JPH0527678A - Poute search method of on-vehicle navigation system and map data storage medium - Google Patents

Abstract

PURPOSE:To realize a route search method which prevents the increase in the amount of the arithmetic processings during a long range route search, improves the search efficiency and reduces the time required to perform a route search. CONSTITUTION:In the route search method of an on-vehicle navigation system which derives the shortest route from a departure point to the destination based on map data, all roads are divided into plural regions each of which are mutually passable and are stored as map data. The map data contains regional connectivity information which indicates whether each region is passable or not. Then, the system cpmputes a total of the distances which connect the representative points of each region that belongs to the departure point and the destination, sets the total so as to make it a minimum, performs a route search for the roads within the selected regions and then, derives the route.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route search method for searching an appropriate route between two points in a vehicle-mounted navigation system in order to present a driver with a traveling route from a starting point to a destination.

[0002]

2. Description of the Related Art Recently, information about roads is stored,
A device called a navigation system, which presents an appropriate route for traveling between two points when a driver inputs a departure place and a destination, is being put to practical use. In the navigation system, a navigation system that detects a traveling position of the own vehicle and instructs a driving operation for traveling along the presented route has been developed.

Various methods have been considered as to how to express information about roads. For example,
The driver needs to display the map on a screen such as a CRT, but the map drawing information can be used as it is for route searching, or the route searching can be performed separately in a form corresponding to the map drawing information. There is a format that has information for each, and the structure of the information is different. However, in order to perform route search, generally, the roads that connect the intersections are represented by numbers, and the attributes such as the types of the intersections and roads are represented by the numbers. Even if the format of the stored information is different, the route search is performed after being converted into the format represented by such intersections and roads.

As a route search method, various methods have been proposed so that the search can be performed at a higher speed, but a typical method is Dijkstra's shortest path algorithm. This is to use the intersection as a node and the distance of each road connecting the nodes as data, and gradually increase the range of nodes while exploring the shortest route from the node at the starting point to the surrounding nodes, until the node corresponding to the destination. This is a method of exploring the shortest path of. That is, the shortest route is searched from all the routes from the origin to the destination.

[0005]

Although there are differences depending on the method of route exploration, in the case of route exploration, it is necessary to explore all routes from the starting point to the destination. If the distance is long and there are many intersections along the way, the number of routes from the starting point to the destination becomes enormous. Therefore, if the distance calculation is performed for all the routes and the shortest route is searched, there is a problem that the processing amount becomes large and the processing time becomes too long even if a high-speed processing device is used.

The present invention has been made in view of the above problems, and when a long-distance route search is performed, an increase in the amount of processing for the search is suppressed so that the search can be performed efficiently. The purpose is to realize the route search method.

[0007]

In order to solve the above problems, a route search method for an on-vehicle navigation system according to the present invention divides all roads into a plurality of regions and stores them, and also has a connection relation between the regions. It is stored separately, and after selecting an area that connects the two areas to which the starting point and the destination belong, the route search is performed for the roads that belong to the selected area.

That is, the route search method for an on-vehicle navigation system of the present invention is an on-vehicle route for deriving a shortest route between two points from a starting point to a destination based on map data that stores information about roads and road connections. In the route search method of the navigation system for cars, all roads are stored as map data by dividing points on all roads in the area into multiple areas that can travel with each other by passing through the roads in the area. The map data further includes regional connection information indicating whether or not each of the divided regions can drive between adjacent regions, and the route from the departure point to the destination is based on the regional connection information. And after selecting the area connecting the two areas to which the destination belongs so as to minimize the total distance connecting the representative points of each area,
The roads that belong to the selected area will be searched by conducting a route search.

[0009]

1 is a diagram showing the principle of the route search method of the present invention. Information about roads and road connections is stored in the map data. By searching the route based on this information, the shortest route between the two points input as the starting point and the destination can be derived. In the present invention, all roads are divided into a plurality of areas, and points on all the roads in each area can travel by passing through roads in the area. This means that any point in the area can be reached to any other point in the area via only the roads in the area.

[0010] In addition to the above-mentioned information about roads, the map data includes information about the above areas as area connection information. This area connection information indicates whether or not each area can travel between adjacent areas. When conducting a route search from the origin to the destination,
The areas to which the origin and the destination belong are respectively derived, and then the area connecting the two areas is selected based on the area connection information. At this time, naturally, it is considered that there are a plurality of combinations of areas that connect the two areas, but they are selected so as to minimize the total distance between the representative points of each area. Then, the route search from the starting point to the destination is performed in the selected area. By doing so, the amount of target data at the time of route search is significantly reduced.

[0011]

EXAMPLE First, an example of how a road is divided into regions will be described. The shape of the area may be basically any shape. FIG. 2 is a diagram showing an example of regional division, where (a) is a square, (b) is an equilateral triangle, (c) is a hexagon, and (d) is an irregular shape. Of course, it may be rectangular.

When selecting an area connecting between two areas to which a starting point and a destination respectively belong, it is necessary to select the area so that the total distance connecting representative points of each area becomes the minimum. Therefore, a representative point is defined for each region in a manner that corresponds to the actual point on the road, and the distance traveled between the representative points in the neighboring regions where travel is possible is stored as regional connection information, and these are used. The area can be selected. This is always necessary especially in the case of the irregular area shown in FIG.

However, the region selection is a process for limiting the target range for route search based on the road information, and the representative points are not always included in the route search. Therefore, it can be said that the determination of the shortest distance when selecting a region does not require so high accuracy. Therefore, when dividing into regions of a certain shape, as shown in (a), (b) and (c) of FIG. By setting the center of each area as the representative point and keeping the distance from the representative points of the adjacent areas constant, the amount of calculation when selecting the area can be reduced.

Next, the area division when the shape of the area is rectangular and the area connection information will be described with reference to FIG. FIG. 3A is a diagram showing a state in which the road indicated by the solid line is divided into regions indicated by the broken line. When the area division shown in (a) of FIG. 3 is performed, the area connection information becomes as shown in (b) of FIG. In this case, the representative point of the area is the center of each area, and the representative point does not always coincide with the actual road. Further, since the shape of the area is a fixed rectangle, the distance to the adjacent area is constant, but the distance differs depending on the direction. From this, it can be seen that it is desirable that the shapes of the regions are such as shown in (a), (b) and (c) of FIG. 2 where the distance between the regions is constant regardless of the direction.

Next, the procedure of the process will be described by taking as an example the case of searching for a route from point S to point G on the road shown in FIG. It can be seen that points S and G belong to regions 14 and 10, respectively. When the area connecting the area 14 and the area 10 is selected based on the area connection information of FIG. 3B, FIG.
Areas 14, 13, 7, 8, 9, 10 as shown in are selected. Therefore, the route search from the point S to the point G may be performed within the combined area shown in FIG.
It can be seen that the amount of data targeted for exploration is much smaller in (c) than in (a).

When divided into regions, it is necessary that all points on the roads within the region can travel to each other via only the roads within the region. If this is not satisfied, even if a route search is performed with the selected area as the target range, there may be a result that there is no route from the starting point to the destination. FIG. 4 is a diagram showing an example thereof. As shown in FIG. 4 (a), it is possible to partially pass through the neighboring four areas in a certain area, but the area is divided into three parts, and each part travels mutually. Suppose there is no road. Figure 4
When the area is selected from the point S to the point G as shown in (a) of (a), it means that there is no route even if the route search is performed in this range because there is a portion that cannot be connected in the middle. Therefore, in the area, all points on the road must be able to travel to each other via only the road in the area.

Therefore, as shown in FIG. 4 (a), when areas are divided into areas with a certain shape and there are portions that cannot travel with each other within the area, the areas are divided as shown in FIG. 4 (b). Then, regional connection information as shown in FIG. 4C is created. Since the distance between regions will change for this part, it is necessary to indicate this by providing a flag or the like in the data.

The route search method has been described above.
A vehicle-mounted navigation system in which this route search method is executed will be briefly described. FIG. 5 is a diagram showing the hardware configuration of the vehicle-mounted navigation system. In FIG. 5, 1 is a microcomputer and 2 is C
D player, 3 is a display device such as CRT, 4
Is an input device for performing an operation. Information about roads and road connections is stored in a storage medium such as a CD-ROM in the form of map data divided into regions and read by the CD player 2. Regional connection information is also included in the map data.

The microcomputer 1 performs all the processes in this system, converts the information about the road read by the CD player 2 into a map form, displays it on the display device 3, and presents it to the driver. The input device 4 is for inputting a starting point and a destination in addition to operating the entire system, and a mouse or a touch switch panel is preferable for inputting the starting point and the destination from the viewpoint of operability.

FIG. 6 is a flow chart showing an example of the processing by the microcomputer when the route search method of the present invention is executed with the configuration of FIG. Step 1
In 01, the starting point and the destination are input, and in step 102, the correspondence relationship to which area the starting point and the destination belong to is derived by searching the map data. Next, in step 103, the area connection information is read and an area connecting the area where the departure place and the destination belong is selected. In this selection, the distance connecting the representative points of each area is minimized.
It is performed using the same route exploration method as the above-mentioned Dijkstra.

In step 104, information on roads and road connections in the selected area is read out, and in step 10
Only the area selected in 5 is searched for the route from the starting point to the destination, and the shortest route is obtained. When selecting a region, the region is selected so that the total distance connecting the representative points of each region is minimized.Therefore, it is not always the case that the shortest route from the starting point to the destination exists in the selected combination of regions. Absent. However, since the area is selected so that the distance is minimized, the shortest route explored in the selected area rarely becomes longer than the actual shortest route.

However, as shown in FIGS. 2 (a), 2 (b) and 2 (c), when areas are divided into a certain shape and the center of each area is used as a representative point, all areas are adjacent to each other. When all areas are connected, many area combinations may have the same distance when selecting areas. For example (a)
In the combination of regions from n ₁₁ to n ₅₃ ,
(N ₁₁ , n ₂₁ , n ₃₁ , n ₄₁ , n ₅₁ , n ₅₂ , n ₅₃ ) and (n
₁₁ , n ₂₁ , n ₂₂ , n ₃₂ , n ₄₂ , n ₄₃ , n ₅₃ ) have the same distance, and there are many such combinations. This also applies to (b) and (c). In such cases,
It is necessary to select the area along a straight line connecting the origin and destination. For example, in the area from n ₁₁ to n ₅₃ in (a) above, the latter is preferable to the former, and (b)
In 11, the combination of areas 11, 12, 13, 14, 15, 16, 17 is most desirable.

[0023]

As described above, according to the present invention, the amount of calculation processing required for route search in a vehicle-mounted navigation system can be greatly reduced, and the time required for route search can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of a route search method of the present invention.

FIG. 2 is a diagram showing an example of a shape of area division.

FIG. 3 is a diagram showing regional division of roads and regional connection information.

FIG. 4 is an explanatory diagram of necessity of interconnection within a region.

FIG. 5 is a diagram showing a hardware configuration of a vehicle-mounted navigation system.

FIG. 6 is a diagram showing a processing example according to the route search method of the present invention.

[Explanation of symbols]

1. Microcomputer 2 ... CD player 3 ... Display device 4 ... Input device

Claims (3)

[Claims] 1. A route search method for an in-vehicle navigation system for deriving a shortest route between two points from a starting point to a destination based on map data that stores information about roads and connection of the roads. The road is divided into a plurality of regions in which points on all roads in the area can travel with each other by passing through the roads in the area and stored as the map data. It further includes regional connection information indicating whether each of the plurality of regions can travel between adjacent regions, and the route from the departure place to the destination is based on the regional connection information. By selecting the area that connects the two areas to which the destination belongs so that the total distance between the representative points of each area is minimized, and then performing a route search for the roads that belong to the selected area. A route search method for a vehicle-mounted navigation system characterized by being searched. 2. The vehicle-mounted vehicle according to claim 1, wherein the plurality of areas are indefinite, each area has a representative point, and a distance between the areas is represented by a distance between the representative points. Navigation system route search method. 3. A map data storage medium for an on-vehicle navigation system, which stores information about roads and connection of the roads, wherein all roads in the area are points in the area. It is divided into a plurality of regions that can be driven by passing each other and stored, and regional connection information indicating whether or not each of the divided regions can drive a neighboring region is provided. And a map data storage medium.