JPH0895489A - Map data memory device - Google Patents

Abstract

PURPOSE: To shorten the data access time to a map memory by handling finite pieces of meshes arranged in a direction perpendicular to an access direction as one block and arranging data in such a manner that map data can be read out in this block unit. CONSTITUTION: Finite pieces of the meshes arranged in the direction perpendicular to the access direction are handled as one block. For example, the two adjacent south and north meshes are made into block and are stored successively on a CDROM. If it is assumed that the road map data of the meshes 11, 12, 21, 22 be acquired and displayed and that the data to be required next are the meshes 13, 23, 32, 33, it is enough to read out the meshes 13, 23 and thereafter, to read out the meshes 32, 42, 33, 43 resetting a head. In such a case, the number of times to reset the head is two times and is decreased. The reason thereof lies in that the respective meshes are blocked on the CD-ROM and are arrayed sequentially within the block. The meshes within the same block are adjacent to each other and the probability to be simultaneously requested is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention divides a map vertically and horizontally for each mesh to create and store map data, and when the stored map data is read, the data is read in the vertical or horizontal direction of the mesh array. The present invention relates to a map data storage device.

[0002]

2. Description of the Related Art A navigation device is used by being mounted on a vehicle, detects the amount of movement and the amount of change in direction of the vehicle, calculates the estimated position of the vehicle based on the detected output, and displays it together with a road map. It has a function to do. The road map memory for storing the road map is, for example, a CD-R.
The road map data stored in the road map memory, which is composed of OM, is obtained by dividing the road map into meshes and searching for each mesh.

When the current position of the vehicle is calculated, the navigation device acquires road mesh data for several meshes centering on the current position from the road map memory and temporarily stores it in a display memory (hereinafter referred to as "cache memory"). Let Then, the map data of the mesh including the current position of the vehicle is read out from this cache memory and displayed. Since the current position of the vehicle moves as the vehicle travels, it is necessary to update the acquired road map data for several meshes. Specifically, the road map data of a new adjacent mesh is acquired in the traveling direction of the vehicle,
Road map data of the adjacent mesh behind the vehicle will be discarded. In this way, road map data for several meshes centering on the current position is always prepared on the cache memory (Japanese Patent Laid-Open No. 4-43913).
(See Japanese Patent Laid-Open No. 4-256992).

By the way, when acquiring road map data of a new adjacent mesh, access time to the road map memory (time to acquire new road map data.
(msec) is required, so it takes a considerable amount of time. It is important to reduce this time as much as possible from the viewpoint of driving support for vehicles. For this purpose, there is a demand to read as much data as possible with one read head (pickup) alignment. This is because the time for setting the head at a predetermined position on the CD-ROM is so long that it cannot be ignored as compared with the data reading time.

Conversely, to read the same map data, it is effective to reduce the total processing time by setting the number of times the head is set in the CD-ROM as much as possible.

[0006]

However, the conventional CD-
In the memory structure of ROM, the mesh layout of the road map is
No consideration was given to reducing access time.
FIG. 5 shows a mesh layout of a conventional road map. Each mesh had a structure in which the meshes were arranged in a row and were stacked in a row.

Therefore, on the CD-ROM, as shown in FIG.
As shown in FIG. 1, after reading the meshes 11, 12, 13, ...
.. are read out, and then the meshes 31, 32, 33, .. Therefore, as shown in FIG.
Assuming that the road map data of 1, 12, 21, 22 are acquired and displayed, the vehicle is located at the starting point a of the arrow A, and the vehicle is traveling in the direction of the arrow A, the following is required. The data is the data of the meshes 13, 23, 32, 33, but in the storage structure of the CD-ROM, the mesh 1
3 is read out, and then the head is set again (the reason for resetting the head is that if tracing is performed along the track of the CD-ROM, it takes time to reach the necessary mesh data). It was necessary to read the mesh 23 of the next row, reset the head, and read the meshes 32 and 33 of the next row.

In this case, the access time cannot be reduced because the number of times the head is reset is too large. It is clear that the above-mentioned problem similarly occurs even when the meshes of the road map are arranged in one vertical column and are gradually arranged horizontally. Moreover, the above-mentioned problem is caused by the CD-R.
In the case of OM, not only when using a storage medium in which a read head is set on tracks arranged in a spiral, but also in a concentric circle such as a magnetic disk typified by a floppy disk or a mini disk, or a magneto-optical disk. It occurs even when using a storage medium that sets the read head to the located track.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above technical problems and to provide a map data storage device capable of shortening the data access time to the map memory.

[0010]

According to a first aspect of the present invention, there is provided a map data storage device which handles a finite number of meshes arranged in a direction perpendicular to an access direction as one block. The data is arranged so that the map data can be read in block units.

It is preferable that the number of meshes grouped as the block is two (claim 2). The map data may be stored on a CD-ROM (claim 3).

[0012]

The reason why the finite number of meshes arranged in the direction orthogonal to the access direction is treated as one block is that, due to the nature of reading a map, it is highly probable that these finite number of meshes will be requested at the same time. . Therefore, a large amount of data can be obtained with a small number of accesses.

Particularly, when the number of meshes grouped as a block is 2 as described in claim 2, it is premised that the necessity of adjacent mesh data has the same vertical and horizontal probabilities. is there. As described in claim 3,
If the map data is stored on a CD-ROM, the value of the present invention will be greater. Because CD-
This is because the ROM has a structure in which data is read while tracing a track, and thus the time required for reading decreases as the number of accesses decreases.

[0014]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 2 is a block diagram showing a navigation device including the map data storage device of the present invention. This navigation device is used by being installed in a vehicle.
A distance sensor 1 for detecting the amount of movement of the vehicle and a direction sensor 2 for detecting the amount of change in the direction of the vehicle are provided.
The control unit 3 calculates the estimated position of the vehicle based on the output of the vehicle 2, the road map memory 4 storing the road map data, the memory drive 5, and the display device 6.

The road map memory 4 comprises a CD-ROM, and the road map data stored in the road map memory 4 is divided into north, south, east, and west meshes. The mesh is a Japanese road map, for example, a longitude difference of 1
A primary mesh with a vertical and horizontal distance of about 80Km x 80Km divided by 40 degrees and a latitude difference of 40 minutes, and a secondary mesh that divides this primary mesh into 8 equal parts by a total of 10Km x 10Km. When,
This secondary mesh is divided into 10 parts vertically and horizontally, and the vertical and horizontal distance is about 1
It has a triple structure of a third mesh of Km x 1 Km.

When the control unit 3 detects the current position of the vehicle, the road map data of several meshes centering on the current position (which layer of mesh differs depending on the road display range). Is acquired from the road map memory 4 and temporarily stored in a display memory (hereinafter referred to as “cache memory 7”). Then, map data of several meshes including the current position of the vehicle is read out from the cache memory 7 and displayed.

Since the current position of the vehicle moves as the vehicle travels, it is necessary to update the acquired road map data for several meshes. In the present embodiment, the next requested mesh on the cache memory 7 has the same probability in the north, south, east, and west directions. Then, each mesh of the road map is not arranged in one horizontal row or one vertical row, but is divided into blocks and arranged in order within the block.

Specifically, as shown in FIG. 1, the two north-south adjacent meshes are divided into blocks and stored in order on a CD-ROM. On the CD-ROM, as shown in FIG. 3, meshes 11, 21, 12, 22, 22, ... Are arranged in tracks.
And then meshes 31, 41, 32, 42 ,. Since the two north-south adjacent meshes are divided into blocks as described above, the contents of the mesh obtained on the cache memory 7 will be different from the conventional ones even when the mesh is read.

Referring now to FIG. 1, the meshes 11, 12,
The road map data of 21 and 22 has been acquired and displayed, and the next thing required is the mesh 13, 23, 32, 33.
In the present invention, the mesh 13,
23, and then the head is set again to read the meshes 32, 42, 33, 43. in this case,
The number of times of resetting the head is twice, which is smaller than in the conventional case.

The reason for such a decrease is the CD-ROM.
This is because each mesh of the road map is divided into blocks and arranged in order within the block. That is, the meshes in the same block are adjacent to each other and have a high probability of being simultaneously requested (hit). The effects of this embodiment will be described by giving numerical values. 5 hours to set the head
00msec, 200msec for reading mesh data
And Therefore, one reading requires 700 msec. On the other hand, it is assumed that it takes 2 seconds for the driver to move the cursor from the center to the end of the screen to scroll the map, and the control unit 3 needs 300 msec to detect the movement of the cursor and determine its direction. To do. Then, the time margin for reading the next mesh data is only 1700 msec. This 170
If you want to read in 0 msec, the number of times to set the head is 2 times.

Therefore, according to the present invention, each mesh of the road map is divided into blocks and the meshes are arranged in the block.
Under the current technology where head setting time cannot be ignored,
It is effective enough. The present invention is not limited to the above embodiment. In the embodiment, each mesh of the road map is divided into blocks of two north and south, but may be divided into blocks of three north and south as shown in FIG. However, if there are too many blocks to the north and south, the mesh is read in sequence vertically (the reading order in Figure 5 is vertical instead of horizontal), so the number of blocks is finite. Must.

Other various modifications can be made without departing from the spirit of the present invention.

[0023]

As described above, according to the map data storage device of the present invention, since a finite number of meshes arranged in the direction perpendicular to the access direction are handled as one block, necessary data can be accessed with a small number of accesses. The higher the probability that you can get with. Therefore, if used in a navigation device, map data around the vehicle can be acquired in a short time.

[Brief description of drawings]

[Figure 1] Two north-south adjacent meshes are divided into blocks
FIG. 6 is a diagram showing a mesh structure of map data stored in order on a ROM.

FIG. 2 is a block diagram showing a navigation device including a map data storage device of the present invention.

FIG. 3 is an array diagram of mesh data on a CD-ROM.

[Fig. 4] CD for three north-south adjacent meshes
FIG. 6 is a diagram showing a mesh structure of map data stored in order on a ROM.

FIG. 5 is a diagram showing an arrangement of meshes of a conventional road map.

FIG. 6 is an array diagram of the mesh data of FIG. 5 on a CD-ROM.

[Explanation of symbols]

 1 distance sensor 2 direction sensor 3 control unit 4 road map memory 5 memory drive 6 display device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G08G 1/0969 G09B 29/00

Claims (3)

[Claims] 1. A map data is stored in a form in which a map is vertically and horizontally divided for each mesh, and when the stored map data is read out, the mesh data is stored in a vertical direction or a horizontal direction of the mesh array (hereinafter referred to as an access direction). In the map data storage device for reading, a series of finite number of meshes arranged in the direction perpendicular to the access direction is treated as one block, and the mesh data is arranged so that the map data can be read in block units. Characteristic map data storage device. 2. The map data storage device according to claim 1, wherein the number of meshes grouped as the block is two. 3. The map data storage device according to claim 1, wherein the map data is stored on a CD-ROM.