JPH0460416A - Navigation system - Google Patents

Abstract

PURPOSE:To efficiently use data stored in a CD-ROM to improve real time ability of a system by providing a storage memory for temporarily storing map information data read from the CD-ROM. CONSTITUTION:A storage memory 7 is connected to a display processor 4, while the memory 7 stores a part of map information data equal to data stored in a CD-ROM 6. In addition after power is turned ON, a signal processor 3 calculates a current position of a moving body according to signals from a travel distance detector 1 and a direction detector 2. A CD-ROM replay device 5 reads a map corresponding to the current position from the CD-ROM 6. If the map information data is needed at this time, the memory 7 is accessed prior to an access to the CD-ROM 6 to see whether or not the needed map information data has been already stored on the memory 7. When the needed map information data is stored on the storage memory 7, this is utilized thereby reducing the number of accesses to the CD-ROM 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a navigation system, and particularly to a CD-ROM.
The present invention relates to a navigation system characterized by reading map information data stored in a ROM.

[Prior Art] A navigation system is known in which the current position of a moving object such as a moving vehicle is shown on a map and displayed on a display device.

At this time, the map information data is stored in advance in the CD-ROM, and the map information data corresponding to the current position of the moving object is successively read from the CD-ROM and used. Usually, this is called data reading. .

FIG. 3 is a diagram showing the structure of map information data.

Generally, the map information data stored in a CD-ROM includes the CD label and version, map data management information, and multiple scale maps A, as shown in Figure 3 (A).
・The map data is divided into three main parts: B and C. As shown in FIG. 3(C), map management records for the number of maps are stored in the map data management information.

Furthermore, the map management record contains the scale level of the map, the map number, the start address containing each map unit management information, and the latitude and longitude of the top, bottom, left, and right ends of the map data.

The scale map data is divided into a plurality of units as shown in FIG. 3(B), and is controlled by map unit management information indicating one division position and unit data size. Here, the term "unit" refers to a collection of data that is divided into predetermined sizes and made easier to handle in order to reduce the burden on the hardware that reads the data from the CD-ROM.

As shown in FIG. 3(D), the map unit management information is composed of a unit division code indicating the division position and a unit data size.

FIG. 4 is a flowchart showing the procedure for reading map information data from a CD-ROM. First, CD-ROM
The disk label and version of are read (step 401), and then the map data management information and map management record are read respectively (steps 402 and 403).
.

Next, calculate the current position of the mobile object and compare the latitude and longitude of the calculated current position with the latitude and longitude in the map management record read in step 403 to see if they are in the map management record. A check is performed (step 404).

If it is within the range, map unit management information is read (step 405).

If it is not within the range, the process returns to step 403 to read another map management record, and this operation is repeated until the current position is within the range of the map management record in step 404.

Next, search for the necessary unit according to the unit division code and check the map data ↑! ).

During the reading operation in this series of steps, the fifth
As shown in the figure, information must be exchanged between the display processing device and the CD-ROM playback device. That is, first, when the display processing device issues a read request to the CD-ROM playback device, if the request is appropriate, a read request acknowledgment (ACK) is returned to the display processing device, and the CD-ROM playback device returns a read request acknowledgement (ACK) to the display processing device.
The ROM playback device searches for data in the CD-ROM, and requires a time t1 from the read request to the read request ACK. Further, a time t7 is required to search for data in the CD-ROM.

When the search is completed, the CD-ROM playback device performs search A.
CK is sent to the display processing device to start data transfer.

After time t3, the display processing device that has received the data checks the validity of the data, and if the data is valid, returns a read complete to the CD-ROM playback device.

With the above processing, one read operation is completed. In this way, a series of map data reading operations are performed continuously as appropriate while the moving object is moving, and the current position t of the moving object is displayed on the display device together with the map data.

[Problems to be Solved by the Invention] As described above, the operation of reading map data from the CD-ROM is performed as appropriate as the mobile object moves, but access to the CD-ROM exceeds the capability of the display processing device. If the frequency increases, it may become difficult to obtain new map data and the navigation function may deteriorate. That is, as explained in the flowchart of FIG. 4, if the current position of the vehicle is not included in the map management record read in step 403, that is, if it is outside the range,
CI)-R until a given map management record is found.
OM must be accessed.

Considering the worst case, the CD-ROM must be accessed and read for the number of map management records, and as a result, the loading time is equal to the number of repetitions, and the real-time nature of navigation is limited. The problem was that it seriously harmed the

In order to solve the above-mentioned problems, the present invention provides a CD-ROM.
The purpose of the present invention is to provide an excellent navigation system that efficiently uses data stored in the system and does not impair real-time performance, which is a feature of navigation.

[Means for Solving the Problems] The present invention provides a navigation system that uses CD-RO
A storage memory is provided to store the map information data read from M, and the data in this storage memory is used as necessary.

[Operation] In the present invention, when map information data is required, it is possible to
Prior to accessing the ROM, the storage memory is accessed to check whether the necessary N1 diagram information data is already stored on this storage memory. If the necessary map information data is stored in the storage memory,
By utilizing this, the number of accesses to the CD-ROM can be reduced.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a navigation system according to the present invention.

Calculation of the current position of the moving object is executed by the signal processing device 3 based on signals from the moving distance detector 1 and the direction detector 2. Here, the moving distance detector 1 is composed of a photoelectric type or electromagnetic type detector that outputs a pulse signal proportional to the rotation speed of the vehicle's tires, for example, and generates a signal corresponding to the moving distance of the moving object. do. Further, the direction detector 2 detects the moving direction of the moving body and outputs a signal. The signal processing device 3 counts the pulse signals from the moving distance detector 1 to detect the distance of the moving object, determines the traveling direction from the output signal of the direction detector 2, and determines the unit according to each detection 111 signal. The current position of the moving object is determined by calculating the two-dimensional coordinate position for each distance traveled.

On the other hand, the CD-ROMG stores digitalized map information, and the CD-ROM connected to this
The display processing device 4 from which the necessary map information data is read by the playback device displays the map information data corresponding to the position information held by the signal processing device 3 and the current position corresponding to the position information. Display on 8.

On the other hand, in the present invention, a storage memory 7 is connected to the display processing device 4, and a part of the same data as the data stored in the CD-ROM 6 is stored in the storage memory 7. In the system configured as described above, the signal processing device 3 calculates the current position of the moving body according to the signals from the moving distance detector 1 and the direction detector 2 after the power is turned on. Then, the CD-ROM playback device 5 reads a map corresponding to this current position from the CD-ROM 6. At this time, in the present invention,
CD according to the flowchart shown in Figure 2.
- ROM 6 and storage memory 7 are accessed.

At the start, the disc label and version are read from the CD-ROM 6 (step 201).
), then the first time you need map data, use the CD
- Read data from the CD-ROM 6 using the ROM playback device 5. At this time, the read data is also written to the storage memory 7 (step 204). Next time map data is needed, the CD-ROM 6 is read. - Before reading data from the ROM 6, refer to the data in the storage memory 7 (step 202). If there is necessary data in the storage memory 7, use that data (step 203), CD-ROM 6 The map data management information is read from the CD-ROM 6 only when there is no data in the storage memory 7 (step 204).
), in that case, the read map data management information is also written into the storage memory 7 (step 205).

Therefore, by accessing data according to such a procedure, the number of accesses to the CD-ROM 6 is reduced, and necessary data can be obtained in a short time. If a readable non-volatile memory such as E"FROM is used as the storage memory 7, the data in the CI)-ROM 6 that has been read once is stored even after the power is turned off. This data can be used as is the next time the power is turned on.

[Effect of the invention] As described above in detail based on the embodiments.

In the present invention, a CD-ROM is used to store map data.
In addition, a storage memory containing part of the same data as the CD-ROM is provided separately, and when data is read from the CD-ROM, the same data is also stored in this storage memory. When this happens, if there is necessary data in this storage memory, that data is used.

Therefore, as shown in FIG. 5, the time T-1, tg from read request to search AC,K can be significantly reduced, and necessary data can be obtained in a short time. Therefore, in the navigation system, there is an advantage that real-time map display and the like can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the navigation system according to the present invention, FIG. 2 is a flowchart showing the operating procedure of the present invention, and FIG. 3 is a diagram showing the configuration of map information data used in the navigation system. 4 is a flowchart for explaining the operation of a conventional navigation system, and FIG. 5 is a schematic diagram showing the exchange of signals between a display processing device and a CD-ROM reproducing device in the navigation system. In the figure, 1... moving distance detector, 2-...-
... Direction detector, 3 ... Signal processing device, 4.
...Display processing device, 5...CD-ROM
Playback device, 6-...CD-ROM, 7...
-Storage memory, 8...Display device. (1 other person)! d1 Roof's Nebekyou 4 Figure 3 (C-n Figure 3 CD)

Claims (2)

[Claims] (1) In a navigation system that appropriately reads map information data corresponding to the current position of a moving body from a CD-ROM and displays it on a display device together with the current position, the map information data read from the CD-ROM is A navigation system characterized in that a storage memory is provided to store the map information data, and when the map information data is required, the storage memory is accessed prior to accessing the CD-ROM. (2) The navigation system according to claim (1), wherein the storage memory is a nonvolatile memory.