current location of the running body and the imaginary straight line is shorter than a predetermined value, the running body is running on a straight line and the linear running portion is extracted therefrom.
According to a still further aspect of the invention there is provided an apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen - 3a -having a map previously displayed thereon, comprising: means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; and means for bringing the current location into line with the road to which the matching has been effected; wherein the means for extracting the linear road portion includes (a) means for defining an area by parallel lines having a predetermined width therebetween on both sides of the linear running portion extracted from the travel path, and (b) means for determining whether a linear road portion has (i) a predetermined minimum length and (ii) a running direction which falls within a predetermined range.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:-Fig. 1 is a block diagram showing an embodiment of thecurrent location display apparatus according to the present invention;
Fig. 2 shows an example of the display produced by the - 3b -embodiment shown in Fig. l;
Fig. 3 shows the status of the display where the travel path has come off the road on the map;
Fig. 4 is a flow chart showing the process of extracting a linear travel segment;
Fig. S is a diagram showing an example of the travel path of the vehicle to extract the linear trajectory;
Fig. 6 is a diagram showing a road searching area for extracting the linear road segment;
Fig. 7 is a diagram showing an example of the travel path of the vehicle relative to the map;
Fig. 8(a) is a diagram showing the linear trajectory taken from the travel path shown in Fig. 7;
Fig. 8(b) is a diagram showing a proposed linear road segment taken from roads on the map corresponding to the linear trajectory;
Fig. 9 is a diagram showing a straight line on X-Y
coordinates;
Fig. 10 is a diagram showing a point on e-gamma coordinates according to Hough Transformation;
Fig. 11 is a diagram showing combinations of four linear trajectories; and Fig. 12 is a diagram showing combinations of proposed linear - 3c -1 337~25 road segments on the map depending upon the selected combination of the four linear trajectories.
In the accompanying drawings, Fig. 1 shows an embodiment of the fundamental construction of the current location display apparatus according to the present invention.
The essential components comprise a distance sensor 1 of photoelectric, electromagnetic, mechanical contact type or the like, for generating pulse signals corresponding to the distance travelled of the vehicle, depending on the rotation of the wheels of said vehicle, for example; a direction sensor 2 for generating signals proportional to the amount of change of direction of the vehicle, consisting of a gyroscope for detecting change in the yaw angular velocity, for example; a signal processing unit 3 for counting the number of the pulses sent from the distance sensor 1 to measure the distance travelled of the vehicle and to determine the change of course of the vehicle on the basis of the output signal of the direction sensor 2 to successively compute the current location of the vehicle on the two-dimensional coordinates at every unit distance of travel to effect centralized control of the whole system, the unit 3 including a CPU, a programming ROM, a controlling RAM, etc.; a travel path storing means 4 for successively storing the data of the constantly changing location on the two-dimensional coordinates obtained by the signal processing unit and holding the data as finite and continuous location information corresponding to the current locations of the vehicle; a map information storage medium 5 in which a plurality of file units of map informations are previously stored; a storage medium reader unit 6 for selectively reading out the desired map file from the storage medium 5; a display unit 7 for displaying a map on a display screen in accordance with the read-out map information and renewably displaying the current locations of the vehicle, the travel path, and current course and other information on the same 1 337~25 display screen on the basis of the location data stored in the storage unit 4, and a manual operating unit 8 for giving a command for operation to the signal processing unit-3 and for effecting various operations including selection of the map to be displayed on the display unit 7, setting of the starting point of the vehicle on the displayed map, change of directions of the displayed map and the trajectory, shifting of the displayed position, change of the setting of the display such as the partial enlargement of the display of the map and the travel path, selection of the reduced scale and the like.
In the construction as described above, the map, which has been selectively read out, is displayed on the display unit 7, as shown in Fig. 2., and a display mark Ml indicating the current location of the vehicle on the X-Y map, depending upon a predetermined map reduction rate previously set by the signal processing unit 3 in accordance with the travel of the vehicle from a starting point set on the map, a display mark M2 indicating the direction of travel at the current locations and a display mark M3 indicating the trajectory from the starting point S to the current location are simulatively displayed thereon, depending upon the running status of the vehicle.
The above-described construction and its operation are the same as those of the known travel path display apparatus as hereinbefore described. Accordingly, this travel path displaying apparatus has the disadvantage that the current location and the travel path increasingly come off the road on the map as the vehicle proceeds, owing to the integrated error described above, as shown in Fig. 3 until the driver becomes unable to see where he is driving on the map.
In order to avoid such disadvantage, the current location display apparatus according to the present invention comprises means for extracting a linear travel segment from 1 337g25 the travel path of the moving body, means for extracting a linear road segment from adjoining roads on a map which corresponds to the extracted linear travel segment,.means for effecting a matching between the extracted linear travel segment and the extracted linear road segment in accordance with the positional relationship thereof and means for bringing the current location into line with the road to which the matching has been effected.
In practice, these means are executed in the signal processing unit 3. The means for extracting a linear travel segment from the travel path of the vehicle is executed in the following manner. The processing thereof is shown by the flow chart of Fig. 4.
Firstly, an initial position A and a direction of travel eO
at the position of the moving body, as shown in Fig. 5, are memorized and then a direction of travel e, at the time when the moving body has moved a preset distance Ll is determined.
A variation delta e of the direction of travel at this stage is calculated (deltae = ¦e~ -eol).
Next, the variation delta e of the direction of travel and a preset threshold value eth are compared with each other. If delta e < eth~ it is determined that the direction of travel at this time is stable and the vehicle is moving along a straight line, whereas if delta e >= eth, it is determined that not moving along a straight line. If it is determined that the vehicle is moving along a straight line, a supposed straight line A-A' is drawn from the initial position A in the direction eO and a distance d between the current location P of the vehicle and the supposed straight line A-A' is found.
The found distance d and the preset threshold value D are compared with each other. As long as the relation d < D is met, it is determined that the vehicle is continuously moving on the straight line. The value of D is set in such degree that it is not effected by a change of traffic lane. When the relation becomes d >=D, it is supposed that the.
travelling of the vehicle on the straight line has terminated. Then, the travel distance on the straight line Lx between the current location P of the moving body and the initial position A is found and the found travel distance on straight line Lx and the preset threshold value Lth are compared with each other. If Lx > Lth, it is assumed that a linear travel segment having a length longer than a predetermined value has been detected and the respective positions on the coordinates of an starting point and an terminating point of the linear travel segment are memorized.
If LX =< Lth, it is assumed that the linear travel distance of the vehicle is short and this linear travel segment is excluded, and it is not subjected to the matching process.
The same steps are repeated and the linear travel segments are successively detected as the travel path proceeds. In this case, the linear travel segment having a distance shorter than a predetermined value is not subjected to the matching process. However, it is possible to set the threshold value Lth stepwise so that the threshold value can be set at a lower value in the case where the vehicle is running on a curved mountain road, for example, so that the shorter linear travel segment may be subjected to the matching process.
The means for extracting the linear road segment from the adjoining roads on the map which corresponds to the linear travel segment extracted from the travel path is executed in the following manner. When a linear travel segment a-b is detected from the travel path of the vehicle, as shown in Fig. 6, a road searching area W having a width of 2R is defined by parallel lines on both sides of the linear travel segment a-b. Within this area W, a linear road segment having a predetermined minimum road length L min and defined by lines having difference in angle relative to the linear travel segment a-b within a threshold value ~ is extracted.
Now, it is assumed that the travel path of the vehicle relative to the road in the map is as shown by a broken line in Fig. 7.
According to the present invention, firstly linear travel lines 11, 12, 13, and 14 are extracted from the travel path, as shown in Fig. 8(a).
The segment between the points b and c, in Fig. 8(a), indicates that the vehicle moves on a road which is not shown on the map. The segments d-e and f-g indicate that the vehicle curves at intersections.
Then, proposed linear road segments ml.1 and ml.2, which correspond to the extracted linear travel segment 11, proposed linear road segments m2.1 and m2.2, which correspond to the extracted linear travel segment 12, a proposed linear road segment m3.0, which corresponds to the extracted linear travel segment 13, and a proposed linear road segment m4.0 which corresponds to the extracted linear travel segment 14 are extracted respectively, as shown in Fig. 8(b).
Then, the matching rate between each of the extracted travel path segments and each of the extracted road segments is found from the positional relationship therebetween. The found matching rate is compared with a predetermined threshold value. The linear road segment having the matching rate larger than the threshold value is determined as the optimum one for the proposed linear road segment, and the linear travel segment in the travel path, which corresponds to the optimum one of the proposed linear road segments is brought into line with the linear travel segment.
1 33~ ~2~
If a plurality of linear road segments, having the matching rate higher than the threshold value are found, the optimum one of the proposed road segments is not determined.at this time, and the decision is effected depending upon the matching process of the succeeding linear segments, according to a so-called indecisive algorithm.
A coordinate transformation may be effected to indicate a straight line on X-Y coordinates by points on the e - gamma coordinate, according to Hough Transformation, for example, the respective points corresponding to the linear segments extracted from the travel path and the road on the map are subjected to the matching process, and the positions of the points on the e - gamma coordinates are adopted as characteristic values to which the matching process is effected. In this coordinate system, e is the angle of a perpendicular drawn from a straight line on the X-Y
coordinates to an origin of the coordinates and gamma is the length of the perpendicular. For example, a straight line L
on the X-Y coordinates shown in Fig. 9 is expressed by a point el on the e-gamma coordinates, as shown in Fig. 10.
In this case, therefore, the matching process can be easily effected by simply comparing the positions of the respective points corresponding to the linear segments extracted from the travel path and the road on the map.
It is, of course, possible to directly subject the linear segments extracted from the travel path and the road on the map to the matching process so that the matching is effected on the basis of the characteristic amounts including the positions on the X-Y coordinates, the length, the inclining direction, the inclining angle, etc. but in such case many characteristic values to be subjected to the matching process are included and, therefore the matching process is troublesome.
The above matching process is collectively effected every time a predetermined number of the linear travel segments extracted from the travel path have been obtained as the vehicle proceeds on its path.
Now, it is assumed that the matching process is collectively effected very time four linear travel segments have been extracted from the travel path, for example. In this case, the relationship is as shown in Fig. 8 and the combination of the selected four linear travel segments 11 - 14 is as shown in Fig. 11.
This case includes the combination of (24-1) from the case where all of 11 - 14 are selected to the case where only one of 11 - 14 is selected.
For example, it is assumed that the vehicle is running in such a state that the linear travel segment 13 of the travel path is on a road which is in parallel with a proposed linear road segment and is not shown in the map. Then, the linear travel segment 13 is not selected and the combination includes the linear travel segments 11, 12 and 14.
Such a combination of the proposed linear road segments on the map is effected. Depending upon the selected combination of the linear travel segments of the travel path.
For example, the combinations of the proposed linear road segments on the map corresponding to the combination of selection of the linear travel segments 11, 12 and 14 of the travel path includes four sets ~ - ~ as shown in Fig. 12.
The matching process is executed on combinations including the selected combinations of the linear travel segments 11 -14 and the combinations of the proposed linear road segments on the map.
Good precision of matching is obtained by executing the matching process on all of the combinations. However, it is not always necessary to execute the matching process on all combinations, and the matching process may be executed on properly selected combinations.
Further, it is not always necessary to collectively effect the matching process. It is, of course, possible to successively execute the matching process as the linear travel segments are extracted from the travel path.
When the travel path is brought into line with the road to which the matching has been effected, it is possible to individually and successively bring the linear travel segment extracted from the travel path into the optimum one of the linear road segments to which the matching has been effected.
In the case where the matching process is collectively effected, it is possible to calculate an average of vectors including the differences in direction between the corresponding linear travel segments and linear road segments and the sizes of these segments, and to displace a group of the linear travel segments by a predetermined distance in a predetermined direction, depending upon the calculated average of the vectors.
Thus, it will be understood that the present invention provides an apparatus in which the matching between the travel path of the vehicle and the road on the map can be easily and precisely effected, with a small amount of information, by a partial matching process of the linear segments so that the load applied to the signal processing unit 3 is decreased and the matching process can be effected at high speed.
When the coordinate transformation, for example, a Hough transformation is applied to transform the linear segments extracted from the travel path and the road on the map into 1 33782~
the points, it is possible to effect the matching process by simply comparing the positions of the points on the map, which is more advantageous, Furthermore, in the apparatus of the present invention, the S matching between the travel path and the road on the map is effected on the basis of the discontinuous linear travel segments extracted from the travel path without requiring a process for searching related road segments as in the conventional apparatus, so that even if the vehicle runs on a road which is not shown on the map, the matching process can be effected without being affected thereby.
According to the present invention the collective process is effected on the combination in which the linear travel segment extracted from the travel path is assumed to be located outside of the road shown on the map, and accordingly the travel segment outside the road on the map is automatically cancelled at the time of effecting the matching process so that precision of matching is improved.
Furthermore, according to the present invention, a deformation of the map at a curved portion does not affect the matching process of the present invention, and with regard to deformation of the map at a straight segment, the matching rate is rather improved by cancelling the deformation. Thus, resistance to deformation of the map is increased. For example, a map of a town in which a detailed road map is shown and another map of a suburb in which only main roads are shown have no corresponding relation with each other. In such a case, the present invention can be effectively applied since it does not depend upon the interrelation between one map and another.
Thus, the present invention provides a current location display apparatus in which a linear travel segment is extracted from a travel path of a vehicle while a linear road 1 3~7S325 segment corresponding thereto is extracted from a road on a map; a matching process is effected between the extracted linear travel segment and linear road segment depending upon a positional relationship therebetween, and the current location is brought into line with the road to which the matching has been effected.
Accordingly, the processing is not interrupted even if the vehicle tentatively comes off a road on a map and the matching process is effected always in an optimum manner so that the travel path of the vehicle on the map is displayed with high precision.
The present invention relates to a current location ~ displaying apparatus in which a path of travel of a vehicle, such as an automobile, is displayed on a display screen with a map displayed thereon.
In an attempt to provide guidance to a driver of an automobile to prevent the driver from loosing his way while driving, for example in a strange place, a current location display apparatus has been developed. In this apparatus the distance travelled and direction of travel of the vehicle are detected from time to time, and the current location of the vehicle on a two-dimensional coordinate system is successively computed from the results of the detection, whereby the current location of the vehicle is successively displayed on a map, which is previously displayed on the screen.
In such an apparatus, it is difficult to avoid the occurrence of a positional error owing to accuracy of detection at the time of detecting the distance and the direction during running of the vehicle, and such positional error is progressively integrated, as the vehicle continues on its ~`
'~
1 337~2J
course with the result the current location on the map appears to run off the road and the driver becomes unable to see where he is driving.
It has been usual practice to correct this positional error by matching the road pattern with the trajectory of the vehicle, which is obtained by storing and holding data of the successively changing current locations as the vehicle continues its course, thereby enabling correction of the current location which has gone off the road. According to this method a plurality of roads, which are considered to be the roads through which the vehicle has passed are selected from a complicated road network, and adaptability of the pattern of each of the extracted roads and the trajectory is examined. Then the road having highest matching rate is - la -133~825 assumed to be the road where the vehicle is actually travelling and the correction in position is effected to bring the current location of the vehicle comes onto the road to which the matching has been effected.
In such a method, if the map includes complicated roads, a considerable number of road patterns must be matched to the actual trajectory. It is, therefore, necessary to effect matching of the pattern of the travel path to each of the road patterns, and so the processing becomes very complicated and requires considerable time. This method has the further disadvantage that if the vehicle passes through a road which does not exist on the map, the pattern matching cannot be effected, with the result that the correction of the current location becomes impossible.
In view of the disadvantages of the prior art, the present invention provides a current location display apparatus in which a current location of the vehicle which has come off its course is corrected by effecting matching of the pattern of a road on a map and the pattern of a travel path of the vehicle, which permits processing to continue even if the vehicle temporarily passes through a road which does not exist on the map, and to effectively and precisely effect matching between a road pattern and a travel path pattern.
According to an aspect of the present invention there is provided an apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen having a map previously displayed thereon, comprising: means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; means for bringing the current location into line with the road to which the matching has been effected; means for effecting coordinates transformation to transform the linear running portion extracted from the travel path and the linear road portion extracted from the road on the map in correspondence with said linear running portion on a first coordinate system into points on a second coordinate system; and means for effecting the matching between the linear running portion and the linear road portion on said second coordinate system, wherein the coordinates transformation is effected by using Hough Transformation.
According to a further aspect of the invention there is provided an apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen having a map previously displayed thereon, comprising: means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a 1 337~25 travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; and means for bringing the current location into line with the road to which the matching has been effected; wherein the means for extracting the linear running portion includes (a) means for ascertaining if a change in running direction is substantially zero at the time when the running body has moved for a predetermined distance from an initial position, (b) means for imposing an imaginary straight line in a running direction of the running body from the initial position, (c) means for determining a distance between the current location of the running body and the imaginary straight line, and (d) means for deciding that the running body is running on a straight line on the basis that as long as the distance between the current location of the running body and the imaginary straight line is shorter than a predetermined value, the running body is running on a straight line and the linear running portion is extracted therefrom.
According to a still further aspect of the invention there is provided an apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen - 3a -having a map previously displayed thereon, comprising: means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; and means for bringing the current location into line with the road to which the matching has been effected; wherein the means for extracting the linear road portion includes (a) means for defining an area by parallel lines having a predetermined width therebetween on both sides of the linear running portion extracted from the travel path, and (b) means for determining whether a linear road portion has (i) a predetermined minimum length and (ii) a running direction which falls within a predetermined range.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:-Fig. 1 is a block diagram showing an embodiment of thecurrent location display apparatus according to the present invention;
Fig. 2 shows an example of the display produced by the - 3b -embodiment shown in Fig. l;
Fig. 3 shows the status of the display where the travel path has come off the road on the map;
Fig. 4 is a flow chart showing the process of extracting a linear travel segment;
Fig. S is a diagram showing an example of the travel path of the vehicle to extract the linear trajectory;
Fig. 6 is a diagram showing a road searching area for extracting the linear road segment;
Fig. 7 is a diagram showing an example of the travel path of the vehicle relative to the map;
Fig. 8(a) is a diagram showing the linear trajectory taken from the travel path shown in Fig. 7;
Fig. 8(b) is a diagram showing a proposed linear road segment taken from roads on the map corresponding to the linear trajectory;
Fig. 9 is a diagram showing a straight line on X-Y
coordinates;
Fig. 10 is a diagram showing a point on e-gamma coordinates according to Hough Transformation;
Fig. 11 is a diagram showing combinations of four linear trajectories; and Fig. 12 is a diagram showing combinations of proposed linear - 3c -1 337~25 road segments on the map depending upon the selected combination of the four linear trajectories.
In the accompanying drawings, Fig. 1 shows an embodiment of the fundamental construction of the current location display apparatus according to the present invention.
The essential components comprise a distance sensor 1 of photoelectric, electromagnetic, mechanical contact type or the like, for generating pulse signals corresponding to the distance travelled of the vehicle, depending on the rotation of the wheels of said vehicle, for example; a direction sensor 2 for generating signals proportional to the amount of change of direction of the vehicle, consisting of a gyroscope for detecting change in the yaw angular velocity, for example; a signal processing unit 3 for counting the number of the pulses sent from the distance sensor 1 to measure the distance travelled of the vehicle and to determine the change of course of the vehicle on the basis of the output signal of the direction sensor 2 to successively compute the current location of the vehicle on the two-dimensional coordinates at every unit distance of travel to effect centralized control of the whole system, the unit 3 including a CPU, a programming ROM, a controlling RAM, etc.; a travel path storing means 4 for successively storing the data of the constantly changing location on the two-dimensional coordinates obtained by the signal processing unit and holding the data as finite and continuous location information corresponding to the current locations of the vehicle; a map information storage medium 5 in which a plurality of file units of map informations are previously stored; a storage medium reader unit 6 for selectively reading out the desired map file from the storage medium 5; a display unit 7 for displaying a map on a display screen in accordance with the read-out map information and renewably displaying the current locations of the vehicle, the travel path, and current course and other information on the same 1 337~25 display screen on the basis of the location data stored in the storage unit 4, and a manual operating unit 8 for giving a command for operation to the signal processing unit-3 and for effecting various operations including selection of the map to be displayed on the display unit 7, setting of the starting point of the vehicle on the displayed map, change of directions of the displayed map and the trajectory, shifting of the displayed position, change of the setting of the display such as the partial enlargement of the display of the map and the travel path, selection of the reduced scale and the like.
In the construction as described above, the map, which has been selectively read out, is displayed on the display unit 7, as shown in Fig. 2., and a display mark Ml indicating the current location of the vehicle on the X-Y map, depending upon a predetermined map reduction rate previously set by the signal processing unit 3 in accordance with the travel of the vehicle from a starting point set on the map, a display mark M2 indicating the direction of travel at the current locations and a display mark M3 indicating the trajectory from the starting point S to the current location are simulatively displayed thereon, depending upon the running status of the vehicle.
The above-described construction and its operation are the same as those of the known travel path display apparatus as hereinbefore described. Accordingly, this travel path displaying apparatus has the disadvantage that the current location and the travel path increasingly come off the road on the map as the vehicle proceeds, owing to the integrated error described above, as shown in Fig. 3 until the driver becomes unable to see where he is driving on the map.
In order to avoid such disadvantage, the current location display apparatus according to the present invention comprises means for extracting a linear travel segment from 1 337g25 the travel path of the moving body, means for extracting a linear road segment from adjoining roads on a map which corresponds to the extracted linear travel segment,.means for effecting a matching between the extracted linear travel segment and the extracted linear road segment in accordance with the positional relationship thereof and means for bringing the current location into line with the road to which the matching has been effected.
In practice, these means are executed in the signal processing unit 3. The means for extracting a linear travel segment from the travel path of the vehicle is executed in the following manner. The processing thereof is shown by the flow chart of Fig. 4.
Firstly, an initial position A and a direction of travel eO
at the position of the moving body, as shown in Fig. 5, are memorized and then a direction of travel e, at the time when the moving body has moved a preset distance Ll is determined.
A variation delta e of the direction of travel at this stage is calculated (deltae = ¦e~ -eol).
Next, the variation delta e of the direction of travel and a preset threshold value eth are compared with each other. If delta e < eth~ it is determined that the direction of travel at this time is stable and the vehicle is moving along a straight line, whereas if delta e >= eth, it is determined that not moving along a straight line. If it is determined that the vehicle is moving along a straight line, a supposed straight line A-A' is drawn from the initial position A in the direction eO and a distance d between the current location P of the vehicle and the supposed straight line A-A' is found.
The found distance d and the preset threshold value D are compared with each other. As long as the relation d < D is met, it is determined that the vehicle is continuously moving on the straight line. The value of D is set in such degree that it is not effected by a change of traffic lane. When the relation becomes d >=D, it is supposed that the.
travelling of the vehicle on the straight line has terminated. Then, the travel distance on the straight line Lx between the current location P of the moving body and the initial position A is found and the found travel distance on straight line Lx and the preset threshold value Lth are compared with each other. If Lx > Lth, it is assumed that a linear travel segment having a length longer than a predetermined value has been detected and the respective positions on the coordinates of an starting point and an terminating point of the linear travel segment are memorized.
If LX =< Lth, it is assumed that the linear travel distance of the vehicle is short and this linear travel segment is excluded, and it is not subjected to the matching process.
The same steps are repeated and the linear travel segments are successively detected as the travel path proceeds. In this case, the linear travel segment having a distance shorter than a predetermined value is not subjected to the matching process. However, it is possible to set the threshold value Lth stepwise so that the threshold value can be set at a lower value in the case where the vehicle is running on a curved mountain road, for example, so that the shorter linear travel segment may be subjected to the matching process.
The means for extracting the linear road segment from the adjoining roads on the map which corresponds to the linear travel segment extracted from the travel path is executed in the following manner. When a linear travel segment a-b is detected from the travel path of the vehicle, as shown in Fig. 6, a road searching area W having a width of 2R is defined by parallel lines on both sides of the linear travel segment a-b. Within this area W, a linear road segment having a predetermined minimum road length L min and defined by lines having difference in angle relative to the linear travel segment a-b within a threshold value ~ is extracted.
Now, it is assumed that the travel path of the vehicle relative to the road in the map is as shown by a broken line in Fig. 7.
According to the present invention, firstly linear travel lines 11, 12, 13, and 14 are extracted from the travel path, as shown in Fig. 8(a).
The segment between the points b and c, in Fig. 8(a), indicates that the vehicle moves on a road which is not shown on the map. The segments d-e and f-g indicate that the vehicle curves at intersections.
Then, proposed linear road segments ml.1 and ml.2, which correspond to the extracted linear travel segment 11, proposed linear road segments m2.1 and m2.2, which correspond to the extracted linear travel segment 12, a proposed linear road segment m3.0, which corresponds to the extracted linear travel segment 13, and a proposed linear road segment m4.0 which corresponds to the extracted linear travel segment 14 are extracted respectively, as shown in Fig. 8(b).
Then, the matching rate between each of the extracted travel path segments and each of the extracted road segments is found from the positional relationship therebetween. The found matching rate is compared with a predetermined threshold value. The linear road segment having the matching rate larger than the threshold value is determined as the optimum one for the proposed linear road segment, and the linear travel segment in the travel path, which corresponds to the optimum one of the proposed linear road segments is brought into line with the linear travel segment.
1 33~ ~2~
If a plurality of linear road segments, having the matching rate higher than the threshold value are found, the optimum one of the proposed road segments is not determined.at this time, and the decision is effected depending upon the matching process of the succeeding linear segments, according to a so-called indecisive algorithm.
A coordinate transformation may be effected to indicate a straight line on X-Y coordinates by points on the e - gamma coordinate, according to Hough Transformation, for example, the respective points corresponding to the linear segments extracted from the travel path and the road on the map are subjected to the matching process, and the positions of the points on the e - gamma coordinates are adopted as characteristic values to which the matching process is effected. In this coordinate system, e is the angle of a perpendicular drawn from a straight line on the X-Y
coordinates to an origin of the coordinates and gamma is the length of the perpendicular. For example, a straight line L
on the X-Y coordinates shown in Fig. 9 is expressed by a point el on the e-gamma coordinates, as shown in Fig. 10.
In this case, therefore, the matching process can be easily effected by simply comparing the positions of the respective points corresponding to the linear segments extracted from the travel path and the road on the map.
It is, of course, possible to directly subject the linear segments extracted from the travel path and the road on the map to the matching process so that the matching is effected on the basis of the characteristic amounts including the positions on the X-Y coordinates, the length, the inclining direction, the inclining angle, etc. but in such case many characteristic values to be subjected to the matching process are included and, therefore the matching process is troublesome.
The above matching process is collectively effected every time a predetermined number of the linear travel segments extracted from the travel path have been obtained as the vehicle proceeds on its path.
Now, it is assumed that the matching process is collectively effected very time four linear travel segments have been extracted from the travel path, for example. In this case, the relationship is as shown in Fig. 8 and the combination of the selected four linear travel segments 11 - 14 is as shown in Fig. 11.
This case includes the combination of (24-1) from the case where all of 11 - 14 are selected to the case where only one of 11 - 14 is selected.
For example, it is assumed that the vehicle is running in such a state that the linear travel segment 13 of the travel path is on a road which is in parallel with a proposed linear road segment and is not shown in the map. Then, the linear travel segment 13 is not selected and the combination includes the linear travel segments 11, 12 and 14.
Such a combination of the proposed linear road segments on the map is effected. Depending upon the selected combination of the linear travel segments of the travel path.
For example, the combinations of the proposed linear road segments on the map corresponding to the combination of selection of the linear travel segments 11, 12 and 14 of the travel path includes four sets ~ - ~ as shown in Fig. 12.
The matching process is executed on combinations including the selected combinations of the linear travel segments 11 -14 and the combinations of the proposed linear road segments on the map.
Good precision of matching is obtained by executing the matching process on all of the combinations. However, it is not always necessary to execute the matching process on all combinations, and the matching process may be executed on properly selected combinations.
Further, it is not always necessary to collectively effect the matching process. It is, of course, possible to successively execute the matching process as the linear travel segments are extracted from the travel path.
When the travel path is brought into line with the road to which the matching has been effected, it is possible to individually and successively bring the linear travel segment extracted from the travel path into the optimum one of the linear road segments to which the matching has been effected.
In the case where the matching process is collectively effected, it is possible to calculate an average of vectors including the differences in direction between the corresponding linear travel segments and linear road segments and the sizes of these segments, and to displace a group of the linear travel segments by a predetermined distance in a predetermined direction, depending upon the calculated average of the vectors.
Thus, it will be understood that the present invention provides an apparatus in which the matching between the travel path of the vehicle and the road on the map can be easily and precisely effected, with a small amount of information, by a partial matching process of the linear segments so that the load applied to the signal processing unit 3 is decreased and the matching process can be effected at high speed.
When the coordinate transformation, for example, a Hough transformation is applied to transform the linear segments extracted from the travel path and the road on the map into 1 33782~
the points, it is possible to effect the matching process by simply comparing the positions of the points on the map, which is more advantageous, Furthermore, in the apparatus of the present invention, the S matching between the travel path and the road on the map is effected on the basis of the discontinuous linear travel segments extracted from the travel path without requiring a process for searching related road segments as in the conventional apparatus, so that even if the vehicle runs on a road which is not shown on the map, the matching process can be effected without being affected thereby.
According to the present invention the collective process is effected on the combination in which the linear travel segment extracted from the travel path is assumed to be located outside of the road shown on the map, and accordingly the travel segment outside the road on the map is automatically cancelled at the time of effecting the matching process so that precision of matching is improved.
Furthermore, according to the present invention, a deformation of the map at a curved portion does not affect the matching process of the present invention, and with regard to deformation of the map at a straight segment, the matching rate is rather improved by cancelling the deformation. Thus, resistance to deformation of the map is increased. For example, a map of a town in which a detailed road map is shown and another map of a suburb in which only main roads are shown have no corresponding relation with each other. In such a case, the present invention can be effectively applied since it does not depend upon the interrelation between one map and another.
Thus, the present invention provides a current location display apparatus in which a linear travel segment is extracted from a travel path of a vehicle while a linear road 1 3~7S325 segment corresponding thereto is extracted from a road on a map; a matching process is effected between the extracted linear travel segment and linear road segment depending upon a positional relationship therebetween, and the current location is brought into line with the road to which the matching has been effected.
Accordingly, the processing is not interrupted even if the vehicle tentatively comes off a road on a map and the matching process is effected always in an optimum manner so that the travel path of the vehicle on the map is displayed with high precision.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for displaying a current location of a running body in which a continuously changing location of the running body on X-Y coordinates is successively computed and a current location of the running body is displayed, in accordance with data thus computed, on a display screen having a map previously displayed thereon, comprising:
means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; and means for bringing the current location into line with the road to which the matching has been effected; wherein the means for extracting the linear running portion includes (a) means for ascertaining if a change in running direction is substantially zero at the time when the running body has moved for a predetermined distance from an initial position, (b) means for imposing an imaginary straight line in a running direction of the running body from the initial position, (c) means for determining a distance between the current location of the running body and the imaginary straight line, and (d) means for deciding that the running body is running on a straight line on the basis that as long as the distance between the current location of the running body and the imaginary straight line is shorter than a predetermined value, the running body is running on a straight line and the linear running portion is extracted therefrom.
means for detecting running distance and moving direction of the running body; means for calculating a current location from the running distance and the moving direction and obtaining a travel path; means for extracting a linear running portion from the travel path of the running body obtained by storing and holding data of the current location thus obtained; means for extracting a linear road portion from a predetermined area on the map which corresponds to the extracted linear running portion; means for effecting matching between the extracted linear running portion and the extracted road portion by comparing the extracted linear running portion and the extracted road portion and determining whether a positional relationship therebetween is satisfied; and means for bringing the current location into line with the road to which the matching has been effected; wherein the means for extracting the linear running portion includes (a) means for ascertaining if a change in running direction is substantially zero at the time when the running body has moved for a predetermined distance from an initial position, (b) means for imposing an imaginary straight line in a running direction of the running body from the initial position, (c) means for determining a distance between the current location of the running body and the imaginary straight line, and (d) means for deciding that the running body is running on a straight line on the basis that as long as the distance between the current location of the running body and the imaginary straight line is shorter than a predetermined value, the running body is running on a straight line and the linear running portion is extracted therefrom.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32115 | 1988-02-15 | ||
| JP63032115A JP2618254B2 (en) | 1988-02-15 | 1988-02-15 | Travel route display device |
| CA000590761A CA1327635C (en) | 1988-02-15 | 1989-02-10 | Vehicle location system on a map display |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000590761A Division CA1327635C (en) | 1988-02-15 | 1989-02-10 | Vehicle location system on a map display |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1337825C true CA1337825C (en) | 1995-12-26 |
Family
ID=25672437
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000616593A Expired - Fee Related CA1337875C (en) | 1988-02-15 | 1993-02-10 | Vehicle location system on a map display |
| CA000616568A Expired - Fee Related CA1337825C (en) | 1988-02-15 | 1993-02-10 | Vehicle location system on a map display |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000616593A Expired - Fee Related CA1337875C (en) | 1988-02-15 | 1993-02-10 | Vehicle location system on a map display |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA1337875C (en) |
-
1993
- 1993-02-10 CA CA000616593A patent/CA1337875C/en not_active Expired - Fee Related
- 1993-02-10 CA CA000616568A patent/CA1337825C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA1337875C (en) | 1996-01-02 |
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