JP3374805B2 - Route setting device and navigation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route setting device capable of setting a route to a destination and further setting a return route when the vehicle departs from the destination route, and a travel guide for the set route. The present invention relates to a navigation device.

[0002]

2. Description of the Related Art A current position is detected by GPS or the like as a vehicle travels, the current position is displayed on a display together with a road map, and an appropriate route from the current position to a destination is set to guide the driver. The navigation system is known and contributes to smoother driving. In addition, even if the vehicle leaves the set destination route automatically, or automatically according to the user's instruction,
The return route for returning to the original route can be set.

Conventionally, when setting the return route, road data including the current position of the vehicle is used.
Specifically, the farthest point located farthest from the current location on the destination route existing in the currently used road data is used as the calculation end point to perform the route calculation from the current location. The route calculated in this way is used as the return route, and the destination route, which is the route before the departure, is reused for the route after the farthest point, which is the calculation end point. This makes it possible to provide the return route in a shorter time than recalculating the route from the current position to the destination after the departure.

[0004]

However, in the setting of such a return path, the following problems occur. For example, assuming that the road data to be used is a rectangular area having a side of 4 km, the upper limit of the distance to the return point is about 5.7 km, which is the diagonal length of the rectangular area having a side of 4 km. Therefore, for example, in the case of a mountain road or a bypass road, the situation is likely to occur, but if there is no intersection between the departure position and the return point in the road data being used, the return route is May be set to go back.

On the other hand, it is possible to set the return point further by using the adjacent road data, but in that case, the following problems occur.
In other words, in the prior art, the purpose is to set a return route as early as possible after leaving, so by reducing the road data used for route calculation, the return route is set early even if the route quality is sacrificed to some extent. Have chosen to do. Therefore, if the road data is increased in this way and the conventional method is adopted as it is, it ignores the fundamental demand for early setting of the return route.

Therefore, an object of the present invention is to improve the route quality by increasing the road data used for the calculation of the return route without increasing the time required for the calculation of the return route.

[0007]

Means for Solving the Problems and Effects of the Invention A route setting device of the present invention made to achieve the above object is based on Dijkstra based on link information of links connecting nodes and connection information between links. Method to calculate the minimum route evaluation value (also referred to as route cost) from the calculation start point to each node using the search method or its equivalent, and based on the result of the evaluation value calculation process, It is assumed that the destination route is set by connecting the links whose total evaluation value from the starting point to the destination becomes smaller.

Here, before the return route evaluation value calculation processing means determines that the route has been departed by the route departure determination means, based on the road data in use at that time,
The evaluation value calculation process is executed using a predetermined return point on the destination route as a calculation start point. This calculation result is stored in the evaluation value calculation result storage means. When the return route setting means determines that the route has departed from the route, the return route setting means determines from the current position to the return point based on the evaluation value calculation result stored in the evaluation value calculation result storage means. A return route is set by connecting a link whose total evaluation value becomes smaller.

In setting the return path of the present invention, the following characteristics of the Dijkstra method or a search method based on it are used. That is, the characteristic is that "after the evaluation value calculation process is completed, the route from the calculation start point to all points in the calculation range can be calculated". By using this identification and executing the evaluation value calculation process with the predetermined return point on the destination route as the calculation start point as described above, by using the calculation result, all points in the calculation range from the calculation start point The route to can be calculated. Therefore, when leaving the route, it is possible to set the return route in a very short time by connecting the links whose total evaluation value from the current position to the return point becomes small.

In the case of the conventional method, since the return route is set early after leaving the route, the road data used for setting the return route is reduced as much as possible. In the above example, only the road data of 4 km square will be used.
Therefore, the route quality is inevitably sacrificed to some extent.
In other words, instead of allowing the route quality to decline, the merit of early setting of the return route was enjoyed.

On the other hand, in the case of the present invention, as described above, the setting of the return route which is actually performed at the time of leaving the route can be realized in a short time, so that the merit of early setting of the return route can be enjoyed. Then, the route quality, which has been sacrificed by the conventional method, is determined by how the evaluation value calculation process is performed. Since the evaluation value calculation process is performed before leaving the route, there is relatively sufficient time. That is, the time is not extremely limited in order to meet the request for the early setting of the route unlike the conventional method. Therefore, a relatively wide range of road data can be targeted for the evaluation value calculation process, and as a result, the route quality can be improved.
As described above, according to the route setting device of the present invention, it is possible to improve the route quality by increasing the road data used for the calculation of the return route without increasing the time required for the calculation of the return route. . Also, with the destination as the return point,
If the evaluation value calculation process for road is executed,
It is not necessary to update and store the calculation result. Therefore, the present invention
According to the route setting device of
Evaluator for return route even if it passes the boundary of road data
Do not execute arithmetic processing.

Regarding the return point, for example, claim 3
It is preferable to adopt the farthest point as shown in. Here, the farthest point is defined as follows. In other words, it is on the destination route existing in the road data being used, is on the destination side of the departure point, and is the farthest position on the way of the destination route from the departure point. In addition, as a matter of course, when a destination exists in the road data being used, the destination is set as the farthest point according to the above definition.

Here, in order to clarify the difference between the conventional method and the method of the present invention, description will be given with reference to the drawings. First, the numbers (1 to 8) shown in FIG. 10 will be described. “1” is road data where the current location is located, and covers a relatively narrow range of, for example, 4 km square. “2” is the original route (that is, the destination route that has already been set and used for guidance), and “3” is the current position. Also, "4" is the ideal return route,
“5” indicates a return route in the conventional technique, and “6” indicates a return point in the conventional technique. Further, "7" is the adjacent road data, and "8" is the return point in the present invention.

In the conventional method, as shown in FIG. 10, after returning from the route, the return route is set using only the road data 1 where the current position is. Return point 6 at that time
Is the farthest point in the road data 1 where the current position is located. In this situation, the route indicated by "5" in FIG. 10 is set as the return route. However, considering the adjacent road data 7 as well, as a result, it can be seen that the return route 5 in the conventional technique is a detour.

On the other hand, in the case of the present invention, even if the adjacent road data 7 is used, the time required for the process of setting the return route when leaving the route is short. Therefore, the return point 8 when the adjacent road data 7 is taken into consideration is the farthest point including the adjacent road data 7. In this way, the ideal return route 4 can be set. It should be noted that, in FIG. 10, for the sake of clarity, a description has been given as a specific example using up to adjacent road data. However, as described above, the evaluation value calculation process is performed before leaving the route, so there is a relatively sufficient time. . Therefore, there is no problem even if a wider range of road data is used, and further improvement of route quality can be expected.

By the way, as the calculation timing by the return path evaluation value calculation processing means, it is considered that the calculation timing is as shown in claim 4 . That is, it is determined based on the current position detected by the current position detection means whether or not the road data boundary is crossed, and if the road data boundary is crossed, the evaluation value calculation process for the return route is executed. And
It is conceivable that each time the return path evaluation value calculation processing means executes the return path evaluation value calculation processing, the calculation result is updated and stored in the evaluation value calculation result storage means.

As described above, the evaluation value calculation process needs to be performed before leaving the route. However, it is unknown when the departure from the route will occur. Therefore, if the evaluation value calculation processing is performed when the vehicle passes through the boundary of the road data, the calculation result can be used regardless of the timing at which the route leaves.

As described in claim 5 , it is conceivable to execute the evaluation value calculation processing for the return route every time the boundary of the road data is passed n times (n is a natural number). n = 1
In that case, the evaluation value calculation process is executed every time the road data boundary is crossed. For example, if n = 3, the evaluation value calculation process is executed each time the road data boundary is crossed. If it is executed every time, the accuracy is improved, but the processing load is increased. Therefore, n may be set in consideration of the balance between them.

[0019]

As the road data used for the evaluation value calculation process, it is possible to use roads of a plurality of layers, as set forth in claim 6, for example. That is, road data is used in which the same area is covered by road data of a plurality of layers, and the road data of a higher layer covers a wider area but the roads recorded are limited. For example, in the case of a three-layer structure, if the road data of the first layer, which is the lowest layer, covers an area of 4 km square, the road data of the second layer, which is one layer above, covers an area of 16 km square. , The road data of the third layer, which is the top layer, is 64
It is set so as to cover the Km square area.

When the evaluation value calculation processing for the return route is executed by using the road data of a plurality of layers in this way, there are the following advantages. (1) Further improvement in the quality of the return route can be expected. For example, when only the road data of the lowest layer that covers the smallest area is used, the road data including the original route becomes long and thin, and thus the longer the return point becomes, the narrower the calculation range becomes. Therefore, the set return path is along the original path. However, it may be a more appropriate return route if it does not follow the original route.

In such a case, by using the road data of the upper hierarchy, it is possible to prevent the situation where the calculation range becomes long and narrow, and in that case, there is a high possibility that a more appropriate return route can be set. Become. (2) The return point can be further extended.

The road data having the above-mentioned three-layer structure will be described as an example. For example, in order to set the return point 100 km ahead using only the first layer road data of 4 km square, 25
One piece of road data is required. On the other hand, 16km
When the road data of the second layer on all sides is also used, the road data of the second layer is 7 sheets (for 112 km) and the road data of the first layer is 1 sheet, that is, a total of 8 pieces of road data. Furthermore, 64 km
When the road data of the third layer on all sides is also used, two pieces of road data of the third layer (for 128 km) and the road 1 of the second layer are used.
4 pieces of road data, that is, one piece of road data for the first layer and one piece of road data for the first layer.

That is, even when trying to secure the distance to the same return point, the number of road data used can be reduced by using the road data of the upper hierarchy. Since the evaluation value calculation process is executed before leaving the route, it is preferable to finish the process early in view of the fact that it is not known when the route leaving will occur, although there is a relative time margin. Therefore, if it is assumed that the processing is completed within a predetermined processing time, it is better that the number of road data used is smaller, and if a farther point is set as the return point with a small number of road data, the upper hierarchy It is effective to use the road data of.

(3) The evaluation value calculation process can be expected to be speeded up. For example, when it is desired to secure a point 100 km ahead as a return point, the boundary of road data of the upper layer including the point 100 km ahead is set as the return point. When the road data of the second layer is used, even if the current location is moved to the next road data in the unit of road data of the first layer, 1
It is considered that the point 00 km ahead exists in the same road data of the second layer. In this situation, 1
As long as the point of 00 km ahead does not move into the different road data of the second layer, only the part of the return route using the road data of the first layer needs to be updated. The part can be reused as it is.
Therefore, the evaluation value calculation process can be speeded up. As described above, it is preferable that the evaluation value calculation process be completed earlier, and thus such speeding up of the process is very effective.

When the road data of the upper layer is used, it is preferable to use the road of the lowermost layer with respect to the present location as described in claim 7. Then, as described in claim 8, when the destination is included in the road data of the upper hierarchy being used, it is preferable to use the road data of the lowest layer for the destination. In this case, it is not necessary that the current location and the destination are included in the road data of the same upper hierarchy. For example, if the road data of the adjacent upper layer is 2
If the current location is included in the first sheet and the destination is included in the second sheet in the situation where one sheet is used, it is preferable to use the road data of the lowest layer for the destination.

As described above, in the present invention,
It is premised that the evaluation value calculation process for setting the return route is completed at the stage of leaving the route. However, if it is necessary to leave the route and calculate the return route while updating the evaluation value calculation processing for the return route, such as immediately after passing the boundary of road data, The calculation result must exist. Therefore, in order to deal with such a case, the method described in claim 2 may be adopted.

That is, two storage areas are prepared in the evaluation value calculation result storage means, and if the calculation result is already stored in one storage area, the other storage area is used to evaluate the return path evaluation value. The calculation by the calculation processing means is performed, and after the calculation result is stored in the storage area, the calculation result in the other storage area is erased. By doing this, even if it becomes necessary to set a return route during the updating of the calculation result of the evaluation value, the route can be set using the calculation result before the update, so that the above case can be appropriately handled. .

Further, as described in claim 9 , it can be also realized as a navigation device provided with the above-mentioned route setting device and a guide means for performing travel guidance for the route set by the route setting device. It should be noted that the function of realizing the above-described processing relating to the route setting on the computer system can be provided as, for example, a program started on the computer system side. In the case of such a program, for example, FD , magneto-optical disk, C
It can be used by recording it in a computer-readable recording medium such as a D-ROM or a hard disk, and loading it into a computer system and activating it as necessary. In addition, the program may be recorded by using a ROM or a backup RAM as a computer-readable recording medium, and the ROM or the backup RAM may be incorporated into a computer system for use.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments to which the present invention is applied will be described below with reference to the drawings. Needless to say, the embodiment of the present invention is not limited to the following embodiments, and various forms can be adopted as long as they are within the technical scope of the present invention.

FIG. 1 is a schematic configuration diagram when applied as a vehicle-mounted navigation device 1. The navigation device 1 of the present embodiment inputs a position detector 12 that detects the current position of the vehicle, an operation switch group 20 for inputting various commands to the device, and various commands similar to the operation switch group 20. A remote control sensor 21 for inputting a signal from a possible remote control terminal (hereinafter referred to as a remote control), a map data input device 22,
A display device 26 for performing various displays such as a map display screen and a TV screen, a speaker 28, and the position detector 1 described above.
2, the operation switch group 20, a map data input device 22, and a navigation control circuit 30 that executes various processes in response to inputs from a remote controller (not shown) and controls the display device 26 and the speaker 28.

The position detector 12 is a GPS (Global Position).
Ionization system) satellites transmit radio waves from GPS
A vehicle including a GPS receiver 12a that receives via an antenna and detects the position, direction, speed, etc. of the vehicle, a gyroscope 12b that detects the magnitude of rotational movement applied to the vehicle, a vehicle speed sensor, a wheel sensor, and the like. And a vehicle speed sensor 12c for detecting the traveling distance of the vehicle. And
Each of the sensors and the like 12a to 12c has errors of different natures, and thus is configured to be used while complementing each other. Depending on the accuracy, only a part of the above-mentioned sensors 12a to 12c may be used, and it is also possible to use a geomagnetic sensor that detects an absolute azimuth based on the geomagnetism or a rotation difference between the left and right steered wheels. A sensor or the like that accumulates the obtained steering angles of the vehicle to obtain the direction may be used.

As the operation switch group 20, there are used touch switches which are integrally formed with the display device 26 and are set on the display screen, and mechanical key switches provided around the display device 26. The touch switch is composed of infrared sensors that are arranged in rows and columns on the screen of the display device 26. When the infrared rays are blocked by, for example, a finger or a touch pen, the blocked position indicates a two-dimensional coordinate value (X, Y). ) Is detected as. by this,
A predetermined instruction can be input by directly touching the display screen.

The operation switch group 20 is various switches for operating the vehicle-mounted navigation device 20, and more specifically, a switch for switching the display content displayed on the display device 26 and a user Includes switches for setting the route to the destination.

On the other hand, the map data input device 22 is a device for inputting from the storage medium various data including so-called map matching data for improving the accuracy of position detection and road data representing road connections. As the storage medium, a CD-ROM or a DVD is generally used because of its data amount, but another medium such as a memory card may be used.

By the way, the format of this road data includes link information, node information, and link connection information. The link information may be a "link ID", which is a unique number for identifying the link, or a highway, for example.
Information about the link itself, such as the "link class" for identifying toll roads, general roads or installation roads, "starting coordinate" and "ending coordinate" of the link, and "link length" indicating the length of the link is there. On the other hand, the node information is “node I” which is a number unique to the node connecting the links.
There are information such as "D", prohibition of right and left turns at intersections, and the presence or absence of traffic lights. Further, in the inter-link connection information, for example, data indicating whether one-way traffic is allowed or not is set. Even if the same link is used, for example, in the case of one-way traffic, it is possible to pass from one link but not from another link. Therefore, passage or non-passage is determined only by the connection mode between the links.

The display device 26 is a color display device in this embodiment, and its screen has a mark indicating the current position of the vehicle detected by the position detector 12 and a map data input device 22.
It is possible to display the input road data and the additional data such as the guide route, the name, and the mark displayed on the map in an overlapping manner. Further, it is possible to provide a display for a notification for guidance and a notification for attention, which will be described later.

The speaker 28 informs the user of voice information for various guidance processed by the navigation control circuit 30. The navigation control circuit 30 mainly includes a well-known microcomputer including a CPU, a ROM, and a RAM, and controls the entire apparatus. Here, the navigation control circuit 30
The internal configuration of will be described with reference to the functional block diagram shown in FIG.

As shown in FIG. 2, the navigation control circuit 30
A current position calculation unit 31, a destination setting unit 32, a display control unit 33, a guidance control unit 34, a route calculation unit 35, a return route cost calculation result storage unit 36, and a route search result storage unit 37. Is equipped with. The current position calculation unit 31 uses the GP
The current position is calculated on the basis of the input from the S receiver 12a, the gyroscope 12b, and the vehicle speed sensor 12c, and the map data acquired from the storage medium via the map data input device 22. In addition, the destination setting unit 32 stores the destination input via the operation switch group 20 and the remote control sensor 21.

The route calculation unit 35 monitors the passage of the road data boundary corresponding to the current position based on the current position output from the current position calculation unit 31, and recognizes the passage of the road data boundary after the route search is completed. In this case, necessary road data is read from the storage medium via the map data input 22 and the cost calculation process for the return route search is performed. The cost calculation result is the return route cost calculation result until the next road data boundary is crossed. It is stored in the storage unit 36.

The display control unit 33 includes a route search result storage unit 3
The route search result stored in 7 is highlighted on the road data and displayed on the display device 26. Guidance control unit 34
Detects the current position in the route search result stored in the route search result storage unit 37 based on the output from the current position calculation unit 31, and provides voice guidance such as the traveling direction of the route by the speaker 28. When it is determined that the current position is not on the destination route, the route calculation unit 35 is instructed to calculate the return route.

Upon receiving the instruction to calculate the return route, the route calculation unit 35 creates a return route based on the stored contents of the return route cost calculation result storage unit 36 and stores it in the route search result storage unit 37. When the route calculation unit 35 automatically sets the optimum route, a method such as the Dijkstra method is used.

In this Dijkstra method, first, an initial cost is set to the calculation start point on the link or both end nodes of the link where the calculation start point is located. After that, the process of searching for a node having the minimum cost value, adding the cost of the link connecting to the node to the cost of the node, and setting the cost to the node on the opposite side of the link is repeated. At this time, if the cost has already been set for the node on the opposite side of the link, it is updated only when the cost becomes small.

The cost calculation at each link in the Dijkstra method is performed using the following equation, for example. Cost = link length × road width coefficient × road type coefficient Here, the road width coefficient is a coefficient set according to the road width,
The road type coefficient is a coefficient set according to the road type such as a toll road.

Further, in each node, the previous link (or node) that is the cost calculation source when setting the cost for the node is stored. In addition, the node searched as the node having the minimum cost value is excluded from the next search target, so that the calculation is completed as long as the number of nodes is finite.

A series of these processes is called a cost calculation process. In FIG. 3, the destination 1 indicated by “⊚” is used as the starting point of the cost calculation, and from there, the nodes indicated by “∘” are connected in a mesh shape via links indicated by thin arrows. After this cost calculation processing is completed, the node or link corresponding to the calculation end point is searched from the cost calculation processing result, and the previous link (or node) in the cost calculation processing result is sequentially traced from that link. By going
A series of link strings up to the calculation start point can be created. This is the route search result. In the case of FIG. 3, if the node or link in which the current position 2 exists is used as the calculation end point and the thin arrow is traced backward from there, the route search result indicated by the thick arrow is created.

As can be seen from these explanations, since the calculation end point has nothing to do until the completion of the above-described cost calculation processing, if the calculation start point is the destination, the calculation is completed at the time when the cost calculation processing is completed. The route from any point within the specified range to the destination can be easily calculated. Therefore, in the present embodiment, this "state in which the route from any point in the calculated range to the destination can be easily calculated" is created before leaving the route. That is, the cost calculation process is executed, and the calculation result is stored in the return route cost calculation result storage unit 36.

Then, the route leaving occurs and the guidance control unit 3
Route calculation unit 35 that has received a return route calculation instruction from
Detects the current link at the time of departure. next,
A link string from the current position to the destination (cost calculation start point) is created based on the stored contents of the return route cost calculation result storage unit 36. With this alone, the return route can be created. This process can be performed in a very short time, and the return route can be provided in a shorter time than the conventional method.

As described above, in the case of the conventional method, the return route early setting after leaving the route is realized by reducing the road data used for setting the return route as much as possible. Therefore, the route quality is inevitably sacrificed to some extent. In other words, instead of allowing the route quality to decline, the merit of early setting of the return route was enjoyed.

On the other hand, in the case of the present embodiment, since the time-consuming cost calculation process is executed before the departure of the route, the setting of the return route performed when the actual departure of the route can be realized in a short time. You can enjoy the merit of setting the return route early. The following advantages can be obtained by performing the cost calculation process before leaving the route. In other words, the time for cost calculation processing is not extremely limited,
The road data in a relatively wide range can be the target of the cost calculation process, and as a result, the route quality can be improved. The route quality becomes lower as the return point, which is the starting point of the cost calculation, is closer to the current position, and conversely becomes higher as the distance is farther. This is because if the return point is close to the current position, a return route along the original route is set, which may result in a detour. Therefore, by using a wide range of road data, you can inevitably set the return point far,
The route quality is high.

As described above, according to the navigation apparatus 1 of this embodiment, the route quality is improved by increasing the road data used for the calculation of the return route without increasing the time required for the calculation of the return route. Is possible. The above is a description of the basic characteristic part regarding the setting of the return route executed by the navigation device 1 of the present embodiment, but it can be implemented in various modes as described below. I will explain it in order.

[Return Point] Regarding the return point, it is preferable to adopt the farthest point shown below. What is the farthest point?
On the destination route that exists in the road data being used,
It is also on the destination side of the departure point and is the farthest position on the way of the destination route from the departure point. According to this definition, when a destination exists in the road data being used, the destination is naturally set as the farthest point.

[Update Timing of Return Route Cost Calculation Results] The return route cost calculation results are as follows:
Since it is preferable to update it regularly, do the following. In the state shown in FIG. 4 (a), the route guidance (destination route) 3 to the destination 2 is set, and the return route cost calculation with the return point 4 as the calculation start point is completed. It is in a state. Here, it is assumed that the return route cost calculation is performed by using the road data including the current position 1 to the road data three ahead.

From that state, even if the current position 1 moves in the adjacent road data as shown in FIG.
The cost calculation result for the return route obtained in the state of (a) can be used. However, since the distance from the current position 1 to the return point 4 is shortened, it is updated in order to further improve the route quality. Better. Therefore, as shown in FIG. 4C, the return route cost calculation using the return point 4 when using the road data four points ahead of the current location 1 at that time as the calculation start point is executed again, The calculation result is updated and stored.

In this way, if the cost calculation result is updated and stored when the road data boundary is crossed, the latest calculation result can always be used. From this point of view, it is preferable to update and store the cost calculation result every time the road data boundary is crossed. However, if it is executed every time, the accuracy is increased, but the processing load is increased. Therefore, it may be possible to update and store each time the boundary of two or more road data is passed.

Further, in the example shown in FIG. 4, when the destination 2 is included in the road data four points ahead of the current location 1, the destination 2 may be set as the return point 4. In that case, it is not necessary to update and store the cost calculation result as the road data passes through the boundary thereafter.

[Regarding Road Data Used for Cost Calculation Processing] As road data, the same area is covered by road data of a plurality of layers, and the road data of a higher layer covers a wider area, but is recorded. The road data of a plurality of layers in which the roads are limited are used.
Here, a three-layer structure has the following cover area and recorded data.

As shown in FIG. 5, the road data 1 of the first layer, which is the bottom layer, covers an area of 4 km square,
All roads are stored. In addition, the road data of the second layer, which is one level higher, covers an area of 16 km square and stores roads of national roads and prefectural roads and above. Furthermore, the road data of the third layer, which is the uppermost layer, covers an area of 64 km square and stores roads of national level and above. Therefore, the road data for the first and second layers is
4 × 4 sheets are included in the road data of the second layer and the road data of the third layer, which are the road data of the upper hierarchy.

FIG. 6 shows the return route cost calculation result using the road data of the upper hierarchy. In this case, for the first layer of road data, only one sheet including the current location is used, and for the other layers, the second layer of road data is used. Therefore, the return point 4 is the farthest point in the road data of the second layer, and the return route cost calculation is executed with this return point 4 as the calculation start point.

Although only one second layer road data is used in FIG. 6, two or more road data may be used. Further, although FIG. 6 shows an example of use up to the second layer, it is also possible to use up to the third layer which is a higher layer. When the evaluation value calculation processing for the return route is executed using the road data of a plurality of layers in this way, there are the following advantages.

(1) Further improvement in the quality of the return path can be expected. When using only the first layer road data,
When the road data including the original route is connected, it becomes longer and narrower. Therefore, the longer the return point, the narrower the calculation range becomes. In the example of FIG. 7, since four road data 4 of the first layer are connected in series, a long and narrow range of 4 Km × 16 Km as a whole is the target range for cost calculation for the return route. Since it is not possible to set a return route beyond the road data range used in this cost calculation, the set return route 8 follows the original route. However, it may be a more appropriate return route if it does not follow the original route.

In such a case, by using the road data 5 of the second layer, it is possible to prevent a situation where the calculation range becomes long and slender, so that there is a high possibility that a more appropriate return route can be set. For example, in FIG. 7, the return route 9 set by using the road data 5 of the second layer is the road data 4 of the first layer.
It can be seen that it is more appropriate than the return route 8 set by using only.

(2) The return point can be further extended. For example, 100K using only the first layer road data
In order to set the return point m ahead, 25 pieces of road data are required. On the other hand, when the road data of the second layer is also used, the road data of the second layer is 7 (112 Km) and the road data of the first layer is one, that is, a total of 8 road data.
Further, when the road data of the third layer is also used, the road data of the third layer is 2 sheets (for 128 Km), the road data of the second layer is one sheet, and the road data of the first layer is one sheet. All you need is road data.

That is, even when trying to secure the distance to the same return point, the number of road data to be used can be reduced by using the road data of the upper hierarchy. Since the cost calculation process is executed before the departure from the route, it is preferable to end the process early considering that it is not known when the departure from the route will occur, although there is a relative margin of time. Therefore, if it is assumed that the processing is completed within a predetermined processing time, it is better that the number of road data used is smaller, and if a farther point is set as the return point with a small number of road data, the upper hierarchy It is effective to use the road data of.

(3) The cost calculation process can be expected to be speeded up. For example, when it is desired to secure a point 100 km ahead as a return point, as shown in FIG.
The boundary of the second layer road data 5 including the previous point is set as the return point 6. In this case, from the current location 1 ((1
00 + α1) Since the point 6 km ahead is the return point 6, even if the current location 1 is moved to the next road data in units of 4 units of road data of the first layer, the point 100 km ahead from that point is
It also exists in the same second layer road data 5. In this case, the point which is (100 + α2) Km away from the current position 1 is the return point 6. Note that α1> α2.

In such a situation, when securing the return point 100 km ahead, the point 100 km ahead moves into the road data of the second layer different from the road data 5 of the second layer in which the return point 6 is set. Unless otherwise, only the return route portion using the first layer road data 4 needs to be updated, and the return route portion using the second layer road data 5 can be reused as it is. Therefore, the cost calculation process can be speeded up.

[Supplement when using road data of upper layer] When using road data of the upper layer, it is preferable to use the lowermost road for the current location. Then, as shown in FIG. 9, when the destination is included in the road data of the upper hierarchy in use, it is preferable to use the road data of the lowest layer for the destination. For example,
In the case shown in FIG. 9, the current position 1 and the destination 2 are included in the same second layer road data 5, but in this case, the current position 1
In addition to the destination 2, the road data 4 of the first layer is used. In FIG. 9, the same second layer road data 5
Although the present location 1 and the destination 2 are included therein, they may be included in the different second layer road data 5 respectively. For example, when the current location 1 is included in the first sheet and the destination 2 is included in the second sheet in the situation where two pieces of adjacent second layer road data are used, the destination 2 is also included in the first layer road data 4 Is preferably used.

[Others] (1) In the above embodiment, it is premised that the cost calculation process for setting the return route has been completed at the stage of leaving the route. However, if it is necessary to leave the route and calculate the return route while updating the cost calculation process for the return route, such as immediately after passing through the boundary of road data, the cost calculation result will be It must exist. In order to avoid such inconvenience,
The following method may be adopted.

That is, two storage areas are prepared in the return route cost calculation result storage unit 36 shown in FIG. For example, the first storage area and the second storage area are used. Then, when it becomes necessary to update the cost calculation result, the return route is set using the storage area (for example, the second storage area) that is free at that time, and the old data is stored after the setting is completed. The data in the first storage area that is being deleted is erased. In this way, even if it becomes necessary to set the return route during the update of the cost calculation result, the return route can be set using the cost calculation result before the update, so that the inconvenience described above can be avoided.

(2) In the above embodiment, a three-layer structure is used as an example when a plurality of layers are used, but of course, a two-layer structure or a structure of four or more layers may be used.
Further, the size of the road data of each layer described above is merely a specific example and is not limited to such a numerical value.

(3) In the above embodiment, the explanation has been made on the premise that the route is set only by using the information from the static information source, but the information from the dynamic information source such as an external information center is also taken into consideration. Then, the route may be set. For example, in addition to the configuration shown in FIG. 1, a communication device for communicating with an information center which is an external information source, an FM broadcast signal is received via a radio antenna (not shown), and a VICS arranged near a road. An external information input / output device for receiving a radio beacon signal and an optical beacon signal from a fixed station for service is provided. By doing so, for example, congestion information can be obtained in real time, and the degree of congestion on the road can be taken into consideration when setting the route. In this case, the cost calculation formula is, for example, link length × road width coefficient × road type coefficient × congestion degree.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a navigation device as an embodiment of the present invention.

FIG. 2 is a functional block diagram of a navigation control circuit according to the embodiment.

FIG. 3 is an explanatory diagram showing an outline and a result of a cost calculation process using the Dijkstra method.

FIG. 4 is an explanatory diagram of update timing of a cost calculation result for a return route.

FIG. 5 is an explanatory diagram of road data of a plurality of layers used for cost calculation processing.

FIG. 6 is an explanatory diagram showing a return route cost calculation result using road data of an upper layer.

FIG. 7 is an explanatory diagram showing that the quality of a return route is improved when road data of an upper layer is used.

FIG. 8 is an explanatory diagram showing that high-speed cost calculation processing can be expected when road data of an upper layer is used.

FIG. 9 is an explanatory diagram showing a countermeasure when the current location and the destination are included in the road data of the same upper hierarchy.

FIG. 10 is an explanatory diagram specifically showing a difference in route setting between the conventional technique and the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Navigation device 12 ... Position detector 12a ... GPS receiver 12b ... Gyroscope 12c ... Vehicle speed sensor 20 ... Operation switch group 21 ... Remote control sensor 22 ... Map data input device 26 ... Display device 28 ... Speaker 30 ... Navigation control circuit 31 ... current position calculation unit 32 ... destination setting unit 33 ... display control unit 34 ... guidance control unit 35 ... route calculation unit 36 ... return route cost calculation result storage unit 37 ... route search result storage unit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01C 21/00 G08G 1/0969

Claims (9)

(57) [Claims] 1. A minimum route evaluation value from a calculation start point to each node is calculated using a Dijkstra method or a search method based on the link information of links connecting nodes and the connection information between the links. Performs the evaluation value calculation process to calculate, and based on the result of the evaluation value calculation process, in the route setting device that sets the destination route by connecting the links whose total evaluation value from the starting point to the destination becomes smaller, The current position detection means for detecting, and the route departure determination means for determining whether or not the route is departed based on the current location detected by the current location detection means, and before the route departure determination means determines that the route is departed. Based on the road data currently in use,
The return route evaluation value calculation processing means for executing the evaluation value calculation processing using the predetermined return point on the destination route as the calculation start point, and the result calculated by the return route evaluation value calculation processing means. When it is determined that the route has been departed by the evaluation value calculation result storage means to be stored and the route departure determination means, based on the evaluation value calculation result stored in the evaluation value calculation result storage means, A return route setting means for setting a return route by connecting a link having a smaller total evaluation value until reaching the return point , wherein the return route evaluation value calculation processing means sets the destination ahead of the destination.
The evaluation value calculation process for the return route is executed as the return point.
If you do, then pass the road data boundary.
However, the route setting device is characterized in that the evaluation value calculation process for the return route is not executed . 2. Link information of links connecting nodes
Dijkstra method or based on connection information between links
Using the search method according to it,
Evaluation value calculation to calculate the minimum route evaluation value to reach
Processing, and based on the result of the evaluation value calculation processing, departure
Link the general comment value from the ground up to the destination becomes smaller
In a route setting device that sets a destination route by connecting the current location, a current location detection means for detecting the current location, and a current location based on the current location detected by the current location detection means
Route departure determining means for determining whether or not the vehicle has left the route
And the route departure determination means determines that the route has left.
Based on the road data currently in use before
A predetermined return point on the destination route is used as the calculation start point.
To perform the evaluation value calculation process described above, return path evaluation value calculation
Results calculated by the processing means and the return path evaluation value calculation processing means
Of determination and evaluation value calculation result storage means for storing, and left the route by the route deviation judgment means
If the evaluation value is calculated, it is stored in the evaluation value calculation result storage means.
Based on the evaluation value calculation result,
The total evaluation value up to
A return path setting means for setting a return path , and the evaluation value calculation result storage means has two storage areas.
The calculation result is already stored in one of the storage areas.
In case of the recovery path, use the other storage area
Calculation by the evaluation value calculation processing means, and the calculation result
Is stored in the relevant storage area, then the other storage area
The route setting device is characterized in that the calculation results in are deleted . 3. A routing device according to claim 1 or 2, wherein the return point, the a on the destination path that exists in the road data of the in-use, and there at the destination side of the withdrawal point And a farthest point which is the farthest position on the way of the destination route from the departure point. 4. The route setting device according to claim 1, wherein the return route evaluation value calculation processing means passes through a boundary of road data based on the current location detected by the current location detecting means. It is determined whether or not the boundary of road data has passed, the evaluation value calculation processing for the return route is executed, and the evaluation value calculation result storage means is the return path evaluation value calculation processing means. A route setting device that updates and stores the calculation result every time the evaluation value calculation process for the return route is executed. 5. The route setting device according to claim 4 , wherein the return route evaluation value calculation processing means evaluates the return route every time the boundary of the road data is passed n times (n is a natural number). A route setting device characterized by executing a value calculation process. 6. The route setting device according to claim 1, wherein the road data is such that the same area is covered by road data of a plurality of layers, and the road data of a higher layer is wider. However, the return route evaluation value calculation processing means executes the return route evaluation value calculation process by using the road data of the plurality of layers. Route setting device. 7. The route setting device according to claim 6, wherein the lowermost road data is used for the current location. 8. The route setting device according to claim 6 or 7, wherein when the destination is included in road data of an upper hierarchy being used, the road data of the lowest layer is set for both destinations. A path setting device characterized by being used. 9. A navigation device comprising: the route setting device according to any one of claims 1 to 8 ; and guide means for performing travel guidance on a route set by the route setting device.