JPH11351890A - Route searching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely obtain a road link closest to a set point in a route searching device for searching for a route using a map mesh that is divided into a plurality of portions. SOLUTION: When a road link closest to a set point is to be extracted, a road link 54 closest to peripheral road meshes 32-39 may exist even if a road link 53 is extracted only within a map mesh 31. With the above possibility as a specific condition, a corresponding peripheral map mesh is to be extracted as a road link when the specific condition is met.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route search device that sets a starting point and a destination point, obtains a route between them by calculation, and displays the route on a screen.

[0002]

2. Description of the Related Art In a route search apparatus, a starting point, a destination, and a passing point are set as set points prior to a route search. When a set point is set, a road link closest to the point is selected, and a route between the selected road links is obtained by calculation. The route obtained as a result of the calculation is displayed on the display device so as to overlap the map.

Here, the road data used for the route search is
For each map mesh divided into a plurality of rectangular shapes, a CD-
It is stored in a storage medium such as a ROM. When selecting the road link closest to the set point, the conventional route search device selects the road link closest to the set point in a map mesh including the set point for simplicity.

[0004]

However, the road link closest to the set point is not always present in the map mesh including the set point. That is, a road link in another map mesh (peripheral map mesh) around the map mesh may be closer to the set point than a road link in the map mesh including the set point. In this case, selecting a road link in the surrounding map mesh is likely to be an appropriate route. However, in the conventional route search device, since a road link is selected only within the map mesh including the set point, an appropriate route may not be selected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a route search device for performing a route search using a plurality of divided map meshes, which can reliably obtain a road link closest to a set point. Is what you do.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object. The present invention provides a starting point,
It has a point setting means for setting a destination as a set point, an extracting means for extracting a road link from a map mesh including the set point, and a route calculating means for calculating a route between the road links extracted by the extracting means. In the route search device, a road link is extracted from the map mesh including the set point by the extraction means, and as a result, it is determined whether or not the surrounding map mesh around the map mesh satisfies a specific condition. Means are provided. When the determination unit determines that the specific condition is satisfied, the extraction unit also extracts a road link of a peripheral map mesh existing around the map mesh including the set point.

There are various specific conditions. As one of them, there is a possibility that a road link is not extracted from a map mesh including a set point, and a road link close to a surrounding map mesh exists. In this case, in the conventional route search device, the search is terminated on the assumption that there is no road link close to the set point. However, according to the present invention, since the extraction means sets the road link of the surrounding map mesh as an extraction target. , An appropriate route can be determined.

As described above, when no road link is extracted from the map mesh including the set point, it is desirable to search for a road link in the surrounding map mesh.
If the distance between the set point and the road link is too large, the validity of the searched route is not guaranteed. Therefore, when searching for a surrounding map mesh, a finite-sized road link extraction area centered on the set point is formed, and a surrounding map mesh that at least partially overlaps the road link extraction area is extracted. It can be. As a result, a road link having a distance equal to or more than the predetermined value is not selected. Further, the time required for the road link extraction processing is reduced.

In another specific condition, the distance between the set point and the surrounding map mesh is shorter than the distance between the road link extracted from the map mesh including the set point and the set point. A map mesh may be present. By searching for road links in the surrounding map mesh using this as a specific condition, even if a road link can be extracted in the map mesh including the set point, the road link in the surrounding map mesh is closer to the set point. In this case, it is possible to extract a closer road link.

[0010] Further, when a plurality of corresponding peripheral map meshes exist when the road link of the peripheral map mesh is to be extracted, the extraction means starts from a peripheral map mesh having a small distance between the set point and the peripheral map mesh. The road link extraction processing is performed with priority. As a result, the time for searching for a road link closest to the set point is reduced, and processing can be performed efficiently.

By the way, in the map mesh, the road links are represented by coordinates, and the coordinates have a closed coordinate system for each map mesh. When calculating the distance between the set point and the road link in the surrounding map mesh, the distance cannot be calculated between map meshes having different coordinate systems. Therefore, in the present invention, the coordinate system of each map mesh is set to a common coordinate. By using a system, the distance can be calculated correctly.

Specifically, when extracting the road links of the peripheral map mesh, the extracting means converts the coordinates of the road links of the peripheral map mesh to relative coordinates based on the coordinate system of the map mesh including the set point. Conversion is performed, or the coordinate system of the set point is converted into relative coordinates based on the coordinate system of the surrounding map mesh. The present invention, as described above,
If there is a surrounding map mesh that meets certain conditions,
The extraction means extracts a peripheral map mesh satisfying a specific condition and ends the road link extraction process when there is no peripheral map mesh satisfying the specific condition. As a result, road links can be extracted efficiently.

When a road link is extracted from a peripheral map mesh satisfying specific conditions, the map mesh is read from the storage medium each time. On this occasion,
Reading the address of the map mesh necessary for each reading from the storage medium requires reading via a data management unit or the like, so that the data reading processing is unnecessarily increased. According to the present invention, when reading a map mesh including a set point, the address of a peripheral map mesh stored as additional information in the data is simultaneously read and stored in the map mesh address storage means.

Thus, when reading the peripheral map mesh, the storage medium can be directly accessed based on the address stored in the map mesh address storage means, and the peripheral map mesh can be read efficiently.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A route guidance apparatus to which the present invention is applied will be described with reference to the drawings. The route guidance device of the present example is mounted on an automobile and guides a route to a user. FIG. 1 is a diagram illustrating a circuit configuration of the route search device. The control unit 11 includes a CPU 12, a ROM 13, and a RAM 14. An input device 16 for the user to set a starting point, a passing point, and a destination point is connected to the data bus 15 of the control unit 11.

A CD-ROM 17 storing map data is loaded into a CD-ROM driver 18. CD-ROM
The driver 18 is connected to the data bus 15 via a CD-ROM decoder 19. A direction sensor 21, an angular velocity sensor 22, a distance sensor 23, and a GPS 24 are connected to the data bus 15 via an interface 25 to detect the current position of the vehicle.

A graphic memory 26 is connected to the data bus 15 via a graphic controller 27. A display device 28 is connected to the data bus 15 via a display controller 29. The control unit 11 operates according to a program stored in the ROM 13. In the route search, the starting point, the passing point, and the
A destination point or the like is input as a set point. Control unit 11
Reads the map mesh from the CD-ROM 17, extracts the road links closest to the set point, and calculates the distance between the road links. The calculated route is displayed on the screen of the display device 28 so as to overlap the map. This map is CD-
It is created based on the map data read from the ROM 17 and the graphic data stored in the graphic memory 26.

The map mesh will be described with reference to FIG. In the following example, a description will be given assuming that the set point is a starting point. The map data (road data) stored in the CD-ROM 17 is divided into rectangular map meshes 31, 32,... 39 as shown in FIG. Now, the road links 51, 52, 53 are included in the map mesh 31, and the nodes 61, 6
2, 63, and 64, and the map mesh 36 includes the road link 54 and the nodes 65 and 66.

Here, when the starting point 41 is set in the map mesh 31, the starting point 4 is set in the map mesh 31.
53 is selected as the road link closest to 1. However, actually, the road link 54 on the map mesh 36 on the right side is the road link closest to the set point 41. In the present specification, a map mesh around the map mesh 31 including the set point is referred to as a peripheral map mesh. Further, the peripheral map mesh is not necessarily the one adjacent to the map mesh 31.

In the situation shown in FIG. 2, the route search includes:
It is preferable to select the road link 54 of the surrounding map mesh 36. Therefore, in the present invention, a condition that can determine that a road link having a peripheral map mesh is more likely to be closer to a set point is defined as a “specific condition”. To be extracted.

Hereinafter, specific examples of specific conditions will be described with reference to the drawings. FIG. 3 is a diagram illustrating a first example of a specific condition. The first example is a map mesh 31 including a starting point 41.
, There is no road link. In this case, there is a high possibility that there is a road link closest to the starting point 41 in the surrounding map meshes 32 to 39. Therefore, in this example, the case where no road link exists in the map mesh including the set point is set as the specific condition. In the illustrated example, the surrounding map meshes 32 to 39 are to be extracted as road links.
As a result, the road link 54 in the surrounding map mesh 39
Is selected.

FIG. 4 is a diagram for explaining a second example of the specific condition. When there is no road link in the map mesh 31 including the starting point 41 as in the example of FIG. 3, it is often preferable to search for road links in the surrounding map mesh. However, in the example shown in FIG. 4, the distance between the starting point 41 and the road link 54 of the surrounding map mesh 36 is too large. Therefore, in the example of FIG. 4, if this road link 54 is selected, the validity as the search route is not guaranteed.

On the other hand, in this example, a road link extraction area 42 having a finite size is provided around the starting point 41, and the road link extraction area 42 may include a road link. Only the surrounding map mesh is to be extracted. In other words, if a road link is not extracted in the map mesh 31 including the starting point 41 and there is a peripheral map mesh partially overlapping with the road link extraction area 42, the corresponding peripheral map mesh is To be extracted.

In the example shown in FIG.
A road link extraction area 42 having a size that can be expected to be valid for the search route is set. Peripheral map meshes 33 and 38 partially overlap with this area 42, and the peripheral map mesh 39 does not overlap. Therefore, the surrounding map meshes 33 and 38 are targets for road link extraction. On the other hand, since the surrounding map mesh 39 is not an extraction target,
A road link 54 having low validity is not selected.

FIG. 5 is a diagram for explaining a third example of the specific condition. The third example is a case where a road link 53 having the closest distance L in the map mesh 31 including the starting point 41 can be extracted. Even if the road link 53 can be selected in this manner, there is a possibility that a short road link shorter than the distance L exists in the surrounding map meshes 32 to 39. In the example of FIG. 5, the road links 54 in the surrounding map mesh 36
That is it.

Here, the distance from the starting point 41 to each of the surrounding map meshes 32 to 39 is represented by L2 to L9. Of these, the distances L3, L4, L6, L8, L9 are shorter than the distance L between the starting point 41 and the road link 53. Therefore, since there is a possibility that a road link exists at a distance shorter than the distance L in the peripheral map meshes 33, 34, 36, 38, and 39, these peripheral map meshes are regarded as peripheral map meshes satisfying specific conditions. It becomes an extraction target.

In the example of FIG. 5, there are a plurality of surrounding map meshes to be extracted. in this case,
Among the corresponding peripheral map meshes, the extraction processing is preferentially performed from the peripheral map mesh located at the shortest distance (in the example of FIG. 5, the peripheral map mesh 36 at the distance L6). In this way, when a road link with a short distance Ln is found, the surrounding map mesh that is shorter than the distance Ln is gradually limited. Therefore, there is a high possibility that a desired road link is found before the extraction processing is performed for all the surrounding map meshes, and the processing can be completed in a short time.

The overall flow of the process from setting of a set point to extraction of a road link will be described with reference to the flowchart of FIG. First, the overall flow will be briefly described. The operator inputs the starting point 41 from the input device 16 (step S11). The control unit 11 reads the map mesh 31 including the set starting point 41 from the CD-ROM 17, which is a storage medium storing the map data (Step S1).
2).

In the read map mesh 31, a process of extracting a road link closest to the set point is performed (step S13). It is determined whether or not the extraction result satisfies a specific condition (step S14). Next, it is determined whether there is a peripheral map mesh that satisfies the specific condition (step S15). Here, when there is no surrounding map mesh that satisfies the specific condition, that is, the road link 53 is extracted in the map mesh 31 including the starting point 41, and the distance L between the starting point 41 and the road link 53 is L.
If there is no surrounding map mesh within a shorter distance, it is determined that an optimum road link has been extracted, and the process is terminated.

On the other hand, if there is a peripheral map mesh that satisfies the specific condition in step S15, the process proceeds to step S16, and the corresponding peripheral map mesh is read from the CD-ROM 17. Then, a process of extracting road links from the read surrounding map mesh is performed (step S17). Here, a road link is extracted, and the road link and the starting point 4 are extracted.
If the distance to 1 is shorter than the distance to the already extracted road link, it is updated to a new road link.

Thereafter, the process returns to step S14 to determine whether or not the extraction result satisfies a specific condition. Next, it is determined whether there is a peripheral map mesh that satisfies the specific condition (step S15). . Here, if there is no next surrounding map mesh that satisfies the specific condition, this process is terminated. If there is still a surrounding map mesh that satisfies the specific condition, the process from step S16 is executed.

When the extraction of the road links of the surrounding map mesh is completed by the above processing, the starting point 4
A road link that is said to be close to 1 is employed. next,
Details of the processing in FIG. 6 will be described. FIG. 7 shows the details of the map mesh reading process in steps S12 and S16 of the process in FIG.

In step S121, it is determined whether the map mesh address is stored in the map mesh address storage unit provided in the RAM 14. In step S12 of FIG. 6, since the reading of the map mesh is performed for the first time, the result is No here, and
At 122, an address is obtained from the data management unit of the CD-ROM 17, and the map mesh 31 is read according to the address.

Normally, the map mesh contains address information of the peripheral map mesh as additional information. Therefore, at the time of reading in step S122, the address information of the surrounding map mesh is also read, and
At 124, this is stored in the map mesh address storage. Here, the address information stored in the map mesh address storage unit includes the address of the map mesh on the CD-ROM 17, the size of the map mesh, and the distance from the starting point 41 to the map mesh. Also, even if the absolute coordinates (latitude, longitude) of the map mesh are stored instead of the distance from the starting point 41 to the map mesh, the distance can be correctly calculated.

Next, in the case of reading the surrounding map mesh in step S16 in FIG. 6, the address is often stored in the map mesh address storage unit. Therefore, if the address of the peripheral map mesh to be read is stored here, the process proceeds from step S121 to step S123. In step S123, the peripheral map mesh is directly read from the CD-ROM 17 using the address stored in the map mesh address storage unit. Therefore, the time required for reading the map mesh is reduced, and extraction can be performed efficiently. In addition, even if reading of the surrounding map mesh, if the address is not stored in the map mesh address storage unit in step S121, the process proceeds to step S121.

FIG. 8 shows details of the road link extraction processing of step S13 in FIG. 6, that is, the road link extraction processing of the map mesh including the starting point 41. Step S131
Then, it is determined whether or not the search for the road link has been completed for all the roads in the map mesh. If the search has not been completed, an unsearched road link is searched in step S132.
In this road link search process, the process used in the conventional route search device can be employed as it is, and thus the description thereof is omitted here.

In step S133, it is determined whether or not the searched road link is closer to the road link which has been searched so far and is considered to be closest to the starting point 41 at the present time. Here, if the road link searched this time is closer, the closest road link is updated in step S134, and the process returns to step S131. If No in step S133, the process directly returns to step S131.

When the search is completed for all the road links in the map mesh, the processing in FIG. 8 ends. here,
The processing of steps S14 and S15 in FIG. 6 will be described. In step S14, it is determined whether a specific condition is satisfied by the method described with reference to FIGS. If the specific condition is satisfied, it is determined in step S15 whether there is a peripheral map mesh satisfying the specific condition. If there is a surrounding map mesh that satisfies the specific condition, the process proceeds to step S16.

In step S15, it may be determined that there are a plurality of peripheral map meshes that satisfy a specific condition. In this case, the peripheral map mesh with the shortest distance from the starting point 41 is preferentially selected, and the road link is extracted after step S16. In the example of FIG. 5 described above, the surrounding map meshes satisfying a specific condition are 33, 3
4, 36, 38 and 39, these peripheral map meshes are to be extracted. Also, here, the starting point 41
The road link of the peripheral map mesh 36 located at the distance L6 closest to the target is set as the first extraction target. As a result, the road link 54 is extracted as the closest road link. FIG.
This shows a state where the road link 54 has been extracted.

In FIG. 9, the starting point 41 and the road link 5
4 is L ′. Distance L shorter than this distance L '
The peripheral map meshes 38 and 39 at 8 and L9 are left as extraction targets, but the peripheral map meshes 33 and 34 at farther distances L3 and L4 are excluded from the extraction targets. In this way, as the extraction process proceeds, the number of surrounding map meshes to be extracted decreases. Then, when there is no surrounding map mesh to be extracted, the process is terminated at that time. As described above, when there are a plurality of peripheral map meshes to be extracted, the efficiency can be improved by preferentially performing the road link extraction processing from the peripheral map mesh with a short distance to the starting point 41.

FIG. 10 is a flowchart for explaining the details of the road link extraction processing of the surrounding map mesh in step S17 in FIG. Since the flowchart of FIG. 10 is substantially the same as the flowchart of FIG. 8, steps having the same functions as the steps in FIG. 8 are given the same step numbers as in FIG. As is apparent from FIG. 10, in FIG.
Since only step S171 has been inserted during the period 132, the description here will be made only for the coordinate transformation of step S171.

The road links correspond to the respective map meshes 31 to 39.
If is displayed in absolute coordinates such as latitude and longitude, the distance between each map mesh can be easily calculated. However, the road link is often a closed coordinate system for each of the map meshes 31 to 39. In this case, from the starting point 41 in the map mesh 31 to the surrounding map meshes 32 to 3
When calculating the distance to the road link in No. 9, it is necessary to convert to a common coordinate system in step S17.

FIG. 11 shows an example of this, and FIG. 11A shows a state before the coordinate system is transformed. The map mesh of the starting point 41 has four coordinates (0, 0) (X, 0) (0, Y)
(X, Y). The surrounding map mesh 36 is also represented by the same coordinates (0, 0) (0, Y)...
4 is represented by two coordinates (X1, 0) (X2, Y2).

When converting to the common coordinate system, in the example of FIG.
1 coordinate system. As shown in FIG.
The surrounding map mesh 36 has two coordinates on the left (X,
0) (X, Y), and the coordinates of the road link are (X + X)
1,0) (X + X2, Y). In this way, by converting to the common coordinate system, the distance from the starting point 41 to the road link 54 can be directly calculated.

FIG. 12 shows a modification of the example of FIG. FIG. 12A shows a state before conversion, which is the same as FIG. 11A. (B) is a map mesh 3 including a starting point 41.
1 is converted to the coordinate system of the surrounding map mesh 36, and the coordinates of the starting point 41 are (X1-X, Y1). This makes it possible to directly calculate the distance from the starting point 41 to the road link 54, as in the example of FIG.

[0046]

According to the present invention, in a route search device for performing a route search using a plurality of divided map meshes, not only a map mesh including a set point but also a surrounding map mesh is extracted as a road link extraction target. Therefore, an appropriate route can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a route search device to which the present invention is applied.

FIG. 2 is a diagram illustrating a map mesh.

FIG. 3 is a diagram (part 1) for explaining specific conditions in the embodiment of the present invention.

FIG. 4 is a view (part 2) for explaining specific conditions in the embodiment of the present invention.

FIG. 5 is a diagram (part 3) for explaining specific conditions in the embodiment of the present invention.

FIG. 6 is a flowchart illustrating an overall flow of a road link extraction process according to the embodiment of the present invention.

FIG. 7 is a flowchart showing details of a map mesh reading process in FIG. 6;

FIG. 8 is a flowchart showing details of a road link extraction process in FIG. 6;

FIG. 9 is a diagram showing a method for determining a specific condition in FIG. 6;

FIG. 10 is a flowchart showing details of a process of extracting a road link of a surrounding map mesh in FIG. 6;

FIG. 11 is a view for explaining coordinate conversion in FIG. 10;

FIG. 12 is a view showing a modification of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Control part 12 ... CPU 13 ... ROM 14 ... RAM 15 ... Data bus 16 ... Input device 17 ... CD-ROM 18 ... CD-ROM driver 19 ... CD-ROM decoder 21 ... Azimuth sensor 22 ... Angular velocity sensor 23 ... Distance sensor 24 GPS 25 Interface 26 Graphic memory 27 Graphic controller 28 Display device 29 Display controller 31 Map mesh including starting point 32 to 39 Peripheral map mesh 41 Starting point 42 Road link extraction area 51 to 54 … Road links 61-65… Nodes

Claims (12)

[Claims] 1. A point setting means for setting a starting point and a destination as set points, an extracting means for extracting road links from a map mesh including the set points, and a route between the road links extracted by the extracting means. A route search device having a route calculating means for calculating a road link from the map mesh including the set point by the extracting means, and as a result, a peripheral map mesh around the map mesh is identified. Determining means for determining whether or not the above condition is satisfied. When the determining means determines that the specific condition is satisfied, a road link of a corresponding peripheral map mesh is to be extracted. A route search device characterized by the following. 2. The specific condition is that the road link is not extracted from a map mesh including the set point, and there is a possibility that a nearby road link exists in the surrounding map mesh. The route search device according to the above. 3. The specific condition is that the road link is not extracted from a map mesh including the set point, and that a finite road link extraction area centered on the set point is formed, 2. The route search device according to claim 1, wherein a peripheral map mesh at least partially overlapping with the extraction area exists. 4. The specific condition is that the distance between the set point and the surrounding map mesh is shorter than the distance between the road link extracted from the map mesh including the set point and the set point. The route search device according to claim 1, wherein a mesh exists. 5. The method according to claim 1, wherein when extracting a plurality of road links of the surrounding map mesh, if there are a plurality of surrounding map meshes to be extracted, a distance between the set point and the surrounding map mesh is determined. The route search device according to claim 1, wherein the road link extraction processing is preferentially performed from a surrounding map mesh having a small size. 6. The method according to claim 1, wherein, when extracting a road link of the peripheral map mesh, the extracting unit sets a coordinate of the road link of the peripheral map mesh as a relative coordinate with respect to a coordinate system of the map mesh including the set point. The route search device according to claim 1, wherein the conversion is performed to 7. The method according to claim 1, wherein the extraction unit converts the coordinate system of the set point into relative coordinates based on the coordinate system of the peripheral map mesh when extracting a road link of the peripheral map mesh. Route search device. 8. The route search device according to claim 1, wherein the extraction means sets a case where there is no peripheral map mesh satisfying a specific condition as an end condition of the road link extraction processing. 9. A map mesh address storage means for holding address information for a map mesh, wherein a map mesh including the set point is read from a storage medium.
2. The route search device according to claim 1, wherein the address information of the peripheral map mesh included in the additional information of the map mesh is stored in the map mesh address storage means. 10. When the extraction means reads the peripheral map mesh from the storage medium, if address information of the peripheral map mesh is stored in the map mesh address storage means, the address information is used. The route search device according to claim 9, wherein a map mesh is read from the storage medium. 11. The route search device according to claim 9, wherein the address information includes an address of the map mesh on the storage medium, a size, and a distance from the set point to the map mesh. 12. The route searching device according to claim 9, wherein the address information includes an address of the map mesh on the storage medium, a size, and absolute coordinates of the map mesh.