JP3376873B2 - Stereo map drawing method and navigation system using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to the three-dimensional map drawing method can be used in automotive or portable navigation systems, and relates to navigation cis <br/> te beam to use it.

[0002]

2. Description of the Related Art Conventionally, as stereoscopic map display software, for example, "Bird's Vi" of the Japan Map Center.
ew ”is known. This conventional 3D map display software can display 3D topographic shapes based on elevation mesh data.
The data is displayed as a three-dimensional image, and line data such as administrative boundaries, roads, railways, rivers, etc. called FD maps and point data such as place names and government offices are superimposed and displayed.

[0003]

However, in such a conventional stereoscopic map display software, a stepped color (a predetermined different display color depending on the altitude is displayed in a stepwise manner to display the topographic shape three-dimensionally. Doing) and shading etc. calculate and determine the display color of each point inside the program based on the elevation data, so the amount of calculation becomes enormous.
It takes a long processing time, and in particular, when it is installed in an on-vehicle or portable navigation system and executed, the characteristic of its nature is that the map display position changes momentarily due to the movement of the current position, and it also has a limited processing capacity. It was impossible to put it into practical use because it could only be equipped with a processor.

The present invention has been made in view of the above conventional problems, and is provided with elevation division, environment division, land use division, etc. as terrain image data, and the elevation value data is given to this image to form a three-dimensional shape. converted to, and reduce the amount of arithmetic processing by displaying, three-dimensional map drawing method can be accelerated drawing processing speed, and to provide a navigation system to use it.

[0005]

According to a first aspect of the present invention, a display target area is determined based on input information of a display reference point position coordinate and a line-of-sight direction angle, and terrain image data, elevation data of the display target area, and The map element data is read from the storage means, the elevation value of each point belonging to the display target area is calculated based on the elevation data, and each point belonging to the display target area is compared with the terrain image data of the display target area. And a height value thereof are used to create a three-dimensional model that represents the topographical shape, and the map element data of the display target area is given a height value based on the height data as necessary, and is necessary for drawing. Display element data having display position coordinates and display attributes is created, parameters required for conversion processing from 3D map coordinates to 2D drawing coordinates are calculated, and the 3D model and Three-dimensional map drawing data in which the display element data is coordinate-converted using the coordinate conversion parameter, and an actual display color is assigned to the color information of the three-dimensional model and the display element data by referring to the color table. Create the color table, display the
Elevation area close to the elevation value based on the elevation value of the reference point
Increase the change in display color with respect to the change in
Change of display color for elevation change in elevation area away from high price
The three-dimensional bird's-eye view map is changed so that the display means displays the three-dimensional bird's-eye view map.

[0006]

The navigation system according to the invention of claim 2
Tem is terrain image data, elevation data and map elements
Storage means for storing data, display reference point position coordinates and
An output means such as a display reference point for outputting the line-of-sight direction angle;
Display reference point position coordinates output by output means such as display reference point
And the display target area is determined based on the information of the viewing direction angle
However, the terrain image data and elevation data
Data and map element data from the storage means,
Draw the three-dimensional map by executing the arithmetic processing required to display the bird's-eye map
The arithmetic processing means for creating data and the arithmetic processing means
The 3D bird's-eye view map is displayed by the created 3D map drawing data.
And a display means for displaying the
It has the means of (a)-(g),
is there. (A) Based on the display reference point position coordinates and the line-of-sight direction angle
Display target area determining means for determining the display target area by: (b) the elevation value of each point belonging to the display target area;
Elevation determining means for calculating based on elevation data, (c) for the terrain image data of the display target area
The altitude of each point belonging to the display area
Terrain shape that creates a three-dimensional model that represents the terrain shape based on
Shape model creating means, (d) is required for the map element data of the display target area.
If necessary, give an elevation value based on the elevation data and draw
Display element with display position coordinates and display attributes required for drawing
Display element data creating means for creating data, (e) Conversion processing from 3D map coordinates to 2D drawing coordinates
Of coordinate conversion parameters to calculate parameters required for
Means, (f) using the coordinate conversion parameters for the three-dimensional model
Coordinate conversion, and the 3D model and display element data
The color table illuminates the color information of the data
Then, assign the actual display color and calculate the 3D map drawing data.
The drawing processing means to be output , and (g) the three-dimensional model and the display element data have
The color table for making the color information corresponding to the actual display color
Based on the elevation value of the display reference point,
The change in the display color with respect to the elevation change in the elevation area close to the value is large.
Kikushi, versus altitude changes in altitude region remote from the target height value
Colors that change so as to reduce the change in display color
Table change means.

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

According to the three-dimensional map drawing method of the first aspect of the present invention, the terrain shape of a certain display target area determined based on the display reference point and the line-of-sight angle from a certain viewpoint is used as the terrain image data and the map element. Since it can be displayed as a color 3D bird's-eye view map that includes the contents of data, it improves visibility.
Elevation area that can be raised and is close to the elevation reference point
The change in the display color with respect to the elevation change of
Change of display color for elevation change in elevation area away from point
So that the user can visually
It becomes possible to easily grasp the difference in elevation.

The navigation system of the invention of claim 2
According to the view reference point and the line-of-sight angle,
The terrain shape of a certain display target area determined by
3D bird including contents of image data and map element data
It can be displayed as a top-down map on the display and
Visually easy for users, even in areas with little change
Color three-dimensional bird's-eye view that makes it possible to grasp the difference in elevation
You can draw a diagram.

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a functional configuration of a navigation system that uses a stereoscopic map drawing method according to an embodiment of the present invention. This navigation system includes an external storage device 1 that reads out necessary data from a recording medium in which terrain image data 101, elevation data 102, and map element data 103 are recorded, and a position and a direction of a map displayed during a 3D map drawing process. Display reference point etc. output device 2 for measuring and outputting information necessary for defining display reference point position coordinates and line-of-sight direction angle, display reference point input from this display reference point etc. output device 2 An arithmetic processing unit 3 that reads necessary map data from the external storage unit 1 based on the data of the position coordinates and the line-of-sight angle and executes arithmetic processing described later to create three-dimensional map drawing data.
And an image display device 4 for displaying a three-dimensional map based on the three-dimensional map drawing data.

The external storage device 1 includes, for example, a CD-RO.
A drive is used in which a large-capacity storage medium such as an M, DVD, or MO disc is mounted, and necessary data is read from and output from the storage medium.

The terrain image data 101 stored in the external storage device 1 includes elevation classifications, environmental classifications such as lakes and forests, deserts, wilderness, beaches, farmlands, reclaimed land, urban areas, commercial areas, factories, parks, Green areas, amusement parks, golf courses,
It is image data that represents land use categories such as station buildings and airfields in the form of two-dimensional image information such as a bitmap.
For example, in the example shown in FIG. 2, the sections A to E are each less than an altitude of 70 m, 70 to 80 m, 80 to 90 m,
Each region of 90 to 100 m and 100 m or more is shown.
In addition, here, X indicates the region of the golf course regardless of the altitude. The terrain image data 101 is shown in FIG.
As shown in, the inside of the golf course area Y is also divided into a plurality of areas according to the altitude, and it looks more three-dimensional,
A shade Z can be attached together with the elevation section so that those data are also included. Further, in the terrain image data 101 shown in FIGS. 2 and 3, the elevation division and the shaded area are divided with a clear boundary line, but the image data is a gradation that is continuously changed using an intermediate color. Can also be

Such terrain image data 101 is
In principle, it is stored in the storage medium of the external storage device 1 in the form as shown in FIG. That is, the display color (A, B, C, X, etc.) of each dot forming the image is represented by, for example, a code of 8 bits = 1 byte, and arranged in an array corresponding to each dot position. . However, with this form as it is, a huge amount of data storage is required, that is, the number of bytes equal to the total number of dots. Therefore, in general, for example, when the same display color code is continuously arranged as shown in FIG. 5, data compression is performed in a format in which a byte representing the number of dots whose display color is continuous is added to the 1-byte display color code. The way to do is taken. However, when the continuous number is 1, the data length is rather increased by adding the dot number bytes, and in that case, only the display color code is arranged. In this case, since it becomes necessary to identify the display color code and the number of consecutive dots, for example, the most significant bit of each byte is used as an identifier. Data compressed in this way generally has a variable length. Now, in the data string of FIG. 5, the D color is 11 dots, the C color is 11 dots, and the B color is
The colors are arranged in this order such as 10 dots, ....

However, in the case of the present invention, the image data is compressed and stored in the form shown in FIG. 6 for the following reason. As will be described later, the terrain shape model creation unit 304
Shape modeling of the terrain by dividing the terrain image data into several rectangular areas and giving elevation values to the vertices. At this time, if the image data is compressed in display screen units and has variable length data as shown in FIG. 5, the process of cutting out the image corresponding to the specified rectangular area becomes complicated, and each divided area is divided. The processing speed is reduced when trying to form a shape model. Therefore, in the present embodiment, a rectangular division unit constituting the terrain shape model is determined in advance, and the terrain image data is compressed and stored by dividing the dots into ranges corresponding to this.

For example, one screen of the terrain shape model shown in FIG. 4 has square regions R1, R2, R of 8 × 8 dots each.
As shown in FIG. 6, the terrain image data is divided into a range corresponding to 8 dots, and byte data “Brk” representing a division code at each end as shown in FIG.
It is compressed and stored in the form that is added. In FIG. 6, for example, reference numeral R1-1 is a display color data string corresponding to 8 dots in the first row of the square area R1, and reference numeral R7-2 is a square area R7.
Represents a display color data string corresponding to 8 dots in the second row. Thus, when creating the terrain shape model, an image corresponding to a predetermined square area can be identified and cut out by searching and counting this delimiter code.

In the case of cutting out the 8 × 8 dot square area R7 in FIG. 4, the pointer is first advanced to the 8th row × 4 = 32th delimiter code and further skipped to two delimiter codes. That is, the square regions R1 to R
6 The data row corresponding to 8 dots in the first row of each 6 is skipped. Then, up to the next delimiter code, the designated area R
It is read as data 7 and then skipped again up to 5 delimiter codes. That is, the square regions R8 to R
The data row corresponding to 8 dots in the first row of each 12 is skipped. By repeating this process eight times,
The image data for 8 rows of the square region R7 of R7-1 to R7-8, that is, for 8 × 8 dots can be extracted. If the image data is compressed and stored in the form of FIG. 6, 16
It is possible to easily cut out a region having a size of an arbitrary integer multiple of the division unit, such as × 16 dots or 24 × 24 dots.

Further, in the above embodiment, the method of compressing the same-color dots continuous in the one-dimensional lateral direction has been exemplified, but the compression method itself is not limited to this, and, for example, dot partial rows of the same pattern appear repeatedly. In this case, a unique index is added to this and registered, and the appearance position of the pattern is replaced with the byte code indicating the index, or any other compression method is used to create a predetermined shape model. It is possible to compress and store each divided processing unit.

FIG. 7 shows an example of another compression method.
In this compression method, a square area of 8 × 8 dots is used as a division processing unit, and “D” is sequentially arranged from the top for 8 dots in the vertical direction.
The pattern of “3 dots in color, 4 dots in C color, 1 dot in B color” is registered by adding the index “α”, and the index “β” is “2 dots in D color, 4 in C color”.
A unique index is added and registered for each color arrangement pattern in which a pattern of dots and 2 dots of B color is registered. The image data is stored in a unit of a square area of 8 × 8 dots by a combination of this index and the number of consecutive patterns, and a delimiter code “Brk” is added between the image data strings of the square area. Remember. For patterns X1, X2, etc. for which no index is registered, the image data is compressed and stored in the form of the color code and the number of continuous dots thereof.

These compression methods are particularly effective for portable or vehicle-mounted navigation systems that can use only a limited number of colors for color display of maps.

The altitude data 1 02 stored in the external storage device 1 of the storage medium is an actual data of elevation values of the terrain, latitude, specifies the horizontal position by the altitude of the location such as longitude The data format does not matter as long as the value can be read, but in the case of the present embodiment, in order to simplify the correspondence with the terrain image data 101, as shown in FIG. The data in the mesh format is used in which elevation values are added to the intersections of the longitudes (horizontal points). As another data format that can be adopted here, for example, a format such as contour line vector data may be used.

The map element data 103 stored in the storage medium of the external storage device 1 includes position information of elements such as roads and place names displayed on the map, and attribute information of those elements if necessary. is there. The position information is described in two-dimensional coordinates corresponding to longitude and latitude, or in three-dimensional coordinates that combine elevation values. For example, a road is expressed in the form of a straight line or a continuous straight line group, and the position coordinates of a series of point sequences indicating each end point are used as the position information of the road. If necessary, the road type and the like are provided as attribute information. Regarding the place name, the point coordinates indicating the position where the character string is displayed on the map are used as the position information, and the character string itself, the type, etc. are given as the attribute information.

The display reference point output device 2 is composed of a GPS sensor or a vehicle speed sensor, which is a means for measuring and outputting the current position and traveling direction of this device, and a gyro sensor, and the measured current position and traveling direction. Is output as the display reference point and the line-of-sight direction angle.

The arithmetic processing unit 3 stores a RAM for storing various variable data and a ROM in which a three-dimensional map drawing program is registered (this includes a ROM that can be re-registered when the program is upgraded, such as a flash memory). Sometimes adopted), a small computer with an input / output interface is used.

The arithmetic processing unit 3 creates the stereoscopic map drawing data by executing the stereoscopic map drawing processing program registered in the ROM. The main processing functions of this program are shown in FIG. As shown, the display target area determination unit 301, the altitude determination unit 302,
The coordinate conversion parameter determining unit 303, the terrain shape model creating unit 304, the display element data creating unit 305, the color table changing unit 306, and the drawing processing unit 307 are included.

The display target area determination unit 301 determines the target area on the map to be displayed on the screen according to the information on the current position and the traveling direction input from the output device 2 such as the display reference point,
Required terrain image data 101, elevation data 102,
A process of reading the map element data 103 from the external storage device 1 is performed. The altitude determining unit 302 performs a process of determining altitude values of various points based on the read altitude data, and the coordinate conversion parameter determining unit 303 determines the display reference point and its altitude value (the altitude determining unit as described later). (Determined in step 302), the processing for determining the viewpoint position and line-of-sight direction angle required for coordinate conversion is performed.

Further, the terrain shape model creating unit 304 uses the elevation determining unit 302 for the read terrain image data.
Then, the display element data creation unit 305 gives the elevation value to the read map element data by the elevation determination unit 302 if necessary. , Processing for creating display element data having position coordinates and display attributes necessary for drawing. Then, the color table changing unit 306 performs a process of changing a color table that associates the actual display color with the color information of the terrain shape model and the display element data at the time of the drawing process based on a predetermined condition. Part 30
Numeral 7 refers to the color table changing unit 306 to execute a drawing process by converting the coordinates of the created terrain shape model and the display element data, and assigns a display color according to the altitude classification to display an image as a stereoscopic map image. The process of outputting to the device 4 is performed.

Next, the three-dimensional map drawing process executed by the navigation system having the above configuration will be described.
FIG. 9 shows a flowchart of a stereoscopic map drawing program executed by the arithmetic processing unit 3. This three-dimensional map drawing program determines a display target area (step S01), a process of reading topographic image data, altitude data and map element data (step S02), determines an altitude value of a display reference point (step S03), and a three-dimensional map. Determination of coordinate conversion parameters from coordinates to two-dimensional display coordinates (step S04),
Creation of terrain shape model (step S05), creation of display element data (step S06), determination of color table (step S07), execution of coordinate conversion (step S0).
8), a series of processes of the drawing process (step S09) on the display device 4 is repeatedly executed until the display process stop command is input (step S10).

First, the display target area is determined (step S0
In 1), the object on the map which the display target area determination unit 301 intends to display on the screen of the display device 4 based on the position coordinates and the line-of-sight angle of the display reference point output by the output device 2 such as the display reference point. Determine the area. Here, the display reference point is a representative point in the display screen for determining the position of the displayed map, and the line-of-sight direction angle is the azimuth angle of the line of sight of the bird's-eye view of the map in the horizontal plane. In the in-vehicle navigation system, when displaying a map around the current position of the host vehicle, the current position and traveling direction measured by the GPS sensor or the vehicle speed sensor and the gyro sensor are used as display reference points. It is used as position coordinates and line-of-sight direction angles.

FIG. 10 shows the positional relationship between the display reference point and the line-of-sight direction angle and the display target area.

The map projection method may be arbitrary, but in the present embodiment, the perspective projection method centered on the viewpoint defined above the display reference point is used. Therefore, if the height of the viewpoint coordinates is set to an offset value h from the display reference point elevation value, and the line-of-sight depression angle θ, the display reference point display position δ, the viewing angle β, and the display screen horizontal / vertical ratio (aspect ratio) s are given, The display target area can be specified by a (x, y) two-dimensional coordinate system corresponding to longitude and latitude within a virtual horizontal plane having the same elevation as the display reference point, regardless of the display reference point elevation value. Two-dimensional position coordinates (Px, Py) excluding the elevation value of the display reference point,
When the line-of-sight direction angle φ is given from the output device 2 such as the display reference point, the display target area is obtained using parameters such as h, θ, δ, β, and s. Here, parameters such as h, θ, δ, β, and s may be uniquely set according to the device specifications, or some or all of the high-performance devices may be arbitrarily set by the user. Let's assume that it has already been set to a specific value.

Next, the display target area determination unit 301 reads from the external storage device 1 the terrain image data, the altitude data and the map element data in a range which sufficiently covers the display target area obtained in the previous step S01 (step S0).
2). At the time of this reading, if some or all of the necessary data has been used for the previous display processing and has already been saved in the internal memory of the arithmetic processing unit 3, the duplicated part is saved in the memory instead of being read again. You will use the one you have.

Then, the altitude determining unit 302 calculates the altitude value Pz of the display reference point using the read altitude data (step S03). That is, since the horizontal position coordinates (Px, Py) of the display reference point are given from the display reference point etc. output device 2, this is applied to the read elevation data to read the elevation value of the corresponding position. . In the case of the elevation data in the mesh format shown in FIG. 8, Pz is to be obtained by interpolation using the elevation values of the grid points of several points closest to the given horizontal position coordinates (Px, Py). become. For example, as shown in FIG. 11, in order to obtain the elevation value Pz of the point P from the three points A, B, and C that are close to the display reference point P, the horizontal position coordinate of the point A is (Ax, Ay), and the elevation is The value is Az, and the horizontal position coordinate of the point B is (Bx, B
y), the elevation value is Bz, and the horizontal position coordinate of the point C is (C
x, Cy) and the elevation value is Cz,

[Equation 1] Is calculated.

Further, from the four points A, B, C, D to the display reference point P
To obtain the elevation value Pz of, the coordinates of point D are (Dx, D
y, Dz),

[Equation 2] Is calculated. However,

[Equation 3] Is.

Next, the coordinate conversion parameter determination unit 303
Calculates various parameters required for coordinate conversion from the map coordinate system to the display screen coordinate system (step S04). Since the terrain shape model and display element data are described in three-dimensional coordinates (map coordinate system) equivalent to the real world, this is
This coordinate conversion process is necessary for projecting on the display screen (screen coordinate system) of the display device 4 which is a dimensional plane. In this embodiment, perspective projection conversion is performed with a viewpoint defined above and behind the display reference point as the center of projection. Therefore, first, the viewpoint coordinates (Vx, Vy, Vz) are obtained.

Horizontal position coordinates of display reference point (Px, Py)
And the line-of-sight direction angle φ have already been given, and the elevation value Pz of the display reference point is also obtained in the previous step S03.
Since the viewpoint height offset value h, the line-of-sight depression angle θ, and the display reference point display position δ have already been determined at the stage of determining the display target area in step S01, the viewpoint coordinates (Vx, Vy, Vz) can be obtained by the following arithmetic expression.

[0062]

[Equation 4] Further, the coordinate conversion formula is obtained as follows using the formula (4).

[0063]

[Equation 5] Here, M (bold type) is the map coordinate system (Mx, M) to be converted.
y, Mz) is a homogeneous coordinate obtained by adding 1 as the fourth component. Ds represents the distance from the viewpoint to the display screen in pixel units, and is a value theoretically obtained from the viewing angle β and the number of pixels on the display screen. Further, f and n may be any positive real numbers (theoretically, the upper limit and the lower limit of the depth coordinate in the line-of-sight direction are meant, but the details are omitted).

The homogeneous coordinate T obtained by this conversion formula
For (bold type) = (Tx, Ty, Tz, Tw), the two-dimensional screen coordinates (Sx, Sy) used for drawing are obtained by Sx = Tx / Tw, Sy = Ty / Tw.

Next, the terrain shape model creating unit 304 gives the read terrain image data an altitude value corresponding to the altitude data to create a three-dimensional model representing the terrain shape (step S05). That is, the terrain image data shown in FIG. 2 is regarded as one plane figure obtained by mapping the image on the surface, and this is divided into several rectangles. The size of division is a size determined in advance as a unit of division processing, or an arbitrary integral multiple thereof, as described in the method of compressing and storing terrain image data. Then, for each apex of the divided rectangle, as in the case of the display reference point in step S03, from the position coordinates and the elevation value of the adjacent three or four grid points, the formula 1 to the formula 3 are obtained. The corresponding elevation value is calculated by interpolation calculation using the formula. Here, if the rectangle is divided so that the positions of the vertices of the divided rectangle completely match the altitude description positions of the mesh-type altitude data shown in FIG. 8, interpolation calculation is not necessary, and the altitude is increased. The process of giving a value is simple. By the process of step S05, each rectangle becomes a three-dimensional figure, and as a result, the entire topographical shape is modeled in the form as shown in FIG. The terrain image is stored as display color information of each divided figure.

When dividing the terrain image, FIG.
As shown in 3, by giving the elevation value densely to the part close to the viewpoint and sparsely providing the part far from the viewpoint, the number of divisions can be reduced and the processing speed can be improved without impairing the display quality of the terrain shape model. You can For example, with respect to the region closest to the viewpoint, the size of the rectangle to be divided is set to the size of a predetermined division processing unit, and as the distance from the viewpoint increases, it becomes an integral multiple such as 2 × 2 times or 4 × 4 times. Divide by a rectangle of widening size. In the bird's-eye view display of a three-dimensional map, the area close to the viewpoint is relatively enlarged, and the area far from the viewpoint is relatively compressed and displayed. Therefore, by performing such processing, each divided figure on the display screen will be displayed. Since the sizes are made uniform, the amount of calculation required for modeling the terrain shape can be reduced while optimizing the display quality.

Next, the display element data creating unit 305 creates display element data, that is, graphic data directly delivered to the drawing process, based on the read map element data (step S06). When the map element data has position information of each element such as roads and place names only in the form of two-dimensional coordinates, first, an elevation value is given to this based on the elevation data to make it three-dimensional position information ( However, from the beginning 3
This is not the case if given as dimensional coordinates). Also here, the method of calculating the elevation value of the map element is the same as the method of calculating the display reference point by the equations 1 to 3 in step S03. However, for position information that is not necessarily on the ground surface, for example, for internal constituent points of road links that correspond to tunnels and overpasses, after making a conditional decision based on the attribute information that the map element data has, the elevation of the end points of the link Exceptional processing such as obtaining the elevation value from the data and obtaining the elevation value of the internal constituent points by linear interpolation between both end points can be performed.

When the position information (coordinate values of the drawing figure) as the display element data is fixed, then its display attribute is determined. For example, if the map element data is a road, and if it is to be displayed in different display colors depending on the type of the road, the attributes related to the display color according to the road type given as the attribute information of the map element data. To decide. If the attribute information of the map element data describes that it is a tunnel, it is displayed as a broken line, and a broken line pattern is given to the display attribute. Further, with respect to the map element data representing the place name, different fonts are given as the display attribute of the character string according to the type described in the attribute information. In this way, the display attribute of the corresponding display element data can be determined by appropriately processing the attribute information of the map element data.

Next, the color table changing unit 306 changes the color table if necessary based on a predetermined condition (step S07). The terrain shape data has display color information as the terrain image data mapped on the surface of each divided figure, and the display element data has display color information as its display attribute.
Performs drawing processing by associating the actual display color with these color information. At this time, the drawing processing unit 306 refers to this color table in order to determine which color corresponds to which information. Therefore, it is possible to draw the data having the same color information in completely different display colors without changing the processing speed, only by replacing the color tables in advance.

In this embodiment, a method of changing the display color according to the altitude value of the display reference point is adopted. The method is as follows. As shown in FIG. 12, in the case of drawing a terrain shape using the terrain image data centered on the altitude division, it is possible to visually express the height difference of the terrain by changing the display color. It is easier to understand the shape than when drawing. However, for example, in a terrain where there is not much difference in elevation such as the center of the city, the whole area is included in one elevation section, and as a result, it is often displayed in a single color. On the other hand, the number of display colors that can be used is naturally limited, and especially when the hardware is restricted, such as in a navigation system, and especially when high-speed drawing is required, the restrictions are particularly large. Even if they are taken, they cannot all be assigned different colors.

On the other hand, in the present embodiment, since the display target area of the three-dimensional map is set within a limited range centered on the display reference point, elevation can be finely colored in the vicinity of the display reference point. It is enough if possible. Therefore, by changing the correspondence of the display colors according to the elevation value of the display reference point, it is possible to obtain a stereoscopic map image that can sufficiently express the elevation difference in the display screen even with a small number of colors.

FIG. 14 is a schematic representation of this method. When all the altitude categories are made to correspond to display colors uniformly with a limited number of colors, the color table is as shown in FIG. As shown in the figure, the first to fourth colors are assigned in two groups. Since the elevation value of the display reference point has already been obtained in step S03, if the color table is changed according to the value Pz, it becomes as shown in FIG. For example, if the elevation value Pz of the display reference point is equal to the relatively low point A, the first color distant from the elevation value Pz of the display reference point is assigned over 5 sections, and the second to fourth colors are assigned. If the color table is assigned to each one of the divisions and conversely the elevation value Pz of the display reference point is equal to the relatively high point B, the fourth color distant from the elevation value Pz of the display reference point is divided into four sections. The operation is performed by changing the color table so that the color tables are assigned to each of the first to third colors and assigned to each of the two categories, one category and one category. As a result, although the total number of colors does not change, different display colors are always assigned to adjacent elevation sections in the vicinity of the display reference point Pz, and fine gradation can be achieved in the vicinity of the display reference point.

This color table changing process is not performed every time this process is repeated, but is performed when the altitude of the display reference point changes to a certain extent or more, the amount of calculation can be reduced and the drawing speed can be increased. Can be achieved. In the case of a simplified specification in which the correspondence between the color information and the display color is always constant without changing the color table, the processing in step S07 is skipped, and the calculation is performed in this case as well. The amount can be reduced.

In the color table, display colors are assigned to display color information other than altitude classification, for example, display attributes of display element data such as roads and classifications indicating golf courses indicated by reference symbol X in FIG. Therefore, for these specifications, when the specification is such that a constant color is assigned regardless of the elevation value of the display reference point, a color table that changes only the necessary parts will be used. On the contrary, the elevation value Pz of the display reference point
When the specification is such that the entire display color can be changed according to conditions other than the above, for example, when the specification is such that the overall color tone of the display screen is changed depending on the time zone, the season, and the weather, the hue of the color table as shown in FIG. , The lightness or the saturation is changed from the first color to the fourth color for all the colors (here, the first color to the fourth color). For example, the time zone changes to whitish in the morning, vividly changes in the daytime, and changes to grayish in the night. As for the weather, it changes so that the sky becomes vivid and the cloudy or rainy weather becomes grayish.

Next, the drawing processing unit 307 performs step S05.
The coordinate transformation from the map coordinate system to the screen coordinate system is executed by the equation 5 for each divided figure of the terrain shape model created by the processing of 1. and the individual display element data created in step S06 (step S08). . Then, each figure is drawn with reference to the color table of the color table changing unit 306 to create three-dimensional map image data, which is output to the image display device 4 to generate one three-dimensional map as shown in FIG. It is displayed as a screen (step S09).

When one map screen is displayed on the image display device 4 through the series of processing in the above steps S01 to S09, it is next judged whether or not the map display should be continued, and if so, step S01. Return to and create the next screen, and repeat the process for displaying. If it is not continued, the series of procedures is ended, and the process shifts to another process such as locating and route calculation provided in the navigation system (step S10).

In the above embodiment, the three-dimensional map drawing method executed by the navigation system having the hardware configuration shown in FIG. 1 has been described. However, a program for executing this three-dimensional map drawing method is a CD-ROM as application software. It can be recorded on a recording medium such as a ROM, a DVD, an FD or the like and handled as one product. In this case, a navigation system having an execution program update registration function is used, the external storage device 1 is loaded with the recording medium, and a predetermined operation is performed to write in the internal memory of the arithmetic processing device 3. By doing so, the navigation system can execute the above three-dimensional map drawing processing based on this program.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing an example of terrain image data.

FIG. 3 is an explanatory diagram showing another example of terrain image data.

FIG. 4 is an explanatory diagram showing dot color information of terrain image data.

FIG. 5 is an explanatory diagram of a general compressed data string of terrain image data.

FIG. 6 is an explanatory diagram showing an example of a compressed data string divided into 8 × 8 dot square areas of terrain image data.

FIG. 7 is an explanatory diagram showing another example of a compressed data string divided into 8 × 8 dot square areas of terrain image data.

FIG. 8 is an explanatory diagram of elevation data.

FIG. 9 is a flowchart of a stereo map drawing process according to one embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a positional relationship between a display reference point and a display target area.

FIG. 11 is an explanatory diagram showing a method of calculating an elevation value of a display reference point using elevation data of grid points in the vicinity thereof.

FIG. 12 is an explanatory diagram showing an example in which an elevation value is given to the terrain image data to form a terrain shape model.

FIG. 13 is an explanatory diagram showing a method of dividing the terrain image in the display target region by changing the density according to the distance from the viewpoint.

FIG. 14 is an explanatory diagram showing a method of changing a color table according to an altitude value of a display reference point.

FIG. 15 is an explanatory diagram showing a method of changing the color tone of the entire color table.

FIG. 16 is an explanatory diagram showing a three-dimensional map screen obtained by the three-dimensional map display method of the above embodiment.

[Explanation of symbols]

1 External storage device 2 Display reference point output device 3 arithmetic processing unit 4 Image display device 101 Terrain image data 102 elevation data 103 map element data 301 Display target area determination unit 302 Altitude determination unit 303 Coordinate conversion parameter determination unit 304 Terrain shape model creation unit 305 Display element data creation part 306 Color table change section 307 Drawing processing unit

─────────────────────────────────────────────────── --Continued front page (56) References JP-A-9-138136 (JP, A) JP-A-9-160482 (JP, A) JP-A-6-36013 (JP, A) JP-A-9- 91600 (JP, A) JP-A-10-187029 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G09B 29/00-29/14

Claims (2)

(57) [Claims] 1. A display target area is determined based on input information of a display reference point position coordinate and a line-of-sight direction angle, terrain image data, elevation data and map element data of the display target area are read from a storage means, and the display is performed. The elevation value of each point belonging to the target area is calculated based on the elevation data, and with respect to the terrain image data of the display target area, the terrain shape is calculated based on each point belonging to the display target area and its elevation value. A three-dimensional model is created, and an elevation value is given to the map element data of the display target area based on the elevation data as needed, and a display element having display position coordinates and display attributes necessary for drawing Data is created, parameters required for conversion processing from 3D map coordinates to 2D drawing coordinates are calculated, and the 3D model and the display element data are set to the coordinates. Coordinate transformation using the transformation parameters, and create a three-dimensional map drawing data by assigning actual display color in light of the color table for the color information to which the 3D model and display element data has, the color table Is based on the elevation value of the display reference point
As for the elevation change in the elevation area close to the elevation value,
Increase the change in the display color to increase the altitude range far from the altitude value.
To reduce the change in display color due to the change in altitude of the area
And a stereoscopic bird's-eye view map is displayed on the display means according to the stereoscopic map drawing data. 2. The storage means for storing the terrain image data, the altitude data and the map element data, the display reference point etc. output means for outputting the display reference point position coordinates and the line-of-sight direction angle, and the display reference point etc. output means. The display target area is determined based on the information of the display reference point position coordinates and the line-of-sight direction angle to be output, and the terrain image data, elevation data and map element data of the display target area are read from the storage means,
An arithmetic processing unit that performs arithmetic processing necessary for three-dimensional bird's-eye view map display to create three-dimensional map drawing data, and a three-dimensional map drawing data created by the arithmetic processing unit, and a display unit that displays a three-dimensional bird's-eye view map, The navigation system, wherein the arithmetic processing means includes the following means (a) to (g) . (A) display target area determining means for determining the display target area based on the display reference point position coordinates and the line-of-sight direction angle, (b) the altitude value of each point belonging to the display target area based on the altitude data Elevation determining means for calculating, (c) A terrain shape model that creates a three-dimensional model representing a terrain shape based on each point belonging to the display target area and its elevation value with respect to the terrain image data of the display target area. Creating means, (d) giving an elevation value to the map element data of the display target area based on the elevation data as needed, and displaying the display element data having display position coordinates and display attributes necessary for drawing. display element data creating means for creating, (e) coordinate transformation parameter determining means for calculating a parameter required for the conversion process from the three-dimensional map coordinates to a two-dimensional drawing coordinates, (f) prior to The three-dimensional model is subjected to coordinate conversion using the coordinate conversion parameter, and the actual display color is assigned to the color information held by the three-dimensional model and the display element data by assigning an actual display color to the three-dimensional map drawing data. Drawing processing means for calculating , and (g) the three-dimensional model and the display element data have
The color table for making the color information corresponding to the actual display color
Based on the elevation value of the display reference point,
The change in the display color with respect to the elevation change in the elevation area close to the value is large.
Combining the changes in altitude in the altitude area away from the altitude
Colors that change so as to reduce the change in display color
Table change means.