JPH04177119A - Apparatus for determining optimum route - Google Patents

Abstract

PURPOSE:To determine and display a route within a short time by calculating the optimum route to each objective point from each selected specific point and allowing a part of the beginning thereof to correspond to each specific objective point as the initial route to store the same and searching one's destination by the indication thereof. CONSTITUTION:When not only an objective point but also the specific point close to the present position of a vehicle is set by the operation of a driver, an initial setting part 6 refers to a route table 3B to obtain the initial route starting from the specific point close to the present position of the vehicle. This initial route continues to the next specific point where the optimum route passes and the driver can be guided to the point. Further, when the initial setting part 6 sets the next specific point along the optimum route, the next initial route reaching the objective point can be obtained using the specific point as a starting point. Hereinafter, by successively and continuously calculating the initial route in the same way, all of the optimum routes reaching one's destination can be displayed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides the
Optimal route determination that reads road map data in a range including a departure point and a destination point from road map data stored in a road map memory, and determines the optimal route from the departure point to the destination point based on this road map data. It is related to the device.

<Prior Art> Route guidance devices have been known that have been developed to display the position and direction of a vehicle on a screen to facilitate driving in unfamiliar territory or at night.

The above route guidance device has a display, a direction sensor, a distance sensor, a road map memory, and a computer mounted on the vehicle, and stores direction data input from the direction sensor, mileage data input from the distance sensor, and road map memory. The vehicle position is detected based on the match with the road pattern, and the vehicle position and destination point are displayed on the display together with the road map.

In this case, the driver is responsible for determining the driving route from the starting point to the destination point.

However, in recent years, computers have been able to automatically calculate the route from the departure point to the destination point according to the destination point input by the driver, and display the route superimposed on the road map before or while driving. It is proposed to do so.

The so-called Dijkstra method is used to calculate the route from the starting point to the destination point.
et, “III proven 5hortest P
athAIgOrithffi ror Tran
sportation Netvork-, Tran
s-portation Research, Vol.
, 12.1978), this method divides a number of roads to be calculated, uses the divided points as nodes, routes connecting the nodes as links, and uses the node or link closest to the starting point as the starting point. , assume a tree of links from the start point to the end point, with the node or link closest to the destination as the end point, and sequentially add the link costs of all routes that make up the tree to find the one with the lowest link cost to reach the destination point. This method calculates fewer routes. Here are some things to consider when estimating link costs:
There are other items set according to the driver's preferences, such as travel distance, travel time, use of expressways, number of right and left turns, probability of driving on main roads, avoidance of accident-prone areas, and others.

If you calculate a route using this method, as long as there is a route from the starting point to the destination point, you will definitely reach the destination point.

<Problem to be solved by the invention> However, in the Guistra method described above, the calculation time is determined depending on the number of nodes and links in the area to be calculated, and the nodes and links are Since there are a considerable number of objects in the target area, calculations usually take a considerable amount of time.

Therefore, the driver has to wait patiently after setting the destination point until the optimal route is calculated, which poses a problem in practicality when in a hurry.

The present invention has been made in view of the above problems, and when calculating a route from a departure point to a destination point by reading road map data from a road map memory according to the destination point setting by the driver, It is an object of the present invention to provide an optimal route determining device that can quickly obtain an optimal route without performing route calculations on the spot.

Means for Solving the Problems> The optimum route determining device of the present invention to achieve the above object is to select a specific point from among the points constituting road map data according to a certain standard, The optimal route starting from each specific point and reaching each destination point is calculated in advance, and among this optimal route, the initial route from the specific point to at least the next specific point that this optimal route passes through is calculated in advance. , a route table stored in correspondence with the destination point and the specific point of departure, and the destination point, as well as a specific point near the vehicle's current position or a specific point along the optimal route. and initial route acquisition means for searching a route table and obtaining an initial route according to the setting of a destination point and the setting of a specific point by the initial setting means, and the route table includes:
When storing information about the same initial route for different destination points, the information about the initial route is stored in association with a set that includes the destination points.
Claim 1).

The destination point may be selected from all the points that make up the road map data, or may be selected from several points set based on certain criteria corresponding to destinations frequently traveled by drivers. It may be something.

The specific point is preferably selected from the main points on the road map, but may correspond to all points on the road map.

In addition, the route table not only stores the initial route from a specific starting point to the next specific point;
A route beyond the next specific point may also be stored at the same time.

The above-mentioned optimal route determination device uses each specific point as the route starting point and calculates the route to each destination point, but conversely, it uses a specific point as the route end point and calculates the route to each starting point, When a route table stores information about the same final route for different starting points,
Information regarding the same final route may be stored together in correspondence with the set of departure points (Claim 2).

Further, the road map data may be composed of a combination of nodes and links, and points on the road map may be specified by nodes or links (Claim 3).
.

Further, the route table may store information regarding the initial route or the final route only when the distance between the destination point and the departure point is longer than a certain reference value (Claim 4). .

According to the optimal route determining device of claim 1, when a destination point is set by a driver's operation or the like and a specific point close to the current position of the vehicle is set, the initial route acquisition means determines the route. A table can be searched to obtain an initial route starting from a particular point near the vehicle's current location.

This initial route is part of the optimal route to the destination point, and continues from the specific starting point to at least the next specific point along the optimal route.
It can be guided from the above specific point to the next specific point.

Furthermore, when the initial setting means sets the next specific point along the optimal route, the initial route acquisition means starts from this next specific point and selects the next initial route that is part of the optimal route to the destination point. You can get directions.

Therefore, the next initial route starting from the next specific point can be shown to the driver.

Thereafter, by the same procedure, continuous initial routes can be shown to the driver, and finally all optimal routes leading to the destination can be shown to the driver.

In addition, when the above route table stores information regarding the same initial route for points corresponding to different destination points, the route table stores information about the same initial route for points corresponding to different destination points. Correspondingly, information regarding the one initial route is stored. This reason why the initial route is sometimes shared even if the destinations are different can be understood by applying the empirical rule that if the destinations are on the same side, the same route is initially taken. be. Therefore, even if the destinations are different, if the initial route is the same, the destinations will be grouped together,
Information regarding one initial route is stored for each set, thereby saving storage capacity.

Also in the optimal route determining device according to claim 2, the order of calculation is performed from the destination side, and information regarding the same final route is stored collectively in correspondence with the set (region) of the departure points. By showing continuous final routes, it is possible to finally show the optimal route from the destination point to the departure point, and to save storage capacity by storing information related to the same final route all at once. The present invention is similar to the optimal route determining device according to claim 1 in that it aims at the following. Therefore, in the following description and the description of the embodiments, it is assumed that the route is acquired from the departure point side as described in claim 1.

Note that the format of the information regarding the initial route stored in the route table varies depending on how the route information is presented to the driver. For example, if the above road map data is composed of a combination of nodes and links, and points on the road map can be specified by notes or links, then if a row of arrows along the initial route, that is, a row of links, is displayed. , Is it necessary to store the link string in the route table? If points are to be displayed along the initial route, it is necessary to store node strings in the route table. If only the intersections along the initial route are to be displayed, a string of links or a string of nodes corresponding to the intersections may be stored.

In addition, if the information about the initial route is stored in the route table only when the distance between the specific points serving as the destination point and the departure point is longer than a certain reference value, the departure point and the destination can be compared. If the targets are close, the route table memory capacity can be saved by directly calculating the optimal route without using the route table.

<Embodiments> Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

The optimal route determination device of this embodiment is incorporated into a route guidance device that guides a vehicle by displaying the optimal route on a screen or outputting audio.

As shown in FIG. 1, the route guidance device includes a display 1, a console 2, a direction sensor 10, a distance sensor 9, a road map memory 3A storing road map data, and a route table. The stored route memory 3B, the memory drive 4 that reads stored data from each of the memories 3A and 3B, the travel distance detected by the distance sensor 9, and the amount of change in the travel direction detected by the direction sensor 10 are integrated, respectively. A locator 11 that detects the vehicle position based on a comparison between the integrated data and the road map data read out by the memory drive 4, and a display for searching and obtaining an initial route, displaying road maps of a predetermined range, and guiding the vehicle. A processing section 7 (this processing section 7 also functions as an initial route acquisition means) performs various controls such as generation of data for use, control of the audio output device 15, and control of the locator 11, and an output from the processing section 7. a main memory 8 that stores display data to be displayed, an output controller 12 that controls the display 1, and an initial setting section 6 that sets initial data input from the console 2.
and has.

To explain in more detail, the console 2 consists of a key board (key board) that allows you to start and stop the device, move the cursor on the screen, set initial data such as destination points, scroll the road map displayed on the screen, etc. (not shown).

The orientation sensor 10 detects changes in orientation as the vehicle travels, and can use a geomagnetic sensor, a gyro, or the like.

The distance sensor 9 detects the traveling distance based on the speed of the vehicle or the number of rotations of the wheels, and a wheel speed sensor, a vehicle speed sensor, etc. can be used.

The locator 11 calculates travel trajectory data by integrating the distance data detected by the distance sensor 9 and the direction change data detected by the orientation sensor 10, and stores the travel trajectory data and the road map memory 3A. Comparison with road patterns (so-called map matching method,
The vehicle position is detected based on Japanese Patent Application Laid-Open No. 64-53112).

Note that a beacon receiver or a GPS receiver may be added to improve the accuracy of position detection.

A transparent touch panel 5 is attached to the display device 1 on a screen such as a CRT or a liquid crystal panel.

Each of the memories 3A and 3B is a CD-1 which is a mass storage medium.
? It consists of memory such as ON, IC memory card, and magnetic tape.

The road map memory 3A stores road maps (highway national highways, urban expressways, general national roads, major local roads, - general prefectural roads,
(including general city roads and other community roads in designated cities) is divided into meshes, and data combining nodes and links is stored in each mesh. In addition, background data for display such as railroads, rivers, place name columns, famous facilities, points registered in advance by the driver, and contour lines may be included.

The above mesh is based on the Japanese road map with a longitude difference of 1 degree and a latitude difference of 4 degrees.
Divide by 0 minutes and make the vertical and horizontal distance approximately 80+aX 80km
The first mesh is 8 in length and width.
It has a double structure with a secondary mesh (see Figure 2), which is divided into equal parts and has a vertical and horizontal distance of approximately 10 km x IOKm.

A node is generally a coordinate position for specifying a branch point or turning point on a road, and a node representing a turning point is called a turning point node, and a node representing a turning point on a road (excluding turning points). is sometimes called an interpolation point node. The node data includes a node number, an address of an adjacent mesh node corresponding to the node, an address of a link connected to the node, and the like.

A link is a connection between branch nodes.

The link data includes the link number, the addresses of the start and end nodes of the link, the distance of the link, the direction of passing through the link, the time required in that direction, the road type,
It consists of traffic regulation data such as road width, one-way streets, and toll roads.

In this way, since the link data contains the addresses of the start point node and the end point node of the link, it is possible to specify a point using only the link. Note that when a link specifies the starting point of a link, that link is called an "exit link," and when the end point of a link is specified, the link is called an "entering link." Furthermore, since the link data includes the direction in which the vehicle passes through the link, by specifying one link, the direction in which the vehicle is traveling can also be specified. FIG. 4 illustrates four exit links that specify a crossroads, and FIG. 5 illustrates four entry links that specify a crossroads.

In the following example, it is assumed that an approach link is used to specify a point.

Route memory 3B includes major intersections, leisure facilities, stations,
The optimal route from a specific link corresponding to a parking lot, expressway on-ramp or off-ramp, service area, roadside beacon, etc. to all links corresponding to the destination point is calculated using set route calculation conditions (shortest route, The shortest distance route, route with fewer left/right turns, route with wide road width, etc.) is calculated in advance (for example, before the optimal route determination device is shipped from the factory), and out of this optimal route, from the specific link mentioned above, A link string forming an initial route through which this optimal route reaches at least the next specific link is stored in correspondence with the mesh to which the specific link and the destination point belong.

Furthermore, the structure of the route memory 3B will be explained in detail using drawings and tables. FIG. 2 shows a primary mesh M1 and an adjacent primary mesh M2. It is a figure showing M3. A particular point along the road is an approach link P i (i
-0, L, 2. ...) is defined. One of the secondary meshes m1 in the primary mesh M1 has a departure point link PO (a specific link closest to the departure point).

The secondary meshes adjacent to the secondary mesh m1 are m2 to m9.
For example, let mlO be a secondary mesh that is not adjacent to the secondary mesh m1. Furthermore, arbitrary second-order meshes in another first-order mesh M2 are assumed to be m21 and m22.

The secondary meshes m1 to m9 are shown enlarged in FIG. In Fig. 3, in addition to the above-mentioned specific link Pl, general links that are not specific links are indicated by the lowercase letter p 1k (k-1,
2,...).

Referring to FIG. 3, if the destination is an adjacent secondary mesh, for example,
In the case of the next mesh m2, the optimal route L1 to each destination (only links Q 1, Q 2, and Q 3 corresponding to three destinations are shown) is illustrated. The optimal route L1 includes a starting point link Po and a subsequent link p11. p
12. They share an initial route J1 consisting of P1.

In this case, the route table has different destination links Ql
, Q2. One initial route J1 is stored for each Q3.

Next, referring to Figure 2, if the destination is the same primary mesh M1
For example, a secondary mesh m that exists in but is not adjacent to
lo, the optimal route L2 to each destination (only links Q4 and Q5 corresponding to the two destinations are shown) is the starting point link Po and the following links 21. p22.
p23. Assume that the initial route j2 consisting of P2 is shared. In this case, the route table includes all destination links Q4. Q5, etc. are treated as a group, and the initial route i2 is stored correspondingly.

If the destination is in another primary mesh, for example primary mesh M2, then each destination (two destination links Q 6, Q 7
) is the optimal route L3 to the starting point link Po and the following link p31. p32゜p33. p3
4. When sharing the initial route j3 consisting of P3, the route table handles all the destination links in the primary mesh M2 as a group, and stores the initial route J3 correspondingly.

The configuration of the route table will be explained below. The route table is
It has four types of blocks defined for each origin link. These four types of blocks are primary mesh blocks, secondary mesh blocks, link blocks, and initial route blocks. The number of primary mesh blocks is one for one origin link, the number of secondary mesh blocks is equal to the number of primary meshes, and the number of link blocks is equal to the number of secondary mesh blocks including the origin link and this. There are as many meshes as there are adjacent secondary meshes. Although the number of initial route blocks is one, it contains data of all initial routes starting from the origin link.

Each primary mesh block has an address to another block corresponding to each primary mesh. Specifically, if the origin link is PO, the primary mesh M1 to which the link PO belongs has the relative address of the secondary mesh block corresponding to the primary mesh M1, and the link PO does not belong to it. The primary mesh M2, etc. has the relative address of the initial route data (included in the initial route block) corresponding to the primary mesh M2, etc. Table 1 shows an example of a primary mesh block. (Left below) Table 1 Primary Mesh Blocks Secondary mesh blocks also have addresses to other blocks in correspondence with each secondary mesh. Specifically, the secondary mesh m1 to which the origin link PO belongs and the secondary meshes m2 to m9 adjacent thereto correspond to relative addresses to the link blocks corresponding to the secondary meshes m1 to m9, The secondary mesh m10, . . . which is not adjacent to the secondary mesh m1 has its secondary mesh m10.
...corresponds to the relative address of the initial route data. Table 2 shows an example of a secondary mesh block.

(Left below) Table 2 Secondary Mesh Block A link block is set for each secondary mesh, and the starting point link is set for each link in the secondary mesh to which the link block belongs. Contains the address of the initial route block from Po to each link. Table 3 shows examples of link blocks corresponding to the secondary mesh m2.

Table 3 link block (Specific 9222011 mesh Ml.

The initial route block contains data j of all initial routes starting from the departure point link Po.1. j2. J 3. ...
Contains. Table 4 shows examples of initial route blocks.

Table 4 Initial Route Block (Departure Point Link PO) Next, the operation of the optimal route determining device having the above configuration will be explained with reference to FIGS. 2 and 3.

The initial setting procedure is as follows. That is, when a road map including a starting point P that matches the input conditions is displayed on the screen, the driver scrolls the road map as necessary to search for a destination point, and touches the display position of the destination point. The touched position is input to the initial setting section 6. Further, the initial setting unit 6 stores the current position P of the vehicle output from the locator 11.

When determining the optimal route from the starting point P to the destination point, the processing section 7 selects a specific link closest to the starting point P (link PO in the case of FIG. 6) based on information from the initial setting section 6.
) and set the destination link corresponding to the destination point.

After the initial settings are input as described above, the processing unit 7 returns to the display map of the starting point P and searches the route table stored in the route memory 3B. Each case will be explained below.

(1) When the destination link is in another primary mesh, for example, primary mesh M2, the processing unit 7 first accesses the primary mesh block of the route memory 3B through the memory drive 4, and - Find the address #J3 of the initial route program corresponding to the source number M2ζ (see Table 1). Next, access the initial route program and retrieve the data p corresponding to address #J3.31. p32. p 3
3. p34. Obtain P3 (see Table 4). As a result, the route p3 whose starting point is the departure point link PO
t-*p32-p33→p34 can be specified as the initial route. This route is displayed on the display 1 as explained later.

■Destination links are within the same primary mesh and are not adjacent 2
For example, when the next mesh is within mlO, the processing unit 7
Access the next mesh block, mesh number M1,
and find the secondary mesh pro-tsuku #m10 (see Table 1). Then, using this as a clue, access the secondary mesh block and obtain the address #J2 of the initial route block corresponding to the mesh number mlO (see Table 2).
. Additionally, access the initial route block to address #
Data p21. corresponding to J2. p 22. p 23
．． Obtain P2 (see Table 4).

(3) When the destination link is in the same secondary mesh within the same primary mesh or in an adjacent secondary mesh, for example m2, the processing unit 7 accesses the primary mesh block, mesh number M1, and find the secondary mesh block #m2 (see Table 1). Then, using this as a clue, the secondary mesh block is accessed and the link block corresponding to the mesh number m2 is found. and,
Access the destination link included in this link block, for example Q2, and use the initial route program address #J.
1 (see Table 3). Furthermore, the initial route block is accessed and data pH, p corresponding to address #J1 is accessed.
12. Obtain Pl (see Table 4).

As described above, it is possible to search the route table and obtain initial route data for any destination located near or far.

Furthermore, for slightly distant destinations in non-adjacent secondary meshes within the same primary mesh, one initial route is memorized for each secondary mesh, as shown in Table 2.
For distant destinations located in nine different primary meshes, one initial route is stored for each primary mesh as shown in Table 1. This allows significant savings in memory capacity.

However, within the same primary mesh, initial routes were not stored together for nearby destinations in the same or adjacent secondary mesh (as can be seen from Table 3, different destinations Ql.

Q2. (Address #J1 of the same initial route block is stored redundantly for Q3) This is because it was thought that since the range of the same or adjacent secondary mesh is limited, the amount of stored data can be small. be. However, if the initial routes for these destinations are compiled, it is of course possible to combine them into one piece of information in the same way as for distant destinations.

In the embodiment described above, if there is a problem, is it true that all destination links in other primary meshes or all destination links in other non-adjacent secondary meshes share the same initial route? This may not necessarily be the case.

However, even in this case, the initial route shared by the largest number of destination links is considered to be the initial route corresponding to all destination links within the mesh. If such a majority rule is introduced, the considered initial route will not be part of the optimal route for some destinations, but as long as each destination is located on the same side from the starting point, Since it is unlikely that the initial route determined by the majority vote deviates significantly from the optimal route, there is no practical problem.

In the above case, instead of using majority voting, a representative point within the mesh may be determined and the initial route of this point may be used as the initial route corresponding to the mesh. Alternatively, instead of uniquely determining the initial route, a plurality of initial routes may be displayed for the driver to make a decision.

As described above, an initial route starting from a specific link was obtained, but the time required to complete this initial route (for example, by using the time spent waiting at a traffic light at an intersection, ), the processing unit 7 reads the initial route data using the same procedure with the next specific link that is the end point of the initial route as the starting point link.
The following initial route can be obtained. Thereafter, initial routes are obtained one after another in the same manner, and finally all route data up to the destination link can be obtained.

In the above case, the route from the vehicle's initial position P to the first specific link P1 is not included in the route table, so it cannot be immediately shown to the driver, but since it is usually a short distance, it can be shown as usual. If you calculate the route using this method, you can obtain the optimal route in a relatively short time, so there is no problem. If there is no risk of the driver getting lost because the link is nearby, it may be sufficient to simply indicate a specific link Pi without calculating the route.

Also, if the distance between the destination and departure points is short,
The initial route may not be stored in the route table, but the route may be calculated directly. This is because if the distance between the destination point and the departure point is short, the memory capacity will increase, and if the distance between the destination point and the departure point is short, the route calculation time will not be so long.

FIG. 6 is a diagram showing a route guidance flow for guiding a vehicle along an optimal route. In step S1, a display map within the area to be displayed centered on the current position of the vehicle is obtained from the road map memory 3A, and in step S2, the display map is drawn on the frame memory according to a predetermined enlargement ratio. Then, in step S3, from the route memory 3B,
Obtain initial route data using the procedure described above.

In step S4, it is checked whether the initial route to be displayed has been acquired, and if the initial route has not been acquired (as mentioned above, the distance between the destination point and the starting point is short and the initial route is not displayed in the route table). ), the process advances to step S7, where only the vehicle's current position mark is drawn on the frame memory, and the contents of the frame memory are displayed on the display in step S8. At this time, the route may be calculated as usual and the calculated route may be displayed.

If the initial route to be displayed has been determined in step S4, the initial route is drawn as a link string on the currently drawn road display map in step S5. Then, in step S6, the initial route is displayed along the road using the direction vector.

As described above, links representing specific points provided in the road map data corresponding to major intersections, leisure facilities, stations, parking lots, expressway on/off ramp areas, service areas, beacons, etc. are used as departure points. , for each destination link, calculate the optimal route to the destination link in advance, and store only the initial route, which is a part of the optimal route, on a CDROM, IC card, or DAT.
Alternatively, by storing the route in the route memory 3B such as a cassette tape, the driver can enter the destination and drive, and after the vehicle has passed a specific point, the route table can be used to immediately retrieve the destination. You can search and display the initial route to the ground. Then, until the initial route is completed, an initial route starting from the next specific point is searched and displayed, and the same steps are repeated thereafter to display the optimal route to the final destination point on the screen. be able to.

Furthermore, destinations that share a common initial route are grouped together, and one initial route is stored for a set (region) of these destinations, so the capacity of memory for storing the initial route is:
Significant savings.

Although the present invention has been described above based on examples, the present invention is not limited thereto. For example, in the above embodiment, a mesh structure is used to group destinations that share a common initial route, but as shown in FIG. It is also possible to use

For example, as shown in the same figure, if rl<r2<r3 and the straight line distance r≦r1, the initial route will not be grouped together, but if rl<r≦r2, it will be a fan-shaped area divided by a constant angle θ1. , If r2<r≦r3, it is possible to divide the area into a fan-shaped area by a constant angle θ2 that is larger than θ1, and if r3<r, it is also possible to divide the area into a fan-shaped area by a constant angle θ3, which is even larger.

The above example is an example in which the area where the initial route is grouped increases as the distance from the departure point link increases according to a fan-shaped area according to a certain rule, but the route to the destination includes an expressway. In this case, as shown in Figure 8,
It is also possible to group nearby areas by focusing on expressway off-ramps. In this case, the way to group the regions is
All you have to do is calculate the actual route and combine areas that use the same off-ramp into one.

Further, in each of the above embodiments, an exit link is used to specify a point, but an entry link may be used instead of an exit link. Alternatively, nodes may be used.

Also, it was said that road map data is composed of links or nodes related to all roads, large and small, but if the number of links and nodes is large and the capacity of the route memory 3B is insufficient, it is assumed that road map data is composed of links or nodes related to all roads, large and small. It may also be composed of links and node data.

Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, according to the optimal route determining device of claim 1 of the present invention, the optimal route from each specific point to each destination point is calculated in advance, and The first part is stored as the initial route in the route table corresponding to each specific point and each destination point, so this initial route can be searched from the route table according to the driver's destination setting. can be shown to the driver. and,
After that, the next initial route starting from a specific point that is the end point of the above initial route can be searched from the route table using the same procedure. Determine the optimal route to the destination,
It can be shown to the driver.

Furthermore, when the route table stores information regarding the same initial route for different destination points, the information regarding the initial route is stored in correspondence with the area that includes the destination point. Therefore, the capacity of the route table can be significantly saved.

Further, in the optimal route determining device of claim 2, the optimal routes from each starting point to each specific point are calculated in advance, and the last part of the optimal routes is set as the final route. Since the route table is stored in correspondence with each point and each departure point, the final route can be retrieved from the route table and shown to the driver in accordance with the driver's settings such as the destination. Then, the next final route whose ending point is the specific point that is the starting point of the final route can be searched from the route table using the same procedure. The optimal route from the initial starting point can be determined and shown to the driver.

In this case, if the route table stores information about the same final route for different departure points, the information about the final route is stored together in correspondence with the region that includes the particular departure point. Similarly to the first aspect of the invention, the capacity of the route table can be greatly reduced by doing so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a route guidance device for implementing the optimal route determining device of the present invention, FIG. 2 is a mesh map for explaining the structure of a route table, FIG. 3 is a partially enlarged view, and FIG. Figure 5 shows exit links at crossroads, respectively.
Figure 6 is a diagram showing an example of an approach link, Figure 6 is a diagram showing a vehicle guidance flow, Figure 7 is a map divided by polar coordinates instead of meshes, and Figure 8 is a map showing areas near expressway off-ramps. . P...Departure point, Po...Departure point link, Qj...Destination link, 3
A... Road map memory, 3B... Route memory, 6.
... Initial setting section, 7... Processing section (initial route acquisition means) Patent applicant Sumitomo Electric Industries Co., Ltd. Agent Patent attorney Hiroshi Kamei (and 2 others) Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Area

Claims (4)

[Claims] 1. According to the driver's destination point settings, road map data for the range including the departure point and destination point is read from the road map memory, and the optimal route from the departure point to the destination point is determined based on this road map data. An optimal route determining device that calculates in advance an optimal route to each destination point starting from a plurality of specific points selected according to certain criteria on the road map, and A route table is stored in which information about the initial route taken by this optimal route up to at least the next specific point is stored in association with the destination point and the specific point of departure, and the destination point is set. In addition, an initial setting means for setting a specific point near the current position of the vehicle and a specific point along the optimal route, and searching a route table according to the setting of the destination point and the setting of the specific point by the initial setting means. and an initial route acquisition means for acquiring information regarding the initial route, and when storing information regarding the same initial route for different destination points, the route table is configured to correspond to a set of destination points. , an optimal route determining device that stores information regarding the same initial route. 2. According to the driver's destination point settings, road map data for the range including the departure point and destination point is read from the road map memory, and the optimal route from the departure point to the destination point is determined based on this road map data. In the optimal route determining device, the optimal route is calculated in advance from each starting point using a plurality of specific points selected based on certain criteria as the destination on the road map, and the optimal route is calculated in advance from each starting point. a route table that stores information about the final route between the point and at least the next specific point along which this optimal route passes, in correspondence with the specific point serving as the starting point and the destination; and an initial setting means for setting a specific point near the travel destination and a specific point along the optimal route; and a route table according to the setting of the departure point and the setting of the specific point by the initial setting means. and a final route acquisition means for searching for information on the final route and acquiring information on the final route, and when storing information on the same final route for different departure points, the route table corresponds to a set of said departure points. and storing information regarding the same final route. 3. Claim 1 or 2, wherein the road map data consists of a combination of nodes and links, and points on the road map are identified by nodes or links.
The optimal route determination device described. 4. 3. The route table according to claim 1, wherein the route table stores information regarding the initial route or the final route only when the distance between the destination point and the departure point is longer than a certain reference value. Optimal route determination device.