JP2849230B2 - Route search method - 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 search method for a navigation device, and more particularly to a route search method for narrowing a route search range and reducing a time required for the route search.

[0002]

2. Description of the Related Art A navigation apparatus for a vehicle has a large-capacity storage device such as a CD-ROM for storing a large amount of map data, a display device, a current position detection device for measuring the current position of the vehicle, and the like. The read map data is read from the CD-ROM, a map is drawn on the display screen based on the map data, and the vehicle position mark (location cursor) is set at a predetermined position on the display screen (for example, the center position of the display screen). ) Is fixedly displayed, and the map is scroll-displayed according to the movement of the vehicle.

The map stored in the CD-ROM is divided into regions of appropriate longitude and latitude widths according to the scale level, and roads and the like are represented by vertices (nodes) expressed in latitude and longitude. Are drawn by connecting each node in order with a straight line. A portion connecting two or more nodes is called a road link.

Such a navigation device has a route search function of searching for a guide route so as to be the shortest distance from a departure point to a destination and guiding a driver. The vehicle 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 to the destination along the guide route.

A method called Dijkstra's method has been proposed as a method for obtaining the shortest route from a departure point to a destination. The Dijkstra method searches for the shortest route from the departure point to the destination in consideration of an area having a radius of a straight line connecting the departure point and the destination, or all intersections existing in an area larger than the area. . FIG. 12 is a schematic explanatory diagram of the Dijkstra method, which is a graph in which a road is a straight line and an intersection is an intersection of a straight line. The distance between the intersections is known, STP is the departure place (intersection), and DSP is the destination ( Intersection).

In the Dijkstra method, the departure point STP
The primary intersections A1 to A4 adjacent to are obtained, and the zeroth-order intersection (departure point) and the distance from the departure point are stored in correspondence with each of the primary intersections A1 to A4. Then, at each primary intersection A1
The secondary intersection Bij is determined for .about.A4, and the distance from the primary intersection and the departure point is determined in correspondence with each secondary intersection.
For example, for the primary intersection A2, three secondary intersections B
11, B12, B13 are obtained, and each secondary intersection B11, B12, B
Corresponding to 13, B11: distance from primary intersection A2 and departure point d11 B12: distance from primary intersection A2 and departure point d12 B13: distance from primary intersection A2 and departure point d13 ··· (a) Is stored. In addition, three secondary intersections B21, B22, and B23 are obtained for the primary intersection A3, and the secondary intersections B21 and B23 are obtained.
Corresponding to B22 and B23, B21: distance from primary intersection A3 and departure point d21 ··· (b) B22: distance from primary intersection A3 and departure point d22 B23: primary intersection A3 and distance from departure point The distance d23 is stored, and for the other primary intersections A1 and A4, secondary intersections are similarly obtained and predetermined data is stored. By the way, the intersections B13 and B21 are the same intersection. As described above, when intersections where data should be stored overlap, the magnitudes of the distances d13 and d21 from the departure point are compared, and only the smaller data is stored. For example, if d13> d21, the data of (b) is finally stored as the data of the intersection B13 (= B21).

Thereafter, similarly, a tertiary intersection Cij is determined for each secondary intersection, a distance from the secondary intersection and the departure point is determined and stored in correspondence with each tertiary intersection, and generally each i-th intersection is calculated.
If the (i + 1) -th intersection is determined for the next intersection, and the distance from the i-th intersection to the departure point is determined and stored in correspondence with each (i + 1) -th intersection, the destination D is finally determined.
Reach SP.

When the vehicle reaches the destination DSP, the destination (m
(The next intersection) is stored (m-
1) the next intersection, the (m-1) next intersection stored in correspondence with the (m-1) next intersection,... The primary stored in correspondence with the secondary intersection The shortest route is a route that sequentially connects the zeroth-order intersection (departure point) stored in association with the intersection and the primary intersection.

[0009]

According to the Dijkstra method, the shortest path can be obtained in a graph theory. However, the shortest path exists in an area having a radius of a straight line connecting the starting point and the destination or an area larger than the area. Since the shortest route from the departure point to the destination must be searched in consideration of all intersections, the number of intersections to be considered becomes very large, and there is a problem that it takes a long time to find the shortest route.

Accordingly, an object of the present invention is to provide a route search method that reduces the number of intersections to be considered when obtaining the shortest route and shortens the shortest route search time.

[0011]

FIG. 1 shows the principle of the present invention. According to the present invention, according to the present invention, in correspondence with an intersection, a map number and a unit code of a map including the intersection, an intersection netlist having at least an intersection adjacent to the intersection and a distance therebetween are provided. Means for determining a unit of a map including the set departure point and destination, and means for determining a rectangular area larger than a rectangular area having a unit of the map including the departure point and destination as a diagonal unit as a search range. Is achieved by means for eliminating intersections that do not exist in the unit in the determined rectangular area from the targets of the route search.

[0012]

In accordance with an intersection, a map net number and a unit code of a map including the intersection, an intersection netlist having at least an intersection adjacent to the intersection and a distance between the intersections are provided, and a set departure place is provided. And a unit of the map including the destination, determine a rectangular area larger than a rectangular area having these units as diagonal units as a search range, and refer to an intersection netlist to determine an intersection in the determined rectangular area. It is checked whether the unit exists, and if it does not exist, the intersection is excluded from the targets of the route search and the route search is performed. As described above, since the shortest route search range is narrowed, the number of intersections to be considered when obtaining the shortest route can be reduced, and the route search time can be reduced.

[0013]

FIG. 1 is a block diagram of an embodiment of the present invention. Reference numeral 11 denotes a CD-ROM (map data storage) for storing a road map. Map data consists of (1) node tables, adjacent node lists,
A road layer consisting of a road list, an intersection configuration node list, and an intersection netlist; (2) a background layer for displaying objects on a map; and (3) a character layer for displaying names of municipalities and national roads. It is composed of

Reference numeral 12 denotes a display device (CRT) for drawing a map corresponding to the current position of the vehicle, a vehicle position mark, a guide route searched by a route search function, and the like, and 13 denotes a travel distance and an azimuth of the running vehicle. It is a current position detection unit that calculates the current position based on the current position. Although not shown, the current position detection unit 13 includes a direction sensor for detecting the traveling direction of the vehicle, a vehicle speed sensor for detecting the traveling distance, and a position calculation CP for calculating the current position (longitude and latitude) of the vehicle based on the direction and traveling distance.
U.

An operation unit 14 includes a map search key, a map scroll key, a route search mode key, a set key, a search start key, and the like, and a reference numeral 15 denotes a map display control device, which is a map around the present location based on map data. In addition to generating an image, a car position mark and a guide route image are generated.

[0016] In the map display control unit map display control device 15, 15a based on the location data, the map data (e.g., 9 screen of the map data) in the range larger than the screen display range current position around the CD-RO
A map image drawing unit that reads out from M11 and generates a dot image map image based on the map data.

A guide route drawing unit 15b generates a guide route image based on the guide route data from the departure point to the destination obtained by the guide route search processing. A video RAM 15c stores a map image and a guide route image. It is. The map image drawing unit 15a rewrites the video RAM 15c at any time as the vehicle runs 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 traveling of the car and stores the guide route image in the video RAM 15c.

Reference numeral 15d denotes a reading control unit for reading a map image for one screen from the video RAM 15c so that the current position of the vehicle is located at the center of the display screen. The reading position is specified by the map image drawing unit. 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. When a departure place and a destination are input in the route search mode, the map data is displayed. The shortest route from the departure point to the destination is calculated as a guidance route based on the included road layer information. A guidance route storage unit 15g sequentially stores nodes constituting a guidance route from a departure place to a destination.

Reference numeral 15h denotes a synthesizing unit, which is a video RAM 15h.
(c) The map image, the guide route image, and the vehicle position mark image read from the vehicle position mark generation unit 15e are combined and output to the CRT 12 for display.

The map stored in the map data CD-ROM 11 has a hierarchical structure of a plurality of stages with different scales, for example, a hierarchical structure with different scales from level 9 to level 0. And
The level 0 map includes view sets (hereinafter, referred to as units) A, B, and C having different display areas. Unit A is map data for one screen at a certain reference scale (for example, 1 / 50,000 scale), and unit B is for enlarging and displaying a quarter of the area displayed by unit A (25,000 min.). Unit C is map data for one screen, and unit C is map data for one screen for enlarging and displaying a further quarter of the area displayed in unit B.
, Bi, and Ci, the relationship of the ranges displayed on one screen is as shown in FIGS. Focusing on the unit A ₅ (see FIG. 2A), the unit A ₁
~A _4, A ₆ ~A ₉ becomes adjacent map data of the area displayed by the unit A _5, B ₁ ~B ₄ is enlarged map (child view leaves) data. Focusing on unit B ₁ (see FIG. 2B), unit A ₅ is a reduced map (parent map leaf).
C ₁ , C ₂ , C ₅ , and C ₆ become enlarged map (child map leaf) data.

FIGS. 3 and 4 are explanatory diagrams of map management information (foliage management information) for managing a map stored in a CD-ROM. The map of each scale is managed by being divided into rectangular areas (areas of a predetermined longitude width and a predetermined latitude width) called map leaves.

The CD-ROM 11 has a disk label LB
The disc label LB records a pointer P1 indicating the location where the leaf management information is stored in addition to the disc name, the maker name, and the production date. The leaf management information MCI is obtained by arranging pointers P21, P22, P23,... Indicating locations for storing the leaf management records of each leaf by the number of leaves.
They are arranged in descending order of the leaf level (scale level).

The leaf management record MRD indicated by the pointer Pij includes (1) scale level, (2) leaf number, (3) child leaf number and leaf number, and (4) adjacent leaf. , (5) the address of the unit management information VSA (pointer P3), (6) the longitude at the left end and right end of the figure, and the latitude data at the upper and lower ends.

The unit management information VSA includes a pointer Pu to an upper unit, a pointer Pd to a lower unit, pointers Pn1 to Pn8 to adjacent units, map address information U1, U2,. . Etc. As shown in FIG. 2, the relationship between the units Ai, Bi, and Ci is such that the start address of the unit Bi is indicated by the pointer Pd of the unit Ai, the start address of the unit Ci is indicated by the pointer Pd of the unit Bi, and The unit Bi is determined by the pointer Pu.
Of the unit Ai is indicated by the pointer Pu of the unit Bi. If there is no lower unit or upper unit, the pointers Pd and Pu are set to specific values (for example,
1).

The map address information U1, U2,. . Indicates a CD-ROM address for storing map data. That is, when there is a large amount of map data, the data cannot be stored in a storage area of a predetermined size. Therefore, the data is divided and stored in several subunits. Is done.

FIG. 5 is an explanatory diagram of the unit code.
The sheet is divided into four parts as necessary. A unit code 0000 is assigned to a unit A having the same size as the figure, and a unit B is assigned to a unit B obtained by dividing the figure (unit A) into four parts. Code 1000, 2000, 3000, 400
0 is added, and 1 is assigned to the unit C obtained by dividing the unit B into four.
100, 1200, 1300, and 1400 are assigned, and similarly, unit codes are assigned to the unit C.

The map image drawing section 15a is a CD-ROM
In order to read out map data corresponding to the position of the vehicle from 11, (1) find a leaf management record of the leaf where the automobile is located, and (2) point to the pointer P3 of the leaf management record. When the map address information of the unit A is obtained from the address and the map at the A level is displayed on the CRT,
The map data is sequentially read from the address indicated by the map address information. (3) When the map at the B level is displayed on the CRT, management information of the unit B indicated by the pointer Pd of the unit A is obtained, and the map information is obtained. The map data is read sequentially from the address indicated by the address information,
(4) When the map at the C level is displayed on the CRT, the management information of the unit C indicated by the pointer Pd of the unit B is obtained, and the map data is sequentially read from the address indicated by the map address information.

The road layer included in the road layer map data has the data structure shown in FIG. Among them, the road list RDLT gives attribute information of the corresponding road link, and includes the total number of nodes on the link, each node constituting the link, and the type of road (national road, expressway, width, and other types). )). The intersection node configuration list CRLT is a set of nodes (intersection configuration nodes) closest to an intersection on a link connected to the intersection for each intersection on the map. Bull NDTB is a list of all nodes on the map, and position information (longitude, latitude),
An intersection identification flag indicating whether or not the node is an intersection. If the node is an intersection, the intersection data indicates the intersection. If the node is not an intersection, the pointer indicates a link to which the node belongs. Have been.

The adjacent node list NNL is composed of a leaf number to which the node belongs, a unit code, a pointer pointing to its own node on the node table, and the like, and the intersection netlist CRNL is shown in FIG. As shown in (1), for each intersection, (1) map leaf number including the intersection, (2) unit code, (3) intersection sequential number of the unit, intersection ID and (4) intersection configuration node Number (5) Sequential number of each adjacent intersection (6) Distance to each adjacent intersection (7) Attributes of road to each adjacent intersection (road type, width), etc., are used in route search processing. As described above, the intersection netlist CRNL may be stored in advance in the CD-ROM 11 as a road layer.
In the route search processing, road layer information (road list RDLT, intersection node configuration list CRLT, node table NDTB, adjacent node list NNL) is not stored in the ROM, and only necessary intersections are softly stored. You may make it create using it.

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

At the time of route search, a route search mode is set by using a route search key on the operation unit 14. Then, the map search key is operated, and the starting point,
A predetermined map is displayed on the display screen for each of the destinations, and thereafter, the car position mark is positioned at the departure point and the destination using the map scroll keys, and the departure point and the destination are set (step). 101).

When the departure place STP and the destination DSP are set, the route search section 15f sends the map leaf number MNo. And a unit code UCD, and a search range to be searched for a route is determined based on the figure number and the unit code (step 102). For example, FIG.
0, a rectangular area R1 having diagonal units UNS and UNE respectively including a starting point STP and a destination DSP, or a rectangular area R larger than the rectangular area.
2 is determined as the search range. Large rectangular area R2
For example, the unit UNS 'and UNE' which are adjacent to the units UNS and UNE in an oblique outer direction are obtained, and these two units are obtained as a rectangular area having a diagonal unit. The specific method of obtaining the search range is described in the unit UNS.
And the unit code of the unit horizontally adjacent to the unit UNS so that the unit UNE is a diagonal unit, and then the unit of the unit vertically adjacent to each unit is determined. This is done by finding the code. In this case, since the units have different sizes, a rectangular area may not be accurately formed as shown in FIG. 11, but in the present invention, the rectangular area is defined including these.

When the route search range is determined, the route search unit 1
5f sets the search order i to 0 (0 → i, step 10
3) Check whether there is an intersection adjacent to the ith intersection by referring to the intersection netlist CRNL (step 1).
04). Note that the zero-order intersection is the departure point.

If it exists, the map number and the unit code of the unit to which the adjacent intersection belongs are entered into the intersection netlist C.
From the RNL, it is checked whether the unit is included in the unit within the search range obtained in step 102 (step 10).
5) If not included, the process returns to step 104, and it is checked whether an intersection adjacent to the focused ith intersection still remains and the subsequent processing is repeated.

If the adjacent intersection exists in the unit within the search range in step 105, the total distance D from the departure point to the adjacent intersection is calculated (step 10).
6). The distance d ₁ from the departure point to the ith intersection is stored in a storage unit (not shown) corresponding to the ith intersection, as described later, and the distance d ₂ from the ith intersection to the adjacent intersection Is stored in the intersection netlist CRNL, the total distance D from the departure point to the adjacent intersection is obtained by the following equation d ₁ + d ₂ → D.

Next, the search order of the adjacent intersection is (i +
(1) is checked (step 107). If not (i + 1), the following data is associated with the adjacent intersection (1) the sequential number of the i-th intersection currently focused on, (2) the departure place (3) The search order (i + 1) of the adjacent intersection is stored in the storage unit (Step 108). Thereafter, the flow returns to Step 104, and the intersection adjacent to the ith intersection of interest is The remaining processes are checked to see if they remain, and the subsequent processing is repeated.

On the other hand, if the degree of the adjacent intersection is (i + 1) in step 107, in other words, if the adjacent intersection is referred to as an intersection adjacent to another i-th intersection (step 108). If the data of (1) to (3) is already stored), the accumulated distance D 'from the departure point stored corresponding to the adjacent intersection and step 10
Compare the magnitude of the distance D obtained in step 6 (step 10).
9).

If D <D ', the sequential number of the i-th intersection stored in correspondence with the adjacent intersection is replaced with the sequential number of the i-th intersection currently focused on. , Rewrite distance D 'with D (D →
D ', step 110), and thereafter, the process returns to step 104, and it is checked whether or not the intersection adjacent to the focused ith intersection still remains, and the subsequent processing is repeated. Also, D ≧
In the case of D ', the process returns to step 104 without changing the content stored corresponding to the adjacent intersection.

On the other hand, in step 104, if there is no longer an intersection adjacent to the ith intersection of interest, it is checked whether another ith intersection exists (step 11).
1) If it exists, the other i-th intersection is set as the target i-th intersection (step 112), and the processing from step 104 onward is repeated.

In step 111, if there is no other i-th intersection, it is checked whether the destination has been reached.
In other words, it is checked whether the destination is included in the (i + 1) th intersection (step 113), and if it is not included, the search order is incremented by one (i + 1 → i, step 11).
4) Repeat the processing of step 104 and subsequent steps.

However, when the vehicle reaches the destination, it is stored in association with the destination (the intersection of the m-th order) (m
-1) the next intersection, the (m-1) next intersection stored corresponding to the (m-1) next intersection,... 1 stored corresponding to the second intersection Next intersection, 0th intersection (departure point) stored in association with the primary intersection
Are sequentially connected to determine the shortest path (step 115), and the path processing ends.

In the above description, the intersection netlist is CD-R
OM is stored in advance, but the CD-ROM
At the time when the unit within the route search range is determined without using the road layer information, all the intersections included in the unit within the route search range are determined, and an intersection netlist CRNL is created for the intersection and stored in the RAM. It can also be configured to store.

[0043]

As described above, according to the present invention, the map leaf number and the unit code of the map including the intersection are associated with the intersection.
And an intersection netlist having at least an intersection adjacent to the intersection and a distance between the intersections, a unit of a map including the set departure point and destination is obtained, and a rectangular area having these units as diagonal units is obtained. Large rectangle
The shape area is determined as a search range, and it is checked whether or not the intersection exists in the unit in the determined rectangular area by referring to the intersection netlist. If the intersection does not exist, the intersection is excluded from the route search target and the route is removed. Since the search is performed, the route search range can be narrowed, so that the number of intersections to be considered when finding the shortest route can be reduced, and the route search time can be shortened. According to the present invention,
The optimal route by expanding the route search area
Can be found at Also, according to the present invention, a map map
The search range is defined in map units obtained by further subdividing leaves.
Since the enclosure is determined, the required search range is narrowed
Route search time can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a unit.

FIG. 3 is an explanatory diagram of first map management information.

FIG. 4 is an explanatory diagram of second map management information.

FIG. 5 is an explanatory diagram of a unit code.

FIG. 6 is an explanatory diagram of a road layer.

FIG. 7 is an explanatory diagram of an intersection net list.

FIG. 8 is a first flowchart of a route search process.

FIG. 9 is a second flowchart of the route search process.

FIG. 10 is an explanatory diagram of a search range.

FIG. 11 is an explanatory diagram of units in a search range.

FIG. 12 is an explanatory diagram of the Dijkstra method.

[Explanation of symbols]

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

Claims (1)

(57) [Claims] 1. A route search method of a navigation device for displaying a map corresponding to a vehicle position, searching for a shortest route from a departure point to a destination in consideration of an intersection on the map, and guiding a driver. In correspondence with the intersection, a map net number and a unit code of a map including the intersection, and an intersection netlist having at least an intersection adjacent to the intersection and a distance between the intersections are provided. Find the units of the map that includes the ground and make them larger than the rectangular area with these units as diagonal units.
A rectangular area is determined as a search range, and an intersection netlist is referenced to check whether an intersection exists in a unit within the determined search range. If not, the intersection is excluded from path search targets. A route search method characterized by the following.