JP3596939B2 - Current position calculation device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a current position calculation device provided in a navigation system mounted on a vehicle that moves with the rotation of wheels and calculates a current position of the vehicle, and in particular, estimates a road on which the vehicle is traveling. It is about technology.
[0002]
[Prior art]
Generally, in a navigation system, as shown in FIG. 2, a mark 20 representing the current position of the vehicle is displayed on a display so as to be superimposed on a CD-ROM or the like. At this time, since the vehicle is traveling on the road, the mark 20 indicating the current position of the vehicle must be displayed so as to overlap the road.
[0003]
Conventionally, in a navigation system, a current position of a vehicle is calculated based on a traveling direction of the vehicle measured by a direction sensor such as a gyro, and a traveling distance of the vehicle measured by a vehicle speed sensor or a distance sensor. .
[0004]
In general, the mileage of a vehicle is determined by measuring the output shaft of a transmission and the number of rotations of tires, and multiplying the number of rotations by a mileage coefficient which is the distance the vehicle travels per tire rotation. be able to.
[0005]
However, an error often occurs between the calculated current position of the vehicle and the position where the vehicle actually exists. Therefore, if the calculated current position of the vehicle is displayed as it is, the mark 20 indicating the current position of the vehicle is displayed. It will not overlap the road shown on the display. Therefore, before displaying the mark 20 representing the current position of the vehicle, it is necessary to estimate the road on which the vehicle is traveling and to correct the current position of the vehicle.
[0006]
As described above, a technique for calculating the current position of the vehicle and correcting the current position of the vehicle calculated by estimating the road on which the vehicle is traveling is described in, for example, Japanese Patent Publication No. Hei 6-13972. There is a technique that is used, and this kind of technique is generally called a map matching process.
[0007]
The map matching process is a process that is performed each time the vehicle travels a predetermined distance, and a specific process will be briefly described below.
[0008]
First, after calculating the current position of the vehicle, the deviation of the angle between the measured direction of travel of the vehicle and the road described on the map within a predetermined distance D from the calculated current position is determined by a threshold value. The vehicle travels on a road that is less than or equal to T and has a shortest distance from the current position (the length of a vertical line drawn from the current position to the road) that is less than or equal to a threshold L. Road as a candidate.
[0009]
Subsequently, one of the roads selected as candidates is finally estimated to be the road on which the vehicle is traveling.
[0010]
Finally, a point at which the estimated road intersects a perpendicular drawn from the current position is defined as the corrected current position.
[0011]
As described above, the map matching process is a process necessary for displaying the mark indicating the current position of the vehicle so as to overlap the road.
[0012]
[Problems to be solved by the invention]
By the way, as can be seen from the fact that the road is represented by a single line as shown in FIG. 2 and displayed on the display, in the map stored in the storage medium as the map data, the road is actually Is described as a single line despite having a road width, and this single line is described as passing through the center of the road.
[0013]
Therefore, the shortest distance between the road and the current position, which is required when performing the map matching processing, represents the shortest distance between the center of the road and the road width of the road. Therefore, there are the following problems.
[0014]
For example, as shown in FIG. 3A, if the calculated shortest distance 1 between the road 31 having the road width W1 and the road 32 having the road width W2 is the same as the current position 30, the road 31 has Even if the vehicle is traveling away from the location 31, the vehicle may be traveling on the road 32 on the road 32. However, in the above-described map matching processing, the roads 31 and 32 are all evaluated equally.
[0015]
As described above, there is a problem that the same evaluation is given even though the road widths of the roads are different.
[0016]
Further, for example, as shown in FIG. 3B, in the road 31 having the road width W1 and the road 32 having the road width W2, the shortest distance l between the calculated current position 30 and the current position 30 is the same. If it is larger than the threshold value, none of the roads 31 and 32 will be selected. However, on the road 31, the current position 30 and the end of the actual road 31 are certainly far apart, but on the road 32, the current position 30 and the end of the actual road 32 may be close.
[0017]
As described above, there is a problem that the road may not be selected if the road has a large width.
[0018]
Further, for example, as shown in FIG. 3C, when the road 31 having the road width W1 and the road 32 having the road width W2 are parallel to each other, the shortest distance between the calculated current position 30 and the road 31 is determined. Even if l1 (≦ L) is shorter than the calculated shortest distance l2 (≦ L) between the current position 30 and the road 32, actually the vehicle is not on the road 31 having the road width W1, but on the road width W2. May be traveling on the road 32 having However, in the above-described map matching processing, the road 31 is estimated as the road on which the vehicle is traveling.
[0019]
As described above, when the road widths of the roads are different, there is a problem that a road different from the road which is originally desired to be estimated may be estimated as a road on which the vehicle is traveling.
[0020]
That is, conventionally, when estimating the road on which the vehicle is traveling, the width of the road has not been taken into account, so the calculated current position has the shortest distance from the road described on the map. However, it cannot be said that the shortest distance from the actual road is correctly reflected, and some problems have occurred as described with reference to FIG.
[0021]
Therefore, an object of the present invention is to change a threshold value used for selecting a road as a candidate for a road on which a vehicle is traveling in consideration of the road width of the road in the current position calculation device in accordance with the road width. Technology to provide
[0022]
[Means for Solving the Problems]
To achieve the above object, the present invention is provided in a navigation system mounted on a vehicle that moves with the rotation of wheels, a current position calculation device that calculates a current position of the vehicle,
(1) map data storage means for storing map data representing at least a map describing a road, the map data including road width information indicating a road width of each road;
(2) measuring means for measuring the traveling direction and the traveling distance of the vehicle,
(3) current position calculating means for calculating the current position of the vehicle based on the traveling direction and the traveling distance measured by the measuring means;
(4) From among the roads described within a predetermined distance from the current position calculated by the current position calculation means, of the maps represented by the map data stored in the map data storage means, The shortest distance between the current position calculated by the current position calculating means and a road having a deviation of an angle between the traveling direction measured by the measuring means and the first threshold value is equal to or less than a first threshold value. Driving road estimating means for selecting roads that are equal to or less than the threshold value and estimating one of the selected roads as a road on which the vehicle is traveling;
(5) current position correction means for correcting the current position calculated by the current position calculation means so as to be located on the road estimated by the traveling road estimation means;
And the travel road estimation means is included in the map data stored in the map data storage means for each of the roads described in the range within the predetermined distance. And a second threshold value changing means for changing the second threshold value according to the road width indicated by the road width information corresponding to the road.
[0023]
It is preferable that the second threshold value changing means increases the second threshold value as the road width increases.
[0024]
For example, the second threshold value changing means may include, for each range of the road width divided into a plurality of ranges, a table storing means storing a table describing a second threshold value corresponding to the range. In such a case, the second threshold value described in the table stored in the table storage unit is set to a new value in association with the range to which the road width belongs. It can be a second threshold.
[0025]
Further, for example, the second threshold value changing means may set a result obtained by multiplying the road width by a predetermined constant as a new second threshold value.
[0026]
[Action]
In the current position calculation device of the present invention, when estimating the road on which the vehicle is traveling, the second threshold value is changed according to the road width of the road. Specifically, the larger the road width, the larger the second threshold value.
[0027]
Conventionally, when estimating the road on which the vehicle is traveling, the width of the road is not taken into account, so the shortest distance between the calculated current position and the road described on the map is actually 3 does not accurately reflect the shortest distance to the road, and as described with reference to FIG. 3, there have been some problems. However, in the present invention, the road width of the road is taken into consideration. However, since the second threshold value is changed according to the road width, such a problem can be solved.
[0028]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
FIG. 1 is a block diagram illustrating a configuration of a navigation system to which the current position calculation device according to the present embodiment is applied.
[0030]
As shown in FIG. 1, the navigation system according to the present embodiment detects an angular velocity sensor 101 that detects a change in the traveling direction of a vehicle by detecting a yaw rate of the vehicle, and detects a traveling direction of the vehicle by detecting terrestrial magnetism. And a vehicle speed sensor 103 that outputs pulses at time intervals proportional to the rotation speed of the output shaft of the transmission of the vehicle.
[0031]
The navigation system according to the present embodiment includes a display 107 that displays the current position of the vehicle and a map around the display, a switch 104 that receives an instruction from the user to switch the scale of the map displayed on the display 107, And a driver 106 that reads map data from the CD-ROM 105.
[0032]
The navigation system according to the present embodiment includes the controller 108 that controls the operation of each of the above-described peripheral devices.
[0033]
The controller 108 includes an A / D converter 109 that converts an output value (analog signal) of the angular velocity sensor 101 into a digital signal, and an A / D converter 110 that converts an output value (analog signal) of the azimuth sensor 102 into a digital signal. And a counter 116 for counting the number of output pulses of the vehicle speed sensor 103 every 0.1 second, a parallel I / O 111 for inputting whether or not the switch 104 has been pressed, and the map data read from the CD-ROM 105 by the driver 106 are transferred. A direct memory access (DMA) controller 112 and a display processor 113 that displays a map of the current position of the vehicle and its surroundings on a display 107.
[0034]
Further, the controller 108 further includes a microprocessor (MPU) 114 and a memory 115.
[0035]
The MPU 114 outputs the output value of the angular velocity sensor 101 obtained through the A / D converter 109, the output value of the azimuth sensor 102 obtained through the A / D converter 110, and the output pulse of the vehicle speed sensor 103 counted by the counter 116. The current position of the vehicle is calculated by inputting the number, the presence / absence of depression of the switch 104 obtained via the parallel I / O 111, and the map data obtained via the DMA controller 112, and performing processing based on these. In addition, the MPU 114 causes the display 107 to display the calculated current position of the vehicle and a map around the calculated current position via the display processor 113.
[0036]
The display of the current position of the vehicle is performed by superimposing a mark (here, an arrow) 20 on the map already displayed on the display 107 as shown in FIG. Thereby, the user can know the current position of the vehicle.
[0037]
The memory 115 includes a ROM that stores programs to be executed by the MPU 114 and tables to be described later, and a RAM that the MPU 114 uses as a work area.
[0038]
Hereinafter, the operation of the navigation system according to the present embodiment will be described.
[0039]
First, a travel distance / travel direction calculation process for calculating the travel distance and travel direction of the vehicle will be described.
[0040]
FIG. 4 is a flowchart of the traveling distance / traveling direction calculation process.
[0041]
This process is a program routine of the MPU 114 that starts the process at a fixed period, for example, every 100 ms.
[0042]
As shown in FIG. 4, in this process, first, the output value of the angular velocity sensor 101 is read from the A / D converter 109 (step 401). Since the output value of the angular velocity sensor 101 is a value indicating a change in direction (angular velocity), only the relative traveling direction of the vehicle can be detected. Therefore, subsequently, the output value of the direction sensor 102 is read from the A / D converter 110 (step 402), the absolute direction indicated by the read value of the direction sensor 102, and the angular velocity sensor 101 read in step 401. The traveling direction V of the vehicle is determined using the change in the direction indicated by the output value (step 403).
[0043]
Note that the determination of the traveling direction V is made, for example, when the vehicle speed is low for a long time because the error of the angular velocity sensor 101 is large. This is done by using only
[0044]
Subsequently, the count value of the counter 116, which counts the number of output pulses from the vehicle speed sensor 103 every 0.1 second, is read (step 404), and the read count value is multiplied by the travel distance coefficient R to obtain 0.1. The travel distance K traveled by the vehicle per second is obtained (step 405). The running distance coefficient R indicates the distance that the vehicle travels per tire rotation.
[0045]
Subsequently, the travel distance K obtained in step 405 is added to the integrated value ΣK of the travel distance K, and it is determined whether or not the integrated value ΣK has reached a certain distance (for example, 20 m) (step 406). If not, this process ends. When the integrated value ΣK has reached 20 m, the integrated value ΣK is initialized (step 407), and a current position calculation process to be described later is started (step 408), followed by terminating the current process.
[0046]
Next, a current position calculation process for calculating the current position of the vehicle will be described.
[0047]
FIG. 5 is a flowchart of the current position calculation process.
[0048]
This process is a program routine of the MPU 114 started in step 408 of FIG. Therefore, this processing starts every time the distance traveled by the vehicle reaches 20 m. This process is a process corresponding to the map matching process.
[0049]
As shown in FIG. 5, in the present process, first, based on the traveling direction V and 20 m determined in step 403 of FIG. 4, the movement amount of the vehicle is obtained for each of the latitude direction and the longitude direction. The current position A, which is the position where the current vehicle is estimated to be present, is obtained by adding the amount of movement in each direction to the position of the vehicle candidate point obtained in the previous process of obtaining the vehicle candidate point ( Step 501). Details of this candidate point will be described later.
[0050]
If there is no candidate point obtained in the previous process of obtaining a candidate point for the vehicle, for example, immediately after the start of the navigation system, a separately set position is used as the position of the previously obtained candidate point. , The current position A is determined.
[0051]
Subsequently, map data representing a map around the current position A obtained in step 501 is read from the CD-ROM 105 via the driver 106 and the DMA controller 113 (step 502).
[0052]
Subsequently, when the candidate point used for obtaining the current position A is a candidate point on a road (line segment) described in the map represented by the read map data, a predetermined distance D from the current position A And extracts a line segment connected to the line segment or a line segment connected thereto. If the line segment is not a candidate point on a road (line segment), a line segment within a predetermined distance D from the current position A is extracted. (Step 503).
[0053]
At this time, D may be made variable based on the reliability of the candidate point used for obtaining the current position A. That is, a line segment included in a narrower range is selected for the current position A obtained from the candidate point with high reliability, and conversely, a line segment included in the current position A obtained from the candidate point with low reliability is selected for a wider range. Select the line segment included in. The reason for making D variable based on the reliability is that if the reliability is low, it is considered that the credibility of the accuracy of the current position obtained last time is low, so it is better to search for a road by searching a wider range. This is because it is appropriate for obtaining a correct current position.
[0054]
In addition, as shown in FIG. 6, for example, a road is approximated by a plurality of line segments 60 to 63 connecting two points, and a line represented by the coordinates of the start point and the end point is used. Has become. In the example shown in FIG. 6, the line segment 62 is represented by its start point (x3, y3) and end point (x4, y4). Further, since the road has a road width, the line segment passing through the center of the road is adopted as these line segments.
[0055]
Therefore, in the present embodiment, the map data represents a map describing a road and the described road, so that the threshold value L used later can be changed according to the road width of the road. For each case, road width information indicating the road width of the road is included.
[0056]
Subsequently, from the line segments extracted in step 503, all the line segments whose angle deviation θ between the line segment and the traveling direction V determined in step 403 in FIG. A primary selection is made (step 504).
[0057]
Subsequently, a threshold value L corresponding to the road width W of each road is obtained for all of the first-selected line segments (step 505). That is, the road width W indicated by the road width information included in the map data is obtained for all the primary selected line segments, and the road width W is associated with the obtained road width W by referring to the table stored in the ROM. The threshold value L described in the following is obtained.
[0058]
As shown in FIG. 8, the table is a table in which for each range when the road width W is divided into a plurality of ranges, the threshold value L corresponding to the range is described in association with each range. Here, the threshold L is described as a value that increases as the road width W increases.
[0059]
Subsequently, a perpendicular line is drawn from the current position A to all of the first selected line segments, and the length l of the perpendicular line (the shortest distance between the current position A and the line segment) 1 is obtained (step 506). .
[0060]
Subsequently, all the line segments whose obtained shortest distances l are equal to or smaller than the threshold value L obtained in step 505 are secondarily selected (step 507), and the error cost ec = α is calculated for all the secondarily selected line segments. × θ + β × l is obtained (step 508).
[0061]
Here, α and β are weighting coefficients, which are used when estimating the road on which the vehicle is traveling, when the angle θ between the traveling direction and the road and the current position A and the road Can be changed depending on which one of the shortest distances l is important. For example, when emphasizing a road close to the current position A, β is set to be larger than α.
[0062]
Here, the candidate points will be described.
[0063]
In an initial state, such as immediately after the start of the navigation system, the current position A is uniquely determined by, for example, the user inputting predetermined information using the switch 104, and the current position A is a line corresponding to the road. Minutes above. However, after the vehicle runs, the current position A may not exist on the road (line segment) due to errors of various sensors. As a result, for example, when the road is branched, that is, when two line segments appear from the node of the road (line segment), it is clearly determined which line segment the vehicle is on on the road. Often it is not possible.
[0064]
Therefore, in such a case, in the present embodiment, a predetermined point existing on two possible line segments (a point at which a perpendicular drawn from the current position A intersects the line segment) is set as a candidate point, The current position A, the error cost ec, the accumulated error cost es described later, and the like are each stored in the RAM of the memory 115.
[0065]
Now, when the error cost ec is obtained for all the line segments, based on the obtained error cost ec and the accumulated error cost es related to the candidate point obtained in the previous process, for each of these line segments, The cumulative error cost es in the current process defined by the following equation is obtained (step 509).
[0066]
es = (1−k) × ec + k × ec
Here, k is a weight coefficient larger than “0” and smaller than “1”. The accumulated error cost es indicates how much the error cost ec determined in the previous process is reflected on the error cost ec determined in the current process.
[0067]
Further, for each of all the candidate points, a reliability trst defined by the following equation is obtained based on the obtained cumulative error cost ec (n) (step 510).
[0068]
trst = 100 / (1 + es)
As is clear from this equation, as the cumulative error cost es increases, the reliability trst decreases and approaches “0”. Conversely, as the cumulative error cost es decreases, the reliability trst increases, and its value approaches “100”.
[0069]
By performing such processing, the reliability trst for each line segment existing within a predetermined range D from the current position A for a certain candidate point is obtained.
[0070]
Finally, the line segment with the highest reliability trst is estimated to be the road on which the vehicle is traveling (step 511), and the point where the estimated line segment intersects with the perpendicular drawn from the current position A is corrected. After setting the current position B (step 512), the current process is terminated.
[0071]
Next, a display process for displaying the current position and a map around the current position will be described.
[0072]
FIG. 7 is a flowchart of the display process.
[0073]
This process is a program routine of the MPU 114 which starts the process at regular intervals, for example, every 1S.
[0074]
As shown in FIG. 7, in the present process, first, it is determined whether or not the switch 104 is pressed to switch the scale of the map by looking at the contents input by the parallel I / O 111 (step). 701). If the switch 104 is pressed, a predetermined scale flag is set accordingly (step 702).
[0075]
Subsequently, the current position B corrected in step 512 in FIG. 5 and the traveling direction V determined in step 403 in FIG. 4 are read (step 703), and the scale corresponding to the contents of the scale flag set in step 702 is read. The map is displayed on the display 107 via the display processor 113, for example, as shown in FIG. 2 (step 704).
[0076]
Subsequently, the current position B of the vehicle and the traveling direction V of the vehicle are superimposed on the map displayed on the display 107, for example, as shown in FIG. Displayed at 107 (step 705).
[0077]
Finally, a north mark 21 indicating north and a distance mark 22 corresponding to the reduced scale are displayed on the display 107 via the display processor 113, as shown in FIG. 2, for example (step 706).
[0078]
In the present embodiment, as described above, the current position and the traveling direction of the vehicle are indicated using the arrows, but the display form of the current position B and the traveling direction V of the vehicle is such that these are clearly shown. If so, it may be arbitrary. The same applies to the north mark 21 and the like.
[0079]
As described above, in the present embodiment, as the road width W of the road is larger, the threshold value L used for selecting a road as a candidate for the road on which the vehicle is traveling is larger.
[0080]
Conventionally, when estimating the road on which the vehicle is traveling, the road width W of the road is not taken into account, so that the shortest distance l between the calculated current position and the road described on the map is calculated. However, it cannot be said that the shortest distance from the actual road is correctly reflected, and some problems have occurred as described with reference to FIG. 3. However, in this embodiment, the road has Since the threshold value L is changed according to the road width W in consideration of the road width W, such a problem can be solved.
[0081]
In this embodiment, the threshold value L corresponding to the road width W is obtained by referring to the table shown in FIG. 8. However, the threshold value is obtained by multiplying the road width W by a predetermined constant a. The value L may be obtained. In addition, as the road width data, the number of lanes of the road may be used in addition to the actual road width.
[0082]
Further, in the present embodiment, a line segment whose angle deviation θ with respect to the traveling direction V is equal to or less than the threshold value T is firstly selected, and a line segment whose shortest distance l is equal to or less than the threshold value L is secondarily selected. Selected, but may be reversed.
[0083]
In this embodiment, the line segment having the maximum reliability trst obtained in step 511 in FIG. 5 is estimated to be the road on which the vehicle is traveling. If the road is an automobile exclusive road such as a road, it is considered that the vehicle is traveling on the automobile exclusive road again, so even if the obtained reliability trst is not the maximum, the automobile exclusive road is given priority. Alternatively, it may be estimated that the road is on which the vehicle is traveling. In order to do this, it is necessary that the map data further include road type information indicating at least whether or not the road is a motorway.
[0084]
【The invention's effect】
As described above, according to the current position calculation device of the present invention, the threshold used for selecting a road as a candidate for the road on which the vehicle is traveling is set to the road width in consideration of the road width of the road. Can be changed accordingly.
[0085]
Therefore, the conventional problem caused by not considering the road width of the road can be solved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a navigation system to which a current position calculation device according to an embodiment is applied.
FIG. 2 is an explanatory diagram showing a display example of a display.
FIG. 3 is an explanatory diagram showing a conventional problem.
FIG. 4 is a flowchart of a traveling distance / traveling direction calculation process in the embodiment.
FIG. 5 is a flowchart of a current position calculation process in the embodiment.
FIG. 6 is an explanatory diagram showing an expression format of a road.
FIG. 7 is a flowchart of a display process in the embodiment.
FIG. 8 is an explanatory diagram of a table used in the embodiment.
[Explanation of symbols]
101: angular velocity sensor, 102: bearing sensor, 103: vehicle speed sensor, 104: switch, 105: CD-ROM, 106: driver, 107: display, 108: controller, 109, 110: A / D converter, 111: parallel I / O, 112: DMA controller, 113: Display processor, 114: Microprocessor, 115: Memory, 116: Counter.

Claims (4)

  A current position calculation device mounted on a vehicle and calculating a current position of the vehicle,
  Road data storage means for storing in advance road data including a road width of each of a plurality of roads constituting the map,
  Measuring means for measuring the traveling direction and the traveling distance of the vehicle,
  A current position calculating unit that calculates a current position of the vehicle based on a traveling direction and a traveling distance of the vehicle measured by the measuring unit;
  A first road extracting unit that extracts the road within a first distance from the current position of the vehicle calculated by the current position calculating unit with reference to the road data storing unit;
  Comparing the azimuth of the road extracted by the first road extraction unit with the traveling azimuth of the vehicle, and the azimuth difference between the azimuth of the road extracted by the first road extraction unit and the traveling azimuth of the vehicle is determined. Second road extracting means for extracting the road that is equal to or less than a second threshold,
  With reference to the road data storage unit, based on the road width of the road extracted by the second road extraction unit, for each of the roads extracted by the second road extraction unit, the larger the road width is, the larger the road width is. Threshold value determining means for determining a third threshold value,
  A third road extracting a road whose distance from the current position of the vehicle calculated by the current position calculation unit is equal to or smaller than the third threshold value, from the roads extracted by the second road extraction unit; Extraction means;
  Traveling road estimation means for estimating one of the roads extracted by the third road extraction means as the road on which the vehicle is currently traveling;
  A current position correction unit that corrects the current position calculated by the current position calculation unit on the road estimated by the traveling road estimation unit;
A current position calculation device, comprising:   The current position calculation device according to claim 1,
  The threshold determining means,
  A table storage unit that stores the third threshold value in advance for each of the road width ranges divided into a plurality of ranges,
  With reference to the road data storage unit, the road width of the road extracted by the second road extraction unit is read, and the third threshold value corresponding to the range including the read road width is stored in the table storage unit. Reading means for reading from
A current position calculation device, comprising:   The current position calculation device according to claim 1,
  A current position calculating device, wherein the threshold value determining unit refers to the road data storage unit and multiplies the road width of the road extracted by the second road extracting unit by a fourth constant.   A current position calculation method in a current position calculation device mounted on a vehicle and calculating a current position of the vehicle,
  The current position calculation device,
  Each of the plurality of roads on the map is approximated by a straight line, and the positions of both ends of each of the straight lines on the map are stored in advance in road data storage means as road data corresponding to the respective road widths of the plurality of roads. And
  Measure the heading and mileage of the vehicle,
  Based on the measured heading and travel distance of the vehicle, calculate the current position of the vehicle,
  With reference to the road data storage means, extract the road within a first distance from the calculated current position of the vehicle,
  Comparing the azimuth of the road within the first distance with the traveling azimuth of the vehicle, and determining the azimuth difference between the azimuth of the road within the first distance and the traveling azimuth of the vehicle as a second threshold value Extract the road that is:
  Referring to the road data storage unit, based on the road width of the road that is equal to or less than the second threshold, for each of the roads that is equal to or less than the second threshold, a value that increases as the road width increases becomes larger. Determine a threshold of 3,
  Extracting the road whose calculated distance from the current position of the vehicle is equal to or smaller than the third threshold, from the roads equal to or smaller than the second threshold;
  Estimating one of the roads that is equal to or less than the third threshold as the road on which the vehicle is currently traveling,
  A current position calculation method, wherein the calculated current position of the vehicle is corrected on the estimated road.

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