JPH08314375A - Data compression method and its device, and data restoration method and its device - Google Patents

Abstract

PURPOSE: To provide a data compression method and its device capable of reducing the size and cost of the device and to provide a data restoration method and its device capable of restoring an original plotting data from the compressed data, by compressing a plotting data corresponding to a route stored in a nonvolatile memory as a storage medium and reducing a memory capacity in the pertinent nonvolatile memory. CONSTITUTION: This device forms compressed plotting data 50 including at least a starting point intersection number data 52 to be a route start point and a branch number data 53 of a branch road at each intersection, and stores the compressed plotting data 50 in a nonvolatile memory. The data reconstruction method and its device restore the plotting data based on the road data and the intersection data stored in the compressed plotting data and other storage media, and execute road painting or the like of the pertinent route.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data extraction method and device and a data restoration method and device, and more particularly, to a drawing device for drawing a desired road on a display device in a navigation device. When storing in a predetermined storage medium, the drawing data is compressed and stored,
Further, the present invention relates to a data restoration method and device for restoring the drawing data from the stored data.

[0002]

2. Description of the Related Art Currently, for example, as a positioning device for various moving bodies such as automobiles, aircrafts, ships, etc., the position of the moving body is set at the point on the map including the point where the moving body is currently present. There is known a so-called navigation device that superimposes and displays the indicated position mark and guides a route to a destination based on the superimposed position mark. Among these navigation devices, the vehicle navigation devices installed in a vehicle are roughly classified into a self-contained navigation device and a GPS (Glob).
al Positioning System) type navigation device.

The former is a direction sensor provided in a moving body,
The moving direction and the moving distance of the moving body are obtained by the speed sensor and the angular velocity sensor, and the current position is calculated by adding them to the reference point. Based on the calculated current position, the position mark and the corresponding map are displayed on the display screen. Is displayed.

The latter receives radio waves from a plurality of GPS satellites launched into outer space and calculates the current position of the moving body by a three-dimensional survey method or a two-dimensional survey method based on the reception result. The position mark and the corresponding map are displayed on the display screen based on the calculated current position.

More recently, vehicle navigation systems having both the above-mentioned self-supporting type and GPS type functions have been becoming popular. According to the vehicle navigation device described above, the user (driver) can recognize the current position of the user and the map near the current position in association with each other, so that the user can pass through the area for the first time without hesitation. , Can reach the destination.

[0006] Here, in the conventional navigation device, in order to display a route to a preset destination on the display device, the road corresponding to the route is displayed in a different color from other roads ( In the following, it is called "color painting of roads".

The coloring of the road will be described more specifically below. First, when the user sets a route in advance, coordinate data of intersections on the route and passage points of the road (drawing points to be drawn on the display device) are stored in the CD-ROM.
(Drawing data for roads corresponding to the route is formed by reading from road data and intersection data stored in advance in (Compact Disk-Read Only Memory) or the like and arranged in order of the route.

This drawing data has a structure as shown in FIG. 8, for example. In FIG. 8, the drawing data 100
Is composed of the drawing point number data 101 indicating the number of drawing points (intersections and road passing points) on the route, and the coordinate data 102 of each drawing point in the order of the drawing points on the route.

Then, the formed drawing data 100 is
Non-volatile RAM (Random) included in the navigation device
Access Memory). This non-volatile RAM
Are SRAM (Static RAM) and EPROM (Erasable
Programmable Read Only Memory) etc.,
The drawing data 100 is once written in the SRAM, and then
Transferred to EPROM and held. This non-volatile RA
Since M can retain the stored contents even when the power is turned off, the drawing data 100 will not be lost even if the power of the navigation device is turned off after the route is set.

When the road is colored, the CPU constituting the navigation device reads the drawing data 100 from the non-volatile RAM, and based on the read data 100, the road is colored with a predetermined color at each drawing point. And display it.

According to the above-described road color painting processing, a road designated as a route can be distinguished from other roads at a glance, and when the route is deviated, the road can be immediately recognized, and further progress should be made in the future. Since the specific target object on the road can be grasped in advance, the own vehicle can be guided to the destination more reliably.

[0012]

However, in the conventional road painting process, the drawing data 100 itself shown in FIG. 8 is stored in the nonvolatile RAM.

Here, in actual vehicle operation, it is not uncommon that the total distance of a preset route exceeds 100 km, but in such a case, the number of intersections and passing points on the route is also increased. This is a huge amount, and therefore, a non-volatile RA for storing the drawing data 100 based on the path.
A huge amount of memory capacity is required for M, and the nonvolatile R
Since the volume for mounting the AM is large, it is impossible to downsize the entire navigation device.
There is a problem that the cost for M becomes high.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to compress drawing data stored in a non-volatile RAM as a storage medium and to perform necessary storage in the storage medium. (EN) Provided are a data compression method and a device which can reduce the capacity and size and cost of the device, and a data decompression method and a device which can restore the original drawing data from the compressed data. .

[0015]

In order to solve the above problems, the invention according to claim 1 specifies road data including branch number data different for each branch road from an intersection and the intersection. A data compression method for compressing drawing data necessary for drawing a predetermined road based on intersection data including intersection number data, and based on route data corresponding to a preset route, a start point of the route and Starting point intersection number data extraction step for extracting starting point intersection number data corresponding to the starting point intersection from the intersection data, and based on the route data, from one intersection on the route to an intersection on the route to be passed next A branch number data extraction step of extracting branch number data corresponding to the branch road to reach from the road data, and based on the route data Constructed and a compressed drawing data forming step of forming a compressed drawing data including at least the starting point intersection number data and the branch number data.

According to a second aspect of the present invention, a predetermined road is displayed based on road data including branch number data different for each branch road from the intersection and intersection data including the intersection number data for specifying the intersection. A data compressing device for compressing drawing data required to perform, based on route data input from the outside corresponding to a preset route, starting point intersection number data corresponding to a starting point intersection which is a starting point of the route. Starting point intersection number data extracting means such as CPU for extracting from the intersection data, and the branch road for reaching from the one intersection on the route to the next intersection on the route based on the route data. Based on the branch number data extracting means such as a CPU for extracting the corresponding branch number data from the road data and the route data, With C to form a compressed drawing data including the start point intersection number data and the branch number data
And a compressed drawing data forming means such as a PU.

The invention according to claim 3 is a data decompression method for decompressing the compressed drawing data obtained by the data compression method according to claim 1, wherein the starting point intersection number included in the compressed drawing data Based on the data and the branch number data, it comprises a drawing data extraction step of extracting the drawing data from the intersection data and the road data.

The invention described in claim 4 is a data decompression device for decompressing the compressed drawing data obtained by the data compression device according to claim 2, and is included in the compressed drawing data input from the outside. Based on the starting point intersection number data and the branch number data, the drawing data extracting means for extracting the drawing data from the intersection data and the road data is provided.

[0019]

According to the first aspect of the present invention, in the starting intersection number data extracting step, the starting intersection number data corresponding to the starting intersection of the route is extracted from the intersection data based on the route data.

Next, in the branch number data extraction step,
The branch number data is extracted from the road data based on the route data. Then, in the compressed drawing data forming step,
Compressed drawing data including at least starting point intersection number data and branch number data is formed based on the route data.

Therefore, if the branch road corresponding to the branch number data at the intersection is designated by the branch number data, the intersection to be passed next is determined. Therefore, the intersection corresponding to each intersection on the route. Drawing data for drawing a road corresponding to a route using the compressed drawing data by forming and storing compressed drawing data including the start intersection number data and the branch number data without using the data. Can be restored, the storage capacity of the storage medium for storing the drawing data can be reduced, and the recording medium can be downsized.

According to the second aspect of the present invention, the starting point intersection number data extracting means corresponds to the starting point intersection which is the starting point of the route based on the route data inputted from the outside corresponding to the preset route. Starting intersection number data is extracted from the intersection data.

Next, the branch number data extracting means extracts, from the road data, the branch number data corresponding to the branch road from the intersection on the route to the intersection to be passed next based on the route data.

Then, the compressed drawing data forming means forms the compressed drawing data including at least the starting point intersection number data and the branch number data based on the route data. Therefore, if the branch road corresponding to the branch number data at the intersection is designated by the branch number data, the intersection to be passed next is determined. Therefore, use the intersection data corresponding to each intersection on the route. Instead, by forming and storing compressed drawing data that includes starting point intersection number data and branch number data, the drawing data for drawing the road corresponding to the route can be restored using the compressed drawing data. Therefore, the storage capacity of the storage medium for storing the drawing data can be reduced, and the size of the recording medium can be reduced.

According to the invention described in claim 3, in the drawing data extracting step, based on the starting point intersection number data and the branch number data included in the compressed drawing data obtained by the data compression method according to claim 1. , Drawing data is extracted from the intersection data and the road data.

Therefore, since the starting intersection number data and the branch number data are obtained from the compressed drawing data, the drawing necessary for the road drawing is performed based on these data and the road data and the intersection data stored in the other storage medium. Data can be completely restored.

According to the invention described in claim 4, the drawing data extracting means is obtained by the data compressing device according to claim 2, and the starting point intersection number data and the branch included in the compressed drawing data inputted from the outside. Based on the number data
Drawing data is extracted from intersection data and road data.

Therefore, since the starting point intersection number data and the branch number data are obtained from the compressed drawing data, the drawing required for the road drawing is performed based on these data and the road data and the intersection data stored in the other storage medium. Data can be completely restored.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. In each of the following examples,
A case where the present invention is applied to a vehicle navigation device in an automobile or the like will be described. (I) Device Configuration and Basic Data Structure First, the overall configuration of the vehicle navigation device of this embodiment will be described with reference to FIG.

The vehicle navigation system S according to the embodiment includes a geomagnetic sensor 1 which outputs direction data in the traveling direction of the vehicle and an angular velocity sensor 2 which detects angular velocity when the vehicle rotates and outputs angular velocity data. , A mileage sensor 3 that outputs mileage data by detecting and integrating the number of revolutions of a drive shaft connected to a wheel, and G that receives radio waves from GPS satellites and outputs GPS positioning data.
A PS receiver 4; a system controller 5 that controls the entire navigation device based on azimuth data, angular velocity data, mileage data, and GPS positioning data;
Under the control of the input device 11 such as a remote control device for inputting various data and the system controller 5, the CD-
A CD-ROM drive 12 that reads and outputs various data such as road data and intersection data from the ROM disk DK, a display unit 13 that displays various display data under the control of the system controller 5, and a control of the system controller 5 A sound reproducing unit 18 which reproduces and outputs various audio data below, and is configured.

The system controller 5 also stores an interface section 6 for interfacing with an external sensor such as the geomagnetic sensor 1, a CPU 7 for controlling the entire system controller 5, a control program for controlling the system controller 5, and the like. ROM (Read Onl
y Memory) 8 and a non-volatile memory (not shown),
Under the control of the CPU 7, a RAM 9 that stores various data such as compressed compressed drawing data in a writable manner is provided, and an input device 11, a CD-ROM drive 12, a display unit 13, and a sound reproduction unit 18 are provided. Are connected via a bus line 10.

Further, the display unit 13 is the bus line 1
A graphic controller 14 that controls the entire display unit 13 based on control data sent from the CPU 7 via 0 and a memory such as VRAM (Video RAM), and temporarily stores image information that can be immediately displayed. Based on the image data output from the buffer memory 15 and the graphic controller 14, liquid crystal, CRT (Ca
a display controller 16 for controlling the display 17 such as a thode Ray Tube).

The sound reproducing unit 18 is a D / A for D / A converting the audio digital data sent from the CD-ROM drive 12 or the RAM 9 via the bus line 10.
It is configured to include a converter 19, an amplifier 20 that amplifies a voice analog signal output from the D / A converter 19, and a speaker SP that converts the amplified voice analog signal into voice and outputs the voice.

In the above structure, the RAM 9 is a non-volatile RAM for temporarily storing compressed compressed drawing data.
And a DRAM (Dynamic RAM) for recording the drawing data restored for the actual color painting of the road.

Further, the CPU 7 included in the system controller 5 functions as a starting point intersection number data extracting means, a branch number data extracting means, a compressed drawing data forming means and a drawing data extracting means.

Before describing the operation of the vehicle navigation system S, road data and intersection data, which are the basis for executing the color painting of the road corresponding to the route, will be described with reference to FIGS. 2 and 3. To do.

First, in order to simplify the description, as a premise, in this embodiment, the route P in the map M shown in FIG. 2 is used.
Coloring processing is performed on a road corresponding to R (a path starting from the intersection C ₀ and passing through the intersections C ₁ and C ₂ to reach the intersection C ₃ ).

Further, in this embodiment, for all intersections stored in advance on the CD-ROM disc DK,
Intersection numbers unique to each intersection (C _{0 to} C _{3 in} FIG. 2)
Is recorded. Furthermore, for each intersection, the branch roads that branch from the intersection are recorded with branch numbers (D _{0 to} D _{3 in} FIG. 2) assigned to all the branch roads. If you follow, you will reach the next intersection. Here, when focusing on one branch road, there are two branch numbers seen from each of the two intersections that are the ends of the branch road.

Regarding this branch number D _N , more specifically, for example, at the intersection C ₀ shown in FIG. 2, there are three branch roads from the intersection C ₀ , but for these branch roads, Branch numbers D _{0 to} D ₂ are given clockwise around the intersection C ₀ . Further, regarding the intersection C _1, there are four branch roads from the intersection C ₁ , but with respect to these branch roads, the branch numbers D _{0 to} D ₃ are similarly clockwise around the intersection C _1. Has been granted. Hereinafter, similarly, branch numbers are similarly given to the intersections C ₂ and C ₃ . In FIG. 2, reference numerals a to h indicate passage points of roads that are not intersections, and the passage points corresponding to the route PR and the intersections are drawing points when the road is colored. Further, in FIG. 2, reference numerals N _{0 to} N
₇ (corresponding to the map M.) One area in the road data called node (node point) corresponding to the end of that show end. Each passing point in FIG. 2 also corresponds to a node. Next, structures of road data and intersection data corresponding to roads and intersections in the area corresponding to the map M will be described with reference to FIG.

As shown in FIG. 3, the above intersection data and road data are recorded on the CD as recording data DR as a whole.
-CD-RO stored in the ROM disk DK and under the control of the system controller 5 as necessary.
It is read out via the M drive 12.

As shown in FIG. 3, the recording data DR is roughly divided into an intersection data part DRa and a road data part DRb. Further, the intersection data part DRa is
It is composed of a plurality of intersection data 30 corresponding to each intersection, beginning with the intersection number data 21 indicating the number of intersections in the area (the map M in FIG. 2 in the present embodiment) corresponding to the recording data DR. And one intersection data 30
Is composed of a plurality of branch road data 32 corresponding to each branch road, with the branch number data 31 indicating the number of branch roads at the intersection as a head. Furthermore, one branch road data 32 includes a head address and an element number for reading the coordinates of each drawing point included in the branch road. Here, the element is a general name of the intersection and the passing point, and corresponds to the drawing point in the above description. More specifically, on the road from the intersection C ₀ to the intersection C ₁ in FIG. 2, the elements mean the intersection C ₀ , the passage a, and the intersection C ₁ .

On the other hand, the road data portion DRb has an area corresponding to the recording data DR (in this embodiment, the map M in FIG. 2).
The number of roads 22 indicating the total number of roads inside the road (in this embodiment, the roads connecting the intersections are counted as one road, so the number is 11 in the case of FIG. 2). It is composed of a plurality of road data 40 that Then, one road data 40 has a plurality of element coordinate data 42 corresponding to the coordinates of the elements (drawing points) included in the road, beginning with the element number data 41 indicating the number of elements included in the road. Starting point data 43 indicating the address where the intersection data 30 corresponding to the starting point of the road is recorded, and ending point data 44 indicating the address where the intersection data 30 corresponding to the ending point of the road is recorded. It is composed by. Further, one element coordinate data 42 includes the X coordinate and the Y coordinate of the element.

Here, with respect to the mutual relationship between the intersection data portion DRa and the road data portion DRb, the map M shown in FIG.
Will be specifically described as an example. First, intersection data section D
In the intersection count data 21 at the beginning of Ra, in the case of FIG. 2, since there are four intersections in the map M, “4” is stored. The intersection data 30 starting from the address P _S0 includes branch road data corresponding to one intersection (for example, the intersection C ₀ ). In the case of FIG.
Since there are 3 branch roads at the intersection C ₀ , the branch number data 3
1 becomes “3”, followed by the number of branch roads, 3
The branch road data 32a to 32c (corresponding to the branch roads indicated by the branch numbers D _{0 to} D ₂ ) are stored. Further, the intersection data 30 starting from the address P _S1 includes branch road data corresponding to another intersection (for example, the intersection C ₁ ). In the case of FIG. 2, the intersection C ₁
Since there are four branch roads, the branch number data 31 is "4".
Then, four pieces of branch road data 32d to 32e, which are the number of branch roads (corresponding to the branch roads indicated by the branch numbers D _{0 to} D ₃ at the intersection C ₁ ) are stored. In addition, "P" in the branch road data 32
_{R *} ”is road data 4 not shown in FIG.
An address of 0 is shown.

Now, focusing on the branch road data 32b,
In the branch road data 32b, the corresponding branch road D₁
Address to read the coordinates of each element included in
"P _R0, And element number “0”. This top
Address P_R0The address specified in
D₁Contains the coordinates of each element contained in. Sanawa
Address P_R0Looking at the road data 40 starting from
Branch road D₁, The number of elements (number of intersections and passing points)
The sum of the numbers is 3 (intersection C₀, Passing point a and intersection C
₁), The element number data 41 becomes “3”, and
Each element between element 0 and element 2 (each intersection
C₀, Passing point a and intersection C₁Corresponding to. ) On the map
Coordinates (X coordinate and Y coordinate) are described. example
For example, in the element coordinate data 42a corresponding to the element 0, the intersection
Point C₀X coordinates and Y coordinates of are described. And
After the element coordinate data 42, the intersection data part DRa
Return to the corresponding start intersection data and end intersection data of
There are start point data 43 and end point data 44 for
For example, in the case of the starting point data 43 of FIG. 3, the intersection of FIG.
C₀Branch road D seen from₁Is the intersection C₀Is
And address P_S0Return to the intersection data 30 starting from
First of all, "P_S0Is described. Also, the end point data 44
In the case of, the intersection C of FIG.₀Branch road D seen from₁of
End point is intersection C₁Therefore, the address P_S1start from
To return to the intersection data 30, "P_S1Is described
It

On the other hand, paying attention to the branch road data 32d, the branch road data 32d has a corresponding branch road D _0.
The head address “P _R0 ” and the element number “2” for reading the coordinates of each element included in are included. Therefore,
By looking at the coordinates of the element 2 of the road data 40 indicated by the address P _R0 , the coordinates of the intersection C ₁ which is the starting point of the branch road D ₀ seen from the intersection C ₁ can be read.

As described above, between the intersection data DRa and the road data DRb in the recording data DR, the address and the element number are described so that mutually necessary coordinate data can be read. Note that FIG.
Although omitted, in the actual recording data DR, only the intersection data 30 and the road data 40 having the number of intersections (“4” in FIG. 2) and the number of roads (“11” in FIG. 2) are included.
Will exist.

Based on the structure of the recorded data DR described above, the data compression operation and the decompression operation in the vehicle navigation device S according to the present invention will be described below with reference to flowcharts.

The operations shown in the flow charts in the following embodiments are mainly executed by the CPU 7. A program corresponding to the flowcharts in the following embodiments is a ROM as a control program.
8 is stored in advance and is read out as needed. (II) Data compression operation First, the formation of compressed drawing data by the data compression operation according to the invention described in claims 1 and 2 will be described with reference to FIGS. 4 and 5. In the data compressing operation of the present embodiment, the compressed drawing data 50 stored in the nonvolatile memory of the RAM 9 only by the starting intersection number corresponding to the starting point of the route and the branch number of the road to proceed from each intersection to the next intersection. Is formed. Note that FIG. 5 shows the structure of the compressed drawing data 50 formed by the data compression operation.

As shown in FIG. 4, in the data compression operation of this embodiment, first, the branch number storage number data 51 indicating the number of branch numbers to be stored as initialization is initialized (step S1). . Next, based on the route data corresponding to the preset route (see PR in FIG. 2), the intersection (the intersection C in FIG. 2) corresponding to the starting point of the route is set.
The intersection number C _{0 of 0} ) is stored in the area of the non-volatile memory corresponding to the starting intersection number data 52 (step S).
2).

Next, based on the above route data, the road data is traced from the starting intersection (intersection C ₀ ) and it is judged whether or not the first drawing point (element) after the starting intersection is the intersection ( Step S3). For example, in the case of FIG. 2, since the first drawing point after the starting point intersection (intersection C ₀ ) is the passing point a, in this case, it is not the intersection (step S3; NO), so that the nonvolatile RAM is stored. The writing operation is not performed, and the process proceeds to step S7. Step S7
In, it is determined whether or not the processing has been completed for all the drawing points (elements), but since the processing has not been completed for all the drawing points (step S7; NO),
Returning to step S3, it is determined whether or not the next drawing point is an intersection (step S3). In the case of FIG. 2, since the drawing point next to the passing point a is the intersection C ₁ , step S3 is “YES”, and then the road common to the intersection C ₁ and the starting intersection (intersection C ₀ ) ( In the case of FIG. 2, intersection C
The start address of the intersection data 30 indicating the branch road corresponding to the branch number D ₁ when viewed from ₀ is calculated, and the road branch number (in the case of FIG. 2, the branch number D ₁ ) of the road corresponding to the calculated start address is acquired. Yes (step S4). Then, the branch number D ₁ is stored at the head of the branch number data 53 (branch number data 53a) in the nonvolatile RAM (step S
5). After that, the stored branch number is incremented by 1 (step S6), and the process proceeds to step S7.
In step S7, since the processing has not been completed for all drawing points (step S7; NO), the process returns to step S3 again. Then, the processing after step S3 is executed, but in the case of FIG. 2, the drawing point next to the intersection C ₁ is the intersection C ₂ , so that the step S3 is “Y”.
ES ”, the processing of steps S4 to S6 is executed between the intersection C ₁ and the intersection C ₂ , and this time, the branch number D ₁ viewed from the intersection C ₁ is the position of the next branch number data 53 (branch number data 53b). Hereinafter, the same operation is executed for all drawing points (elements) on the route PR.

When the processing is completed for all the drawing points (elements) (step S7; YES), the finally incremented branch number storage number is stored in the area corresponding to the branch number storage number data 51 of the nonvolatile RAM. Store
The compressed drawing data 50 is completed.

After that, the compressed drawing data 50 corresponding to the route PR is held in the non-volatile RAM. Here, when the completed compressed drawing data 50 (see FIG. 3) is associated with the actual operation, the branch number data 53a is
It is shown that the vehicle starts at the starting intersection (intersection C ₀ ) and first proceeds on the road corresponding to the branch number D ₁ .
Here, the road corresponding to the branch number D ₁ is the next intersection C ₁
Since the vehicle is connected to the intersection C ₁ , the vehicle arrives at the intersection C ₁ and then travels from the intersection C ₁ on the road corresponding to the branch number D ₁ at the intersection C _{1 as} shown in the branch number data 53b. Then, since the vehicle arrives at the intersection C ₂ , the road corresponding to the branch number D ₂ at the intersection C ₂ is advanced from there as shown in the branch number data 53c. And
Finally, the vehicle arrives at the intersection C ₃ which is the destination, and the initial route PR can be reliably traced only by the information included in the compressed drawing data 50.

As described above, according to the data compression operation of this embodiment, the compressed drawing data to be stored in the nonvolatile RAM can be compressed, so that the nonvolatile RA
It is possible to reduce the storage capacity of M, reduce the size of the nonvolatile RAM, and reduce the cost. (III) Data Restoration Operation Next, the operation of forming drawing data necessary for color painting of roads from the compressed drawing data 50 by the data restoring operation corresponding to the invention described in claims 3 and 4 will be described with reference to FIGS.
Will be explained. In the data restoring operation of this embodiment, the compressed drawing data 50 compressed by the data compressing operation and held in the nonvolatile RAM and the recording data D shown in FIG.
By R, the drawing data 60 necessary for coloring the road is restored. Note that FIG. 7 shows the structure of the drawing data 60 formed by the data restoration operation, and the drawing data 60 is stored in the DRAM of the RAM 9.

As shown in FIG. 6, in the data decompression operation of this embodiment, first, the counter in which the CPU 7 includes the branch number storage number based on the branch number storage number data 51 stored in the compressed drawing data 50. Is set (step S10). This is because the processes of steps S12 to S19 described below are repeated by the number of branch numbers stored in the compressed drawing data 50, and thus the number is set in the counter in advance.

When the number of stored branch numbers is set in the counter (step S10), next, the intersection data of the starting intersection (in the case of FIG. 2, the intersection C ₀ ) is obtained based on the starting intersection number data of the compressed drawing data 50. It is acquired from the intersection data 30 (step S11).

Next, the branch number (branch number D _{1 in} the case of FIG. 2) from the start intersection is acquired from the branch number data 53a of the compressed drawing data 50 (step S12).
Then, based on the branch number D ₁ , the head address of the road data of the road corresponding to the branch number D ₁ at the starting intersection (in the case of FIG. 2, the address P _{R0 of} FIG. 3) is set (step S13).

Then, the first element coordinate data (in the case of FIG. 3, the element coordinate data 42a) of the road data of the road data portion DRb (see FIG. 3) corresponding to the head address is read (step S14), and the read corresponding The element coordinate data (coordinate of the intersection C ₀ ) is stored at the head (coordinate data 62a) of the coordinate data 62 in the drawing data 60 (step S15). Then, it is determined whether or not the next element coordinate data is an intersection (step S16). In the case of FIG. 3, since the next element coordinate data 42b corresponds not to the intersection but to the passing point a, step S16 becomes “NO”, the process returns to step S14, and the element coordinate data 42 concerned.
b is read (step S14) and stored in the next coordinate data area (coordinate data 62b) in the drawing data 60 (step S15).

Then, the determination at step S16 is made again. However, since the next element coordinate data 42c is the element coordinate data corresponding to the intersection C ₁ , step S16 becomes "YES", and the process for one branch road is performed. Is decremented by 1 (step S17), it is then determined whether the counter is "0" (step S18), and if it is not "0" (step S1).
8; NO), it is determined that there is a branch road corresponding to the unprocessed intersection.
The address of the intersection data 30 corresponding to ₁ ) is calculated and acquired (step S19), and the processes of steps S12 to S18 are executed for the intersection C ₁ . Thereafter, in the same manner, step S1 is performed until the counter becomes "0".
The processing from 2 to S19 is repeated.

When the counter is "0" (step S18; YES), the coordinate data of the intersection (in the case of FIG. 2, the intersection C ₃ ) corresponding to the final intersection which is the destination of the route PR is set as the road data. It is read from the corresponding element coordinate data of 40 and stored in the corresponding position of the drawing data 60 (the coordinate data 62g in the case of FIG. 7) (step S2).
0). The process of step S20 is performed on the final intersection because the coordinate data of the final intersection (intersection C ₃ ) is obtained when the operations up to step S19 shown in FIG. 6 are executed based on the compressed drawing data 50 shown in FIG. Drawing data 60
Since the counter is set to “0” before being stored in, the coordinate data of the final intersection is not stored in the drawing data 60 and the route PR
This is because the drawing data 60 corresponding to is not completed.

In step S20, when the coordinate data of the final intersection is stored in the drawing data 60, it is assumed that the processing is completed for all the branch numbers stored in the compressed drawing data 50, and the final number of drawing points is drawn. The data 60 is stored in the area corresponding to the drawing score data 61 of the data 60 (step S21), the data restoration process is completed, and the drawing data 60 is stored.
Will be stored in the DRAM in the RAM 9.

Thereafter, the corresponding road is displayed in a different color from the other roads based on the drawing data 60 on the DRAM. As described above, according to the data decompression operation of this embodiment, the compressed drawing data 5 stored in the nonvolatile RAM 5
0 and the recording data DR (road data and intersection data) stored in the CD-ROM, the drawing data 60 for road color painting is restored and the color painting is executed, so compressed drawing data is stored. Even if the storage capacity of the storage medium is small, the drawing data can be completely restored, the storage capacity of the nonvolatile RAM can be reduced, and the nonvolatile RAM can be downsized and the cost can be reduced.

In the above-described embodiment, the road is painted to display the route PR preset by the user, but the present invention is not limited to this, and traffic congestion from the outside may occur. Based on the information, route data may be formed corresponding to the congested road and the congested road may be colored, or a recommended drive course or demonstration course at a preset tourist destination. It is also possible to form the route data corresponding to, and display the drive course or the demo course by coloring.

[0063]

As described above, according to the invention described in claim 1 or 2, if the branch road corresponding to the branch number data at the intersection is designated by the branch number data, the next route should be taken. Since the intersection will be decided, without using the intersection data corresponding to each intersection on the route, by forming and storing the compressed drawing data including the start intersection number data and the branch number data, Using the compressed drawing data, the road drawing data corresponding to the route can be restored.

Therefore, the storage capacity of the storage medium for recording the drawing data can be reduced, and the size and cost of the recording medium can be reduced. According to the invention described in claim 3 or 4, since the starting point intersection number data and the branch number data are obtained from the compressed drawing data, based on these data and the road data and the intersection data stored in another storage medium. Thus, the drawing data necessary for drawing the road can be completely restored.

Therefore, even if the storage capacity of the storage medium for storing the compressed drawing data is small, the drawing data can be completely restored, so that the storage capacity of the storage medium is reduced and the recording medium is miniaturized. It is possible to reduce the cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a vehicle navigation device according to an embodiment of the present invention.

FIG. 2 is a diagram showing examples of intersection numbers and branch numbers.

FIG. 3 is a diagram showing an example of intersection data and road data.

FIG. 4 is a flowchart showing a data compression operation.

FIG. 5 is a diagram showing a compressed drawing data structure.

FIG. 6 is a flowchart showing an operation of data restoration.

FIG. 7 is a diagram showing a structure (I) of drawing data.

FIG. 8 is a diagram showing a structure (II) of drawing data.

[Explanation of symbols]

1 ... Geomagnetic sensor 2 ... Angular velocity sensor 3 ... Distance sensor 4 ... GPS receiver 5 ... System controller 6 ... Interface 7 ... CPU 8 ... ROM 9 ... RAM 10 ... Bus line 11 ... Input device 12 ... CD-ROM drive 13 ... Display Unit 14 ... Graphic controller 15 ... Buffer memory 16 ... Display control unit 17 ... Display 18 ... Sound reproduction unit 19 ... D / A converter 20 ... Amplifier SP ... Speaker 21 ... Intersection number data 22 ... Road number data 30 ... Intersection data 31 ... Branch number data 32, 32a, 32b, 32c, 32d, 32e ... Branch road data 40 ... Road data 41 ... Element number data 42, 42a, 42b, 42c ... Element coordinate data 43 ... Start point data 44 ... End point data 50 ... Compressed drawing Data 51 ... Branch No. number of stored data 52 ... start point intersection number data 53, 53 a, 53b, 53c ... branch number data 60, 100 ... drawing data 61,101 ... drawing number data 62,62a, 62b, 62c, 62d, 62e, 62
f, 62g, 102, 102a, 102b, 102c,
102d, 102e, 102f ... coordinate data DR ... recording data DRa ... intersection data unit DRb ... road data unit _{C 0, C 1, C 2} , C 3 ... intersection _{(number) N 0, N 1, N} 2, N 3, N ₄ , N ₅ , N ₆ , N ₇ ... Node ends a, b, c, d, e, f, g, h ... Passage points D ₀ , D ₁ , D ₂ , D ₃ ... Branch number R ... Road PR … Route M… Map

Claims (4)

[Claims] 1. Drawing data necessary for drawing a predetermined road based on road data including branch number data different for each branch road from an intersection and intersection data including intersection number data for specifying the intersection. Is a data compression method for compressing data, and based on route data corresponding to a preset route, starting-point intersection number data extraction for extracting starting-point intersection number data corresponding to a starting-point intersection that is a starting point of the route from the intersection data. Step and branch number data for extracting branch number data corresponding to the branch road from one intersection on the route to an intersection on the route to be passed next based on the route data from the road data An extracting step, and a pressure including at least the starting intersection number data and the branch number data based on the route data. And a compressed drawing data forming step of forming reduced drawing data. 2. Drawing data necessary for displaying a predetermined road based on road data including branch number data different for each branch road from the intersection and intersection data including intersection number data for specifying the intersection. A data compression device for compressing, based on route data corresponding to a preset route, starting-point intersection number data extraction for extracting starting-point intersection number data corresponding to a starting-point intersection that is a starting point of the route from the intersection data. Means, and branch number data for extracting from the road data branch number data corresponding to the branch road from one intersection on the route to an intersection on the route to be passed next based on the route data Extracting means, and a pressure code including at least the starting point intersection number data and the branch number data based on the route data. A data compression device, comprising: compressed drawing data forming means for forming reduced drawing data. 3. A data decompression method for decompressing the compressed drawing data obtained by the data compression method according to claim 1, wherein the starting point intersection number data and the branch number data included in the compressed drawing data are A data restoration method comprising: a drawing data extracting step of extracting the drawing data from the intersection data and the road data based on the intersection data and the road data. 4. A data decompression device for decompressing the compressed drawing data obtained by the data compression device according to claim 2, wherein the starting point intersection number data included in the compressed drawing data input from the outside and A data restoration device comprising: drawing data extracting means for extracting the drawing data from the intersection data and the road data based on the branch number data.