JPH11257987A - Course selecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for selecting a minimum cost course as an optimal course in a short time. SOLUTION: A map storing section 301 stores a map data required for course search and point setting reads out from a recorder 103. A point setting section 302 sets start and goal nodes on a map, respectively, at the current position of a vehicle detected at a position detecting section 201 and a goal inputted by an input device 101. A course searching section 303 performs searching by a known Dijkstra method using start and goal nodes, being set at the point setting section 302 sequentially fro the lowest layer, as search starting points and determines a minimum cost course from a start node to a goal node. A search result data storing section 304 records an intermediate data an course information during search. In parallel with processing at the point setting section 302, a map read parallel processing section 401 reads a map data being used for first search into the map storing section 301.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route selection method, and more particularly to a method 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 a short time, there is a hierarchical search method disclosed in, for example, JP-A-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 long, the intermediate route can be searched using coarse map data. The search time can be shortened as a whole as compared with.

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. According to such a configuration,
Since the search can be performed only by reading only the map data of the necessary blocks from each layer, the access time of the map data can be reduced as compared with the case where all the map data of each layer is read and searched.

[0005]

However, in the above-mentioned prior art, the timing of the map reading process occupying a large weight in the route selection time has not been optimized, and the map data to be searched has to be hierarchized. Since all of them were searched in order, there was a problem that the route selection time was relatively long.

Therefore, an object of the present invention is to provide a method capable of providing a shortest cost route as an optimal route in a short time.

[0007]

Means for Solving the Problems and Effects of the Invention The first invention is a method for selecting an optimum route between arbitrary two points on map data, and a method for searching for the optimum route on the map data.
A step of setting a point, a step of pre-reading map data in a range necessary for a route search while two points are set, and an optimum distance between the two set points based on the pre-read map data. Searching for a route.

As described above, according to the first aspect, the point setting processing and the map reading processing in the range necessary for the search are performed simultaneously, so that the search processing can be started immediately after the point setting, and As a result, the search time can be reduced.

A second aspect of the present invention is a method for selecting an optimum route between arbitrary two points on map data. The method comprises the steps of: setting two points to be searched on map data; A step of reading map data of a certain range, and setting 2 based on the read map data.
Searching for an optimal route between the points, wherein the step of searching for the optimal route repeatedly performs a route search in which the search range is gradually widened until the optimal route between the two set points is determined, The step of reading the map data in a range necessary for the first route search while the two points are set, and the step of searching for the optimum route are the n-th (n is a natural number of 2 or more) route. During the search, map data in a range necessary for the (n + 1) th route search is read.

As described above, according to the second aspect of the present invention, when the optimum route is searched by repeating the route search several times with the range changed between the two set points, the route search in the next range is performed. Since necessary map data is read at the time of searching for a route in the previous range, the search process for the next range can be started immediately after the search for the previous range is completed, and as a result, the search time can be reduced.

A third invention is a method for selecting an optimum route between any two points by using hierarchical map data, comprising the steps of setting two points to be searched on the map data. , According to the set positional relationship between the two points,
A step of determining a search candidate layer excluding an optional search layer; and a step of searching for an optimum route between two set points based on the map data. The search for the optimal route between the two set points is performed while performing the process of shifting to the higher hierarchy between the search candidate hierarchies as the search spreads.

As described above, according to the third aspect of the present invention, a search candidate hierarchy is set by excluding a search hierarchy that can be omitted in accordance with the set positional relationship between the two points. It is possible to reduce the search time of the hierarchized layer, and as a result, the search time can be reduced.

A fourth invention is an invention according to the third invention, wherein the step of searching for an optimum route includes a process of shifting from a certain lower hierarchy included in the search candidate hierarchy to the next higher hierarchy. When performing, it is determined whether or not there is a predetermined number or more of upper transition points that can be moved to the next higher hierarchy. If there are more than the predetermined number of upper transition points, the next If the number of upper transition points is less than the predetermined number, the transition to the lower layer than the next upper layer and excluded from the search candidate layers is performed. It is characterized by.

As described above, according to the fourth aspect, if the number of upper transition points to the search candidate layer is equal to or less than a certain number, a lower layer than the next search candidate layer is set as the next search layer. Therefore, it is possible to prevent the occurrence of a circuitous route due to a shortage of the number of upper transition points, and as a result, it is possible to improve the route quality.

A fifth 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 optimal route between two set points while shifting map data from a lower hierarchy to an upper hierarchy as the search range expands. The step of searching for an optimal route is performed in a certain hierarchy. At the time of the search, the number of points that can be moved to the upper layer is counted, and if the counted number of points that can be moved to the upper layer becomes equal to or more than a predetermined value, the search processing in that layer is terminated, and the upper layer The feature is to shift to.

As described above, according to the fifth aspect, when a certain number or more of the upper transition points can be secured, the search in that layer is stopped and the search layer is shifted to the upper layer. Therefore, it is possible to move to a higher hierarchy within a minimum search range, and the route selection time can be shortened.

[0017]

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 a 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 a diagram for explaining the configuration of the hierarchical map data. In FIG. 3, the map data is divided into, for example, four levels of levels 1 to 4.
Here, hierarchy 1 is the lowest hierarchy, and hierarchy 4 is the highest hierarchy. Further, the map data of each layer is divided into a plurality of blocks.

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 starting 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 detecting 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 means 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.

(1) First Configuration Example of Route Selection Unit 203 FIG. 5 is a functional block diagram showing a first configuration example of the route selection unit 203 shown in FIG. 5, the route selection unit 203 includes a map storage unit 301 and a point setting unit 302.
, Route search unit 303, search result data storage unit 304
And a map reading parallel processing unit 401.

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. Map reading parallel processing unit 401
Reads all map units in the range used for the next search into the map storage unit 301 in parallel with the processing of the point setting unit 302 and the route search unit 303.

The operation of the route selecting unit 203 of the first configuration example configured as described above will be described in detail below with reference to flowcharts.

FIG. 6 is a flowchart showing the operation of the point setting unit 302 in the first configuration example of the route selection unit 203. First, in step S601 of FIG. 6, the point setting unit 302 sends the map data of the lowest hierarchical level (more specifically, the starting point (for example, the position detection unit 2)
The map data of the block including the current position of the vehicle detected at 01 is read and stored in the map storage unit 301, and the node closest to the departure point is set as the departure node, and the arrival cost (for example, 0) is set. . Next, in step S602, the point setting unit 302 sends the lowest level map data (more specifically, the destination (for example,
The map data of the block including the point input by the user via the input device 101) is read and stored in the map storage unit 301, and the node closest to the destination is set as the destination node, and the arrival cost (for example, 0) is set. .

At this time, the map reading parallel processing unit 401
At the same time as the processing of the point setting unit 302 (see FIG. 6) is started, map data in a range necessary for searching for the departure point side of the lowest hierarchy is read from the storage device 103 and is stored in the map storage unit 30.
1 is stored. The map data read at this time includes a plurality of blocks (for example, eight blocks surrounding the block read for point setting) positioned around the block read for point setting in step S601. It is map data. As described above, the reason that a plurality of blocks of map data are required for the search processing is mainly to make it possible to more reliably move to the upper hierarchy.

Next, the route search unit 303 executes a route search process for finding the minimum cost route. FIG. 7 is a flowchart illustrating the operation of the route search process of the route search unit 303 in the first configuration example of 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, if the necessary map data has not been read into the map storage unit 301, the route search unit 303 reads it from the storage device 103 and uses the known Dijkstra method with the departure place side candidate state node as a starting point. While the intermediate data is stored in the search result data storage unit 304, a departure point side search process in a certain area is performed (step S70).
3). 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-side search process assuming that the route has been determined, proceeds to step S711, and stores the search result data storage unit 304
Is constructed from the search results stored in. 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 necessary map data in the map storage unit 301.
If it is not read in from the storage device 103, the intermediate data is stored in the search result data storage unit 304 using the known Dijkstra method with the destination side candidate state node as a starting point, Perform search processing. Next, the route search unit 303 determines in step S7
It is determined whether or not the shortest cost route to the departure point side search end node is determined during the search processing in the fixed area in 05 (step S706). When the shortest cost route to the departure place side search end node is determined, the route search unit 303
Terminates the destination side search processing assuming that a route has been determined, proceeds to step S711, and forms a route from the search results stored in the search result data storage unit 304. On the other hand, when the shortest-cost route to the departure place side search end node is not determined, the route search unit 303 proceeds to step S70.
7 is executed.

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 searches for a node that is a searched node located on the outer circumference of the departure place side search area and is also recorded in the upper hierarchy (hereinafter, the departure place upper hierarchy). A transition node is referred to as a departure-side candidate state, and a searched node located on the outer periphery of the destination-side search area and also recorded in the upper hierarchy (hereinafter, referred to as a destination-side higher transition node) To the destination side candidate state (step S7)
08). Next, the route search unit 303 shifts the search hierarchy to the next higher hierarchy (step S709), and proceeds to step S70.
The process returns to step 3. Thereafter, the route search unit 303 repeats the processing of steps S703 to S709 until a route is obtained.

According to the above-described first configuration example, the search time can be reduced as follows in comparison with the related art. FIG.
9 is a timing chart showing the processing timing of the conventional route selection unit 203. FIG. 9 is a timing chart showing processing timing in the first configuration example of the route selection unit 203 in the present invention. Conventionally, as shown in FIG. 8, after the point setting process has been completed, a process of reading the departure point side search map data of layer 1 which is the lowest layer has been executed. On the other hand, in the first configuration example of the route selection unit 203 in the present invention, the map reading parallel processing unit 401
As shown in FIG. 9, the point setting process executed by the point setting unit 302 and the departure point side search map data executed by the map reading parallel processing unit 401 (hierarchy at the lowest level) And (1) the map data). Thereby, the point setting unit 30
Since the search processing of the route search unit 302 can be started immediately after the second point setting processing, the search time can be shortened as a result.

In the first configuration example, since the point setting process 302 and the map reading parallel processing unit 401 need to operate in parallel, the point setting process 302 and the map reading parallel processing unit 401 are different. The map reading parallel processing unit 401 may be realized by a CPU, or a circuit block (for example, DM) that functions independently of the operation of the CPU.
A transfer device).

(2) Second Configuration Example of the Route Selection Unit 203 FIG. 10 is a functional block diagram showing a second configuration example of the route selection unit 203 shown in FIG. 10, the route selection unit 203 includes a first map storage unit 501, a second map storage unit 502, a point setting unit 302, and a route search unit 30.
3, a search result data storage unit 304, and a map reading parallel processing unit 401.

First and second map storage units 501 and 5
In step 02, map data in a range necessary for route search and point setting is read from the recording device 103 and stored. The point setting unit 302 sets a departure node and a destination node on a map corresponding to each of the current position of the vehicle detected by the position detection unit 201 as a departure point and a point input by the input device 101 as a destination. I do. The route search unit 303 uses the known Dijkstra method or the like to sequentially set the point setting unit 3 from the lowest hierarchy.
A search process is performed using the departure node and the target node set in 02 as search start points, and a minimum cost path from the departure node to the target node is obtained. Search result data storage 3
04 records intermediate data and route information at the time of search. The map reading parallel processing unit 401 stores all map units in the range used for the next search in the first map storage unit 501 or the second map storage unit 502 in parallel with the processing of the point setting unit 302 and the route search unit 303. Read.

The operation of the route selecting section 203 of the second configuration example configured as described above will be described in detail below.
The difference from the first configuration example is that the map storage unit 301 has two parts, the first map storage unit 501 and the second map storage unit 502, and only the processing of the map reading parallel processing unit 401 is performed. Only different parts will be described.

The map reading / parallel processing unit 401 simultaneously stores the map data of the range necessary for the search for the starting point side of the lowest hierarchy at the same time as the start of the point setting processing 302.
3 to the first map storage unit 501. After that, the route search unit 303 executes the departure point side search processing of the layer 1 using the map data read into the first map storage unit 501, and at the same time, the map of the range necessary for the destination search of the lowest layer. Data is stored in the second map storage unit 50 from the storage device 103.
Read into 2. Thus, the map reading parallel processing unit 401
Reads the map data necessary for the next search processing in advance while completing the route search while sequentially switching the duplicated map storage units.

FIG. 11 is a timing chart showing the processing timing in the second configuration example of the route selection unit 203. As described above, according to the second configuration example, the map storage unit is duplicated, and the map reading parallel processing unit 401 is added, so that the point setting unit 302 and the route search unit 303 as shown in FIG. The map data necessary for the next search process performed by the route search unit 303 can be prefetched in parallel with the process performed in step (1). As a result, the search processing for the next section can be started immediately after the search for one section is completed, and as a result, the search time can be reduced.

In the second configuration example, the point setting unit 302, the route search unit 303, and the map reading parallel processing unit 401 need to operate in parallel. Therefore, the map reading parallel processing unit 401 may be realized by a CPU different from the point setting unit 302 and the route search unit 303, or the map reading parallel processing unit 401 functions independently of the operation of the CPU. Circuit block (for example, DM
A transfer device).

(3) Third Configuration Example of Route Selection Unit 203 FIG. 12 is a functional block diagram showing a third configuration example of the route selection unit 203 shown in FIG. 12, the route selection unit 203 includes a map storage unit 301 and a point setting unit 3
02, the route search unit 303, and the search result data storage unit 3
04 and a search hierarchy determination unit 601.

The map storage section 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 a position detection unit 201
The current position of the vehicle detected by
The departure node and the destination node on the map corresponding to each of the points input in step 1 are set as destinations. The search hierarchy determination unit 601 determines a hierarchy to be searched from the departure node and the destination node set by the point setting unit 302. Using a known Dijkstra method or the like, the route search unit 303 searches the search hierarchy determined by the search hierarchy determination unit 601 in order from the lowest hierarchy to the departure node and destination node set by the point setting unit 302, and sets the search start point. And a minimum cost route from the departure node to the destination node is obtained. The search result data storage unit 304 records intermediate data and route information at the time of search.

The operation of the route selecting section 203 of the third configuration example configured as described above will be described in detail below.
The difference from the first configuration example is that the map reading parallel processing unit 401 is eliminated, and the processing in the search hierarchy determination unit 601 and only part of the processing in the route search unit 303 are different. explain.

In the search hierarchy determining section 601, the point setting section 3
From the departure node and the destination node set in 02, a hierarchy to be searched is determined. At that time, the highest hierarchy to be searched is set according to the distance between the departure node and the destination node,
If the number of layers is equal to or greater than a certain number of layers (for example, four layers), the search target layer is set to a certain number of layers (for example,
(3 layers) or less. FIG. 13 is a conceptual diagram when the layer 3 is omitted. In the example of FIG. 13, it is determined from the distance between the departure node and the destination node that the search is performed up to the layer 4, and the layer 3 which is the intermediate layer is omitted. In addition, it is preferable that the omitted middle layers be set at regular intervals in a well-balanced manner.

Further, the operation of the route search processing in the route search unit 303 will be described in detail below with reference to flowcharts. FIG. 14 is a flowchart illustrating a route search process of the route search unit 303 in the third configuration example of the route selection unit 203. This flowchart is based on the route search unit 30 in the first configuration example of the route selection unit 203 shown in FIG.
3 (see FIG. 5), which is almost the same as the flowchart of the route search process, and therefore only different portions will be described.

This flowchart differs from the flowchart (FIG. 7) of the route search process of the route search unit 303 in the first configuration example of the route selection unit 203 in FIG.
901 to S1907 (steps S701 to S70 in FIG. 7)
7) is added after step S1912). Steps S1901 to S1
When the search processing of the current search hierarchy ends by the processing of 907 and no route is found, the route search unit 3
In step S1912, in step S1912, it is determined whether the next higher layer can be omitted according to the determination result of the search layer determining unit 601. If the omission is not possible, the route search unit 303 proceeds to step S1908 (step S70 in FIG. 7).
8), and as described in the first configuration example, the search processing is continued with the immediately higher layer as the search layer. If it is determined in step S1912 that the search can be omitted, the process proceeds to step S1913, where the route search unit 303 determines the next search that is a searched node located on the outer periphery of the departure place side search area and determined by the search hierarchy determination unit 601. The node recorded in the candidate hierarchy is also referred to as a (starting-point-side upper-layer transition node) departure-side candidate state, and is a searched node located on the outer periphery of the destination-side search area.
The node (destination upper-layer shift node) recorded also in the next search candidate hierarchy determined in 1 is set to the destination-side candidate state. Next, the route search unit 303 determines that the number of nodes (departure-side upper-layer transfer node and destination-side upper-layer transfer node) that have shifted to the next search candidate layer is a specific number (for example, 8
(Step S19).
14). If not, the route search unit 303 returns to step S1908, and continues the search process without omitting the next higher layer. On the other hand, if the specified number or more nodes have moved to the next search candidate hierarchy, the route search unit 303 proceeds to step S1915,
The search hierarchy is shifted to the next search candidate hierarchy, and the search process is continued.

As described above, according to the third configuration example, the search hierarchy judging unit 601 is added, and the search of the middle hierarchy excluding the lowest hierarchy and the highest hierarchy to be searched is omitted. Since the search time of the omitted hierarchy is reduced, the search time can be shortened as a result.

In the route search section 303, if the number of nodes shifted to the next search candidate hierarchy determined by the search hierarchy determination section 601 is not more than a certain number, the lower hierarchy than the next search candidate hierarchy is shifted to the next search hierarchy. By using the search hierarchy, it is possible to prevent the occurrence of a circuitous route caused by the shortage of the number of nodes shifted to the upper hierarchy, and as a result, it is possible to improve the route quality.

In the third configuration example, the hierarchy that can be omitted is determined before the search is started. However, after the search of one hierarchy is completed, the number of upper transition points is checked for all the upper hierarchies. It is also possible to make a transition to the uppermost tier among upper tiers in which a certain number or more of higher tiers determined for each tier exist. At this time, the highest hierarchy to be searched may be determined according to the positional relationship between the departure place and the destination.

In the first to third configuration examples described above, when a route cannot be obtained in the current search hierarchy, the search is shifted to the upper hierarchy after the search in a certain area is completed. , Even if the search within a certain area has not been completed,
When a certain number of higher-level transition nodes have been secured,
The search may be stopped to shift to a higher hierarchy.
By doing so, the search hierarchy can be shifted to the upper hierarchy within the minimum search range, so that the route selection time can be shortened.

Further, the first to third configuration examples described above may be configured as hardware or may be configured by a program processing such as multitasking of a microcomputer. Locator 102 may have any configuration as long as it has a function of detecting the current position of the vehicle. The input device 101 specifies the position by scrolling the image of the map displayed on the output device 106. However, the input device 101 may specify the position by selecting a previously stored latitude and longitude. good. Further, the point setting unit 302 may set the departure place according to the position input by the user. 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. Although the Dijkstra method has been described as an example of the search method, any method may be used as long as the method finds the shortest cost route 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 configurations described in the above embodiments may be used in combination.

Further, the present invention is realized by a program, and is recorded on a recording medium such as a floppy disk and transferred, whereby it can be easily implemented by another independent computer system. In this case, the recording medium is not limited to a floppy disk,
Any medium, such as a card or a ROM cassette, capable of recording a program may be used.

[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 illustrating a configuration example of map data.

FIG. 3 is a diagram illustrating a configuration of hierarchical map data.

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

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

FIG. 6 is a flowchart illustrating an operation of a point setting unit 302 in the first configuration example of the route selection unit 203.

FIG. 7 is a flowchart illustrating an operation of the route search unit 303 in the first configuration example of the route selection unit 203;

FIG. 8 is a timing chart showing processing timings of a search processing operation and a map reading operation in a conventional car navigation system.

FIG. 9 is a timing chart showing processing timings of a search processing operation and a map reading operation in the first configuration example of the route selection unit 203;

FIG. 10 is a functional block diagram illustrating a second configuration example of the route selection unit 203 illustrated in FIG. 4;

FIG. 11 is a timing chart showing processing timings of a search processing operation and a map reading operation in a second configuration example of the route selection unit 203;

12 is a functional block diagram showing a third configuration example of the route selection unit 203 shown in FIG.

FIG. 13 shows a third configuration example of the route selection unit 203.
It is a conceptual diagram when the hierarchy 3 is omitted.

FIG. 14 is a flowchart showing a route search process of a route search unit 303 in a third configuration example of the route selection unit 203.

[Explanation of symbols]

 Reference Signs List 101 input device 102 locator 103 recording device 104 communication device 105 navigation device 106 output device 201 position detecting unit 202 information searching / providing unit 203 route selecting unit 204 guiding unit 301 map storing unit 302 point setting unit 303 route searching unit 304 search result data Storage unit 401 Map reading parallel processing unit 501 First map storage unit 502 Second map storage unit 601 Search hierarchy determination unit

Claims (5)

[Claims] 1. A method for selecting an optimum route between two arbitrary points on map data, comprising the steps of: setting two points to be searched on the map data; and setting the two points. A step of prefetching map data in a range necessary for a route search, and a step of searching for an optimal route between the set two points based on the prefetched map data,
Route selection method. 2. A method for selecting an optimal route between two arbitrary points on map data, comprising: setting two points to be searched on the map data; A step of reading map data; and a step of searching for the optimum route between the two set points based on the read map data. The step of searching for the optimum route includes:
Until the optimum route between the points is determined, the route search with the search range gradually expanded is repeatedly performed, and the step of reading the map data is performed in a range necessary for the first route search while the two points are set. While the step of reading the map data and searching for the optimal route is performing the n-th (n is a natural number of 2 or more) route searches, the map data in the range necessary for the (n + 1) -th route search is A route selection method characterized by reading. 3. 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; Determining a search candidate hierarchy excluding an omissible search hierarchy according to the determined positional relationship between the two locations; and searching for the optimal route between the set two locations based on the map data. The step of searching for the optimum route includes searching for the optimum route between the two set points while performing a process of shifting to a higher hierarchy between the search candidate hierarchies as the search range becomes wider. The route selection method. 4. The step of searching for the optimum route, wherein, when performing a process of shifting from a certain lower hierarchy included in the search candidate hierarchy to the next upper hierarchy, an upper migration capable of shifting to the next upper hierarchy It is determined whether or not the points are present in a predetermined number or more. If the upper transition points are present in a predetermined number or more, the transition processing to the next higher hierarchy is performed. The method according to claim 3, wherein when the number of transition points is smaller than a predetermined number, a transition is made to a layer lower than the next upper layer and excluded from the search candidate layer. 5. The route selection method described. 5. A method for selecting an optimum 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 set two points while shifting the map data from a lower hierarchy to an upper hierarchy as the map spreads, wherein the step of searching for the optimal route comprises: At the time of the search, the number of points that can be moved to the upper layer is counted, and if the counted number of points that can be moved to the upper layer is equal to or greater than a predetermined value, the search process in that layer is terminated, A route selection method characterized by shifting to a hierarchy.