JP2781477B2 - Digital map generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital map generator for creating a map based on three-dimensional digital position data, and more particularly to an apparatus for performing a shaded display by height data.

[0002]

2. Description of the Related Art A safe flight can be expected by using a radar together with a radar if a topographic map around or ahead can be displayed in real time on a CRT according to the current position of the aircraft. As such a device, a normal map is read by a scanner and stored in a memory,
In some cases, data corresponding to the own device position is read from a memory and displayed. However, this device merely displays the necessary area from the original map, and cannot process the data, so that a desired map cannot be obtained.

Therefore, a digital map generator that creates a map based on three-dimensional digital data obtained by adding altitude information to two-dimensional position information has been used. According to this device, since the data can be processed at will, a desired map can be obtained.

For example, in order to display a map three-dimensionally with altitude data, there is a color display in which colors are classified according to altitude, and this display is suitable for viewing the distribution of altitude.
Not suitable for viewing terrain conditions such as undulations. Therefore, the terrain on the map is captured as a three-dimensional thing with undulations so that it can be displayed three-dimensionally on a flat map like a bird's-eye view, and by illuminating the light from one direction, the locations illuminated by light can be seen. There is a display method in which a shadow is added to darken a portion that is bright and becomes a shadow of light. As a process for performing shadowing, a normal vector to the terrain processing unit area is obtained by calculation, and the brightness level of the shadow with respect to the surface is determined from the relationship between the normal vector and the light vector (light incident direction). Is adopted.

[0005]

By the way, in the case of the shadow display, a heading-up display mode in which the traveling direction of the aircraft itself is always directly above the display screen is generally adopted, and when the traveling direction of the aircraft is changed. In, the direction of the display on the screen is changed while the orientation of the own device shown in the display screen is fixed. In the direction conversion, the shadow data calculated together with the pixel position data is also rotated.

FIG. 1 shows, for example, a trapezoidal display object having a raised central portion. The light is directed obliquely to the upper left as indicated by an arrow, so that shadows are formed on the lower right slopes C and D. Attached. Assuming that the aircraft has changed its direction by 180 ° from this state, the display object rotates with the shadow.
On the slopes C and D on the upper left. That is, since the direction of light also rotates with the rotation of the display object, the shadow also rotates. However, since the direction of the light is generally determined at the upper left, it does not look trapezoidal in the display of FIG. 2 and may be erroneously recognized as a frame having a concave center.

In order to eliminate such a problem, the lower right slopes A and B in FIG. 2 must be shaded. For that purpose, it is necessary to perform a calculation for shadowing on all the rotated pixels, which requires a huge amount of calculation. Could not be processed. The present invention has been made to solve the above-described problem, and has as its object to provide a digital map generator capable of performing a shadowing operation at high speed.

[0008]

SUMMARY OF THE INVENTION A digital map generator according to the present invention illuminates a map created from a map database having three-dimensional position data with light rays from a certain direction, and determines whether the light rays hit an image in the map. A digital map generator configured to superimpose and display shades of light and shade on the image, wherein, as inclination in each unit area of terrain processing read from a map database, elevation data in the unit area, east-west and north-south directions A slope calculator for calculating a gradient of an altitude difference in the two directions from altitude data of a unit area adjacent to the unit area, and data of a shadow generated when a light beam is applied from a specific direction is stored in advance for each inclination of the unit area. And a shadow table read out from the brightness table ROM. To.

[0009]

According to the present invention, as an inclination in each unit area,
From the elevation difference between adjacent unit areas in the east-west direction and north-south direction and the horizontal distance to the adjacent unit area,
The gradient of the elevation difference in each of the two directions is obtained by the inclination calculator.

On the other hand, when a light beam is applied from a specific direction,
Shadow data indicating what kind of shading occurs when the unit area is inclined (in two directions) is stored in a luminance table ROM as a check table in advance, and this luminance table ROM is referred to. Thereby, the shadow data is read from the inclination calculated by the inclination calculation unit. According to this calculation method, the normal vector in a unit area is obtained, and the calculation can be performed at a higher speed as compared with the conventional calculation method in which shadow data is obtained from a product of the vector in the ray direction. Becomes possible.

[0011]

FIG. 3 is a control block diagram showing one embodiment of the apparatus of the present invention. Reference numeral 1 denotes a map database that stores map data in three dimensions, and uses map data provided from national land numerical information as data to be stored. This map data is a grid of 100m x 100m across Japan.
It is divided into regions (unit area for terrain processing, hereinafter referred to as pixels), and elevation data and information on roads, rivers, railways, etc. are given to each pixel. In this apparatus, based on this map data, the data is subdivided into pixels of 50 m × 50 m by interpolation, and the data is compressed, and the map data of the area of 200 km × 200 km is stored in one memory cassette. By replacement, map data for a desired area can be taken.

Reference numeral 2 denotes a map image generator for reading map data of a desired area from the map database 1. 3 is
This is an interface for map operation data used for changing the position of the own vehicle, the traveling direction, and the display range obtained from the navigation device, and is sent to the map image generation unit 2.
Reference numeral 4 denotes an inclination calculating unit for obtaining the inclination of the pixel from the map image from the map image generating unit 2. The detailed calculation method will be described later. Reference numeral 5 denotes a map image memory for storing map image data (elevation) generated by the map image generation unit 2 and inclination data calculated by the inclination calculation unit 4. 6 is
An elevation color classification look-up table for reading out color data classified by elevation according to the elevation data from the map image memory 5. Reference numeral 7 denotes pre-registered from the inclination data from the map image memory 5 and the light beam direction transmitted from the interface 3. This is a luminance table ROM for reading out shaded data from the luminance table that has been set, and the luminance table ROM 7 will be described later in detail. 8 and 9 are
D / A converters for converting data read from the elevation color classification look-up table 6 and the luminance table ROM 7 from digital to analog.
A modulator for superimposing the shadow data from the D / A converter 9 on the altitude data from the / A converter 8, and 11 is a display.

FIG. 5 shows the calculation performed by the inclination calculator 4.
This will be described below. Each area divided into squares is 50mx
The pixel is 50 m, which corresponds to one pixel on the display 11. The length of each arrow pointing upward indicates the elevation data at each pixel. The slope of each pixel is indicated by the slope between adjacent pixels in the east-west direction and the north-south direction. For example, the inclinations θ ₁ and θ ₂ of the pixel R are represented by θ ₁ = tan ⁻¹ (ΔZx / Δx) and θ ₂ = tan ⁻¹ (ΔZy / Δy). Δx is the length to the pixel S adjacent on the east side, ΔZx is the elevation difference between the pixel R and the pixel S, Δ
y is the length to the pixel T adjacent to the north side, ΔZy is
This is the elevation difference between the pixel R and the pixel T.

When the inclinations θ ₁ and θ ₂ with respect to the adjacent pixels in the two directions are obtained as described above, the inclinations θ ₁ and θ ₂ are calculated as shown in FIG.
As shown in, the angle ranges A to G obtained by dividing 0 ° to 180 ° into seven sections with respect to the east-west and north-south baselines are checked, and codes I to G corresponding to the angle ranges A to G are determined. VII is assigned and map image memory 5
Sent to

FIG. 7 is stored in the map image memory 5.
The data structure of each pixel is shown, and the above-mentioned codes I to VII are added as 3-bit data as inclination data θ ₁ and θ ₂ to 8-bit elevation data.
By increasing the number of bits of the inclination data, the number of sections of the angle range in FIG. 6 can be increased.

FIG. 8 shows that the ray direction is 225 ° as in FIG.
The luminance table ROM 7 includes 360 luminance tables if the resolution in the light beam direction is 1 °. In FIG. 8, if the inclination data θ ₁ and θ ₂ of a certain pixel have codes III and V, “4” is read as shadow data for this pixel. The smaller the value of this shadow data, the more the pixel faces in the ray direction,
Therefore, the shadow for this pixel is light, and conversely, if the shadow data is large, the shadow will be dark.

The operation of the apparatus having the above configuration will be described below. First, when the position of the own device and the traveling direction obtained from the navigation device are input to the map image generating unit 2 via the interface 3, an area for one screen including the position of the own device is read from the map database 1. At that time, the position of the own device can be located not only at the center of the display as shown in FIG. 1, but also at an arbitrary position, and the range of the read area changes accordingly. In the map data obtained from the map image generation unit 2, the elevation data for each pixel is stored at a predetermined address of the map image memory 5. At the same time, FIG.
As described above, the inclination calculator 4 calculates the inclination data for each pixel (I indicating the inclination range in the east-west and north-south directions).
To VII) are calculated and stored in the map image memory 5 together with the altitude data as shown in FIG.

Elevation data and inclination data are read from the map image memory 5 for each pixel, and sent to a color-coded look-up table 6 and a luminance table ROM 7, respectively. In the color-coded lookup table 6,
By referring to the table, the data is read as color data for each altitude, and is converted into an analog signal by the D / A converter 8 and transmitted to the modulator 10. On the other hand, in the luminance table ROM 7, as described above, the shadow data is read from the luminance table of the ray direction 225 ° for each pixel,
The signal is converted into an analog signal by the / A converter 9 and transmitted to the modulator 10. When the shadow data is superimposed on the color data by the modulator 10, the CRT 11 is color-coded according to the altitude, and occurs when a light beam from one direction irradiates a map in which the traveling direction is above the screen. A shadow is added.

The position of the own device is constantly moving, and color data and shadow data are obtained for each pixel of the map data newly read from the map database 1 in the same manner as described above. Then, the map displayed on the display 11 is sequentially moved downward by being displayed on the upper part of the screen on the display 11.

Further, when the traveling direction of the own device is changed by the angle θ, the position data is rotated by θ in polar coordinates in the map image generating section 2, so that the traveling direction is always displayed directly above the display 11. The displayed map will be displayed. Also, the inclination of each pixel is calculated from the rotated position data and the light rays from the fixed direction, and the shadow data is obtained. However, since this calculation is performed at a high speed, the data is displayed on the display 11. For a given map, a shadow in a fixed direction is cast in real time.

FIG. 4 shows a modification of FIG. 3. The table 21 is provided with the functions of the color-coded look-up table and the luminance table of FIG.
Is a single system, and the modulator 10 can be omitted.

[0022]

As described above, the gradient of each elevation difference in the two directions is determined from the elevation difference between the unit areas adjacent in the east-west direction and the north-south direction and the horizontal distance to the adjacent unit area. On the other hand, when a light beam is applied from a specific direction, the shadow data stored in advance as a table corresponding to the gradient of the unit area is read out. Data can be obtained. Therefore, when you change the direction of the aircraft,
In each case, since the shadowing calculation can be performed in real time, the direction of the light beam can be fixed even when the image in the display is rotated due to a change in the direction of the body, and as a result, an easily viewable map can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a shadow of an image when a light beam is applied to a two-dimensional image from one direction.

FIG. 2 is a view showing a shadow caused by an image when the light ray direction is rotated by 180 ° together with the image in FIG. 1;

FIG. 3 is a control block diagram showing one embodiment of a digital map generator of the present invention.

FIG. 4 is a control block diagram showing another configuration example of the digital map generator of FIG. 3;

FIG. 5 is a diagram showing a calculation method of a pixel inclination performed in the digital map generator of the present invention.

FIG. 6 shows the inclination angle calculated in FIG.
The figure which showed the angle range divided into 7 between 0 degrees

FIG. 7 shows data for each pixel stored in the map image memory 5 of FIG.

FIG. 8 is a diagram showing a table of a luminance table ROM of FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 map database 2 map image generation unit 3 interface 4 inclination calculation unit 5 map image memory 6 color lookup table 7 luminance table ROM 8 D / A converter 9 D / A converter 10 modulator 11 display 21 table 22 D / A converter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-200182 (JP, A) JP-A-2-244188 (JP, A) JP-A-2-90191 (JP, A) JP-A-3- 111889 (JP, A) JP-A-2-284197 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G09B 29/00 G06T 1/00 G06T 15/00

Claims (2)

(57) [Claims] 1. A method for irradiating a light beam from a fixed direction on a map created from a map database having three-dimensional position data,
A digital map generator configured to superimpose and display shades of light and shade on the image based on how light rays hit the image in the map, wherein the unit is defined as a slope in each unit area of the terrain processing read from the map database. A slope calculator for calculating the gradient of the height difference between the two directions from the height data in the area and the height data of the unit area adjacent in the east-west direction and the north-south direction; and data of a shadow generated when a light ray is applied from a specific direction. Luminance table RO stored in advance for each inclination of the unit area
A digital map generator comprising M and performing shadowing display based on shadow data read from the luminance table ROM. 2. The luminance table ROM for each direction of a light beam.
2. The digital map generator according to claim 1, further comprising: performing a shadow display when light is applied from an arbitrary direction.