JPH08334344A - Present location calculating device - Google Patents

Abstract

PURPOSE: To pertinently calculate the present location of a vehicle by preventing the deterioration of map matching accuracy which occurs when the vehicle moves straight ahead by setting the retrieving range of segments constituting the road data to be collated wit a virtual present location so that the range can become wider as the reliability of candidate points becomes lower. CONSTITUTION: When a microprocessor 24 executes a map matching process, the microprocessor 24 first separately finds the moving amounts of its own vehicle in the longitudinal and latitudinal direction. Then the microprocessor 24 finds a virtual present location which is estimated to be the present location of the vehicle by adding the moving amount of the vehicle to the candidate points for the present location of the vehicle found as a result of the last candidate point finding process and reads out the road data of a map of the circumferential area from a CD-ROM15 through a driver 16 and DMA controller 22. In this case, the microprocessor 24 makes the road retrieving range variable, based on the reliability of the candidate points used for finding the virtual present location and, regarding a virtual present location found from the candidate point having the highest reliability, selects segments from a narrow range. Regarding a virtual present location found from a candidate point having low reliability, the microprocessor 24 selects segments from a wide range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on a moving body such as a vehicle and measures the traveling distance and traveling direction of the moving body.
Accordingly, the present invention relates to a current position calculation device that calculates the current position of the moving body.

[0002]

2. Description of the Related Art Conventionally, in a current position calculating device for calculating the current position of a vehicle traveling on a road, the current position of the vehicle is the traveling direction of the vehicle measured by a direction sensor such as a gyro and the vehicle speed sensor or the distance. It is calculated based on the travel distance of the vehicle measured by the sensor.

Further, the mileage of a vehicle is generally a distance coefficient which is a distance traveled by the vehicle per one rotation of the tire by measuring the rotational speed of the output shaft of the transmission or the tire. It is calculated by multiplying by.

Further, in order to correct the error of the current position obtained from the traveling direction of the vehicle and the traveling distance in this way, as described in Japanese Patent Laid-Open No. 63-148115, it is obtained so as to match the road. The current position of the vehicle
A so-called map matching technique is known, and this map matching technique can improve the accuracy of current position calculation.

[0005]

By the way, according to the map matching, when the vehicle turns right or left or turns according to the curve of the road, the sensor output is selected by checking the current position on the road by comparing the sensor output with the road data. The cumulative error of is corrected to some extent. However, when the vehicle is traveling straight over a long distance, this correction action does not work, and the cumulative error (particularly the error in the traveling distance in the traveling direction) may increase.

On the other hand, in the conventional map matching, when matching the estimated position of the vehicle with the road data, all roads (line segments) located within a certain range centered on the estimated position are searched. I have to. The search range of this road is preferably narrow from the viewpoint of the processing load of the device.
This is because as the search range becomes wider, the time required for the search process and the time required for calculating the reliability of the obtained current position candidate point on the road increase, and other processes that the device should perform, such as azimuth Reading sensor data,
This is because there may be a case where the reading of the data of the vehicle speed sensor or the distance sensor or the calculation of the traveling distance of the vehicle based on the data of the vehicle speed sensor or the distance sensor cannot be appropriately performed. This problem is particularly noticeable in urban areas where roads are dense.

Under such circumstances, when straight running continues for a long time, there is a problem that the search range of the road may not be appropriate (that is, too narrow) with respect to the magnitude of the accumulated error. there were.

An object of the present invention is to provide a current position calculating device for appropriately calculating the current position of a vehicle by preventing the accuracy of map matching from deteriorating as the vehicle travels straight ahead.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a current position calculating device mounted on a vehicle for calculating the current position of the vehicle, the direction detecting means for detecting a traveling direction of the vehicle, and the traveling distance of the vehicle. Based on the relative displacement obtained based on the traveling direction and the traveling distance, the current position of the vehicle is sequentially estimated as a virtual current position. Then, the virtual current position is collated with the road data of the road data storage means, the candidate point of the current position on the road is calculated together with the reliability indicating its credibility, and when a plurality of candidate points are calculated. Map matching means for recognizing a candidate point having the highest reliability among the plurality of candidate points as the current position, straight running distance calculating means for calculating a straight running distance of the vehicle, and the linear running distance in proportion to the straight running distance. And a reliability correction unit that reduces the reliability calculated by the map matching unit, wherein the map matching unit sets a search range of a line segment that constitutes the road data to be matched with the virtual current position to the virtual current position. The present position calculation device is characterized in that, based on the reliability of the candidate points used to obtain the position, the lower the reliability, the wider the setting.

In this apparatus, the map matching means is a distance to a road around the virtual current position,
And the heading difference between the road heading and the vehicle heading,
The reliability of the candidate point found on the road is calculated.

The straight running distance calculating means preferably fixes the output straight running distance to the predetermined value when the calculated straight running distance exceeds a predetermined value.

[0012] It is desirable that the straight running distance calculating means reduces the straight running distance at the time when the non-straight running is detected. For example, the straight running distance calculation means,
When the non-linear running is detected, the straight running distance at that time is reduced at a predetermined rate.

[0013]

In the present invention, the map matching means successively estimates the current position of the vehicle as a virtual current position based on the relative displacement obtained based on the traveling direction and the traveled distance of the vehicle, and the virtual current position is calculated. By collating with the road data of the road data storage means, a candidate point of the current position on the road is calculated together with the reliability indicating its credibility, and when a plurality of candidate points are calculated, among the plurality of candidate points The candidate point with the highest degree of reliability is identified as the current position. At the same time, the reliability correction means reduces the reliability calculated by the map matching means in proportion to the straight running distance obtained by the straight running distance calculating means. The map matching means, based on the reliability of the candidate points used to obtain the virtual current position, broadens the search range of the line segment that constitutes the road data to be matched with the virtual current position, the lower the reliability. To be set.

As a result, since the road search range is expanded as the straight running becomes longer, it is possible to appropriately deal with the error accumulated with the straight running and perform the proper map matching.

When the straight travel distance exceeds a predetermined value, the output straight travel distance is fixed to the predetermined value to prevent the road search range from being excessively widened.

Further, when non-linear running is detected,
Since it is determined that the cumulative error to some extent has been eliminated, the search range of the road can be narrowed again by reducing the straight running distance at that time.

In a place where straight running becomes long,
It is highly likely that this is not an urban area with dense roads. Therefore, even if the search range of roads is expanded to some extent, the number of roads (line segments) to be picked up does not increase so much. Therefore, it is considered that the expansion of the road search range according to the present invention does not adversely increase the processing time of the device.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of the present position calculating apparatus according to the embodiment of the present invention. As shown in FIG. 1, the present position calculation device 10 includes an angular velocity sensor 11 that detects a yaw rate of a vehicle to detect a change in traveling direction, and a geomagnetic sensor 12 that detects a traveling direction of a vehicle by detecting geomagnetism. And a vehicle speed sensor 13 that outputs pulses at time intervals proportional to the rotation of the output shaft of the vehicle transmission.

Further, a display 17 for displaying a map around the current position and a mark indicating the current position, a switch 14 for receiving a command for switching the scale of the map displayed on the display 17 from a user (driver), and digital map data. CD-ROM 15 for storing the
A driver 16 for reading map data from the ROM 15. Further, the controller 18 for controlling the operation of each peripheral device described above is provided. In the present embodiment, the digital map data described above includes road data composed of coordinates indicating the ends of a plurality of line segments,
Alternatively, it includes road width data indicating the road width of the road, a highway flag indicating whether the road is a highway or a general road, and the like.

The controller 18 includes an A / D converter 19 for converting the signal (analog) of the angular velocity sensor 11 into a digital signal, and an A / D converter 20 for converting the signal (analog) of the geomagnetic sensor 12 into a digital signal. , Vehicle speed sensor 1
A counter 26 that counts the number of pulses output from the CPU 3 every 0.1 seconds, a parallel I / O 21 that inputs whether or not the switch 14 is pressed, and a DMA (that transfers the map data read from the CD-ROM 15 ( Direct Memory Acce
ss) It has a controller 22 and a display processor 23 for displaying a map image on the display 17.

The controller 18 also has a microprocessor 24 and a memory 25. The microprocessor 24 outputs the signal of the angular velocity sensor 11 obtained through the A / D converter 19, the signal of the geomagnetic sensor 12 obtained through the A / D converter 20, and the output pulse of the vehicle speed sensor 13 counted by the counter 26. Number, whether or not the switch 14 is pressed through the parallel I / O 21, and the map data from the CD-ROM 15 obtained through the DMA controller 22 are received and processed based on those signals, The current position is calculated and displayed on the display 17 via the display processor 23. The display of the vehicle position is performed by superimposing an arrow mark or the like on the map which is already displayed on the display 17, as shown in FIG. This allows the user to know the current position of the vehicle on the map. The memory 25 is
It includes a ROM that stores a program that defines the contents of processing (described later) for realizing such operations, and a RAM that is used as a work area when the microprocessor 24 performs the processing.

The operation of the present position calculation device 10 thus configured will be described below.

The operation of the apparatus 10 is generally the process of calculating the traveling direction and the traveled distance of the vehicle, the process of determining the current position of the vehicle from the calculated traveling direction and distance, and the obtained vehicle position and Since it can be divided into three processes, that is, the process of displaying the azimuth, these processes will be described sequentially.

FIG. 3 illustrates the flow of processing for calculating the traveling direction and traveling distance of the vehicle.

This processing is carried out at a constant cycle, for example 100 m.
This is a routine of the microprocessor 24 that is activated and executed for each S.

In this routine, first, the A / D converter 1
The output value of the angular velocity sensor 11 is read from 9 (step 301). Since the azimuth change is output as the output value of the angular velocity sensor 11, only a relative value in the traveling direction of the vehicle can be detected. Therefore, next, the output value of the geomagnetic sensor 12 is read from the A / D converter 20 (step 30
2) The estimated azimuth of the vehicle is determined using the absolute azimuth calculated from the output value of the geomagnetic sensor 12 and the azimuth change (angular velocity output) output from each speed sensor 11 (step 303).

This azimuth determination can be performed, for example, for a long time,
When the vehicle speed is low, the error of the angular velocity sensor is large, so
When the vehicle speed is low for a certain period of time or more, the method is performed by using only the geomagnetic sensor direction.

Next, the number of pulses output from the vehicle speed sensor 13 is counted by the counter 26 every 0.1 seconds, and the counted value is read (step 304). By multiplying the read value by the distance coefficient, the distance advanced in 0.1 second is obtained (step 305).

Next, the traveling distance value per 0.1 second thus obtained is integrated with the value obtained last time,
It is checked whether or not the traveling distance of the vehicle has reached 20 m (step 306).
No, the current process is terminated and a new process is started.

As a result of the traveling distance calculation processing, when the accumulated traveling distance becomes a constant distance, for example, 20 m (Yes in step 306), the traveling direction and traveling distance (20 m) at that time are output. (Step 307).
In step 307, the integrated distance is further initialized,
Start a new mileage integration.

Next, the process of calculating the virtual current position of the vehicle based on the calculated heading and traveling distance and obtaining the candidate point of the vehicle based on the calculated virtual current position will be described.

FIG. 4 shows the flow of this processing.

This processing is a routine of the microprocessor 24 which is started and executed in response to the output of the traveling direction and the traveling distance from FIG. That is, this process is started every time the vehicle advances 20 m.

In this process, first, the traveling azimuth and the traveling distance output in the previous step 307 are read (step 41).

Next, a map matching process is performed (step 42). This includes a process of calculating the reliability of candidate points, as will be described in detail later.

After that, reliability correction processing is performed to correct the reliability of the candidate points obtained by this map matching processing (step 43). In this embodiment, as will be described later, the reliability is corrected according to the length of the straight travel distance.

Finally, based on the corrected reliability, the candidate point with the highest reliability is selected as a display candidate from these candidate points, and this display candidate point data is output (step 44). More specifically, the position, cumulative error cost, reliability, etc., of the candidate point C having the highest reliability value as the display candidate point CD, that is, the candidate point for displaying on the display 17, In addition to being stored in a predetermined area of the RAM of the memory 25, the positions of candidate points other than the display candidate points, accumulated error costs, reliability, status flags, etc. are also stored in a predetermined area of the RAM. The display process will be described in detail later.

In this embodiment, the data related to the seven candidate points can be stored. Therefore, when eight or more candidate points are calculated, among these, various data related to seven candidate points in descending order of the value of the reliability trst are stored in a predetermined area of the RAM of the memory 25. Will be done.

FIG. 5 shows details of the map matching process.

In the map matching process, first,
The amount of movement of the vehicle is obtained separately in the latitude and longitude directions. Further, the movement amount in each of these directions is added to the position of the vehicle candidate point obtained in the previous process for obtaining the vehicle candidate point, and the virtual current position (position where the current vehicle is estimated to exist) ( A) is calculated (step 421).
Details of this candidate point will be described later. If there is no candidate point obtained in the previous process of finding candidate points for the vehicle, such as immediately after the start of the device, the position set separately is used as the position of the previously obtained candidate point and the virtual current is used. Find position (A).

Next, the road data of the map around the obtained virtual current position (A) is read from the CD-ROM 15 via the driver 16 and the DMA controller 23 (step 422).

At this time, the road search range D is made variable based on the reliability (corrected last time) regarding the candidate points used to obtain the virtual current position (A). That is, for the virtual current position obtained from the highly reliable candidate point, the line segment included in the narrower range is selected, and conversely, the virtual current position obtained from the less reliable candidate point is wider range. Select the line segment included in. The reason why the search range D is variable based on the reliability is that the reliability of the accuracy of the current position obtained last time is considered to be low when the reliability is low, so a wider range is searched to search the road. This is because searching is more appropriate for finding the correct current position.

As described above, in this embodiment, the road data is approximated by a plurality of line segments 51 to 55 connecting the two points as shown in FIG. And the coordinates of the end point are used. For example, the line segment 53 has its start point (x3, y
3) and the end point (x4, y4).

Next, from the line segments extracted in step 422, only the line segments whose azimuth is within the predetermined traveling direction and the required traveling direction are selected (step 42).
3). Further, a vertical line is drawn from the virtual current position (A) for all the extracted n line segments, and the vertical line L
The length of (n) is obtained (step 424).

Next, based on the lengths of these perpendiculars, the error cost value ec (n) defined by the following equation is calculated for all the line segments selected in step 423.

Ec (n) = α × | θcar−θ (n) | +
β | L (n) | where θcar is the vehicle direction at the virtual current position (A), θ (n) is the direction of the line segment, and L (n) is the direction from the virtual current position (A) to the line segment. Distance, ie the length of the perpendicular, α
And β are weighting factors. The values of these weighting factors are
It may be changed depending on which of the deviation between the traveling direction and the direction of the road and the deviation between the current position and the road is given priority in selecting the road to which the current position belongs. For example, when a road whose direction is close to the traveling direction is important, α is increased.

Here, details of calculation of the candidate points will be described. In the initial state, such as immediately after starting the device,
In the virtual current position (A), the user (driver) switches 1
It is uniquely determined by inputting predetermined information using 4, and this is located on the line segment corresponding to the road. However, after the vehicle has traveled, the virtual current position (A) may be affected by an error in a sensor such as a gyro.
May not exist on the line segment corresponding to the road.
As a result, as shown in FIG. 7, for example, when the road is branched, that is, when two line segments 64 and 65 appear from the node 68 of the line segment 61 corresponding to the road, which line segment In many cases, it cannot be clarified whether there is a vehicle on the road corresponding to.

Therefore, in such a case, in this embodiment, predetermined points existing on two conceivable line segments are set as candidate points, and their current position, error cost, and accumulation to be described later. Error cost, etc.
The memory 25 is configured to be stored in a predetermined area of the RAM. In addition, in order to facilitate the description, in the following description, one or more new candidate points will be generated from a single candidate point, unless it is clearly indicated that there are a plurality of candidate points.

Next, the calculated error cost ec
According to (n) and the cumulative error cost es related to the candidate points obtained in the previous processing, the cumulative error cost es in the current processing defined by the following formula
(N) is calculated (step 425).

Es (n) = (1−k) × es + k × ec (n) Here, k is a weighting coefficient larger than 0 and smaller than 1. This accumulated error cost es (n) represents how much the error cost calculated in the previous process is reflected in the error cost calculated in this process.

Furthermore, the calculated cumulative error cost es
The reliability trst defined by the following equation based on (n)
(N) is calculated (step 425).

Trst (n) = 100 / (1 + es (n)) As is clear from this equation, the accumulated error cost ec
The reliability trst increases as (n) increases.
(N) decreases and approaches 0 (zero). On the other hand, as it becomes smaller, the reliability trst (n) increases, and its value approaches 100. The reliability obtained here is to be corrected by the reliability correction processing in step 43 of FIG.

By performing such processing, n existing in a predetermined range D from the current position A for a certain candidate point
The reliability trst (n) associated with each line segment is obtained. In this way, the reliability is calculated for each selected line segment, but in the present specification, for the sake of convenience, it is also treated as the reliability for the candidate obtained on that line segment.

Then, based on the calculated reliability trst (n), a point advanced from a certain candidate point along the corresponding line segment by a length corresponding to the distance R traveled by the vehicle,
A new candidate point C (n) is set (step 426). Therefore, when the number of line segments in which a certain candidate point is located or a line segment connected to this is such that the difference between the azimuth and the vehicle azimuth is a predetermined value or less is n, N new candidate points C (n) will be generated.

For example, as shown in FIG. 7, it is assumed that the current position A is represented by the position indicated by the point 63 with respect to a certain candidate point 62 existing on the line segment 61. In such a case, a line segment 64 connected from the current position A to the line segment 61 in which the candidate point 62 is located, and the difference between the azimuth and the vehicle azimuth is a predetermined value or less, 65 is taken out, and the distances L (1), L from the current position A to the line segments 64, 65
(2) is calculated, and the calculated distance, line segment 64,
Based on the angles θ (1) and θ (2) of 65 and the vehicle direction θcar, etc., the related error cost, accumulated error cost, and reliability are calculated. Further, step 307 in FIG.
Based on the travel distance R of the vehicle obtained in
From 2, the position advanced by the length corresponding to the traveling distance R is calculated along the line segments 61 and 64 or the line segments 61 and 65, and the points corresponding to this position are respectively the candidate points 66, 67.

Further, as shown in FIG. 8, with respect to the candidate point 66 on the line segment 64, the new current position A is represented at the position indicated by the point 71, while the candidate on the line segment 65 is selected. Point 67
On the other hand, it is assumed that the new current position A ′ is represented by the position indicated by the point 72. In this case, from the current position A, line segments 73 and 74 which are connected to the line segment 64 and in which the difference between the azimuth and the vehicle azimuth is equal to or less than a predetermined value are taken out, and a new segment is added. From the current position A ′, a line segment 75 which is connected to the line segment 65 and whose difference between the direction and the vehicle direction is equal to or less than a predetermined value is extracted. Then, the distance L from the current position A to the line segments 73 and 74
1 (1) and L1 (2) are calculated, and the distance L2 (1) from the current position A ′ to the line segment 75 is calculated.
Furthermore, the distance calculated in relation to the current position A and the line segment 7
Based on the angles θ1 (1) and θ1 (2) of 3,74, the vehicle direction θcar, and the like, the related error cost, accumulated error cost, and reliability are calculated, as well as the current position A ′. Distance, angle of line segment 75
Based on 2 (1) and the vehicle direction θcar, the related error cost, accumulated error cost, and reliability are calculated.

Further, based on the traveling distance R of the vehicle obtained in step 307 of FIG.
4 and 73, or along line segments 64 and 74,
Alternatively, a position advanced from the candidate point 67 along the line segments 65 and 75 by a length corresponding to the mileage R of the vehicle is calculated, and the points corresponding to this position are respectively set as new candidate points. . FIG. 9 shows the candidate points 81 to 83 newly obtained in this way.

The detailed flow of the reliability correction processing shown in FIG. 4 will be described with reference to FIG.

In the present embodiment, as described above, the reliability is corrected according to the length of the straight traveling distance of the vehicle. This is because the longer the straight running is, the more the error correction in the traveling direction based on the road shape by map matching is not performed, and this is reflected in the reliability. That is, the reliability of the candidate points is corrected so as to be reduced according to the length of the straight traveling distance.

In FIG. 6, first, it is determined whether or not the vehicle is traveling straight ahead (step 431). This can be determined, for example, by whether or not the average value of the successive azimuth change amounts of the vehicle azimuths at a plurality of past times exceeds a predetermined threshold value. If it is determined that the vehicle is traveling straight ahead, the straight traveling distance L is cumulatively updated (step 432). This straight traveling distance is reset to 0 when the apparatus is started. If the updated value of the distance L is equal to or smaller than the upper limit value (16 Km in this case) of the predetermined distance (step 434, No), the process proceeds to step 436, and if it exceeds the upper limit value (step 434, Yes), The distance L is fixed to the upper limit value (step 435). The upper limit of the distance L is set in consideration of the fact that if the reliability is infinitely reduced in accordance with the straight running distance, the harmful effect becomes larger. When it is determined in step 431 that the vehicle is not traveling straight ahead, the distance L is reduced to half (step 433) and the process proceeds to step 436. This is intended to improve the reliability from the present level, considering that the error correction function of map matching works due to non-straight running. The distance L is halved each time the vehicle is determined to be traveling in a non-straight line. Therefore, if the non-straight traveling continues, the distance L approaches 0. Here, the distance L is halved, but it is also possible to reduce the distance L at other ratios.

In step 436, the straight running distance L
The reliability correction amount m is calculated based on This process is shown in FIG.
As shown in FIG. 1, the reliability correction amount m is obtained from the value n obtained by multiplying the distance L by a predetermined coefficient (here, 5/2000). This m is calculated by the following equation.

M = (1−i) × m + i × n (0 <i ≦ 1) where i is a weighting coefficient that determines how much the previous m value is reflected in the current m value, When i is 1, the m value is determined only by the n value, and as the i value becomes smaller, the previous m value is weighted more rapidly and the rapid change in the m value can be suppressed.

Using the value of m, the corrected reliability tr
st (crr) is calculated by the following equation (step 43)
7).

Trst (crr) = trst-m As can be seen from this equation, the value of the reliability trst (crr) decreases as the value of m increases, that is, as the value of n (and thus the straight running distance L) increases. . Also,
Along with this, the search range of the road with respect to the virtual current position obtained from the candidate point is expanded. Each time the vehicle travels in a non-straight line, the straight line travel distance L at that time is halved, and
The reliability of the candidate points will increase somewhat.

As can be seen from the graph of FIG. 11, when the vehicle enters straight running, the reliability (after correction) decreases linearly with the slope of the coefficient for obtaining the n value.

The display candidate points obtained in step 44 of FIG. 4 are displayed on the screen of the display 17 by the processing based on the flowchart shown in FIG.

This process is a routine of the microprocessor 24 which is activated and executed every one second.

First, it is determined whether or not the switch 14 is instructed to change the scale of the map by looking at the contents of the parallel I / O 21 (step 1301). If it is pressed (Yes in step 1301), a predetermined scale flag is set correspondingly (step 130).
2).

Next, the data indicating the position and direction of the display candidate point is read from a predetermined area of the RAM of the memory 25 (step 1303), and a map of a scale according to the content of the scale flag switched in step 1302 is displayed. It is displayed on the display 17, for example, in the state as shown in FIG. 2 (step 1304).

Then, the position and orientation of the display candidate point are displayed by using the arrow symbol "↑", for example, as shown in FIG. 2 above, superimposed on the map (step 130).
5). Finally, the north mark indicating north and the distance mark corresponding to the reduced scale are displayed as shown in FIG. 2 so as to be superimposed on them (step 1306).

In this embodiment, the vehicle position and the direction are indicated by using the arrow symbols as described above. However, the display form of the vehicle position and the direction shows that the position and the traveling direction are
The form may be arbitrary as long as the display state is clearly shown. The same applies to the north mark and the like.

According to this embodiment, the road search range is expanded according to the straight travel distance, so that the accuracy of map matching can be further improved.

In the present specification, the term "means" does not necessarily mean physical means, but also includes the case where the function of each means is realized by software.
Further, the function of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means.

[0075]

According to the present invention, it is possible to provide a current position calculating device for appropriately calculating the current position of a vehicle by preventing the accuracy of map matching from being lowered due to straight running of the vehicle.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a current position calculation device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a display example of a map and a current position according to the present embodiment.

FIG. 3 is a flowchart showing a process of calculating a traveling direction and a traveling distance of a vehicle.

FIG. 4 is a flowchart showing a main process of this embodiment.

FIG. 5 is a flowchart showing details of one step (map matching processing) shown in FIG.

FIG. 6 is a flowchart showing details of another step (reliability correction process) shown in FIG.

FIG. 7 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and a candidate point.

FIG. 8 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and a candidate point.

FIG. 9 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and a candidate point.

FIG. 10 is a diagram for explaining an example of road data according to the present embodiment.

FIG. 11 is a diagram for explaining calculation of a reliability correction amount according to the present embodiment.

FIG. 12 is a flowchart showing a display process according to the present embodiment.

[Explanation of symbols]

 10 Current Position Calculation Device 11 Angular Velocity Sensor 12 Geomagnetic Sensor 13 Vehicle Speed Sensor 14 Switch 15 CD-ROM 16 CD-ROM Read Driver 17 Display 18 Controller

Claims (5)

[Claims] 1. A current position calculating device mounted on a vehicle for calculating a current position of the vehicle, comprising: an azimuth detecting means for detecting a traveling azimuth of the vehicle; and a distance calculating means for calculating a traveling distance of the vehicle. Based on a road data storage unit that stores road data, and a relative displacement obtained based on the traveling direction and the traveled distance, the current position of the vehicle is sequentially estimated as a virtual current position, and the virtual current position is described above. By collating with the road data of the road data storage means, the candidate point of the current position on the road is calculated together with the reliability indicating its credibility, and when a plurality of candidate points are calculated, the reliability of the plurality of candidate points is calculated. A map matching means for recognizing the candidate point with the highest degree as the current position, a straight running distance calculating means for calculating the straight running distance of the vehicle, and a map matching means for calculating the straight running distance in proportion to the straight running distance. The map matching means obtains the virtual current position of the search range of the line segment that constitutes the road data to be collated with the virtual current position. A current position calculation device, characterized in that, based on the reliability of the candidate points used for this purpose, the lower the reliability, the wider the setting. 2. The map matching means calculates the reliability of a candidate point found on the road based on the distance to the road around the virtual current position and the heading difference between the road heading and the vehicle heading. The present position calculation device according to claim 1, wherein 3. The straight running distance calculating means fixes the output straight running distance to the predetermined value when the calculated straight running distance exceeds a predetermined value. 1. The current position calculation device described in 1 or 2. 4. The current position calculation device according to claim 1, wherein the straight running distance calculating means reduces the straight running distance at that time when the non-straight running is detected. 5. The present position calculation device according to claim 4, wherein the straight running distance calculation means reduces the straight running distance at that time when a non-straight running is detected at a predetermined rate.