JPH11248474A - Route selecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a route selecting method and system whereby for a hierarchical search, the shortest cost route can be accurately selected for a short time. SOLUTION: Map data are hierarchically arranged. Each hierarchical map is divided in a plurality of basic blocks (rectangular areas). The map data of each hierarchy is recorded as a set of map units prepared every basic block. Each map unit includes a basic block (screened part) and area overlapped with other basic blocks therearound (area between the screened part and dot line part). In such map unit, the size and shape of the overlapped area are set so that each road outgoing from the basic block reaches at least one higher hierarchy transit point. Using map data composed of such map units, the map at a range always including higher transit points can be read and the transit to a higher hierarchy can be made, without damaging the connection relation of roads.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a route selection method and system, and more particularly, to a method and system for selecting an optimum route between two arbitrary points on map data.

[0002]

2. Description of the Related Art As is well known, a car navigation system detects and displays the current position of a vehicle, automatically searches for an optimum route to a destination, and displays a vehicle along the optimum route with display guidance and It is a system that provides guidance to the destination by voice guidance. In such a car navigation system, it is required to select a practical route for guidance and guidance as soon as possible. Therefore, a method of searching for a route in a short time has been actively researched and proposed.

Conventionally, as a technique for performing a route search in as short a time as possible, there is, for example, a hierarchical search method disclosed in Japanese Patent Application Laid-Open No. Hei 4-301515. This search method by hierarchy has hierarchical map data with different levels of detail, and a search is performed with detailed map data around the departure point and destination, and with coarser map data for intermediate routes. According to such a hierarchical search method, when the distance between the departure point and the destination is a long distance, the intermediate route can be searched with coarse map data, so that compared with the case where the entire route is searched with detailed map data. The search time as a whole can be shortened.

Further, in Japanese Patent Laid-Open No. Hei 4-301515, map data of each layer is recorded by being divided into a plurality of blocks. This is for reducing the amount of map data read at one time and shortening the time required for accessing the map data.

As described above, when the map data of each layer is divided into a plurality of blocks, and the starting point and the destination belong to different blocks, the plurality of blocks are connected between them. You need to do a search. Normally, map data includes node data representing an intersection and link data representing a road connecting the intersections. However, in each block, the road that crosses the boundary block at the boundary with the peripheral block is divided in the middle, and it is impossible to correspond the road between one connected block and another block as it is. If an attempt is made to establish a road correspondence between adjacent blocks, as shown in JP-A-2-56591,
In each block, a virtual node that does not actually exist but is used only for connection to the peripheral block needs to be separately provided at the boundary with the peripheral block. According to such a method, there is a problem in that it is troublesome to create map data and the amount of data is large, so that it takes extra time to search for a route.

Therefore, in Japanese Patent Laid-Open No. Hei 4-301515, an overlap area is provided for each block. This overlap area is an area that extends out of the block when focusing on an arbitrary block, and is an area that overlaps with a peripheral block surrounding the block. In Japanese Patent Application Laid-Open No. Hei 4-301515, map data is recorded with a predetermined area including the block and its overlapping area as one section. According to such a method, it is possible to establish a correspondence between the peripheral blocks and the road without separately providing a virtual node used only for connection.

[0007]

As described above, according to the route search method disclosed in Japanese Patent Application Laid-Open No. Hei 4-301515, roads can be smoothly connected between adjacent blocks in the same hierarchy. However, there is no guarantee that roads can be reliably connected between blocks of different levels. Therefore, there is a problem that the map reading process is performed many times, and the search time increases. Further, if the number of times of the map reading process is forcibly reduced, an unnatural detour route or the like is selected, and the selected route is not necessarily the shortest cost route.

FIG. 12 is a diagram showing an example in which a circuitous route is generated in the route search method disclosed in Japanese Patent Laid-Open No. Hei 4-301515 (hereinafter, referred to as a conventional route search method). In FIG. 12, in the conventional route search method, it is assumed that a total of nine map blocks in which eight peripheral blocks are overlapped with a target block are combined into one map unit. In FIG. 12, it is assumed that the shortest cost route from the vehicle position to the destination local plane is a dotted line. According to a conventional route search method, if one map unit is read, a search is performed up to the unit boundary, and then a search of the upper hierarchy is performed, the node A is not included in the map unit. No, the dotted path cannot be selected. As a result, although not the shortest in terms of cost, the route of the solid line in which the node X which is the transition point is recorded in the map unit is selected.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a route selection method and system capable of accurately selecting the shortest cost route in a short time when performing a hierarchical search.

[0010]

Means for Solving the Problems and Effects of the Invention The first invention is a method for selecting an optimum route between any two points by using hierarchical map data, the method comprising the steps of: And a step of searching for an optimum route between the two set points based on the map data. The step of searching for the optimum route is performed in a higher hierarchy as the search range is expanded. A process of shifting to map data is performed, and the map of each layer is divided into a plurality of basic blocks in advance, and the map data of each layer is recorded as a set of map units prepared for each basic block. , Each map unit includes one basic block serving as a center and an overlapping area overlapping with other surrounding basic blocks, and the size and shape of the overlapping area are defined as the center and the center. Each road exiting from one basic block toward the overlap area is set so as to satisfy a minimum range condition of reaching at least one upper-layer transition point in the overlap area. It is characterized by.

[0011] As described above, according to the first invention, each map unit satisfies the minimum range condition that each road going out of the basic block reaches at least one upper-layer transition point. Since the size and shape of the overlap area are set, when the starting node and the destination node are set in the basic block, the map of the range including the upper transition point can be read without fail. Therefore, if the map reading process is performed once for each layer on both the departure place side and the destination side, the route search can be performed, and the search time can be reduced.

A second aspect of the present invention is a method for selecting an optimum route between any two points using hierarchical map data, the method comprising the steps of setting two points to be searched on the map data. Searching for an optimum route between two set points based on the map data. The step of searching for the optimum route performs a process of shifting to higher-level map data as the search range is expanded. The map of the hierarchy is divided into a plurality of basic blocks in advance, and the map data of each hierarchy is recorded as a set of map units prepared for each basic block. One basic block and an overlapping area overlapping with other surrounding basic blocks, and the size and shape of the overlapping area include a predetermined number or more of upper-layer transition points therein. Characterized in that it is set to satisfy the Mutoyuu minimum range condition.

As described above, according to the second aspect of the present invention, the size and shape of the overlap area are set so as to include a predetermined number or more of upper-layer transition points, so that a single map reading process is performed. In the map unit read by the above, a higher-level transition point equal to or more than a predetermined constant can be secured. As a result, the transition to the upper hierarchy can be performed smoothly, and a roundabout route is less likely to occur.

According to a third aspect of the present invention, in the second aspect, the number of upper-layer transition points to be included in the overlap area is determined by the number of roads exiting from one central basic block toward the overlap area. It is determined depending on.

[0015] In a fourth aspect based on the third aspect, the number of upper-layer transition points to be included in the overlap area is determined by the number of roads that exit from the central basic block toward the overlap area. Is multiplied by a constant magnification α.

In a fifth aspect based on the fourth aspect, the constant magnification α is selected to be one or more.

As described above, according to the fifth aspect, the number of upper-layer transition points included in the overlap area is larger than the number of roads going out of the basic block.
The shift to a higher hierarchical level can be performed more reliably, and a roundabout route can be made harder to occur.

A sixth invention is a method for selecting an optimum route between any two points using hierarchical map data, the method comprising the steps of setting two points to be searched on the map data. Searching for an optimum route between two set points based on the map data. The step of searching for the optimum route performs a process of shifting to higher-level map data as the search range is expanded. The map of the hierarchy is divided into a plurality of basic blocks in advance, and the map data of each hierarchy is recorded as a set of map units prepared for each basic block. One basic block and an overlapping area overlapping with the other basic blocks in the vicinity, and one corresponding map unit of two or more levels can be simultaneously read out. Characterized in that it is knitted of.

As described above, according to the sixth aspect, since the corresponding map units of two or more layers are combined into one unit so that they can be read simultaneously, it is necessary to perform the search in one map reading process. It is possible to read map data of a plurality of hierarchies, and to reduce the map reading time.

A seventh aspect of the present invention is a method for selecting an optimum route between any two points using hierarchical map data, the method comprising setting two points to be searched on the map data. Searching for an optimum route between two set points based on the map data. The step of searching for the optimum route performs a process of shifting to higher-level map data as the search range is expanded. The map of the hierarchy is divided into a plurality of basic blocks in advance, and the map data of each hierarchy is recorded as a set of map units prepared for each basic block. One basic block and an overlapping area overlapping with the other basic blocks in the vicinity, and the map data of the upper layer is used in a search previously performed with the map data of the lower layer. Wherein the road network is described.

As described above, according to the seventh aspect, the road network used in the search performed in the lower hierarchy map data is described in the upper hierarchy map data in advance, so Since no road is recorded, it is possible to solve the problem that an unnatural detour route is selected, and it is possible to select the shortest cost route similar to the case where the search is performed in the lowest hierarchy.

An eighth invention is a system for selecting an optimum route between arbitrary two points using hierarchical map data, and a map data storage unit for storing map data, A point setting unit for setting two points to be searched on the map data stored in the storage unit, and an optimum route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching. The route search unit performs a process of shifting to map data of a higher hierarchy as the search range expands, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Map data is recorded in the map data storage unit as a set of map units prepared for each basic block, and each map unit is composed of one central basic block and another peripheral basic unit. And a overlap region overlapping the block, the size and shape of the overlap region,
For each road exiting from one central basic block toward the overlap area, it is set so as to satisfy the minimum range condition of reaching at least one upper layer transition point in the overlap area. It is characterized by being.

As described above, according to the eighth aspect, each map unit satisfies the minimum range condition of reaching at least one upper-layer transition point for each road going out of the basic block. Since the size and shape of the overlap area are set, when the starting node and the destination node are set in the basic block, the map of the range including the upper transition point can be read without fail. Therefore, if the map reading process is performed once for each layer on both the departure place side and the destination side, the route search can be performed, and the search time can be reduced.

A ninth invention is a system for selecting an optimum route between any two points by using hierarchical map data, comprising: a map data storage unit for storing map data; A point setting unit for setting two points to be searched on the map data stored in the storage unit, and an optimum route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching. The route search unit performs a process of shifting to map data of a higher hierarchy as the search range expands, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Map data is recorded in the map data storage unit as a set of map units prepared for each basic block, and each map unit is composed of one central basic block and another peripheral basic unit. And a overlap region overlapping the block, the size and shape of the overlap region,
It is characterized in that it is set so as to satisfy a minimum range condition that at least a predetermined number or more upper-layer transition points are included therein.

As described above, according to the ninth aspect, the size and shape of the overlap area are set so as to include a predetermined number or more of upper-layer transition points, so that one map reading process can be performed. In the map unit read by the above, a higher-level transition point equal to or more than a predetermined constant can be secured. As a result, the transition to the upper hierarchy can be performed smoothly, and a roundabout route is less likely to occur.

In a tenth aspect based on the ninth aspect, the number of upper-layer transition points to be included in the overlap area is determined by the number of roads going out from one central basic block toward the overlap area. It is determined depending on.

According to an eleventh aspect, in the tenth aspect,
The number of upper-layer transition points that should be included in the overlap area is a number obtained by multiplying the number of roads going from one central basic block toward the overlap area by a constant magnification α.

According to a twelfth aspect, in the eleventh aspect,
The constant magnification α is selected to be one or more values.

As described above, according to the twelfth aspect, the number of upper-layer transition points included in the overlap area is greater than the number of roads going out of the basic block, so that the number of higher-layer transition points is higher. Can be reliably performed, and it is possible to make it difficult to generate a circuitous route.

A thirteenth invention is a system for selecting an optimum route between any two points by using hierarchical map data, wherein a map data storage unit for storing map data, A point setting unit for setting two points to be searched on the map data stored in the storage unit, and an optimum route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching. The route search unit performs a process of shifting to map data of a higher hierarchy as the search range expands, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Is stored in the map data storage unit as a set of map units prepared for each basic block, and each map unit is composed of one central basic block and other peripheral blocks. And a overlap region overlapping with the block, further two or more corresponding map units between the hierarchy, characterized in that it is 1 unitized so as to be simultaneously read.

As described above, according to the thirteenth aspect, 2
Since the map units corresponding to two or more layers are combined into one unit so that they can be read at the same time, map data for multiple layers required for searching can be read in a single map reading process, reducing the time required to read the map. Can be

A fourteenth invention is a system for selecting an optimum route between any two points by using hierarchical map data, wherein a map data storage unit for storing map data, a map data storage unit, A point setting unit for setting two points to be searched on the map data stored in the storage unit, and an optimum route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching. The route search unit performs a process of shifting to map data of a higher hierarchy as the search range expands, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Is stored in the map data storage unit as a set of map units prepared for each basic block, and each map unit is composed of one central basic block and other peripheral blocks. And a overlap region overlapping with the block, the map data of the upper hierarchy, wherein the road network which are utilized in the search made in the map data in advance lower layer is described.

As described above, according to the fourteenth aspect, since the road network used in the search performed in the lower hierarchy map data is described in the upper hierarchy map data in advance, a certain hierarchy is used. Since no road is recorded, it is possible to solve the problem that an unnatural detour route is selected, and it is possible to select the shortest cost route similar to the case where the search is performed in the lowest hierarchy.

A fifteenth invention is a recording medium on which map data used for route search is recorded, wherein the map data is composed of map data of a plurality of layers having different levels of detail, and the map of each layer is stored in advance. It is divided into a plurality of basic blocks, and the map data of each level is recorded as a set of map units prepared for each basic block,
Each map unit has one central basic block,
The size and shape of the overlap area include an overlap area that overlaps with the other basic blocks in the vicinity, and the size and shape of the overlap area are determined for each road exiting from the one basic block toward the overlap area. The lap area is set so as to satisfy a minimum range condition of reaching at least one upper layer transition point.

A sixteenth aspect of the present invention is a recording medium on which map data used for a route search is recorded, wherein the map data is composed of map data of a plurality of layers having different levels of detail. It is divided into a plurality of basic blocks, and the map data of each level is recorded as a set of map units prepared for each basic block,
Each map unit has one central basic block,
An overlap area overlapping with other peripheral basic blocks is included, and the size and shape of the overlap area are set so as to satisfy a minimum range condition that a predetermined number or more of upper-layer transition points are included therein. It is characterized by having.

According to a seventeenth aspect, in the sixteenth aspect,
The number of upper-layer transition points that should be included in the overlap area is determined depending on the number of roads that exit from one central basic block toward the overlap area.

According to an eighteenth aspect, in the seventeenth aspect,
The number of upper-layer transition points that should be included in the overlap area is a number obtained by multiplying the number of roads going from one central basic block toward the overlap area by a constant magnification α.

According to a nineteenth aspect, in the eighteenth aspect,
The constant magnification α is selected to be one or more values.

A twentieth aspect of the present invention is a recording medium on which map data used for a route search is recorded, wherein the map data is composed of map data of a plurality of layers having different levels of detail. It is divided into a plurality of basic blocks, and the map data of each level is recorded as a set of map units prepared for each basic block,
Each map unit has one central basic block,
It is characterized in that it includes an overlapping area that overlaps with other basic blocks in the vicinity, and that the corresponding map units of two or more levels are unitized so as to be simultaneously readable.

A twenty-first invention is a recording medium on which map data used for route search is recorded, wherein the map data is composed of map data of a plurality of layers having different levels of detail, and the map of each layer is stored in advance. It is divided into a plurality of basic blocks, and the map data of each level is recorded as a set of map units prepared for each basic block,
Each map unit has one central basic block,
An overlap area overlapping with other basic blocks in the vicinity is included, and the road network used in the search performed in advance in the lower layer map data is described in the upper layer map data. .

[0041]

FIG. 1 is a block diagram showing the configuration of a car navigation system according to one embodiment of the present invention. In FIG. 1, the car navigation system according to the present embodiment includes an input device 101, a locator 102,
A recording device 103, a communication device 104, a navigation device 105, and an output device 106 are provided.

The input device 101 uses a remote controller, a touch sensor, a keyboard, a mouse, and the like to select functions of the navigation system (change processing items, switch maps, change layers, etc.), set points, select search modes, and the like. The locator 102 includes a GPS, a vehicle speed sensor, an angular speed sensor, an absolute direction sensor, and the like, and collects various information for calculating the current position of the vehicle. The recording device 103
It is composed of an optical disk (CD, DVD, etc.), a hard disk, a large-capacity memory, etc., and stores information on a road network, such as intersections and road connection status, coordinates, shapes, attributes, and regulation information. The communication device 104 includes various wireless communication devices such as an FM multiplex communication device and an optical / radio wave beacon device, and transmits and receives various information such as traffic information and map information. The navigation device 105 usually includes a CPU, a memory (a program memory, a working memory), and the like.
It performs current vehicle position detection, route search / guidance, search and provision of various information (map information, traffic information, peripheral information, etc.). The output device 106 is a display device (liquid crystal display,
A CRT display, etc.), a speaker, and the like are provided, and various types of information and image display of guidance routes and voice guidance are performed.

Here, the map data recorded in the recording device 103 will be described. FIG. 2 is a diagram illustrating a configuration example of the map data. Usually, map data is roughly divided into 2
Consists of three components. The first component is node data that is information about an intersection. The second component is link data that is information of a road connecting the intersection. In the present embodiment, the two components are recorded for each layer. FIG. 3 is an explanatory diagram of hierarchical map data. In FIG. 3, the map data is divided into four levels of levels 1 to 4, and level 1 is the lowest level,
Level 4 is the highest level. The map data of each layer is divided into a plurality of basic blocks. The map data of a certain hierarchy is recorded as a set of map units for each divided basic block. Each map unit includes data of one basic block and data of an overlap area overlapping with a basic block around the basic block. In the present embodiment, the overlap area is set under a predetermined condition. This condition will be described later.

The operation of the car navigation system configured as described above will be described below. The functions of the car navigation system include a route selection / guidance function, a current position display function, an information search / providing function, and the like. Here, a route selection / guidance function that is of interest to the present invention will be described.

First, in the input device 101, the user sets a departure place and a destination. In other words, the user operates the input device 101 to cause the output device 1 to operate.
The user scrolls the map image displayed at 06 and inputs a desired point as a starting point and a destination. Note that the current position of the vehicle detected using locator 102 may be used as the starting point.

Next, the navigation apparatus 105 determines the nearest node or the nearest node on the map of the lowest hierarchy stored in the recording apparatus 103 based on the positions of the departure place and the destination set as described above. The nodes connected to the close link are adopted as the departure node and the destination node. Further, the navigation device 105 calculates the shortest cost route using a well-known Dijkstra method or the like, converts the obtained route into a link sequence, a node sequence, or a coordinate sequence, and sets it as a guidance route. However, the navigation device 105
Using the departure node and the destination node as search start points, calculate the shortest cost route from the lowest hierarchy and expand the search to a predetermined range for each hierarchy, but if no route is found, a wider range Over, the process of calculating the shortest cost route using the map data of the upper layer in which only the main roads are recorded is repeated. At this time, the communication device 10
The route to be selected may be changed using a method such as changing the link cost based on the traffic information obtained in step 4. The navigation device 105 sets a guidance route based on the search result thus selected, calculates the current position of the vehicle from the position information detected by the locator 102, and guides the vehicle on the guidance route to the destination.

Finally, the output device 106 receives an instruction from the navigation device 105 and presents guidance information to the user by voice or display.

FIG. 4 shows the navigation device 1 shown in FIG.
FIG. 5 is a functional block diagram showing a configuration example of the electronic device 05. In FIG. 4, the navigation device 105 includes a position detection unit 2
01, an information search / providing unit 202, and a route selecting unit 203
And a guiding unit 204.

The position detection unit 201 performs map matching on the road network of the map data recorded in the recording device 103 based on the position information detected by the locator 102,
The current position of the vehicle is specified using the vehicle position correction information input from the input device 101. Information search / providing unit 20
2 displays the map data recorded on the recording device 103 on the output device 106 based on the current position detected by the position detection unit 201, or displays the map display range according to the user's request input on the input device 101. It searches and provides various information such as changing the degree of detail and the degree of detail and displaying traffic information obtained by the communication device 104. The route selection unit 203 reads map data in a required range from the recording device 103 and determines a departure point and a destination based on the current position of the vehicle detected by the position detection unit 201 and the point information input by the input device 101. Is determined, and the minimum cost route from the departure point to the destination is selected in consideration of the intersection traffic regulation and the one-way traffic regulation.
Furthermore, based on the guidance route selected by the route selection unit 203, the guidance unit 204 determines in which direction the map data acquired from the recording device 103 and the current position of the vehicle detected by the position detection unit 201 should go. Guide to the destination. Further, hereinafter, the route selection unit 203 that performs the route selection process will be described in detail.

FIG. 5 is a functional block diagram showing an example of the configuration of the route selection section 203 shown in FIG. 5, the route selection unit 203 includes a map storage unit 301, a point setting unit 302, a route search unit 303, and a search result data storage unit 304.

The map storage unit 301 reads map data of a range necessary for route search and point setting from the recording device 103 and stores it. The point setting unit 302 includes the position detection unit 20
The current position of the vehicle detected in step 1
The point input at 01 is set as a destination, and a departure node and a destination node on the map corresponding to each are set. The route search unit 303 performs a search process using the departure node and the destination node set by the point setting unit 302 in order from the lowest layer using a known Dijkstra method or the like as a search start point,
Find the minimum cost path from the departure node to the destination node. The search result data storage unit 304 records intermediate data and route information at the time of search.

The route selector 203 configured as described above
Will be described in detail below with reference to a flowchart. FIG. 6 is a flowchart showing the operation of the point setting unit 302 (see FIG. 5) in the route selection unit 203.

First, in step S601 in FIG.
The point setting unit 302 reads the map data of the lowest hierarchy around the departure place (for example, the current position of the vehicle detected by the position detection unit 201) from the recording device 103, and
01, the node closest to the departure place is set as the departure node, and the arrival cost (for example, 0) is set. Next, in step S <b> 602, the point setting unit 302 reads the map data of the lowest hierarchy around the destination (for example, the point input by the user using the input device 101) from the recording device 103 and stores the map data in the map storage unit 301. , The node closest to the destination is set as the destination node, and the arrival cost (for example, 0) is set.

Next, the route search unit 303 executes a route search process for finding the minimum cost route. FIG. 7 is a flowchart showing the operation of the route search process of the route search unit 303 (see FIG. 5) in the route selection unit 203.

First, in step S701 of FIG.
The route search unit 303 stores the departure node in the departure place side candidate state and the destination node in the destination side candidate state, and stores them in the search result data storage unit 304. Next, the route search unit 303 sets the lowest hierarchy as the first search hierarchy (step S702).

Next, the route search unit 303 stores the intermediate data in the search result data storage unit 304 using the known Dijkstra method starting from the departure place side candidate state node, and stores the intermediate data in the fixed area. A search process is performed (step S703). Next, the route search unit 303 determines whether or not the shortest cost route to the destination-side candidate state node has been determined during the search processing in the fixed area in step S703 (step S704). When the shortest cost route to the destination side candidate state node is determined, the route search unit 303 ends the departure place side search process assuming that the route has been determined, proceeds to step S711, and stores the route in the search result data storage unit 304. A route is constructed from the stored search results. On the other hand, when the shortest cost route to the destination side candidate state node has not been determined, the route search unit 303 executes the process of step S705.

In step S705, the route search unit 303 stores the intermediate data in the search result data storage unit 304 using the known Dijkstra method with the destination side candidate state node as a starting point, The ground side search processing is performed. Next, the route search unit 303 determines whether or not the shortest cost route to the departure point side candidate state node is determined during the search processing in the fixed area in step S705 (step S706). When the shortest cost route to the departure place side candidate state node is determined, the route search unit 303 ends the destination side search process assuming that the route has been determined, proceeds to step S711, and stores the route in the search result data storage unit 304. A route is constructed from the stored search results. On the other hand, when the shortest cost route to the departure place side candidate state node has not been determined, the route search unit 303 executes the process of step S707.

In step S707, the route search unit 303 determines whether the search hierarchy is the highest hierarchy. At this time, if the search hierarchy is the highest hierarchy, the route search unit 303 determines that the search has failed (step S71).
0), the route search process ends. On the other hand, if the search hierarchy is not the highest hierarchy, the route search unit 303 retrieves the searched node (hereinafter, referred to as the departure location upper transition node) recorded in the upper hierarchy located on the outer periphery of the departure location search area. In the departure point side candidate state, the searched node (hereinafter, referred to as the destination side upper transition node) recorded in the upper layer located on the outer periphery of the destination side search area is set to the destination side candidate state (step S708). . Next, the route search unit 303 shifts the search hierarchy to the next higher hierarchy (step S709), and returns to the processing of step S703. Thereafter, until the route is obtained, the route search unit 303 executes steps S703 to S709.
Is repeated.

Here, in order for the above-described route selection unit 203 to select the shortest cost route in a short time by using the same route search method as in the past, the recording device 103 (see FIG. 1)
Map data having a configuration as described below is recorded.
Hereinafter, a configuration example of the map data will be described.

(1) Setting of Minimum Range Condition for Same Layer Overlap Recording Width of Map Data FIG. 8 shows a first configuration example of map data used in the car navigation system of the present embodiment. In this configuration example, as described above, the map of each hierarchy is divided into a plurality of basic blocks (rectangular areas in FIG. 8). One layer of map data is recorded as a set of map units prepared for each of a plurality of divided blocks. Each map unit has one basic block (the shaded portion in FIG. 8),
An overlapping area (an area between a shaded portion and a dotted line portion in FIG. 8) overlapping with other basic blocks in the vicinity is included. In this configuration example, an area satisfying the following minimum range condition is set as an overlap area instead of providing an overlap area unconditionally around a basic block unlike the related art (see FIG. 12). Features.

The minimum range condition of the overlap area in the present configuration example is as follows for each road that exits from the basic block (shaded portion in FIG. 8) toward the overlap area.
To reach at least one upper layer transition point (a point at which it is possible to transition to the next higher layer) in the overlap area. That is, the overlap area in this configuration example is
It is set individually for each basic block, and its size and shape are different for each basic block.

By using the map data composed of the map units satisfying the above conditions (portion surrounded by the dotted line in FIG. 8), when the departure node or the destination node is set in the basic block, , The map of the range including the upper transition point can always be read. Therefore, if the map reading process is performed once for each layer on both the departure point side and the destination side, it is possible to surely shift to the upper layer without impairing the road connection relation.

(2) Setting of Quality Assurance Condition for Same Layer Overlap Recording Width of Map Data FIG. 9 shows a second configuration example of the map data used in the car navigation system of the present embodiment. This configuration example is characterized in that, similarly to the above-described first configuration example, an area that satisfies the following minimum range condition is set as an overlap area.

The minimum range condition of the overlap area in the present configuration example is such that, when a search is performed from each node in the basic block (shaded portion in FIG. 9), the overlap area has a predetermined number of transition points in the upper layer or more. It is to include. Here, the predetermined number is determined depending on, for example, the number of roads exiting from the basic block. As an example, the predetermined number is a number obtained by multiplying the number of roads by a constant magnification α. In this case, the constant magnification α is preferably set to α ≧ 1. As described above, when the predetermined number is determined depending on the number of roads exiting from the basic block, the predetermined number has a different value for each map unit. On the other hand, the predetermined number can be determined without depending on the number of roads exiting from the basic block. In this case, the predetermined number may be fixed for each map unit.

By using the map data composed of the map units satisfying the above conditions (portion surrounded by a dotted line in FIG. 9), a predetermined number of map units are always stored in the map unit read in one map reading process. The above upper-layer transition point can be secured. Then, the constant magnification α is α
When ≧ 1, as shown in FIG. 9, upper-layer transition points A and B that do not exist in the overlap area (see FIG. 8) in the first configuration example can be included in the overlap area. Therefore, it is possible to smoothly move to a higher hierarchical level, and it is possible to make it difficult to generate a circuitous route.

(3) One Unit of Multiple Hierarchy FIG. 10 shows a third example of the configuration of map data used in the car navigation system of the present embodiment. This configuration example uses a map unit having an overlap area overlapping with other peripheral basic blocks, as in the above-described first configuration example. In this configuration example, the map units corresponding to a plurality of layers are further integrated into one unit. FIG.
In this example, the range from layer 1 to layer 4 is integrated into one unit. Here, the map unit of the upper hierarchy has a size that includes all the map units of the lower hierarchy. Also, in one unit of map data,
The size and the shape of the overlap area of the map unit of each layer are set so that the layer can be shifted from the lower layer to the upper layer without fail. Therefore, it is preferable that the overlap area in the map data of this configuration example satisfies the minimum range condition similar to the first or second configuration example.

The map data of a plurality of layers unitized as described above is stored in the continuous recording area of the recording device 103. As a result, the moving distance of the pickup at the time of reading is shortened, so that the reading time of the map data is shortened. On the other hand, conventionally, since the map data of each layer is recorded at discrete positions on the recording device 103, the moving distance of the pickup becomes longer and the reading time of the map data becomes longer.

By using the map data composed of such map units (portions surrounded by the dotted lines in FIG. 10), the map data of a plurality of layers necessary for the departure point side search is read by one map reading process. And the map reading time can be reduced.

In this configuration example, the map data of all the hierarchies is made into one unit, but the map data of some hierarchies (two or more hierarchies) may be made into one unit. Further, only the map data of the hierarchy considered necessary for the search may be extracted and read in accordance with the distance between the departure place and the destination. For example, when the distance between the departure point and the destination is a short distance, only the map data of the lowest hierarchy may be read, and as the distance becomes longer, the number of layers to be read may be increased. As a result, it is possible to prevent the amount of map data to be read at one time from increasing unnecessarily when the distance between the departure place and the destination is short.

(4) Constructing a Higher-Level Road Network from the Search Results of the Lower-Level Hierarchy FIG. 11 is a diagram for explaining a method of constructing map data of a fourth configuration example used in the car navigation system of the present embodiment. . As shown in FIG. 11, in this configuration example,
A search is previously performed between arbitrary points in the lower hierarchy. Then, the road network used in this search is also recorded as the upper-layer road network. For example, consider a case in which all roads are recorded in the lower hierarchy and only main roads (such as national roads) are recorded in the upper hierarchy. In this case, as a result of the search performed in the lower hierarchy, if a non-main road (a road other than a main road, such as a prefectural road or a city road) is used, the non-main road is also recorded in the upper hierarchy. As a result of the search performed in the lower hierarchy, an unused main road may be excluded from the recording data in the upper hierarchy.

By using such hierarchical map data, it is possible to solve the problem that an unnatural detour route is selected because a road is not recorded in a certain hierarchy. The shortest cost route similar to the case can be selected.

As for an arbitrary point to be searched in advance, the center point of each lower-level map unit may be selected, or a plurality of points may be selected from the boundary points of each map unit. In addition, the distance between the arbitrary points may be increased as the hierarchy becomes higher. In addition, the portions around the start and end points of the route between the selected arbitrary points may not be included in the road network reflected in the upper hierarchy.

The embodiment described above may be configured as hardware or a program such as a multitask of a microcomputer. Also,
Locator 102 may have any configuration as long as it can detect the position information of the vehicle. Also, the input device 101
Although the position is designated by scrolling the map image displayed on the output device 106, the position may be designated by a method of selecting a latitude and longitude stored in advance. Further, the point setting unit 302 may set the departure place as the user input position. Further, the nodes closest to the departure place and the destination, respectively, are set as the departure node or the destination node. However, the nodes may be the points on the closest link, or a plurality of points may be set. Also, as a search method,
Here, the Dijkstra method has been described as an example, but any method may be used as long as the method finds the shortest cost path between two points based on the cost information for each link. In the output device 106, guidance is provided by display or voice. However, for example, an automatic control unit may be added to provide the selected route to the control system of the vehicle.

Further, the present invention is realized by a program, and is recorded on a recording medium such as a floppy disk and transferred, so that it can be easily implemented by another independent computer system. In this case, the recording medium is not limited to a floppy disk,
The present invention can be similarly implemented as long as the program can be recorded thereon, such as a C card or a ROM cassette.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a car navigation system according to one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of map data recorded in a recording device 103 of FIG.

FIG. 3 is an explanatory diagram of hierarchical map data.

FIG. 4 is a functional block diagram showing one configuration example of a navigation device 105 shown in FIG.

FIG. 5 is a functional block diagram illustrating a configuration example of a route selection unit 203 illustrated in FIG. 4;

6 is a flowchart showing an operation of a point setting unit 302 in FIG.

FIG. 7 is a flowchart showing a route search processing operation of a route search unit 303 in FIG. 5;

FIG. 8 is a diagram showing a first configuration example of map data used in the car navigation system of the embodiment.

FIG. 9 is a diagram showing a second configuration example of map data used in the car navigation system of the embodiment.

FIG. 10 is a diagram showing a third configuration example of map data used in the car navigation system of the embodiment.

FIG. 11 is a diagram for explaining a method of configuring map data of a fourth configuration example used in the car navigation system of the embodiment.

FIG. 12 is a diagram showing an example in which a circuitous route is generated in the hierarchical route search method disclosed in Japanese Patent Application Laid-Open No. 4-301515.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Input device 102 ... Locator 103 ... Recording device 104 ... Communication device 105 ... Navigation device 106 ... Output device 201 ... Position detection unit 202 ... Information search / providing unit 203 ... Route selection unit 204 ... Guidance unit 301 ... Map storage unit 302 ... Point setting unit 303 ... Route search unit 304 ... Search result data storage unit

Claims (21)

[Claims] 1. A method for selecting an optimal route between two arbitrary points using hierarchical map data, the method comprising: setting two points to be searched on the map data; Searching for an optimal route between the two set points based on the data, wherein the step of searching for the optimal route performs a process of shifting to higher-level map data as the search range is expanded. The hierarchical map is divided into a plurality of basic blocks in advance, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block, and each of the map units serves as a center. A basic block and an overlapping area overlapping with other peripheral basic blocks, wherein the size and shape of the overlapping area are one basic basic block. Each road that exits from the traffic area toward the overlap area is set so as to satisfy a minimum range condition of reaching at least one upper-layer transition point in the overlap area. How to choose a route. 2. A method for selecting an optimal route between two arbitrary points using hierarchical map data, comprising: setting two points to be searched on the map data; Searching for an optimal route between the two set points based on the data, wherein the step of searching for the optimal route performs a process of shifting to higher-level map data as the search range is expanded. The hierarchical map is divided into a plurality of basic blocks in advance, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block, and each of the map units serves as a center. One basic block and an overlapping area overlapping with another surrounding basic block, wherein the size and shape of the overlapping area are within a predetermined number or more. Characterized by being set so as to satisfy a minimum range condition of including a hierarchy transition point,
Route selection method. 3. The number of upper-layer transition points to be included in the overlap area is determined depending on the number of roads that exit from one central basic block toward the overlap area. Item 3. The route selection method according to Item 2. 4. The number of upper-layer transition points to be included in the overlap area is a number obtained by multiplying the number of roads going out from one central basic block toward the overlap area by a constant magnification α. The route selection method according to claim 3. 5. The route selection method according to claim 4, wherein the constant magnification α is selected to be one or more. 6. A method for selecting an optimal route between any two points using hierarchical map data, comprising: setting two points to be searched on the map data; Searching for an optimal route between the two set points based on the data, wherein the step of searching for the optimal route performs a process of shifting to higher-level map data as the search range is expanded. The hierarchical map is divided into a plurality of basic blocks in advance, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block, and each of the map units serves as a center. Includes one basic block and an overlap area that overlaps with other surrounding basic blocks, and the corresponding map units of two or more layers can be read simultaneously. Characterized in that it is 1 unitized as the route selection process. 7. A method for selecting an optimum route between any two points using hierarchical map data, the method comprising: setting two points to be searched on the map data; Searching for an optimal route between the two set points based on the data, wherein the step of searching for the optimal route performs a process of shifting to higher-level map data as the search range is expanded. The hierarchical map is divided into a plurality of basic blocks in advance, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block, and each of the map units serves as a center. It includes one basic block and an overlapping area overlapping with other basic blocks in the vicinity. A route selection method, characterized in that a used road network is described. 8. A system for selecting an optimal route between any two points using hierarchical map data, wherein the map data storage unit stores the map data, and the map data storage unit. A point setting unit for setting two points to be searched on the map data stored in the map data storage unit; and an optimal route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching, wherein the route search unit performs a process of shifting to map data of a higher hierarchy as the search range expands, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Hierarchical map data is recorded in the map data storage unit as a set of map units prepared for each basic block, and each of the map units includes one central basic block. And an overlapping area overlapping with other surrounding basic blocks, and the size and shape of the overlapping area are determined by each road exiting from one central basic block toward the overlapping area. , A route selection system is set so as to satisfy a minimum range condition that at least one upper-layer transition point is reached in the overlap area. 9. A system for selecting an optimal route between any two points using hierarchical map data, wherein the map data storage unit stores the map data, and the map data storage unit stores the map data. A point setting unit for setting two points to be searched on the map data stored in the map data storage unit; and an optimal route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching, wherein the route search unit performs a process of shifting to map data of a higher hierarchy as the search range expands, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Hierarchical map data is recorded in the map data storage unit as a set of map units prepared for each basic block, and each of the map units includes one central basic block. And an overlap area overlapping with other peripheral basic blocks, and the size and shape of the overlap area satisfy a minimum range condition that a predetermined number or more upper-layer transition points are included therein. Characterized in that:
Route selection system. 10. The number of upper-layer transition points to be included in the overlap area is determined depending on the number of roads going from one central basic block toward the overlap area. Item 10. The route selection system according to Item 9. 11. The number of upper-layer transition points to be included in the overlap area is a number obtained by multiplying the number of roads exiting from one central basic block toward the overlap area by a constant magnification α. The route selection system according to claim 10. 12. The route selection system according to claim 11, wherein said constant magnification α is selected to be one or more. 13. A system for selecting an optimum route between any two points using hierarchical map data, wherein the map data storage unit stores the map data, and the map data storage unit. A point setting unit for setting two points to be searched on the map data stored in the map data storage unit; and an optimal route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching, wherein the route search unit performs a process of shifting to map data of a higher hierarchy as the search range is widened, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Hierarchical map data is recorded in the map data storage unit as a set of map units prepared for each basic block, and each of the map units includes one basic basic block. And an overlap area overlapping with other basic blocks in the vicinity, and the corresponding map units of two or more layers are unitized so as to be simultaneously readable. To, route selection system. 14. A system for selecting an optimal route between any two points using hierarchical map data, wherein the map data storage unit stores the map data, and the map data storage unit. A point setting unit for setting two points to be searched on the map data stored in the map data storage unit; and an optimal route between the two points set by the point setting unit based on the map data stored in the map data storage unit. A route search unit for searching, wherein the route search unit performs a process of shifting to map data of a higher hierarchy as the search range is widened, and a map of each hierarchy is divided into a plurality of basic blocks in advance. Hierarchical map data is recorded in the map data storage unit as a set of map units prepared for each basic block, and each of the map units includes one basic basic block. And the overlap area overlapping with the other basic blocks in the vicinity, and the road network used in the search performed in advance in the lower layer map data is described in the upper layer map data. A route selection system. 15. A recording medium recording map data used for a route search, wherein the map data is composed of map data of a plurality of layers having different levels of detail. The map data is divided into blocks, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block. The size and shape of the overlap area is determined for each road exiting from one central basic block toward the overlap area. Characterized by satisfying a minimum range condition that at least one upper layer transition point is reached in the map. Recording medium recording the over data. 16. A recording medium on which map data used for a route search is recorded, wherein the map data is composed of map data of a plurality of layers having different levels of detail. The map data is divided into blocks, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block. And a size and shape of the overlap area are set so as to satisfy a minimum range condition that a predetermined number or more upper-layer transition points are included therein. Characterized by the fact that
A recording medium on which map data is recorded. 17. The number of upper-layer transition points to be included in the overlap area is determined depending on the number of roads going from one central basic block toward the overlap area. Item 17. A recording medium on which the map data according to item 16 is recorded. 18. The number of upper-layer transition points to be included in the overlap area is a number obtained by multiplying the number of roads exiting from one central basic block toward the overlap area by a constant magnification α. A recording medium on which the map data according to claim 17 is recorded. 19. The recording medium according to claim 18, wherein the constant magnification α is selected to be one or more. 20. A recording medium recording map data used for a route search, wherein the map data is composed of map data of a plurality of layers having different levels of detail. The map data is divided into blocks, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block. Characterized in that the map data includes a basic block and an overlapping area overlapping with each other, and that the corresponding map units of two or more layers are integrated into one unit so as to be simultaneously readable. recoding media. 21. A recording medium on which map data used for a route search is recorded, wherein the map data is composed of map data of a plurality of layers having different degrees of detail, and a map of each layer is stored in advance in a plurality of basic maps. The map data is divided into blocks, and the map data of each hierarchical level is recorded as a set of map units prepared for each basic block. Map data comprising an overlap area overlapping the basic block of the map data, wherein the map data of the upper hierarchy describes in advance the road network used in the search performed on the map data of the lower hierarchy. Recording medium on which is recorded.