JPH04319986A - Route search method - Google Patents

Abstract

PURPOSE:To automatically set a virtual departure crossing and a virtual destination crossing at an optimum position without any departure point and destination at a crossing. CONSTITUTION:When at least one of a departure point and a destination is not found on a road, a route search section 15f examines whether there is any road other than an expressway within the range of the predetermined distance from the departure point or destination. If such a road is found, a perpendicular is extended from the departure point or destination to the road, and the foot of the perpendicular is regarded as a crossing. This crossing is further regarded as a virtual departure point or destination. Thereafter, a route is searched, using road layer information saved in a map data memory section (CD-ROM) 11. Also, if there are a plurality of roads within the range of a set distance, the route search section 15f sets a virtual destination point or destination on the nearest road among the widest roads. If there is no road within the range of the set distance, a crossing at the nearest distance is obtained, and this crossing is used as a virtual departure point or destination in searching the route.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route searching method for a navigation device, and more particularly to a route searching method for searching for the shortest route from a departure point to a destination by taking into account intersections on a map.

0002

[Prior Art] An automobile navigation device has a large capacity storage device such as a CD-ROM that stores a large amount of map data, a display device, a current location detection device that measures the current location of the vehicle, etc. The map data is read from the CD-ROM, a map is drawn on the display screen based on the map data, and the car position mark (location cursor) is placed at a fixed position on the display screen (for example, the center position of the display screen). ), and the map is scrolled according to the movement of the car.

[0003] Maps stored in CD-ROMs are divided into regions with appropriate longitude and latitude widths depending on the scale level, and roads, etc. are divided into regions with vertices (nodes) expressed in latitude and latitude ), and these drawings are performed by sequentially connecting each node with a straight line. Note that a portion that connects two or more nodes is called a road link.

[0004] Such navigation devices have a route search function that searches for a guidance route and guides the driver so as to provide the shortest distance from the departure point to the destination point. The guide mark is displayed so as to be distinguishable from the road, or a guide mark is displayed in front of the vehicle position mark to guide the driver along the guide route to the destination.

A method called Dijkstra's method has been proposed as a method for finding the shortest route from a departure point to a destination. Dijkstra's method searches for the shortest route from the starting point to the destination by considering all intersections that exist within an area whose radius is the straight line connecting the starting point and the destination, or within an area larger than the area. . Figure 8 is a schematic explanatory diagram of Dijkstra's method, which is graphed with roads as straight lines and intersections as intersections of the straight lines, and the distance between each intersection is known.
STP is the departure point (intersection), DSP is the destination (intersection)
It is.

[0006] In the Dijkstra method, starting point STP
The first-order intersections A1 to A4 adjacent to are determined, and the zero-order intersection (starting point) and the distance from the starting point are stored in association with each of the first-order intersections A1 to A4. Next, each primary intersection A1
Find the secondary intersection Bij for ~A4, and find the distance from the primary intersection and departure point in correspondence to each secondary intersection. For example, for a primary intersection A2, three secondary intersections B
11, B12, B13 are found, and each secondary intersection B11,
Corresponding to B12 and B13, B11: Distance d11 from primary intersection A2 and departure point
B12: Distance d12 from primary intersection A2 and departure point
B13: Distance d13 from primary intersection A2 and departure point
...Memorize (a). Also, three secondary intersections B21, B22, and B23 are found for the primary intersection A3, and corresponding to each secondary intersection B21, B22, and B23, B21: Distance d21 from the primary intersection A3 to the starting point.
...(b) B22: Distance d22 from the primary intersection A3 to the starting point B23: Store the distance d23 from the primary intersection A3 to the starting point, and then select other primary intersections A1, A
Similarly, for No. 4, a secondary intersection is found and predetermined data is stored. By the way, intersections B13 and B21 are the same intersection. In this way, when the intersections for which data should be stored overlap, the distances d13 and d21 from the starting point are compared in magnitude, and only the smaller data is stored. for example,
If d13>d21, data in (b) is finally stored as data for intersection B13 (=B21).

[0007] Thereafter, in the same way, the tertiary intersection Cij is determined for each secondary intersection, and the distance from the secondary intersection and the departure point is determined and stored in correspondence with each tertiary intersection, and generally for each i-th intersection, If you find the (i+1)th intersection, and then calculate and memorize the distance between the i-th intersection and the departure point in correspondence with each (i+1)th intersection, you will finally reach the destination D.
Reach SP.

[0008] Once the destination DSP is reached, the destination (m
(the next intersection) is stored in correspondence with (m-1
) Next intersection, (m-1) Next intersection stored in correspondence with the next intersection (m-2) Next intersection, ..., Primary intersection stored in correspondence with the second intersection , the shortest route is a route that sequentially connects zero-order intersections (starting points) stored in correspondence with the first-order intersection.

[0009]

[Problems to be Solved by the Invention] According to Dijkstra's method, the shortest route is found using graph theory, but the starting point and destination must be intersections. Therefore, if the starting point and destination of the car are not at an intersection, the user must take the starting point and destination into consideration and input the starting and destination intersections using the Dijkstra method. There are some troublesome issues.

[0010]Furthermore, the conventional route searching method has the problem that the route from the starting point to the starting intersection and the route from the destination intersection to the destination cannot be found.

[0011] From the above, an object of the present invention is to automatically set a virtual starting intersection and a virtual destination intersection at optimal positions even when the starting point and destination are not intersections, and to search for a route. To provide a route search method capable of displaying a rough route from a virtual starting point to a virtual starting point and from a virtual destination to a destination.

0012

[Means for Solving the Problems] FIG. 1 is a diagram showing the principle of the present invention. According to the present invention, when at least one of a departure point and a destination does not exist on a road, a means for checking whether a road other than an expressway exists within a predetermined distance from the departure point or the destination; In this case, this can be achieved by placing a perpendicular line on the road from the starting point or destination and considering the foot of the perpendicular line as an intersection, or by performing route search using the intersection as a virtual starting point or destination.

[0013]

[Operation] If at least one of the departure point and destination does not exist on a road, check whether there is a road other than an expressway within a predetermined distance from the point, and if there is, draw a perpendicular line from the point to the road. , and consider the foot of the perpendicular line to be the intersection,
A route search is performed using the intersection as a virtual starting point or virtual destination. Also, if there are multiple roads within the set distance, the virtual departure point or virtual destination is set on the shortest road among the widest roads, and there are no roads within the set distance. In this case, the intersection with the shortest distance is found, and a route search is performed using the intersection as a virtual starting point or a virtual destination. In this way, it is possible to automatically determine the starting intersection and the destination intersection at the optimal positions, and also display the approximate route from the starting point to the destination.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Overall Configuration FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and 11 is a CD-ROM (map data storage unit) for storing a road map. Map data consists of (1) a road layer consisting of a node table, adjacent node list, road list, intersection configuration node list, and intersection net list, and (2) a background layer for displaying objects on the map. and (3) a character layer for displaying city, town and village names, national highway names, etc.

12 is a display device (CRT) that displays a map, a vehicle position mark, and a guidance route searched by the route search function according to the current location of the vehicle; 13 is a display device that displays the distance and direction of the vehicle while it is running This is a current location detection unit that calculates the current location based on the current location. Although not shown, the current location detection unit 13 includes a direction sensor that detects the traveling direction of the vehicle, a vehicle speed sensor that detects the distance traveled, and a position calculation CP that calculates the current location (longitude, latitude) of the vehicle based on the direction and distance traveled.
It has a U.

14 is an operation unit equipped with a map search key, a map scroll key, a route search mode key, a set key, a search start key, etc.; 15 is a map display control device that displays a map around the current location based on map data; Along with generating an image,
Generates vehicle position marks and guidance route images.

Map display control device In the map display control device 15, 15a stores map data (for example, map data for 9 screens) around the current location in a wider range than the screen display range on a CD-RO based on the current location data.
This is a map image drawing section that reads data from M11 and generates a dot image map image based on the map data.

15b is a guide route drawing unit that generates a guide route image based on the guide route data from the departure point to the destination obtained by the guide route search process, and 15c is a video RAM that stores the map image and the guide route image. It is. The map image drawing unit 15a rewrites the video RAM 15c as the car travels, so that the display range of the display screen does not exceed the image range of the video RAM 15c.
The guide route drawing unit 15b also generates a guide route image according to the travel of the automobile and stores it in the video RAM 15c.

Reference numeral 15d denotes a readout control unit that reads out one screen worth of map images from the video RAM 15c so that the current location of the vehicle is located at the center of the display screen, and the readout position is instructed by the map image drawing unit 15a. 15e is a car position mark generation unit for displaying a car position mark at the center of the display screen, and 15f is a route search unit, which converts map data into map data when the departure point and destination are input in route search mode. Based on the included road layer information, the shortest route from the departure point to the destination is calculated as a guidance route. 15g is the node that makes up the guidance route from the departure point to the destination.
This is a guide route storage unit that sequentially stores codes.

[0020] 15h is a combining section, and the video RAM 15
c. The map image, guide route image, and vehicle position mark image respectively read from the vehicle position mark generating section 15e are combined and output to the CRT 12 for display.

The road layer included in the road layer map data has the data structure shown in FIG. Among these, the road list RDLT provides attribute information of the corresponding road link, including the total number of nodes on the link, each node composing the link, and the type of road (national highway, expressway, width, etc.). ), etc. The intersection node configuration list CRLT is a set of nodes (referred to as intersection configuration nodes) closest to the intersection on links connected to the intersection for each intersection on the map. The node table NDTB is a list of all nodes on the map, and for each node, location information (longitude, latitude),
It consists of an intersection identification flag indicating whether the node is an intersection, a pointer that points to the intersection data if the node is an intersection, a pointer that points to the link to which the node belongs if it is not an intersection, a pointer that points to an adjacent node, etc. . The adjacent node list NNL is composed of a map number to which a node belongs, a unit code, a pointer pointing to the own node on the node table, etc.

As shown in FIG. 3, the intersection netlist CRNL contains, for each intersection, (1) the leaf number of the map that includes the intersection, (2) the unit code, (3) the intersection sequential number in the unit, or higher, Intersection ID (4) Number of intersection nodes (5) Sequential number of each adjacent intersection (6) Distance to each adjacent intersection (7) Road attributes (road type, width), etc. to each adjacent intersection It is used in route search processing. still,
The intersection netlist CRNL may be stored in advance in the CD-ROM 11 as a road layer as described above, but the
Without storing it in D-ROM, during route search processing,
Software-based road layer information (
Road list RDLT, intersection node configuration list CRLT
, node table NDTB, neighbor node list NNL)
It may be created using .

Route Search Control The route search control of the present invention will be explained below according to the flowcharts shown in FIGS. 4 to 6. It is assumed that the intersection netlist CRNL is stored in the CD-ROM 11 in advance.

When searching for a route, the route search key on the operation unit 14 is used to enter the route search mode. Then, by operating the map search key, the map image drawing unit 15a selects the starting point,
A predetermined map for each destination is displayed on the display screen, and then the map scroll key is used to position the car position mark at the departure point and destination, and these departure points and destinations are set (step 101).

[0025] When the departure point STP and destination DSP are set, the route search unit 15f checks whether the departure point is an intersection (
Step 102), if it is an intersection, the process jumps to step 201 and the subsequent processing is performed. On the other hand, if it is not an intersection, it is checked whether the starting point is on the road (step 103).

If the departure point STP exists on the road, the departure point is regarded as a virtual intersection, and an intersection netlist regarding the virtual intersection is created and stored in the storage unit 15f-1 (
Step 104), and thereafter the processing from step 201 onwards is performed. If the departure point STP does not exist on the road (Fig. 7 (a)
), it is checked whether a road exists within the set distance r (step 105), and if there is a road, it is checked whether a general road other than an expressway is included (see Fig. 7 (b), step 106). ), if the road is included, the widest road among the general roads and the closest road is selected (step 107). In addition, in FIG. 7(a), RD1
, RD2 are general roads, and the road RD1 exists within a set distance r from the departure point STP. Further, in FIG. 7(b), RD3 is an expressway and RD4 is a general road, both of which are within a set distance from the departure point STP.

In step 107, when the nearest road is determined, a perpendicular line is drawn from the starting point STP to the nearest road,
The leg STP' of the perpendicular line is virtually regarded as an intersection, and an intersection net list regarding the virtual intersection is created and stored in the storage unit 15.
f-1 (step 108), the virtual intersection is regarded as the virtual departure point (step 109), and from then on, step 2
Processing after 01 is performed.

On the other hand, if there is no road within the set distance in step 105 (see FIG. 7(c)), or if there is a road in step 106 but it is an expressway, the intersection with the shortest distance is selected. Find (Step 11
0), set the intersection as a virtual starting point (step 111),
Processing from step 201 onwards is performed. In FIG. 7(c), C1 and C2 are intersections, and C1 is the shortest intersection.

When the processing for the departure point is completed, the route search unit 15f checks whether the destination is an intersection (step 201), and if it is an intersection, the process jumps to step 301 and performs the subsequent processing. On the other hand, if it is not an intersection, it is checked whether the destination is on the road (step 202).

If the destination DSP exists on the road, the destination is regarded as a virtual intersection, and an intersection netlist regarding the virtual intersection is created and stored in the storage unit 15f-1 (
Step 203), and thereafter the processing from step 301 onwards is performed. If the destination DSP does not exist on the road, it is checked whether there is a road within the set distance r (step 204), and if there is a road, it is checked whether general roads other than expressways are included (step 204). Step 205), if the road is included, the widest road among the general roads and the closest road is selected (Step 206).

When the nearest road is determined, a perpendicular line is placed on the road from the destination DSP, the foot of the perpendicular line is virtually regarded as an intersection, and an intersection net list regarding the virtual intersection is created and stored in the storage unit 15f-1. (step 207)
, consider the virtual intersection as a virtual destination (step 208
), and then the processing from step 301 onwards is performed.

On the other hand, if there is no road within the set distance in step 204, or if the road exists but is an expressway in step 205, the intersection with the shortest distance is found (step 209) and the intersection is virtualized. The destination is set as the destination (step 210), and the processing from step 301 onwards is performed.

When the virtual departure point and virtual destination are found, the route search unit 15f sets the search order i to 0 (0→i, step 301), and determines whether there is an intersection adjacent to the i-th intersection. The intersection netlist stored in the storage unit 15f-1 (created in steps 104, 108, 203, and 207) and the intersection netlist CRNL stored in the CD-ROM are referred to and examined (step 302). still,
The zero-order intersection is the virtual starting point.

If an intersection exists, calculate the cumulative distance D from the virtual starting point to the adjacent intersection (step 303).
. As will be described later, the distance d1 from the virtual starting point to the i-th intersection is stored in the storage unit 15f- in correspondence with the i-th intersection.
1, and the distance d2 from the i-th intersection to the adjacent intersection is stored in the intersection netlist, so the cumulative distance D from the virtual starting point to the adjacent intersection can be found using the following formula d1 + d2 → D. .

Next, the search order of the adjacent intersection is (i+1
) (step 304), and if it is not (i+1), the following data (1) is set corresponding to the adjacent intersection.
The sequential number of the i-th intersection that we are currently focusing on, (2) the cumulative distance from the virtual departure point to the adjacent intersection, (3) the search order of the adjacent intersection (i+1
) is stored in the storage unit 15f-1 (step 305), and thereafter the process returns to step 302 to check whether any intersections adjacent to the i-th intersection of interest still remain, and repeat the subsequent processing.

On the other hand, in step 304, if the degree of the adjacent intersection is (i+1), in other words, if the adjacent intersection is referred to as an intersection adjacent to another i-th intersection (in step 305, Already mentioned (1) to (3)
) is stored, the cumulative distance D' from the virtual departure point stored corresponding to the adjacent intersection is compared with the distance D determined in step 303 (step 306).

If D<D', the sequential number of the i-th intersection stored in the storage unit 15f-1 corresponding to the adjacent intersection is used as the sequential number of the i-th intersection currently being focused on. - Replace distance D' with D
Then, the process is rewritten (D→D', step 307), and thereafter, the process returns to step 302, and it is checked whether the intersection adjacent to the i-th intersection of interest still remains, and the subsequent processes are repeated. If D≧D', the process returns to step 302 without changing the contents stored in the storage unit 15f-1 corresponding to the adjacent intersection.

On the other hand, in step 302, if there is no intersection adjacent to the i-th intersection of interest, it is checked whether another i-th intersection exists (step 308).
), if it exists, the other i-th intersection is newly set as the i-th intersection (step 309), and the processes from step 302 onward are repeated.

In step 308, if another i-th intersection does not exist, it is checked whether the virtual destination has been reached, in other words, it is checked whether the (i+1)-th intersection includes the virtual virtual destination. (step 310), and if it is not included, the search order is incremented by one (i+1→i,
Step 311), repeats the processing from step 302 onwards.

However, once the virtual destination is reached, the (m-1) next Intersection → ■ (m-1) Next intersection stored in correspondence with the next intersection (m-2) → ... → ■ Primary intersection stored in correspondence with the second intersection → ■0th-order intersection (virtual departure point) stored in correspondence with the 1st-order intersection →■
The shortest route is determined by sequentially connecting the starting points STP (step 312), and the route processing is ended.

[0041] In actual route guidance, the distance from the departure point to the virtual departure point and from the virtual destination to the destination are displayed using dotted lines or the like.

[0042] In the above, the intersection netlist is CD-R
This is a case where the data is stored in advance in the OM, but the CD-ROM
It is also possible to create an intersection netlist CRNL for intersections within the route search range using road layer information and store it in the RAM.

[0043]

According to the present invention, when at least one of the departure point and the destination does not exist on a road, it is checked whether there is a road other than an expressway within a predetermined distance from the point, and if there is, The configuration is such that a perpendicular line is drawn from the starting point or destination on the road, the foot of the perpendicular line is regarded as an intersection, and the route search is performed using the intersection as the virtual starting point or virtual destination. A virtual starting point and a virtual destination can be determined, and a rough route from the starting point to the destination can also be determined.

Furthermore, according to the present invention, if there are multiple roads within the set distance, the virtual departure point or virtual destination is set on the road that is the shortest among the widest roads. If there is no road within the set distance, the shortest intersection is found and the route is searched using that intersection as the virtual starting point or virtual destination, so the starting intersection is automatically set to the optimal position. It is possible to determine the target intersection.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a road layer.

FIG. 3 is an explanatory diagram of an intersection netlist.

FIG. 4 is a first flowchart of route search processing.

FIG. 5 is a second flowchart of route search processing.

FIG. 6 is a third flowchart of route search processing.

FIG. 7 is an explanatory diagram of route searching according to the present invention.

FIG. 8 is an explanatory diagram of the Dijkstra method.

[Explanation of symbols]

11...Map data storage unit 12...Display device (CRT) 13...Current location detection unit 15...Map display control device 15a...Map image drawing section 15f...route search section 15g...guidance route storage section

Claims (3)

[Claims] Claim 1: A route search method for a navigation device that displays a map according to the location of a vehicle, searches for the shortest route from a departure point to a destination by taking into account intersections on the map, and guides a driver. , if at least one of the departure point and destination does not exist on the road, check whether there is a road other than an expressway within a predetermined distance from the point, and if there is, draw a perpendicular line from the point to the road. , a route search method characterized in that a foot of a perpendicular line is regarded as an intersection, and a route search is performed using the intersection as a virtual starting point or a virtual destination. [Claim 2] Claim 1, characterized in that when a plurality of roads exist, the virtual starting point or the virtual destination is set on the road that is the shortest among the widest roads.
The route search method described. 3. The route according to claim 1, wherein if there is no road within the set distance, an intersection with the shortest distance is found, and a route search is performed using the intersection as a virtual starting point or a virtual destination. Search method.