JP2517234B2 - How to display map data - Google Patents

Description

TECHNICAL FIELD The present invention relates to a map data display method, and more particularly to a display method for displaying map data stored in a memory in a vehicle-mounted navigation device at a plurality of scales.

BACKGROUND ART In recent years, a vehicle-mounted navigation device that guides a vehicle to a predetermined destination by storing map information in a memory and reading the map information from the memory on a display device together with the current location of the vehicle has been researched and developed. Has been done.

In such a navigation device, when map data of various scales is displayed on the display, if map data of all scales are held, the display can be performed easily and at high speed, but the disadvantage is that the half size of the data becomes large. There is. It is also possible to have only the map data with the largest scale and to represent other scales by simple reduction, but in this case the data size becomes smaller but the display becomes slower.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a map data display method capable of reducing the data size and speeding up drawing.

The map data display method according to the present invention stores only the map data of the maximum scale when the map data is stored in the memory, and regarding the linear portion (polygon and line data) of the map, from the start point to the end point. It is stored as continuous point coordinate data at equal intervals, and when displaying a linear portion, a predetermined number of point coordinate data are extracted and the linear portion is displayed based on the extracted point coordinate data. The predetermined number is displayed so as to increase as the scale ratio increases.

Example Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a vehicle-mounted navigation device according to the present invention. In the figure, 1 is a geomagnetic sensor for outputting azimuth data of a vehicle based on geomagnetism, 2 is an angular velocity sensor for detecting an angular velocity of the vehicle, 3 is a travel distance sensor for detecting a moving distance of the vehicle, Reference numeral 4 denotes a GPS (Global Positioning System) device for detecting the current position of the vehicle from latitude and longitude information and the like, and the outputs of these sensors (devices) are supplied to the system controller 5.

The system controller 5 includes sensors (devices) 1 to 4
Based on the output data of each sensor (apparatus) 1 to 4 which receives the output of the input and performs A / D (analog / digital) conversion, etc. and various image data processing and which is sequentially sent from the interface 6. A CPU (central processing circuit) 7 for calculating the amount of movement of the vehicle, a ROM (read only memory) 8 in which various processing programs of the CPU 7 and other necessary information are written in advance,
RAM (Random Access Memory) 9 where information necessary for executing the program is written and read
And a so-called CD-ROM, IC card, etc., and a recording medium 10 on which digitized (numerical) map information is recorded.
, A graphic memory 11 composed of V-RAM (Video RAM) and the like, and graphic data such as a map sent from the CPU 7 are drawn in the graphic memory 11 and are CR as an image.
It is composed of a graphic controller 13 for controlling the display 12 such as T. The input device 14 is composed of a keyboard and the like, and issues various commands to the system controller 5 by key input by the user.

The map information is recorded on the recording medium 10. The data structure of the map information will be described below. First, as shown in FIG. 2 (A), the whole map of Japan is, for example, 16384 (= 2 ¹⁴ ).
[M] The mesh is divided into four meshes, and one mesh at this time is called a territory. Territory is territory No.
It is identified by (Tx, Ty), and each territory is given a territory No. based on the territory at the lower left of the figure, for example.
The territory No. can be obtained from the current location (Crntx, Crnty).
The territory is the largest management unit in this data structure. The structure of the entire map data file is shown in FIG. 2 (B), and the territory ID file contains the start address of the territory No. (Tx, Ty) file as shown in FIG. 2 (C). Data such as the latitude (real number) at the lower left of the territory, the longitude (real number) at the lower left of the territory, and the declination angle (real number) of the geomagnetism are written for each territory.

The territory file is the most important file in this data structure, and various map data and data necessary for map drawing are written in it. In FIG. 3 (A),
The navigation ID and section table are road and intersection search files in navigation, the picture ID is a display management file, and road section data to intersection data are actual map data. The map data is the third
As shown in FIG. (B), it has a hierarchical structure in which the lowest layer is polygon data of rivers, seas, lakes, etc., the upper line is line data of roads, railways, etc., and the uppermost is character data of various marks, etc. Character data such as a place name is on it, and intersection data is on the uppermost layer. The intersection data of the top layer is the data used for the intersection pull-in described later,
Not displayed on the display.

Next, as shown in FIG. 4 (A), one territory is divided into, for example, 256, and 1024 obtained by this is obtained.
(2 ¹⁰ ) [m] square mesh is called a unit. This unit is also managed by the unit No. (Nx, Ny), and the No. (Nx, Ny) is obtained from the current position (Crntx, Crnty).
A unit is an intermediate management unit, and map information is recorded in this unit, and 256 units form a territory file. Since it is based on this unit when drawing a map, it can be said to be the basic unit for drawing. In the navigation ID file, as shown in Fig. 4 (B), the unit number
Data such as a line start address, an intersection start address, a road section start address, and an intersection start address in a (Nx, Ny) file are written for each unit.

Further, as shown in FIG. 5 (A), one unit is divided into, for example, 16 units, and 256 (2 ⁸ ) obtained by this is obtained.
[M] The four-sided mesh is called a section. This section is also managed by section No. (Sx, Sy),
No. (Sx, Sy) is obtained from the current location (Crntx, Crnty). A section is the smallest management unit, and information about line segments (roads are represented by connecting line segments) and intersections within this range is used as a section table as shown in FIGS. 5 (B) and (C). Further, FIGS. 6 (A) and (B) and FIG. 7 (A),
As shown in (B), it is registered in the territory file as section data.

Further, as shown in FIG. 3A, there is a file called a picture ID for display management in the territory file. In this embodiment, the scale of the map data is set to three types, for example, 15,000 / 10,000 and 1 / 100,000,
As actual map data, we have only the largest scale, 1 / 25,000. The map of each scale is divided into areas as shown in each of FIGS. 8 to 10 (A), and this area is managed by area No. (Anx, Any).
Area No. (Anx, Any) is obtained from the current location (Crntx, Crnty). If the scale is 1 / 2,500, the area number and unit
The No. is the same, and in the case of 1 / 50,000, one area is for 4 unit files, and in the case of 1 / 100,000, it is 1
One area is for 16 units. In addition, as shown in each figure (B) of FIG. 8 to FIG. 10, the picture ID of each scale has the beginning of the polygon, line, character, and character data required to display the map of that scale. Address and data size are recorded.

Next, the polygon data and the line data will be described. Polygon data and line data are shown in Fig. 11 (A).
And as shown in FIG. 12 (A), it is represented by a connected vector (line segment) represented by a start point and an end point. here,
If you express a map of 1 / 50,000 or 1 / 100,000 with the map data of the smallest scale of 1 / 5,000, the start point and the end point will shrink, so all the points are displayed as far as you can see on the display. There are times when it is not necessary to do so. Taking this into consideration, when the information is displayed on the display, the information about the points that can be omitted in appearance is displayed in advance as shown in FIGS. 11 (B) and 12 (B). It is put in each thinning bit of the line data. Then, the number of line segments (vectors) to be displayed can be reduced by checking the thinning bit at the time of displaying each scale and removing the point that the thinning bit contains information as necessary, so-called thinning.

Further, as shown in FIG. 13 (A), serial numbers (xn, yn) are assigned to all the intersections existing in one unit. By the way, there are various kinds of intersections, such as an orthogonal type, a Y-shaped road, and a five-forked road. Especially, at an intersection that has a plurality of roads with similar directions, the accuracy of the sensor when passing through this intersection,
There is a possibility that a road is erroneously selected due to a calculation error, map accuracy, or the like, and the road whose current position is displayed on the display does not match the road actually being traveled.
Therefore, for such an intersection, as shown in FIG. 13 (B), difficulty data indicating the difficulty of the intersection is put in the difficulty bit in the intersection data. Then, when passing through the intersection, by performing processing based on this difficulty level data, it is possible to prevent erroneous road selection. The processing will be described later.

Next, regarding the display of map data, the case where, for example, a V-RAM is used as the graphic memory 11 will be described. The display structure is as shown in FIG. 14 (A).
16 screens on V-RAM of 512 (dots) x 512 (dots)
Divide and display one independent map in each area. One area is one unit of 128 (dots) x 128 (dots), and it is divided into 16 to make 1
The area is one section of 32 (dots) × 32 (dots) (see FIGS. 14B and 14C). The actual in-vehicle display corresponds to the four central screens in Fig. 14 (A).
An area of 256 (dots) × 256 (dots) (area surrounded by a thick line) is displayed, and this area moves on the V-RAM to express the movement of the vehicle's current location.

Next, the basic procedure executed by the CPU 7 will be described with reference to the flowchart of FIG.

The CPU 7 first initializes to execute the program (step S1), and thereafter determines whether or not the current position of the vehicle is set (step S1).
S2). If the current location has not been set, the current location setting routine is executed (step S3), for example, the current location is set by key input on the input device 14. next,
The mileage is set to zero (step S4), and then it is determined whether or not there is a key input from the input device 14 (step S4).
Five).

If there is no key input, the map around the current location is displayed on the display 12, and the current position and direction of the vehicle are displayed on this map, for example, by the vehicle mark, and when the vehicle moves, the map scrolls with the movement. When the vehicle position is likely to exceed the range of the map data currently on the graphic memory 11, the necessary map data is read from the recording medium 10 and displayed on the display 12 (step S6).

If there is a key input, the current position is reset according to the input data (step S7), sensor correction (step S8),
Each routine of destination setting (step S9) and map enlargement / reduction (step S10) is executed.

Further, the CPU 7 performs a process of constantly calculating the heading of the vehicle based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2 at a constant time interval as shown in FIG. 16 by the interruption by the timer (steps S11 and S12). ).

When the data is input from the mileage sensor 3, the CPU 7 further performs an interrupt process by the mileage sensor.
In this interruption processing, as shown in FIG. 17, the present position is calculated from the traveling distance and the azimuth (step S13), right turn or left turn is determined (step S14), and the road is pulled in (step S1).
5), intersection pull-in (step S16), and pull-in by travel distance (step S17) are executed. The respective processes in steps S13 to S17 will be described in detail later.

Also, the latitude and longitude data obtained from the GPS device 4 is
As shown in FIG. 18, it is processed by the GPS data reception interrupt and the coordinates are converted as the current position data (step S1.
8).

The travel distance of the vehicle is obtained from the output of the travel distance sensor 3. As the mileage sensor 3, for example, a configuration is used in which the mileage is obtained by integrating the distance of one rotation from the rotation speed of a so-called speedometer cable of a vehicle (JIS standard: 637 rotations / Km). Inevitably, an error occurs in the traveled distance obtained by the accuracy of the sensor 3. Further, not only the accuracy of the sensor 3, but also the accuracy of the map, the change of the tire air pressure, the slip, etc. are factors of the error of the traveling distance. Therefore, unless the traveling distance is corrected frequently, the distance cannot be accurately obtained. Therefore, the traveling distance sensor 3
By calculating the distance correction coefficient rs from the actually measured distance obtained from the output and the distance obtained from the map data and performing the distance correction using this correction coefficient rs, the traveling distance can always be detected accurately.

The direction of the vehicle is obtained from the output of the geomagnetic sensor 1. This azimuth detection method is described in Japanese Patent Application No. 60-282341, etc., filed by the present applicant. The north indicated by the geomagnetic sensor 1 is magnetic north, not map north.
Therefore, if magnetic north is offset from map north,
As shown in the figure, the estimated current position P ₁ obtained from the output of the geomagnetic sensor 1 will deviate from the actual current position P ₂ when traveling a certain distance from the reference position. Therefore, it is necessary to convert the azimuth obtained from the geomagnetic sensor 1 into a map azimuth. As shown in FIG. 20, this conversion work is performed by the rotation angle obtained by the coordinate conversion of the two-dimensional geometry, that is, the azimuth correction coefficient θs. The azimuth correction coefficient θs changes depending on the region, and also changes due to a mounting error that occurs when the geomagnetic sensor 1 is mounted on the vehicle body.
As shown in FIG. 21, the azimuth correction coefficient θs can be obtained by an error between the current position and the arrival point obtained by inertial navigation while traveling between two points whose positions are known with the coefficient being zero. . By performing the heading correction using the heading correction coefficient θs, the heading of the vehicle can always be detected accurately.

The method of calculating the distance correction coefficient rs and the azimuth correction coefficient θs is described in the specification of Japanese Patent Application No. 60-282344 by the present applicant.

Next, the procedure of interrupt processing by the mileage sensor 3 executed by the CPU 7 will be described with reference to the flowchart of FIG. The estimated point of the current position is calculated at any time based on the output data of the traveling distance sensor 3, and this routine is called at a predetermined timing as a current position recognition routine.

The CPU 7 first determines whether or not it has traveled the unit distance lo (step S20). Here, the unit distance refers to a certain distance that the vehicle actually travels, and is set to 20 [m], for example. Then, this routine is executed for each constant traveling distance, and first, the relationship with the map data, that is, the distance lm to the nearest line segment L, the angle θn of the line segment L with the map north, etc. are obtained. If there are two or more line segments at approximately the same distance, this is indicated by a flag (step S2
1). In addition, the presence / absence of a nearby intersection may be obtained here. Next, the distance lm is a preset threshold l
It is determined whether or not th has been exceeded (step S22). If it does not exceed, it is assumed that the current location is near the line segment,
The error lm is corrected (step S23). This error
lm is caused by a detection error of the traveling distance sensor 3, a digitizing error of map data, and the like. This correction is performed because it is necessary to cancel those errors in order to recognize the current location. After that, the process proceeds to a pattern pull-in routine described later.

On the other hand, if the distance lm exceeds the threshold l th, it is next determined whether or not the vehicle has made a curve (turn right or turn left) (step S24). The method of detecting the curve will be described later. If no curve is made, the difference between the traveling direction θ of the vehicle and the angle θn of the line segment L obtained from the output data of the geomagnetic sensor 1 is compared with the set reference value θth. (Step S2
Five). If | θ−θn |> θth, the process proceeds to the pattern pull-in routine without doing anything. In this case, for example, T
It is conceivable that the player is following a character path in a hitting direction, or traveling on a road that is not stored as map data. Subsequently, it is determined whether or not there is a difficult intersection such as a Y-shaped road with a smaller angle in the vicinity (step
S26). For example, when there is a Y-shaped road in the vicinity, there is a possibility that the road is different from the road on which the vehicle is currently running, so the process proceeds to the pattern pull-in routine without doing anything. Since the data indicating the difficulty level of the intersection is inserted in the difficulty level bit of the intersection data in advance as shown in FIG. 13 (B) when the map is digitized, the CPU 7 can check this bit in step S26. It's good.

If the above two conditions do not apply, it is determined that there is an error in the sensor etc. and it is deviating from the road data,
In this case, the current location is corrected, that is, the road data is pulled in (step S27). New current location guess point Pcpd
As shown in Fig. 24, is the current estimated point calculated from the relative relationship from the previous estimated point Pppd obtained from the sensor output.
Change the display, etc. from Pcp as the point that intersects the perpendicular line drawn to the nearest component L. The distance lm and the coordinates (Xm, Ym) of the current estimated point Pcp are stored as correction values at that point for use in the pattern pull-in routine described later.

If it is determined in step S24 that a curve has been made, an intersection pull-in routine is entered. First, the travel distance lc from the point recognized as the previous intersection is obtained, and the intersection detection threshold l cth is obtained by multiplying the travel distance lc by a constant value ac (step S28). The constant value ac is a value related to the accuracy of the traveling distance sensor 3, and is set to a value of about 0.05, for example. For intersection data entered as map data, current location Pcp
Find the distance lc from each to the intersection (step S29), l
It is determined whether or not there is an intersection with c <l cth (step S30). In step S30, a certain distance range (for example,
It is also judged whether it is within several hundred [m]. here,
If no intersection exists, the process proceeds to the pattern pull-in routine. Also, when it is determined that there are a plurality of neighboring intersections and the distances lc to the intersections are similar to each other and the neighboring intersections cannot be specified (step S31), the process proceeds to the pattern pull-in routine.

When a nearby intersection is specified, the intersection is pulled in as a new current position estimation point Pcpd (step S3).
2). At this time, the distance lc to the intersection and the coordinates (Xc, Yc) of the current position Pcp are stored as the pull-in amount. Also, the current location estimation point Pcpd is stored (updated) as a new recognition intersection.
To do. As a result, when the current position of the vehicle deviates from the road on the map displayed on the display 12, the current position of the vehicle is forcibly placed on the intersection on the map, so-called intersection drawing is performed. Subsequently, the correction coefficients rs, θs for the distance and the bearing are updated based on the coordinates of the previously recognized intersection, the sum of the correction values from the intersection, and the coordinates of the current position (step S33). As described above, when the intersections are recognized, or when the distance between the intersections is long, the correction coefficients rs and θs for the distance and the bearing are updated every time the vehicle travels a certain distance lp, so that the current position can be estimated with higher accuracy. It will be possible.

Next, the pattern pull-in will be described. This routine is executed when running a certain distance l po. Distance l
po has a value of 1000 [m], for example. When the intersection is recognized in step S31, the traveling distance is reset. While traveling a fixed distance l po, the distance lm to the nearest line segment will be measured n = l po / lo [times], and n error correction amounts ei are stored as data. Further, for one measurement, the difference between the error correction amount ei-1 at the previous measurement and the error correction amount ei at this time is calculated as the change amount ci (ei-ei-1).

If it is determined that the vehicle has run a certain distance l po (step S3
4) Calculate the variation in the value of the change amount Ci.
First, the average value (Step S35), and then the deviation α Is calculated (step S36). Then, this value α is compared with a predetermined threshold value αthh (step S37). This value α
Is obtained by considering the detection error of each sensor, the traveling distance, and the like. When α> αthh, it is determined that the pull-in is impossible, and the pattern pull-in is not performed. On the other hand, if α <αthh, it is further determined whether or not retraction is currently performed (step S38). If retraction is not performed, that is, if the current position is at a position deviating from the road data, the current position is the latest. The line segment is pulled in (step S39).
Further, it is compared with the threshold value αthl which is set similarly to the threshold value αthh (step S40), and when α <αthl, the distance and azimuth correction coefficients rs and θs are updated (step S41).

By the method described above, it becomes possible to re-engage on another road after traveling once off the road. That is, when the vehicle travels on a non-digitized road and then on the digitized road again, the road is recognized at the time when the vehicle travels a certain distance, and it becomes possible to accurately estimate the current position. Also, for a fixed distance l po, a longer distance lt
It is also possible to calculate the deviation for and shorten the distance l po to improve the accuracy and shorten the response time. The situation is shown in FIGS. 25 (A) and (B).

As described above, the pull-in to the nearest intersection and the pull-in to the nearest line segment are performed. To perform this pull-in, the road closest to the current location (nearest line segment)
It is necessary to find out the intersection and the nearest intersection. The task of searching for the nearest intersection or the nearest line segment takes a long time if the amount of line segment or intersection data is large, that is, if the search area is large, it may not be possible to smoothly display the current location that changes moment by moment. Become. However, in the present embodiment, as is clear from the data structures shown in FIGS. 2 to 5, the search area from the current position is made as small as possible, and the data of the line segment and the intersection which enter the area are managed. By providing the data (section data, section table), it is possible to search for a line segment or an intersection from the minimum unit section as a search area, so that the time required for the search can be shortened. The procedure of searching for the nearest line segment and the nearest intersection from the current position, which is executed by the CPU 7, will be described below with reference to the flowchart of FIG.

CPU7 first territory from current location (Crntx, Crnty)
No. (Tx, Ty), Unit No. (Nx, Ny), Section No.
(Sx, Sy) are calculated respectively (steps S50 to S52). This can be obtained by a simple calculation (division) because each area is divided into 2 ⁿ units. Next, using the section as a search area, line segments and intersection data existing therein are loaded by referring to the section table and section data (steps S53 to S55). Based on the loaded data, calculate the distance from the current position to all line segments in the search area (length of the perpendicular to the line segment), the distance to all intersections, and compare them to find the nearest line segment. The nearest intersection can be obtained (step S56). The speed at which the search is performed is proportional to the number of line segments and the number of intersections, but the search method based on the above-mentioned data structure has a small search area (section) and the number of line segments to be calculated. Since the number of intersections and intersections is small, high-speed search is possible.

By the way, in the navigation system, when displaying map data of various scales, if map data of all scales are held, the display can be performed easily and at high speed, but the disadvantage is that the data size on the one hand becomes large. There is. On the contrary, when only the map data with the largest scale is included and other scales are represented by simple reduction, there is a drawback that the data size becomes small but the display becomes slow.

On the other hand, in this embodiment, as is clear from the data structures shown in FIGS. 8 to 10, only the smallest map data with the smallest scale is provided in order to reduce the data size. When displaying the reduced scale data, the display management file and the thinning data are used to speed up the display. The procedure for enlarging / reducing the map executed by the CPU 7 will be described below with reference to the flowchart of FIG.

When the CPU 7 first determines that the scale to be displayed is keyed in from the input device 9 (step S60), the current position (C
Area No. (Anx, An that corresponds to the scale from rntx, Crnty)
y) is obtained (steps S61 to S63), then the reduced scale picture ID is referred to (steps S64 to S66), the map data is loaded according to the start address and data size, and V-
Drawing in each of the 16 areas in RAM (step S6
7). In this way, it is possible to refer to the identified map data that should be displayed by using the picture ID for display management (restricting the roads, place names, etc. to be displayed to important ones as the scale increases). Can be realized.

Also, for polygon and line data, as described with reference to FIGS. 11 and 12, there is no problem even if the display is omitted. 1 or 1 / 100,000 of the map is drawn, the thinning bit is checked (step S68), and the points other than the thinning target are drawn (step S6).
9). In this way, when the map is reduced, when it is displayed on the display, the number of line segments to be displayed can be reduced by thinning out the points that may be omitted from the appearance. It is possible to achieve higher speed.

In the above embodiment, the thinning bit is provided for the polygon and the line data, and the information indicating that is included in the thinning bit at which the display may be omitted.
Data of polygons, that is, polygonal shapes and linear parts such as roads are plotted at equal intervals, and a predetermined rule (for example, if the scale is 1 / 50,000 is skipped one by 1 / 100,000)
In the case of, it may be thinned out according to 4 skips, etc.,
The same effect can be obtained.

Next, step S24 in the flowchart of FIG.
The method of judging the curve (right turn / left turn) will be explained.

Basically, for example, a geomagnetic sensor 1 which is a direction sensor
If a right turn or a left turn is determined based on the output data of 1. and a bend is detected, the intersection pull-in is performed by the processing from step S28. However, the geomagnetic sensor 1 is vulnerable to disturbance, and when a large vehicle (for example, a truck or a bus) passes by the vehicle at the level crossing, at the railway bridge, or at the side of the vehicle, a large error is included in the output data. If this data is used as it is for right / left turn determination, it will be mistaken for a straight turn, and the intersection will be pulled in even if it is not an intersection, and the current location will be displaced from the correct position.

Therefore, in this example, in order to determine that the vehicle is bent, the radius of curvature and the vehicle speed are used as criteria for determination,
It is possible to make an accurate right / left turn decision. Below, CPU7
The procedure of the method for determining a right turn / left turn executed by will be described with reference to the flowchart in FIG. 28. First, the CPU 7 determines that a curve (a right turn or a left turn) is made when the vehicle turns a certain angle (for example, 40 degrees) or more while traveling a certain certain distance (for example, 15 [m]) (step S70). However, when curved, the radius of curvature R at that time is a constant value Rmin (for example, 3.5 [m]) that is the minimum criterion turning radius.
In the following cases, it is determined that the data is incorrect and it is not determined that the data is curved (step S71). This is because the vehicle cannot bend below the minimum turning radius of the automobile. Further, the vehicle speed S is a constant speed Smax which is the maximum speed for judgment.
((For example, 40 [Km / h]) or more, it is usually unthinkable to turn at an intersection, so above this speed,
It is not determined that the curve has been made (step S72). In addition, the right turn / left turn can be determined, for example, in the east direction of 0 degrees and in the north direction of 90 degrees.
If the west is 180 degrees and the south is 270 degrees, the direction can be increased or decreased (step S73).
That is, the direction in which the bearing increases turns left (step S74),
Since the direction in which the bearing decreases is the right turn (step S75), it is possible to judge the right turn or the left turn by this.

The radius of curvature R is, as shown in FIG.
Let θ be the angle formed by the azimuth of the vehicle at point b and the azimuth of the vehicle at point b that has traveled a fixed distance 1 from point a, since 1 = R · θ. It can be obtained from the following equation R = 1 / θ.

Also, due to the intersection pull-in performed by the processing according to the flow of FIG. 22, it is controlled so that the current location is always located on the road of the map displayed on the display. For example, the distance between the intersections is long. In this case, the current location is slightly corrected during that time, but the distance difference between the actual current location from the previously pulled-in intersection and the current location on the map is caused by the distance error due to sensor accuracy, calculation error, map accuracy, etc. The error increases as the distance between the intersections increases. In such a case, if there are a plurality of intersections in the vicinity of the intersection so as to be retracted next, there is a possibility that retraction may be performed at an incorrect intersection. Therefore, in this embodiment, when the vehicle travels a certain distance between the intersections, the so-called travel distance is used. The procedure will be described below with reference to the flowchart in FIG.

First, an initial value is set (step S80). As this initial value, a certain fixed current location is required, but this can be the current location when the user first sets it or pulls it to a fixed point such as an intersection, or if it is already fixed If the data is registered in the non-volatile memory, it only has to be set once. The mileage is reset to zero at this confirmed current position (step
S81), turning at an intersection (step S82), and whether the vehicle has run a certain distance (step S83), while constantly observing a certain distance, the point on the map that was reset to zero based on the map data (previous detection position) ) To obtain a point at a certain distance, change the current position to that point, and pull in (step S84). While driving for a certain distance, draw a perpendicular line on the apparently closest line segment and draw in the intersection (step S85) so that the current position of the vehicle is placed on the road of the map displayed on the display. You can When it is detected that the vehicle is bent, the intersection is pulled in (step S86). This intersection pull-in is as described above.

In addition, even if it is judged that the vehicle has made a turn at an intersection, the pull-in based on the traveling distance can be effectively used. That is, it is possible to determine from the map data the curved intersections depending on the distance between the intersections and the traveling distance.

As described above, according to the present invention, when the map data is stored in the memory, only the map data of the maximum scale is stored, and the linear portions of the map are equally spaced from the start point to the end point. Stored as continuous point coordinate data of
When displaying the linear portion, the point coordinate data is extracted every predetermined number, the linear portion is displayed based on the extracted point coordinate data, and the predetermined number increases as the scale increases. By displaying the linear part in this way, it is not necessary to judge whether to thin out or not thin out for each point coordinate data, so there is no information on whether thinning is possible or not for each point coordinate data. Therefore, the data size can be reduced. Further, when the map is reduced, the point coordinate data for displaying the linear portion is reduced, so that the drawing speed can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an in-vehicle navigation device according to the present invention, and FIGS. 2 (A) to (C) to 13 (A) and (B) are stored in the recording medium in FIG. Diagram showing the data structure of map information, Fig. 14 (A) to (C)
Is a diagram showing a screen configuration on the V-RAM, FIGS. 15 to 18 are flowcharts showing basic procedures executed by the CPU in FIG. 1, and FIGS. 19 to 21 are azimuth correction coefficient θs. FIG. 22 is a flow chart showing the procedure of the intersection pull-in routine and the pattern pull-in routine executed by the CPU, and FIGS. 23 and 24 show the positional relationship between the current position on the map and the nearest line segment. Fig. 25 is a diagram showing another method of pulling in a road, Fig. 26 is a flow chart showing a procedure for searching for nearest line segments and intersections, and Fig. 27 is a flow chart showing a procedure for enlarging / reducing a map. , Fig. 28 is a flow chart showing the procedure of the method for determining a right turn or left turn, and Fig. 29 is a diagram showing a method of obtaining a radius of curvature.
FIG. 30 is a flowchart showing the procedure of the pull-in method based on the traveling distance. Explanation of symbols of main parts 1 ... Geomagnetic sensor, 2 ... Angular velocity sensor 5 ... System controller 7 ... CPU, 10 ... Recording medium 12 ... Display, 14 ... Input device

 ─────────────────────────────────────────────────── ─── Continuation of the front page Jury President Judge Ishihisa Yoshihisa Judge Jitsuhiko Koizumi Judge Toshihiko Kino (56) References JP 59-164583 (JP, A)

Claims (1)

(57) [Claims] 1. A display method for displaying map data stored in a memory on a display at a scale selected from a plurality of scales, wherein a minimum scale is used when the map data is stored in the memory. Only the map data of the rate is stored, and for the linear part of the map, the point from the start point to the end point is stored as continuous point coordinate data at equal intervals, and when displaying the linear part, the point Displaying the map data, wherein the coordinate data is extracted every predetermined number and the linear portion is displayed based on the extracted point coordinate data, and the predetermined number increases as the scale increases. Method.