JPH0546076A - Digital map generator - Google Patents

Abstract

PURPOSE:To speed up calculation for a shadowed display and perform real-time processing by reading out shadow data which are stored as a table previously corresponding to gradient of unit area when an object is irradiated with light in a specific direction. CONSTITUTION:Altitude data and inclination data are read out of a map image memory 5, pixel by pixel, and sent out to a color classification look-up table 6 and a brightness data table ROM 7. Then data are read out of the color classification table 6 as color data by altitude and sent out to a modulator 10. Further, the shadow data are read out of the brightness table ROM 7, e.g. a brightness 5 table for a 225 deg. light beam direction, pixel by pixel, and converted by a D/A converter 9 into an analog signal, which is sent out to a modulator 10. In this case, the modulator 10 superposes the shadow data on the color data to add a shadow which is generated at the time of irradiation with light rays in one direction to a map which is colored by altitude on a CRT 11 and has an upward travel direction.

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 a device for displaying a shadow by height data.

[0002]

2. Description of the Related Art If a topographic map of the surroundings or the front of the aircraft can be displayed in real time on the CRT according to the current position of the aircraft, it can be expected to fly safely when used in combination with a radar. As such a device, a normal map is read by a scanner and stored in a memory,
There is a device that reads out the data corresponding to the position of the player from the memory and displays it. However, this device cannot display the desired map because it simply displays the required area from the original map and cannot process the data.

Therefore, a digital map generator has been used which creates a map based on three-dimensional digital data in which altitude information is added to two-dimensional position information. According to this device, the data can be processed arbitrarily, so that a desired map can be obtained.

For example, in order to display a map three-dimensionally with altitude data, there is a color-based display in which the altitude is color-coded, which is suitable for viewing the distribution of altitudes.
It is not suitable for viewing topographical conditions such as ups and downs. Therefore, the topography on the map is captured as a three-dimensional object with undulations so that it can be displayed three-dimensionally on a flat map like a bird's-eye view, and by shining light on it from one direction, the areas illuminated by the light can be identified. There is a display method that gives a shadow that darkens areas that are bright and shadows of light. As the processing for shadowing, the normal vector for the terrain processing unit area is calculated and the brightness level of the shadow on the surface is determined from the relationship between this normal vector and the ray vector (light incident direction). The method of doing is adopted.

[0005]

By the way, in the case of shadowing display, a heading-up display mode in which the direction of travel of the aircraft is always right above the display screen is generally adopted, and when the traveling direction of the aircraft is changed. , The direction of the display on the screen is changed by fixing the orientation of the device shown on the display screen. When the direction is changed, the shadow data calculated along with the pixel position data is also rotated.

FIG. 1 shows, for example, a trapezoidal display object having a raised central portion. Since the light is directed obliquely to the upper left as indicated by the arrow, shadows are formed on the slopes C and D on the lower right side. Attached. If the aircraft changes its direction by 180 ° from this state, the display object rotates with the shadow.
The slopes C and D that came to the upper left are attached. In other words, the shadow also rotates because the direction of the light rotates as the display object rotates. However, since the direction of light is generally set to the upper left, it does not look like a trapezoid in the display of FIG. 2 and may be mistaken for a frame-like shape with a depressed 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 calculation for shadowing on each rotated pixel, which results in a huge amount of calculation, and in a relatively small computer device that can be mounted on an aircraft, real-time processing is required. Could not be processed. The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a digital map generator capable of performing a shadow-casting operation at high speed.

[0008]

The digital map generator of the present invention applies a light ray from a certain direction to a map created from a map database having three-dimensional position data, and determines how the light ray hits an image in the map. A digital map generator for displaying shades of light and shade on the image, as the slope in each unit area of topographic processing read from a map database, elevation data in the unit area, and east-west direction and north-south direction. And an inclination calculator for obtaining the gradient of the elevation difference in the two directions from the elevation data of the unit area adjacent to each other, and the shadow data generated when a light ray is applied from a specific direction, are stored in advance for each inclination of the unit area. And a brightness table ROM for displaying shadow images based on the shadow data read from the brightness table ROM. To.

[0009]

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

On the other hand, when a light beam is applied from a specific direction,
The shade data of what kind of shade (shade in two directions) the unit area has when the shade is generated is previously stored in the luminance table ROM as a table, and the luminance table ROM is referred to. By doing so, the shadow data is read from the inclination calculated by the inclination calculation unit. According to this calculation method, the normal vector in the unit area is obtained, and the calculation can be performed faster than the conventional calculation method in which the shadow data is obtained from the product with the vector in the ray direction. Is possible.

[0011]

FIG. 3 is a control block diagram showing an embodiment of the apparatus of the present invention. Reference numeral 1 is a map database that stores map data in three dimensions, and as the data to be stored, map data provided by national land numerical information is used. This map data is a 100m x 100m grid across Japan.
It is divided into areas (unit area for topographic processing, hereinafter referred to as pixels), and elevation data and information on roads, rivers, railways, etc. are given to each pixel. In this device, based on this map data, it is subdivided into pixels of 50 m x 50 m by interpolation and then data is compressed, and the map data of the area of 200 Km x 200 Km is stored in one memory cassette. By replacing the map data, it is possible to capture map data for a desired area.

Reference numeral 2 is a map image generator for reading out map data of a desired area from the map database 1. 3 is
This is an interface for map operation data used when changing the own position, traveling direction, and display range obtained from the navigation device, and is sent to the map image generation unit 2.
Reference numeral 4 denotes an inclination calculation unit that obtains the inclination of a pixel from the map image from the map image generation unit 2, and the detailed calculation method will be described later. A map image memory 5 stores map image data (elevation) generated by the map image generation unit 2 and inclination data calculated by the inclination calculation unit 4. 6 is
Reference numeral 7 is an elevation color-coded look-up table for reading color data that is color-coded for each altitude according to the elevation data from the map image memory 5, and 7 is registered in advance based on the inclination data from the map image memory 5 and the ray direction sent from the interface 3. This is a brightness table ROM for reading shade data of shades from the existing brightness table, and this brightness table ROM 7 will also be described in detail later. 8 and 9 are
A D / A converter for converting the data read from the elevation color-coded look-up table 6 and the luminance table ROM 7 from digital to analog, and 10 is D
A reference numeral 11 is a modulator for superimposing the shadow data from the D / A converter 9 on the elevation data from the / A converter 8.

FIG. 5 shows the calculation performed by the inclination calculating section 4 described above.
Will be explained. Each area divided into squares is 50m x
It is a pixel of 50 m and corresponds to one pixel on the display 11. The length of each upward arrow 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 to the east side, ΔZx is the elevation difference between the pixel R and the pixel S, ΔZx
y is the length to the pixel T adjacent to the north side, ΔZy is
It is the difference in elevation between pixel R and pixel T.

When the inclinations θ ₁ and θ ₂ with respect to the adjacent pixels in the two directions are obtained in this way, the inclinations θ ₁ and θ ₂ are shown in FIG.
As shown in FIG. 5, it is examined which of the angular ranges A to G is divided into seven sections from 0 ° to 180 ° with respect to the east-west and north-south base lines, and the codes I to G corresponding to the angular ranges A to G are examined. VII assigned, map image memory 5
Sent to.

FIG. 7 shows that the map image memory 5 is stored.
The data structure for each pixel is shown. The above-mentioned codes I to VII are added in 3 bits to the 8-bit elevation data as inclination data θ ₁ and θ ₂ .
By increasing the number of bits of the tilt data, it is possible to increase the number of divisions in the angle range of FIG.

In FIG. 8, the ray direction is 225 ° as in FIG.
In this case, the brightness table ROM 7 includes 360 kinds of brightness 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 pixel have codes III and V, “4” is read as the shadow data for this pixel. The smaller the numerical value of this shadow data, the more the pixel faces the ray direction,
Therefore, the shadow for this pixel is light, and conversely, if the shadow data is large, the shadow is dark.

The operation of the apparatus having the above structure will be described below. First, when the vehicle position and the traveling direction obtained from the navigation device are input to the map image generation unit 2 via the interface 3, a one-screen area including the vehicle position is read from the map database 1. At this time, the position of the own device is not limited to the center of the display as shown in FIG. 1 and can be positioned at any position, and the range of the read area is also changed accordingly. As for the map data obtained from the map image generation unit 2, the altitude data for each pixel is stored in a predetermined address of the map image memory 5. Moreover, at the same time, FIG.
As described above, the tilt calculator 4 calculates the tilt data for each pixel (I indicating the tilt range in the east-west and north-south directions).
~ VII code) is calculated and stored in the map image memory 5 together with the elevation 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 lookup table 6 and a luminance table ROM 7, respectively. In the color-coded lookup table 6,
By referring to the table, it is read as color data for each altitude and converted into an analog signal by the D / A converter 8 and sent to the modulator 10. On the other hand, in the brightness table ROM 7, as described above, the shadow data is read from the brightness table in which the ray direction is 225 ° for each pixel, and D
The analog signal is converted by the / A converter 9 and sent to the modulator 10. This modulator 10 superimposes shadow data on the color data, which causes the CRT 11 to be color-coded according to altitude and to be emitted when a light beam from one direction is applied to a map whose traveling direction is above the screen. A shadow is added.

The position of the vehicle itself 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 accordance with the movement in the same manner as described above. Then, the map displayed on the display 11 is moved downward by being displayed on the display 11 at the upper part of the screen.

Further, when the traveling direction of the aircraft is changed by the angle θ, the position data is rotated by θ in polar coordinates in the map image generation unit 2, so that the traveling direction is always displayed directly on the display unit 11. The map will be displayed. Also, the tilt for 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 high speed, it is displayed on the display unit 11. On the existing map, the shadows of light rays in a fixed direction are added in real time.

FIG. 4 shows a modification of FIG. 3, in which the table 21 has the functions of the color-coded lookup table and the luminance table of FIG.
Is one system, and the modulator 10 can be omitted.

[0022]

As described above, from the elevation difference between the adjacent unit areas in the east-west direction and the north-south direction and the horizontal distance to the adjacent unit area, the gradient of each elevation difference between the two directions. On the other hand, when a light ray 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. You can get the data. Therefore, when you change the direction of travel of the aircraft,
Since the shadowing calculation can be performed in real time each time, the direction of the light beam can be fixed even if the image on the display rotates due to the change in the orientation of the aircraft, and as a result, an easy-to-see map can be provided.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a shadow of an image when the light ray direction is also rotated by 180 ° with the image in FIG.

FIG. 3 is a control block diagram showing an 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.

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

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

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

FIG. 8 is a diagram showing a table of a brightness table ROM of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 map database 2 map image generation part 3 interface 4 inclination calculation part 5 map image memory 6 color-coded look-up table 7 brightness table ROM 8 D / A converter 9 D / A converter 10 modulator 11 indicator 21 table 22 D / A converter

Claims (2)

[Claims] 1. A light beam is applied from a fixed direction to a map created from a map database having three-dimensional position data,
A digital map generator adapted to superimpose shades of light and shade on an image in a map depending on how light rays hit the image, and the unit of the slope in each unit area of terrain processing read from a map database. The slope calculator that calculates the slope of the elevation difference in the two directions from the elevation data in the area and the elevation data of the unit areas adjacent in the east-west direction and the north-south direction, and the shadow data generated when a ray is applied from a specific direction A luminance table RO stored in advance for each inclination of the unit area
A digital map generator including M and performing shadow display based on shadow data read from the brightness table ROM. 2. The brightness table ROM for each direction of light rays
The digital map generator according to claim 1, further comprising: a shadow map display when light is applied from an arbitrary direction.