JP2833353B2 - Navigation device with route calculation function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a navigation device having a function of calculating an optimum route when traveling between two designated points.

[0002]

2. Description of the Related Art Various types of navigation devices have been realized which are mounted on a vehicle to display the current location of the vehicle so as to assist the vehicle in traveling. Conventional navigation devices detect the current location of a vehicle based on, for example, outputs from a direction sensor, a vehicle speed sensor, and the like. On the other hand, a road map including the detected present location is read out from a map memory constituted by a CD-ROM or the like and is electronically displayed. Then, the detected vehicle current position is superimposed and displayed on the displayed road map.

[0003] Navigation devices having a route calculation function have also been put to practical use. In a device having a route calculation function, generally, when a destination is set, a calculation start link near the current position of the vehicle and a calculation end link near the destination are specified, and a road map including a calculation start link to a calculation end link. Data is read from the road map memory, and the optimum route is automatically calculated within the range of the road map data,
Displayed on the display. The vehicle driver can drive safely without hesitation along the displayed optimum route.

In order to execute route calculation in a navigation device, road map data stored in a road map memory is read and transferred to a work area, and a route calculation is performed in the work area based on the Dijkstra method or the like. Here, the Dijkstra method means that when calculating the optimal route from the current location to the destination, the link closest to the destination (departure point) is set as the calculation start link, and the link closest to the departure point (destination) is calculated. In this method, a road map including a link from a calculation start link to a calculation end link is obtained as a calculation end link, and an optimal route between the calculation start link and the calculation end link in the road map is calculated. For this purpose, the link cost from the calculation start link to the calculation end link is sequentially added to form a tree of links, and only the path with the lowest link cost that reaches the calculation end link is selected. Here, items to be considered when estimating the link cost include mileage, travel time, use of highway, right / left turn count, highway running probability, avoidance of accident-prone areas, and other settings according to the driver's preference. There is a matter.

[0005]

By the way, when a road map including a link from a calculation start link to a calculation end link is obtained as described above, a road such as a sea, a lake, a marsh, or a mountain is provided between the calculation start link and the calculation end link. There is a large area that does not exist, and it may become unreachable within the range of the road map.

In such a case, since the optimum route cannot be calculated, it is a commonly conceivable method to extend the range of the road map to the range where the detour road exists and recalculate. However, when the above method is adopted, there are the following problems. That is, the route calculation is first performed on a certain range of road map, but it is not possible to determine whether or not it is possible to reach the calculation end link without actually calculating it. It is a waste of time.

[0007] In connection with this, when it is not possible to reach the calculation end link in the first calculation, it is necessary to predict the extent to which the range of the road map should be expanded to reach the range where the detour road exists, unless the route is calculated. Can not. Therefore, the range is re-calculated by expanding the range by a predetermined fixed ratio, but since the route is calculated each time,
The calculation is repeated many times, wasting calculation time.

Therefore, an object of the present invention is to obtain a road map to be calculated and calculate a route before the calculation from a link from a calculation start link to a calculation end link in an area where no road exists such as a sea, a lake or a mountain. It is an object of the present invention to provide a navigation device capable of predicting in a short time whether or not the road map is to be expanded and how much the range of the road map should be expanded, and calculating a lean route calculation.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a storage means for storing a link code indicating whether each mesh is a mesh including a road or not, and a departure place and a set object before a route calculation. Registration means for setting a route calculation area including the ground and registering all the meshes included in the route calculation area; and among the meshes registered in the registration means, a mesh including a departure place and a mesh including a destination are included. Determination means for determining whether or not the mesh is linked by a mesh having a link code indicating that the mesh includes the road, and the mesh is linked by a mesh having a link code indicating that the mesh is a mesh including the road. In the case where the link is present, the route calculation unit executes the route calculation in the route calculation area, and indicates that the link is a mesh including the road. If not connected by a mesh having a mode, the route calculation area including the departure point and the set destination is enlarged, and the mesh of the mesh by the registration unit is added to the enlarged route calculation area. The registration and the judgment by the judgment means are executed.

[0010]

According to this configuration, first, a link code indicating whether each mesh is a mesh including a road or not is stored for each mesh. In this case, "mesh includes a road" means that at least one link data representing a road is included in the mesh, and it is not determined whether there is a link connection between the mesh and the mesh. Absent.

Prior to the route calculation, a route calculation area including a departure place and a destination is set, and all the meshes included in the route calculation area are registered. It is determined whether or not the meshes are linked by a mesh having a link code indicating that the mesh includes the road. Since this determination may be made based on the link code, the determination can be made in a short time without calculating a route.

If the routes are connected by a mesh having a link code indicating that the mesh includes a road, there is a possibility that the route between the starting point and the destination can be connected by a road when the route is actually calculated. Then, the route calculation is executed in the route calculation area. However, if the routes are not connected by a mesh having a link code indicating that the mesh includes a road, the road cannot be connected between the starting point and the destination even if the route is calculated. Therefore, the route calculation area including the departure place and the set destination is enlarged, and the registration of the mesh by the registration means and the judgment by the judgment means are executed for the enlarged route calculation area. To go. In the enlarged route calculation area, the mesh including the departure place and the mesh including the destination can be connected by a mesh having a link code indicating that the mesh includes the road because of the enlarged area. Therefore, when it is clear that the connection has been made, the route calculation may be performed in the route calculation area at that time.

[0013] If the mesh is not connected by a mesh having a link code indicating that it is a mesh including the road, no matter how much enlargement is performed, the enlargement may be terminated by providing some reference.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a navigation device according to one embodiment of the present invention. This navigation device is mounted on a vehicle and used to support traveling in the vehicle. This device includes, as sensors, a geomagnetic sensor 1 for detecting an azimuth, a vehicle speed sensor 2 for detecting a speed of a vehicle,
Further, a shift sensor 3 for detecting whether the vehicle is moving forward or backward is provided. The detection outputs of these three sensors 1, 2, 3 are determined by the navigation ECU.
4 to a locator 5. Further, a vibration gyro sensor 6 for detecting a turning angle of the vehicle is provided in the navigation ECU 4, and a detection output of the vibration gyro sensor 6 is also provided to the locator 5.

The locator 5 is used to calculate the current position of the vehicle, and calculates the azimuth change amount of the vehicle based on the azimuth detected by the geomagnetic sensor 1 and the turning angle of the vehicle detected by the vibration gyro sensor 6. In addition, the vehicle speed detected by the vehicle speed sensor 2 is integrated, and the moving distance of the vehicle is calculated in consideration of the forward or backward movement of the vehicle provided from the shift sensor 3. Therefore, for example, if the vehicle's accurate initial position data is given to the locator 5 before the vehicle starts moving,
The locator 5 calculates the current position of the vehicle thereafter.

Data representing the current position of the vehicle calculated by the locator 5 is stored in an MIC (Multi Information
Controller) 7. The MIC 7 is a control center of the navigation ECU 4, and has a CPU, a ROM, an R
AM etc. are included. MIC7 is the navigation ECU
Locator 5 and CD drive 8 provided in 4
And to a graphic generator 10 provided outside the navigation ECU 4. A monitor control unit 11 is connected to the graphic generator 10.
A display unit 12 such as T, a plurality of touch switches 13 and a plurality of mechanical switches 14 are provided.

The MIC 7 has a CD drive 8 and a CD drive 8 based on the current position data of the vehicle calculated by the locator 5 and the like.
It controls the autochanger 15. CD drive 8
In response to a control signal given from the MIC 7, road map data corresponding to the current position of the vehicle is read from the pre-loaded map dedicated disk D1, and output to the MIC 7.
The MIC 7 calculates the current location data calculated by the locator 5,
The road map data provided from the CD drive 8 is provided to the graphic generator 10 to generate a map and a vehicle current position mark on the map. The map and the current location mark of the vehicle generated by the graphic generator 10 are provided to the monitor control unit 11 and displayed on the display unit 12.

The CD autochanger 15 is provided with a
In response to a control signal given from C7, the CPU reads route map data for route calculation from the route calculation disk D2 loaded in advance and outputs the map data to the MIC. By operating the touch switch 13 and the mechanical switch 14 on the monitor control unit 11, the display on the display unit 12 is switched or a predetermined control signal is given to the MIC 7.

The map data for route calculation is obtained by dividing a road map (including highway national roads, motorways, national roads, prefectural roads, city roads of designated cities, and other living roads) into meshes. A route composed of a combination of a node and a link is stored in units. Due to the characteristics of the map database, nationwide closed networks are formed for roads higher than national roads among the main roads.

A node is generally a coordinate point for specifying a road intersection, a mesh boundary, a dead end point, and the like. A node representing an intersection may be called an intersection node. What connects each node is a link. The link data includes the link number, the address of the start node and the end node of the link, the distance of the link, the direction of passing through the link, the required time data in that direction, the road type, the road width, one-way traffic, right turn prohibition, left turn prohibition and toll road. And other traffic regulation data.

The mesh described above is obtained by converting a Japanese road map to a longitude difference of one.
°, a primary mesh set by dividing the latitude and longitude by 40 'and the vertical and horizontal distance is set to about 80 km x about 80 km, and this primary mesh is divided into 8 vertical and horizontal sections, and the vertical and horizontal distance is set to about 10 km x about 10 km
And a secondary mesh set as Further, the route calculation map data has a file storing information on whether each secondary mesh is a mesh including a link. For example, a certain secondary mesh may be a mesh corresponding to an area where no road exists, such as the sea, lakes, and mountains. At this time, a code indicating that the secondary mesh does not include any link is stored in the file together with the code of the secondary mesh. However, when at least one link is included in the secondary mesh, a code indicating that the secondary mesh includes a link is stored together with the code of the secondary mesh.

The road map data for position calculation is created from a map database of 1/2500, and is more detailed and precise data than the map data for route calculation.
This is a one-layer data comprising node position information and some link information (road width, etc.). The number of types of link information is small because it does not include required time data or traffic regulation data that is not directly needed for position detection (however, road width may be useful for position detection as well. Is).

As described above, the road map data for position detection and the map data for route calculation are separated. The former requires detailed accuracy for map matching, and the latter requires more accurate route calculation than accuracy. This is because it is necessary to attach various data. The display road map data is 25
Roads, created from a 1:00 map database
It is composed of map data and the like for specifying place names, famous facilities, railways, rivers, and the like.

The MIC 7 uses the Dijkstra method or the like (in the embodiment, a potential method, which is a kind of the Dijkstra method), to move from the current position to the destination based on the route calculation map data read from the route calculation disk D2. Of the optimal route of This potential method is
The link closest to the destination (departure point) is set as the calculation start link, the link closest to the departure point (destination) is set as the calculation end link, and the link costs from the calculation start link to the calculation end link are sequentially added to calculate the link cost. This is a method of constructing a tree and selecting only the route with the lowest link cost that reaches the calculation end link. Here, items to be considered when estimating the link cost include mileage, travel time, use of highway, right / left turn count, highway running probability, avoidance of accident-prone areas, and other settings according to the driver's preference. There is a matter. As a work area for executing the potential method, the MIC 7 stores 5 RAMs on the RAM.
A buffer area of 12 kbytes is prepared.

A beacon unit 16 may be connected to the MIC 7, and a beacon receiver 17 may be connected to the beacon unit 16. Beacon receiver 17
Is for receiving data such as position information and road information (intersection name, destination guidance) radiated from a beacon antenna installed on the road side of a road or the like. The beacon data received by the beacon receiver 17 is provided to the MIC 7 via the beacon unit 16 and is finally displayed on the display unit 12 to display the beacon information to the driver. As an optional device, the locator 5 has a GPS
A GPS receiver 19 may be connected via the unit 18. When the GPS unit 18 and the GPS receiver 19 are provided, it is possible to receive a signal from a GPS satellite and accurately detect the absolute azimuth, or directly detect the current position of the moving object.

FIG. 2 shows the display unit 12 and the mechanical switch 14.
It is an external appearance front view which shows a specific example of the display which has a etc. This indicator is integrated in a motor vehicle, for example, in a front console box. The display unit has a display unit 12 disposed on a main surface of the display unit, and displays various data including a map, a current vehicle position, and an optimum route, as described later. Further, a transparent electrode panel is disposed on the surface of the display unit 12, and when the switch contents, that is, the position to be pressed and the switch type are displayed on the display unit 12, the switch can be operated. A so-called touch switch 13 is provided.

On both sides of the display section 12, several mechanical switches 14 are provided. In this embodiment, a navigation switch 14a for displaying a map, an information switch 14b for displaying various kinds of guidance information, a memo switch 14c for performing a memo function, and returning the display content to the previous screen. Switch 14d for moving the displayed cursor or scrolling the display screen, and a set switch 14f used for setting data.

FIG. 3 is a flow chart showing a schematic control procedure when a route is calculated in the navigation device of this embodiment. Describing according to the flow of FIG. 3, after a destination is set (step S1), the MIC 7 determines whether or not a request for route calculation has been input (step S2). The route calculation request is input, for example, by pressing a touch switch (not shown) displayed on the display unit 12 shown in FIG.

If it is determined that there is a request for route calculation, MI
C7 operates the CD drive 8, reads the route calculation program from the route calculation disk D2 loaded in the CD autochanger 15, and transfers the calculation program to the MIC7.
Is loaded into, for example, an SRAM (step S3). Before the route calculation, a route calculation pre-process related to the present invention is performed (step S4). If the pre-process result is normal (when there is a possibility of reaching the destination), the current position detected by the locator 5 is determined. the nearest link to the calculation start link L _O, as the calculation end link L _D closest link destination set, to calculate the optimal route between the calculation start link L _O and computation termination link L _D ( Step S6). That is, acquiring the road map data from the calculation start link L _O to the calculation end link L _D, to calculate the optimal route between the calculation start link L _O and computation termination link L _D by Dijkstra method. In this case, if the data amount of the general road map exceeds the capacity of the buffer area, the general road layer is divided and obtained, the optimum route is obtained in each of the divided areas, and these optimum paths are added. You can also.

The obtained optimum route is displayed on the display unit 12 (step S7). If the preprocessing result is abnormal (when there is no possibility of reaching the destination), the fact is displayed without calculating the optimum route (step S8).
Hereinafter, the procedure of the route calculation pre-processing of step S4 will be described in detail with reference to a flowchart (FIG. 4).

First, the origin O and the destination D are recognized, and a rectangular route calculation area on the secondary mesh including the origin O and the destination D is set (step S41). For this, the parameter V related to the length of the short side of the rectangle is
And a parameter H related to the length of the long side of the rectangle (see FIG. 5). Then, based on the distance L between the departure place O and the destination D, the parameters V, H are obtained using a graph (FIGS. 6, 7) showing the relationship between these parameters V, H and the distance L.

The rectangular area is selected based on an empirical rule that the calculated optimum route length will not be extremely long compared to the straight line distance between the starting point O and the destination point D. ing. Therefore, the shape is not necessarily limited to a rectangle, and may be, for example, an ellipse having a focus on the starting point O and the destination D. Next, the amounts of change dV and dH of the parameters V and H are set to 0 (step S42).

Then, the data size of the road map on the secondary mesh in the route calculation area is estimated (step S4).
3) It is determined whether or not data is contained in the 512-kbyte buffer area (step S44). If not, the change amounts dV and dH are each set to a negative constant value, and the route calculation area is reduced (step S48).
It is determined whether or not V and H exceed the maximum values (step S49), and if not, step S4.
Return to 3.

In the case of entering into the buffer area of 512 kbytes, the "over sea determination processing" described later is performed (step S).
45). This “over-sea determination processing” will be described in detail with reference to a flowchart (FIG. 8) and a secondary mesh map (FIGS. 9 and 10). First, a code of a secondary mesh (called a destination mesh) M _D including the destination D is defined as MI
It is registered on the first work table in the memory in C7 (step S451). Next are in the route calculation region R, recognize all secondary meshes except destination mesh M _D (step S452), among them, the departure point O
Secondary mesh (called starting point mesh) M _O
Is registered in the second work table (step S453).

Then, it is checked whether or not one or more codes of the secondary mesh are registered in the second work table (step S454).
A code of a secondary mesh adjacent to any of the east, west, north and south of the next mesh (referred to as an adjacent secondary mesh) is extracted (step S455). The adjacent secondary mesh, if it equals the destination mesh M _D (step S45
6) If not equal, it is determined whether or not the adjacent secondary mesh is a mesh including a link (step S457).

If the adjacent secondary mesh is a mesh including a link, it is determined whether the adjacent secondary mesh is included in the route calculation region R (step S458). If it is included, the code of the adjacent secondary mesh is registered in the second work table (step S459). In this way, the code of the secondary mesh (the mesh represented by “C” in FIGS. 9 and 10) that is adjacent to the departure place mesh M _O , includes the link, and is included in the route calculation region R is You can register.

If the above determination is completed for four adjacent secondary meshes in the east, west, north and south directions (step S460),
The secondary mesh which is the center of the east, west, north and south is deleted from the second work table (step S461), and the same determination as above is performed with the registered secondary mesh as the center (step S454). If the above procedure is repeated and all the codes of the secondary mesh registered in the second work table are lost, the route is blocked by an area where no road exists between the departure point and the destination, and The process is terminated with a code (NG code) indicating that it is unreachable in the range of the calculation region R (step S462, see FIG. 9). Further, the adjacent secondary mesh, when equal to the destination mesh M _D is (referred OK code) code that is capable of reaching
, And the process ends (step S463).

If the result of the "overseas determination process" is "OK", a normal code is added and the process ends (step S4).
6) If "NG", change amounts dV and dH are each set to a positive constant value, and the route calculation area is enlarged to R '(step S47, see FIG. 10). Then, it is determined whether V and H exceed the maximum values (step S4).
9) If the value does not exceed the maximum value, the process returns to step S43 and repeats the “over sea determination process”. When the maximum value is reached, an abnormal code is added and the processing ends.

[0039]

As described above, according to the present invention, before actually calculating a route between a departure point and a destination, a link code indicating a mesh including a road is used as a clue to calculate a route in a route calculation area. , It is possible to determine whether there is a possibility of connecting the starting point and the destination by road, and if there is no possibility of connecting the starting point and the destination by road, expand the route calculation area. Thus, the same judgment can be made. Therefore, the actual route calculation only needs to be performed when there is a possibility, so that the calculation time is not wasted.

[Brief description of the drawings]

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

FIG. 2 is an external front view showing a specific example of a display device of the navigation device.

FIG. 3 is a flowchart for explaining a route calculation processing procedure in the navigation device.

FIG. 4 is a flowchart for explaining a route calculation pre-processing procedure in detail.

FIG. 5 is a diagram showing a route calculation area including a departure place and a destination.

FIG. 6 is a graph for determining a rectangular parameter V based on a distance D between a starting point and a destination.

FIG. 7 is a graph for determining a rectangular parameter H based on a distance D between a starting point and a destination.

FIG. 8 is a flowchart for describing in detail a part of the flowchart of FIG.

FIG. 9 is a map composed of a number of secondary meshes including a route calculation area.

FIG. 10 is a map composed of a number of secondary meshes including an enlarged route calculation area.

[Explanation of symbols]

 4 Navigation ECU 5 Locator 7 MIC 8 CD Drive 14 Mechanical Switch 15 CD Autochanger D2 Route Calculation Disk

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01C 21/00

Claims (1)

(57) [Claims] 1. A map is divided into meshes of a fixed size,
Road map storage means for storing road map data in mesh units; input means for inputting a route calculation request signal; stored in the road map storage means in response to the input of the route calculation request signal from the input means. Loading means for reading the road map data and transferring the data to the work area, and an optimal route for traveling between two links which are respectively close to the departure point and the set destination based on the road map data transferred to the work area. A navigation device having a route calculation function, which includes: a route calculation unit for calculating a link code indicating whether each mesh is a mesh including a road or not; and a route calculation unit. Prior to the route calculation, the route calculation area including the departure point and the destination is set, and all the meshes included in this route calculation area are set. And a mesh including a departure place and a mesh including a destination among the meshes registered in the registration means are connected by a mesh having a link code indicating that the mesh includes the road. Determining means for determining whether or not the road is meshed with a mesh having a link code indicating that the mesh includes a road. If not connected by a mesh having a link code indicating that the mesh includes a, the route calculation area including the departure point and the destination is enlarged, for the enlarged route calculation area, A route calculation function having means for executing registration of a mesh by a registration means and judgment by the judgment means. Navigation device having.