JPH10288943A - Three-dimensional topography display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional topography display device by which the difference of elevation can be viewed even in an area where the difference is small. SOLUTION: Based on the display reference point position and the direction angle of a display area outputted from a display reference point output device 5, an object area to be displayed is decided by a display object area decision part 11 and topography data corresponding to the object area is read from an external storage device 3. Then, topography shape data is produced by a shape data producing part 13 and transformed to the coordinate of three-dimensional topography data by a coordinate transformation part 21. On the other hand, the reference height value of a display reference point is decided by a reference height value decision part 15 based on the display reference point position and the topography data. Based on the reference height value, a color function is decided by a color function decision part 17. Next, the display color of the topography shape data is decided by a topography display color decision part 19 based on the respective height values of the topography shape data and the color function. Then, a three-dimensional topographical picture is plotted by a plotting processing part 22 based on the three-dimensional topography data and the display color of the topography shape data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional terrain display device for displaying a terrain shape three-dimensionally on the basis of terrain data, and more particularly to a three-dimensional terrain display device for determining a display color according to the elevation of the terrain.

[0002]

2. Description of the Related Art Conventionally, in an atlas or the like, in order to express altitude information in a plan view, for example, there are scattered examples in which different colors are used according to, for example, different altitude values. Even in the three-dimensional terrain display device, it is necessary to allow the user to easily and easily recognize the terrain shape displayed on the two-dimensional screen as a three-dimensional shape.
It is conceivable to draw the terrain shape by changing the display color according to the altitude.

FIG. 12 schematically shows the correspondence between the terrain elevation and the terrain display color in an atlas or the like. Now, a gradually changing display color series is replaced with a real numerical value c for convenience. That is, a certain display color in the series is uniquely associated with an arbitrary real value c in a certain area. When the number of display colors in the series is finite, a real value c (hereinafter, referred to as a display color index).
May be configured so that one display color corresponds to each section obtained by dividing the entire area into a finite number of sections.

[0004] Here, when the horizontal axis represents the topographic altitude h and the vertical axis represents the display color index c, the correspondence between the topographic altitude and the topographic display color in an atlas or the like is, for example, a straight line A or a curve shown in FIG. As shown in B, it can be expressed by a function c (h) such that the display color index c monotonously increases or decreases with respect to the altitude h.

In a three-dimensional terrain display device for displaying a terrain shape three-dimensionally on the basis of terrain data, if the display color is determined based on this correspondence and the terrain is drawn, for example, FIG.
As shown in FIG. 7, the terrain shape 101 can be visually represented.

[0006]

However, in order to visually represent the height difference of the terrain by using such a method, the variation of the altitude h corresponding to the height difference to be identified must be calculated. It is necessary that the display color specified by the display color index c is changed to an identifiable degree. That is, the altitude h
It is necessary to increase the gradient (change rate) of the display color index c to a certain degree or more. Therefore, as shown in FIG.
When the correspondence of a constant gradient is determined as in the straight line A, there is a problem that a sufficient gradient cannot be guaranteed because the number of colors in the display color series is particularly restricted.

Also, as shown by a curve B in FIG. 12, for example, when the area displayed on the screen is a lowland area L having a relatively low altitude h, the function c is used so that the change in display color becomes sufficiently large. Even if (h) is determined, when the display target area moves to the middle and high altitude area M having a relatively high altitude, the same function c
Even with the application of (h), a sufficient change in display color could not be obtained. That is, since the distribution range of the altitude h of the display target area is arbitrarily changed, there is a problem that it is difficult to visually identify a difference in terrain height in any scene. For example, as shown in FIG. 14, in a region where the height difference is small, a sufficient change in display color may not be obtained.

[0008] The present invention has been made in view of the above,
An object of the present invention is to provide a three-dimensional terrain display device capable of visually recognizing a terrain height difference even in an area where the height difference is small.

[0009]

According to the first aspect of the present invention,
In order to solve the above-mentioned problems, in a three-dimensional terrain display device that determines a display color according to the elevation of the terrain and displays a three-dimensional terrain image, the terrain data corresponding to a reference point position and a direction angle serving as a reference point of a display area is used. Shape data creating means for creating terrain shape data for displaying the terrain, coordinate transformation means for transforming the terrain shape data into three-dimensional terrain data, and determining the elevation value of the reference point from the reference point position and the terrain data A reference altitude value determining means, a coloring function determining means for determining a coloring function representing a terrain display color according to the elevation value of the reference point, and a display color of the terrain shape data from the respective elevation values and the coloring function of the terrain shape data The gist of the present invention is to provide a display color determining means for performing the processing and a drawing processing means for drawing a three-dimensional landform image from the three-dimensional landform data and the display color.

According to a second aspect of the present invention, there is provided a three-dimensional terrain display device for displaying a three-dimensional terrain image by determining a display color according to an elevation of a terrain and displaying a map image. Creates terrain shape data for displaying the terrain from terrain data according to the reference point position and direction angle that is the reference point of the area, and creates map shape data for displaying the map from the map data Means, coordinate transformation means for transforming the terrain shape data into three-dimensional terrain data, and coordinate transformation means for transforming the terrain shape data into three-dimensional map data; and a reference elevation for determining the elevation value of the reference point from the reference point position and the terrain data. Value determining means, coloring function determining means for determining a coloring function representing a terrain display color according to the elevation value of the reference point, and each elevation value and coloring function of the terrain shape data Display color determining means for determining the display color of the terrain shape data from the three-dimensional terrain data and the display color, and drawing the map image from a display color different from the display color in accordance with the three-dimensional map data. The gist of the present invention is to include drawing processing means for drawing.

According to a third aspect of the present invention, in order to solve the above-mentioned problem, the coloring function determining means sets a predetermined display color according to a relative altitude difference between a terrain altitude and a reference altitude value. The gist of the present invention is to determine a corresponding coloring function.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, the coloring function determination means associates a predetermined display color with a terrain elevation when the reference elevation value is the same. In addition, the gist of the present invention is to determine a coloring function that causes a display color to correspond to a predetermined gradient in accordance with a change in the topographical altitude near the reference altitude value.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problem, the coloring function determining means determines a reference elevation value with respect to a terrain elevation, a highest elevation value in a display area, or a lowest elevation value in a display area. If the value is the same as the value, the display color is made to correspond based on each predetermined coloring function, and according to the change in the terrain elevation near the reference elevation value,
The gist of the present invention is to determine a coloring function that makes a display color correspond to a predetermined gradient.

According to a sixth aspect of the present invention, in order to solve the above-mentioned problem, the coloring function determining means calculates a gradient of a display color corresponding to a change in terrain altitude near the reference altitude value, by using an altitude distribution of a display area. Change according to conditions such as
The gist is to determine a coloring function of a display color corresponding to a terrain elevation value.

According to a seventh aspect of the present invention, in order to solve the above-mentioned problem, the display color determining means stores a plurality of topographic display colors in advance corresponding to a locational condition or a temporal condition. And reads the terrain display color from the terrain display color storage means in accordance with the locational condition of the display area or the current time condition, and based on the coloring function determined by the coloring function determining means, The point is to determine the display color.

According to an eighth aspect of the present invention, in order to solve the above-mentioned problem, the coordinate transformation means sets a viewpoint position at a predetermined relative position from the display reference point, and sets the viewpoint position as a projection center, and The gist of the present invention is to perform perspective projection conversion from the terrain shape data to the bird's-eye view.

[0017]

According to the first aspect of the present invention, terrain shape data for displaying terrain is created from terrain data according to a reference point position and a direction angle which are reference points of a display area,
The coordinates of the terrain shape data are converted into three-dimensional terrain data. On the other hand, the altitude value of the reference point is determined from the reference point position and the terrain data, and the coloring function representing the terrain display color corresponding to the altitude value of the reference point is determined. Next, the display color of the terrain shape data is determined from each altitude value of the terrain shape data and the coloring function. Next, by drawing a three-dimensional terrain image from the three-dimensional terrain data and the display color, the target area of the terrain display and the distribution range of the elevation within the area are arbitrarily changed according to the movement of the reference point of the display area. Even in such a case, it is possible to apply an optimum color scheme in each scene, and to express the topographical difference in a visually easy-to-understand manner.

According to the present invention, terrain shape data for displaying terrain is created from terrain data corresponding to a reference point position and a direction angle serving as a reference point of a display area, and map data is generated from map data. Create map shape data for displaying a map. Next, coordinate conversion of the terrain shape data into three-dimensional terrain data and coordinate conversion of the terrain shape data into three-dimensional map data are performed. On the other hand, the altitude value of the reference point is determined from the reference point position and the terrain data, and the coloring function representing the terrain display color corresponding to the altitude value of the reference point is determined. next,
The display color of the terrain shape data is determined from each altitude value of the terrain shape data and the coloring function. Next, by drawing a three-dimensional topographic image from the three-dimensional topographic data and the display color, and drawing a map image from a display color different from the display color according to the three-dimensional map data, the reference point of the display area can be moved. Accordingly, even if the target area of the terrain display and the distribution range of the altitude in the area change arbitrarily, the optimal color scheme can be applied in each scene, and the terrain height difference can be visually determined. In addition to being able to be expressed in an easy-to-understand manner, a map element can be displayed together with a three-dimensional terrain image, and the three-dimensional terrain display device can be applied to a route guidance device such as a navigation system.

According to the third aspect of the present invention, by determining a coloring function for associating a predetermined display color in accordance with a relative altitude difference between a terrain altitude and a reference altitude value, a screen is displayed. It is possible to visually recognize the relative altitude difference from the reference altitude value for an arbitrary point displayed in the box.

According to the present invention, when the reference elevation value is the same as the terrain elevation, a predetermined display color is made to correspond, and the terrain elevation is set near the reference elevation value. By determining a coloring function for making the display color correspond to a predetermined gradient according to the change, the absolute elevation of the display reference point displayed on the screen can be visually recognized.

According to the fifth aspect of the present invention, a reference elevation value with respect to the terrain elevation, or the highest elevation value in the display area,
Or, if it is equal to the lowest elevation value in the display area,
By associating the display color based on each predetermined coloring function, and determining a coloring function that corresponds the display color to a predetermined gradient according to a change in the terrain elevation near the reference elevation value, It is possible to visually recognize the absolute elevation of the display reference point displayed on the screen. In addition, the number of display colors used in each scene can be prevented from increasing more than necessary.

According to the sixth aspect of the present invention, the gradient of the display color corresponding to the change in the terrain elevation near the reference elevation value is calculated as follows:
By changing according to the conditions such as the elevation distribution and display magnification of the display area and determining the coloring function of the display color corresponding to the terrain elevation value, the optimal The color scheme can be determined.

According to the seventh aspect of the present invention, a plurality of terrain display colors are stored in advance in correspondence with the locational condition or the temporal condition, and the locational condition of the display area or the current temporal condition is stored. According to the determined coloring function, the display color of the terrain shape data is determined, and the display color can be changed according to a change in place or time. Appropriate display can be performed according to the section, city area, time zone, and season.

According to the present invention, the viewpoint position is set at a predetermined relative position from the display reference point, and the perspective position is subjected to perspective projection conversion from the terrain shape data to the bird's-eye view using the viewpoint position as a projection center. Thus, it is possible to obtain a bird's-eye view in which the vicinity of the display reference point where the change in the terrain display color is large is enlarged, and the terrain is reduced in a distant region where the change rate is small.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram of a three-dimensional terrain display device 1 according to an embodiment of the present invention. In FIG. 1, the three-dimensional terrain display device 1 includes an external storage device 3, an output device 5 such as a display reference point, an arithmetic processing device 7, and an image display device 9.

The external storage device 3 stores terrain data including elevation data of each point and map data including road information and place name information. The output device 5 such as a display reference point is a GP.
Designate the current position and traveling direction of the vehicle detected by self-contained navigation based on sensor signals from the S sensor, vehicle speed sensor, direction sensor, and gyro sensor, or specify an arbitrary point and traveling direction using a remote control or keyboard Then, the display reference point position coordinates and the line-of-sight direction angle are calculated.

The arithmetic processing unit 7 comprises a CPU capable of high-speed arithmetic processing, an internal storage device, and a computer having an input / output interface. The image display device 9 displays an image signal output from the arithmetic processing device 7.

The terrain data stored in the external storage device 3 stores actual elevation value data for each longitude / latitude coordinate point in the form of matrix table data. That is, for each point (sampling point) arranged in a grid point at a constant density in the horizontal plane direction, for example, at a fixed interval in each of the longitude (y) and latitude (x) directions, the actual elevation value at that point is represented in a matrix table. It is stored in a format.

Further, the external storage device 3 stores such terrain data for sampling points of a plurality of densities.
The described elevation value data is stored as terrain data with different accuracy or as different accuracy. For example, the elevation value data of the sampling points arranged at every 10 m, every 500 m, and every 5 km are separately stored as terrain data with three kinds of accuracy. in this case,
Only one type of elevation value data of sampling points every 100 m, which is physically the highest accuracy, is stored as terrain data, and it is used as it is according to the scale specification at the time of map display. It can be extracted as high-precision terrain data, and data existing every 50 points can be extracted and used as low-precision terrain data.

The data format of the terrain data itself is not limited to this, and may be data represented by actual contour lines. For example, as latitude x and longitude y, z = h (x, y) ) Can be registered in the form of a surface equation given by, and the data format is not particularly limited. The map data stores display elements such as roads and place names displayed on a map, their position information, and, if necessary, accompanying information such as attributes. For example, roads are displayed in the form of a ridgeline or a series of ridgelines, and the position coordinates of a series of point sequences indicating each end point are used as road position information. For surface figures such as polygons, the position coordinates of a series of points indicating each vertex and internal division points are assumed to be displayed in the form of polygons, as the position information of the water system and facilities, and the connection form of each point is attributed Have.

In addition to this, for the names of places and roads,
The coordinates of the position where the character string is displayed on the map are used as position information,
It is assumed that a character string is provided as an attribute. Further, the attribute information added to the road link needs to change the display color depending on whether it is an expressway, a national road, or a prefectural road, and thus indicates the type of the road and whether the road is a normal road, a tunnel, or an elevated road. There is a form. These pieces of position information can be described and stored in two-dimensional coordinates corresponding to longitude and latitude, or can be stored as three-dimensional coordinates including altitude value data.

Next, the configuration of various arithmetic processing functions executed by the arithmetic processing unit 7 will be described. These various arithmetic processing functions
It comprises a display target area determination unit 11, a shape data creation unit 13, a reference elevation value determination unit 15, a coloring function determination unit 17, a terrain display color determination unit 19, a coordinate conversion unit 21, and a drawing processing unit 22. The display target area determination unit 11 determines the target area on the map to be displayed as a display reference point based on the display reference point coordinates and the line of sight output from the display reference point or the like output device 5 as shown in FIG. Determined on a horizontal plane virtually placed at the same elevation.

Here, the positional relationship between the viewpoint, the display reference point, and the display target area will be described with reference to FIG. It is assumed that the display target area is specified in a two-dimensional coordinate system (x, y) corresponding to latitude and longitude regardless of the altitude value. Here, it is assumed that a horizontal plane having the same altitude as the display reference point is a map plane. Further, the height of the viewpoint coordinates is set to a height h from the elevation value of the display reference point.
In this case, the positional relationship shown in FIG. 3 is always established irrespective of the altitude, and the display target area can be specified as in the conventional bird's-eye view display navigation system. That is, when the two-dimensional position coordinates (Px, Py) excluding the elevation of the display reference point and the line-of-sight direction angle φ are given from the output device 5 such as the display reference point, the predetermined viewpoint height h, the line-of-sight depression angle θ, and the like are determined. The display target area can be obtained by using this. In the present embodiment, the above-described perspective projection transformation is used. However, the present invention is not limited to this, and any method such as orthographic transformation can be used.

The shape data creating unit 13 reads the map data corresponding to the display target area determined by the display target area determining unit 11 and determines the position and position of each map element.
Based on the attribute information, data as a figure that can be directly applied in the drawing process, such as a straight line for a road, a character string for a place name, and a polygon for a facility / water system, is created. At this time, if the position information of the map element is described in two-dimensional coordinates, its elevation value is obtained by interpolation,
Create as a three-dimensional figure.

The reference altitude value determination unit 15 calculates the x, y coordinate values (P
x, Py) and the z-coordinate value Pz in the height direction of the display reference point from the topographical shape obtained by the shape data creating unit 13 by interpolation.

The coloring function determination unit 17 determines and holds the correspondence between the topographical altitude and the topographical display color at that altitude according to the determined standard altitude value. Terrain display color determination unit 1
Reference numeral 9 determines a display color of the corresponding display terrain shape data from each elevation value of the display terrain shape data and the correspondence held by the coloring function determination unit 17. The coordinate conversion unit 21 performs coordinate conversion of the shape data of the terrain and map elements created by the shape data creation unit 13 into a screen coordinate system. The drawing processing unit 22
Each data after the coordinate conversion is drawn using the determined display color, and is output to the image display device 9 as a three-dimensional map image.

Next, the operation of the three-dimensional terrain display device 1 will be described with reference to the flowchart shown in FIG. The processing program according to this flowchart is controlled by the arithmetic processing unit 7. The display processing of the three-dimensional terrain on the surface screen of the image display device 9 by the arithmetic processing device 7 is performed every time the display reference point output from the output device 5 such as the display reference point is updated, the display target area is determined, the terrain data, and the map It is executed by repeating a series of arithmetic processing such as data reading, creation of terrain shape data, map element shape data, determination of a reference elevation value, determination of a coloring function, determination of a terrain display color, coordinate conversion, and drawing processing. Hereinafter, each step will be described in detail.

First, in step S10, the display target area determination unit 11 determines the target area to be displayed on the screen based on the position coordinates and the direction angle of the display reference point output from the output device 5 such as the display reference point. decide.

Here, the display reference point is a representative point in the display screen for determining the position of the map to be displayed, and the line-of-sight direction angle is the azimuth of the orthogonal projection of the line of sight on the horizontal plane. It is a corner. In the input of the display reference point, for example, in the case of a vehicle-mounted navigation system, when displaying a map near the center input device with the current position of the own vehicle, an FPS sensor, a vehicle speed sensor, and a gyro sensor are used. The own vehicle measuring device that measures and outputs the position and the traveling direction can be used as the output device 5 such as a display reference point. When the user designates an arbitrary point on the map and displays a map in the vicinity in a desired viewing direction, a point designation means such as a remote controller or a keyboard is used as the display reference point output device 5. It can also be used.

In the present embodiment, for the sake of simplicity, an altitude horizontal plane z = Pz is virtually set at the same height as the altitude value Pz of the display reference point, and the display target area is defined on this virtual plane. And

Next, in step S20, the display target area unit 11 reads, from the external storage device 3, topographic data and map data in a range that sufficiently covers the display target area obtained in step S10. The terrain data is a list of elevation values of representative points for each mesh, a vector representation of contour lines, as long as the elevation value z of the point can be obtained for the given two-dimensional position coordinates (x, y), It may be described in any format such as a mathematical expression. When the terrain data and the map data are read, some or all of the necessary data is also used in the previous display processing, and is already stored in the internal storage device (not shown) of the arithmetic processing unit 7. In this case, the internal storage data is used as the data of the overlapping portion, while only the necessary data is read from the external storage device 3 to reduce the data transfer time.

In step S30, the shape data creation unit 1
3 creates a three-dimensional model of the terrain shape (hereinafter, referred to as terrain shape data) with respect to the read terrain data, and graphically expresses each map element with respect to the read map data (hereinafter, referred to as map data). , Map element shape data).

Specifically, as the topographical shape data, as shown in FIG. 4, for example, a sufficient number of two-dimensional coordinates are determined in and around the display target area, and the elevation value is read for each point. It is assumed that a polyhedral shape is created using the points in the three-dimensional space obtained from the obtained topographic data and given the respective elevation values as vertices. In the subsequent drawing step, polygons representing each surface of the polyhedron are projected and converted for drawing.

As the map element shape data, data expressing individual map elements as figures, such as straight lines for roads, character strings for place names, and polygons for facilities and water systems, is created. At this time, for example, the attribute information of the map element that was held as map data is necessary for drawing a figure, such as setting a different display color depending on the type of road, and expressing a link corresponding to a tunnel with a broken line instead of a solid line. It is replaced as appropriate with appropriate attribute information. Since the display color needs to be clearly distinguished from the terrain shape, it is desirable to use a display color different from the display color series referred to when determining the terrain display color described later.

The map element shape data thus created is in a form that can be directly handled by the drawing processing unit 22 in a subsequent drawing step. Also, since this map element shape data must be created as a three-dimensional figure, especially when the position information of the map element held as map data is described in two-dimensional coordinates, the elevation value is interpolated. Ask by. The method includes step S4
This is similar to the case where the altitude value of the display reference point is obtained at 0.

In step S40, the reference altitude value determining unit 1
5 obtains an elevation value Pz of the display reference point (hereinafter, referred to as a reference elevation value). In general, the output device 5 such as the display reference point does not always output up to the elevation value (z value) of the display reference point, and therefore applies the two-dimensional position coordinates (Pz, Py) to the terrain data read two steps before. To find the corresponding altitude value. Further, an intersection point between the topographical shape data created in the previous stage and a vertical line passing through the two-dimensional position coordinates (Px, Py) may be obtained, and the elevation value may be set to Pz.

In step S50, the coloring function determination unit 17
Is determined on the basis of the reference altitude value Pz for which the is determined. Conceptually, the standard color index c is calculated as a function c (h) of the altitude h, as in the prior art.
(Hereinafter referred to as a coloring function).

Hereinafter, the coloring function c is calculated from the reference elevation value Pz.
Three methods for determining (h) will be described. (First Method) In a first method, a coloring function c (h) is fixed in advance as a function c rel (Δh) of an elevation difference Δh = h−Pz between an input elevation value h and a reference elevation value Pz. It is a method to determine. As shown in FIG. 5, if the coloring function c (h) is determined so that the change rate of the standard color index c with respect to the input altitude h becomes sufficiently large near the altitude difference Δh = 0, the display standard The terrain in the vicinity of the point is drawn in a different display color even for a slight difference in elevation, and an image in which the terrain shape can be easily visually recognized can be obtained.

FIG. 6 shows how the correspondence between the input altitude h and the standard color index c changes as the display reference point moves. A different coloring function c (h) is determined for each scene having a different reference altitude value Pz. However, since the correspondence c rel (Δh) of the standard color index c to the altitude difference Δh is invariable, all the coloring functions c (h) are unchanged. (H) is the correspondence c rel (Δh)
Is translated by a reference altitude value Pz corresponding to the h-axis direction. In each scene, the display reference point is always displayed in the same color cp, and points having the same reference altitude value and the relative altitude difference are also displayed in the same color. It is possible to identify an altitude difference from the display reference point. Since the display reference point is always displayed at one point on the screen, the elevation range of the area displayed in each scene is always distributed around the reference elevation value in each scene, including the reference elevation value. Color cp in display color series
It is possible to perform display using various display colors centered on.

As described above, the coloring function determination unit 17 determines a coloring function that causes a predetermined display color to correspond to a relative elevation difference between a reference elevation value and an input terrain elevation value. Thus, it is possible to visually recognize the relative altitude difference from the reference altitude value at an arbitrary point displayed in the screen.

In step S50, for convenience, the coloring function c (h) is determined and held in accordance with the reference altitude value Pz,
When the display color is determined in the subsequent stage, the input altitude value h is applied to the coloring function c (h) to obtain the display color. In the first method, if the correspondence c rel (Δh) of the standard color index c to the altitude difference Δh is provided in advance in the form of referring to a table or the like, the step S50 is omitted and the display color is determined. In S60, the altitude difference Δh is obtained by one subtraction, and the display color can be determined with reference to this table, so that the calculation amount can be reduced.

(Second Method) Next, a second method for determining the coloring function c (h) will be described. In the first method, the display reference point is always displayed in the same color cp,
In the method of (1), first, the display color of the display reference point is determined by a predetermined relationship according to the reference altitude value Pz.
A coloring function c (h) is determined so as to have a predetermined change rate in the vicinity thereof.

As shown in FIG. 7, it is assumed that the correspondence cp (Pz) between the reference altitude value Pz and the color cp of the display color (index) is predetermined. Here, as a simple example, when the reference altitude value Pz changes from the input altitude value h0 to h1, the color cp changes linearly from c0 to c1.
Although the following function is used, a continuous function that is monotonic in a generally given domain and range may be used.

Next, the coloring function c (h) to be determined is divided into two regions of h ≦ Pz and h ≧ Pz, and they are respectively set as cminus (h) and cplus (h).

Assuming that the rate of change m at h = Pz is given in advance,
The necessary conditions required for each function are: cminus (h0) = c0 cminus (Pz) = cp cminus '(Pz) = m (1) cplus (Pz) = cp cplus (h1) = c1 cplus' (Pz) = M (2) The coloring function c (h) is determined by obtaining and combining monotonous continuous functions that satisfy this. For example, cminus (h) = α / (h + β) + γ (3) For three unknowns α, β, and γ, (1) becomes 3
Given two conditions, cminus (h) can be uniquely determined. Similarly, cplus (h) can be determined.

FIG. 8 shows the coloring function c thus obtained.
(H) shows how it changes with the movement of the display reference point (change of the reference elevation value Pz). As for the display color of the display reference point, the color cp changes from cp1 to cp3 according to the absolute altitude. Therefore, the absolute altitude of the display reference point can always be identified by the display color, and the approximate altitude including the vicinity thereof can be visually recognized. Here, the rate of change m
If is sufficiently large, the terrain in the vicinity of the display reference point is drawn with a different display color even for a slight height difference, and an image in which the terrain shape can be easily recognized regardless of the movement of the display reference point can be obtained. .

As described above, when the reference altitude value is the same as the input terrain altitude, the coloring function determination unit 17 associates a predetermined display color with the input terrain altitude. By determining a coloring function that causes a display color to correspond to a predetermined gradient in accordance with a change in terrain elevation, the absolute elevation of a display reference point displayed on the screen can be visually recognized.

(Third Method) Next, a third method for determining the coloring function c (h) will be described. In this method, as in the second method, first, the display color of the display reference point is determined by a predetermined relationship in accordance with the reference altitude value Pz, and then the point having the highest altitude in the displayed area is determined. A display color (index) corresponding to the lowest point is determined, and finally, a coloring function c (h) that has a predetermined change rate near the reference altitude value is determined.

As shown in FIG. 9, the correspondence cp (Pz)
Display color (index) cp for the reference altitude value Pz based on
First determine the value of. Next, display color indices c high and c low corresponding to the maximum altitude h high and the minimum altitude h low of the area displayed on this surface are obtained.

Here, the maximum altitude h high and the minimum altitude h
The low may be the one previously added to the terrain data for each section. If the shape data creating unit 13 uses a plurality of sections for modeling the terrain shape, the maximum value and the minimum value may be further selected and used from the maximum value and the minimum value. Furthermore, such maximum or minimum information is not added to the terrain data, and these values may be determined and held when the shape data creation unit 13 models the terrain shape. .

The maximum altitude h high and the minimum altitude h l
The display color indices c high and c low corresponding to ow may be determined based on the correspondence cp (Pz), similarly to the display reference point. Further, another function may be used. However, in the former case, when the maximum altitude h high and the minimum altitude h low are close to the value of the reference altitude Pz, c high and c low are also the colors c.
Since p approaches p and a sufficient change in display color cannot be obtained, it is necessary to add an exception process that guarantees a minimum difference between c high and c low and the color cp.
In the examples shown in FIGS. 9 and 10, the colors cp, c high, and c low are all determined based on the same function cp (Pz) for simplification of the drawing.

Further, similarly to the second method, the coloring function c (h) to be obtained is considered by dividing it into two regions of h ≦ Pz and h ≧ Pz, and each of them is represented by cminus (h) and cplus (h). ). The necessary conditions required for each function with respect to the change rate m at h = Pz are h0, h1, c0, and c1 in equations (1) and (2) as hlow and hhigh, respectively.
, C low, and c high, cminus (h) and cplus (h) can be similarly obtained.

FIG. 10 shows that the coloring function c (h) obtained in this manner moves and changes with the change of the reference elevation value Pz. In the display color of the display reference point, the color cp changes from cp1 to cp3 according to the absolute altitude. Therefore, the absolute altitude of the display reference point can always be identified by the display color, and the approximate altitude including the vicinity thereof can be visually recognized. Further, in the display of the low altitude area indicated by the range 1, the high frequency display color near the c1 is not used, and in the case of the range 3, the low frequency display color is not used. It has become.

As described above, the coloring function determination unit 17 determines whether the input terrain elevation is equal to the reference elevation value, the highest elevation value in the display area, or the lowest elevation value in the display area. By making the display colors correspond based on the predetermined coloring functions, respectively, and determining the coloring function that makes the display colors correspond to the predetermined gradient in accordance with the change in the terrain elevation near the reference altitude value. The user can visually recognize the absolute elevation of the display reference point displayed on the screen. In addition, the number of display colors used in each scene can be prevented from increasing more than necessary.

In the above description of each method, the display color change rate m in the vicinity of the reference altitude value has been described as giving a constant value. However, for example, in the case of wide area display with a wide altitude distribution range and a small display magnification. Sets the display color change rate m appropriately according to the conditions so that the display color change rate m is also set to a small value and a sufficient display color change can be obtained even at a location relatively distant from the display reference point. You may make it.

Returning to FIG. 2 again, in step S60, the terrain display color determining section 19 applies each of the terrain shape data created by the shape data creating section 13 to the coloring function c (h) determined as described above. The display color at each point is determined by applying the input elevation value h of the constituent points (polygon vertices). Furthermore, also for the inside of each polygon, the display colors are determined by interpolating from the display colors determined for each vertex, but since these methods use a technique such as shading processing which is a known technique in the field of computer graphics, Details are omitted here.

When the display color index obtained by the coloring function c (h) is determined by referring to the corresponding display color from the display color sequence, the reference table is replaced with another display color sequence. Thus, the color actually displayed can be changed without changing the coloring function c (h) representing the correspondence. Therefore, for example, by using a display color series having relatively low saturation in an urban area, a series based on green in summer in a mountainous area, and white in winter, and a series with low brightness in the nighttime, It can also produce visual effects according to changes in time.

As described above, the terrain display color determination unit 19
A plurality of terrain display colors are stored in advance in correspondence with locational conditions or temporal conditions, and the terrain display colors are read out according to the locational conditions of the display area or the current temporal conditions, and the determined coloring function is used. By determining the display color of the terrain shape data based on it, it is possible to change the display color according to the change in place and time, and as a result, the appropriate display according to the mountainous area, city area, time zone and season Can be performed.

In step S70, in order to display the three-dimensional map image on the two-dimensional screen, the coordinate conversion unit 21 uses the constituent figures (polygons) of the terrain shape data and each element figure (straight line, character string) of the map element shape data. , Etc.) to the screen coordinate system. For example, by setting a viewpoint behind the display reference point as described above and performing perspective projection transformation with this as the projection center, the topographic region including the display reference point can be displayed on the screen as a bird's-eye view. it can. In particular, in the case of such a bird's-eye view display, the terrain near the display reference point is enlarged, and the terrain is reduced and displayed as the distance increases, so that the display color change near the display reference point increases as described above. When the determined coloring function is used, the change in display color on the screen is relatively averaged, and a display with an appropriate color difference can be obtained over the entire screen according to the necessity of the difference in height. This embodiment can be said to be a display color determination method particularly suitable for bird's-eye view display.

As described above, the coordinate transformation unit 21 performs the perspective projection transformation from the terrain shape data to the bird's-eye view by setting the viewpoint position at a predetermined relative position from the display reference point and using the viewpoint position as the projection center. In addition, a bird's-eye view in which the terrain is reduced in a distant region where the change rate is small near the display reference point where the change in the terrain display color is large can be obtained.

In step S80, the drawing processing unit 22 draws the constituent figures (polygons) of the terrain shape data and map element shape data for which the display colors have been determined by converting to the screen coordinate system up to the previous stage, and Output to the display device 9.
At that time, clipping or hidden surface elimination, which is a known CG technique, may be performed as necessary.

Finally, in step S90, it is determined whether or not to continue the display processing. Step S if continuing
Returning to 10, the series of processing is repeated, and if not continued, the processing is terminated.

As described above, the display target area to be displayed on the display screen is determined by the display target area determination section 11 based on the display reference point position and the direction angle of the display area output from the output device 5 such as the display reference point. . Next, the terrain data corresponding to the target area is read from the external storage device 3, and the terrain shape data for displaying the terrain is created by the shape data creation unit 13 based on the terrain data. Next, the coordinate conversion unit 21 converts the terrain shape data into three-dimensional terrain data. On the other hand, the reference altitude value of the display reference point is determined by the reference altitude value determination unit 15 based on the display reference point position of the display area and the topographical data.
Next, based on the reference altitude value, the coloring function determination unit 17 determines a coloring function representing the correspondence between the terrain elevation and the terrain display color at that elevation. Next, the display color of the terrain shape data is determined by the terrain display color determination unit 19 based on each altitude value of the terrain shape data and the coloring function. Next, a three-dimensional topographic image is drawn by the drawing processing unit 22 from the three-dimensional topographic data of the topographical shape data and the display color, and is output to the image display device 9. Even when the distribution range of the altitude in the area is arbitrarily changed, the optimal color scheme can be applied in each scene, and the topographical height difference can be expressed visually so as to be easily understood. As a result, the height difference of the terrain can be visually recognized even in an area where the height difference is small.

Further, based on the display reference point position and the direction angle of the display area output from the output device 5 such as the display reference point, the target area to be displayed on the display screen is determined by the display target area determination section 11.
Determined by Next, the terrain data corresponding to the target area is read from the external storage device 3, and the terrain shape data for displaying the terrain and the map shape data for displaying the map from the map data are generated based on the terrain data. Created by the unit 13. Next, the coordinate conversion unit 21 converts the terrain shape data into three-dimensional terrain data, and also converts the terrain shape data into three-dimensional map data. Next, display map data for displaying a map is created based on the map data, and the display map data is coordinate-transformed into screen coordinate system data. On the other hand, the reference altitude value of the display reference point is determined by the reference altitude value determination unit 15 based on the display reference point position of the display area and the topographical data. Next, based on the reference altitude value, the coloring function determination unit 17 determines a coloring function representing the correspondence between the terrain elevation and the terrain display color at that elevation. Next, the display color of the terrain shape data is determined by the terrain display color determination unit 19 based on each altitude value of the terrain shape data and the coloring function.
Next, a three-dimensional topographic image is drawn from the three-dimensional topographic data of the topographic shape data and the display color, and a map image is drawn by the drawing processing unit 22 from a display color different from the display color according to the screen coordinate system data. By outputting to the image display device 9, even if the target area for terrain display and the distribution range of altitude in the area are arbitrarily changed according to the movement of the display reference point, it is optimal in each scene. It is possible to apply various color schemes, to express the terrain height difference visually easily, and to display the map elements on the three-dimensional terrain image together. It can be applied to a simple route guidance device.

FIG. 11 shows a display example of a three-dimensional topographic image according to the present embodiment. Compared to the conventional display example shown in FIG. 14, it can be seen that the display color changes even with a slight difference in elevation, making it easier to visually grasp the shape.

[Brief description of the drawings]

FIG. 1 shows a three-dimensional terrain display device 1 according to an embodiment of the present invention.
1 is a diagram showing a system configuration of FIG.

FIG. 2 is a flowchart illustrating a processing operation of the three-dimensional terrain display device 1.

FIG. 3 is a diagram illustrating a relationship between a display reference point and a display target area when performing perspective projection.

FIG. 4 is a diagram illustrating a method of modeling a terrain shape.

FIG. 5 is a diagram illustrating a first method for determining a coloring function.

FIG. 6 is a diagram showing a change in a coloring function according to a reference altitude value in the first method.

FIG. 7 is a diagram illustrating a second method for determining a coloring function.

FIG. 8 is a diagram showing a change in a coloring function according to a reference altitude value in the second method.

FIG. 9 is a diagram illustrating a third method for determining a coloring function.

FIG. 10 is a diagram illustrating a change in a coloring function according to a reference altitude value in a third method.

FIG. 11 is a display example of a three-dimensional topographic map according to the present invention.

FIG. 12 is a diagram illustrating a coloring function in a conventional example.

FIG. 13 is a display example of terrain in which a display color is changed according to altitude.

FIG. 14 is a display example of a three-dimensional topographic image in a conventional three-dimensional topographic display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 3D terrain display device 3 External storage device 5 Display reference point output device 7 Arithmetic processing device 9 Image display device 11 Display target area determination unit 13 Shape data creation unit 15 Reference elevation value determination unit 17 Coloring function determination unit 19 Terrain display unit 21 coordinate conversion unit 22 drawing processing unit

Claims (8)

[Claims] 1. A three-dimensional terrain display device for displaying a three-dimensional terrain image by determining a display color according to the elevation of the terrain, wherein a terrain is determined from terrain data corresponding to a reference point position and a direction angle serving as a reference point of a display area. Shape data creation means for creating terrain shape data for display, coordinate transformation means for transforming terrain shape data into three-dimensional terrain data, reference elevation for determining the elevation value of this reference point from the reference point position and terrain data Value determining means, a coloring function determining means for determining a coloring function representing a terrain display color according to the elevation value of the reference point, and a display for determining a display color of the terrain shape data from each elevation value and the coloring function of the terrain shape data A three-dimensional terrain display device comprising: a color determining means; and a drawing processing means for drawing a three-dimensional terrain image from three-dimensional terrain data and a display color. 2. A three-dimensional terrain display device that determines a display color according to the elevation of the terrain and displays a three-dimensional terrain image, and displays a map image. Geometry data creation means for creating terrain shape data for displaying the terrain from the corresponding terrain data and creating map shape data for displaying the map from the map data, and coordinate conversion of the terrain shape data to three-dimensional terrain data Coordinate transformation means for transforming the terrain shape data into three-dimensional map data, reference elevation value determination means for determining the elevation value of the reference point from the reference point position and the terrain data, and A coloring function determining means for determining a coloring function representing a terrain display color, and a display color for determining a display color of the terrain shape data from each elevation value of the terrain shape data and the coloring function. And a drawing processing means for drawing a three-dimensional topographic image from the three-dimensional topographic data and the display color, and drawing a map image from a display color different from the display color according to the three-dimensional map data. 3D terrain display device. 3. A coloring function determining means for determining a coloring function for associating a predetermined display color with a relative elevation difference between a terrain elevation and a reference elevation value. Item 3. The three-dimensional terrain display device according to item 1 or 2. 4. The coloring function determining means, when the reference elevation value is equal to the terrain elevation, associates a predetermined display color with the terrain elevation value and adjusts the terrain elevation change in the vicinity of the reference elevation value. 3. The three-dimensional terrain display device according to claim 1, wherein a coloring function for making a display color correspond to a predetermined gradient is determined accordingly. 5. The coloring function determination means, wherein when the terrain elevation is the same as the reference elevation value, the highest elevation value in the display area, or the lowest elevation value in the display area, the chromatic function determination means is preset. A display function corresponding to the display color based on the predetermined color function, and a color function for making the display color correspond to a predetermined gradient in accordance with a change in the terrain elevation near the reference altitude value is determined. 3. The three-dimensional terrain display device according to 1 or 2. 6. The coloring function determining means changes a gradient of a display color corresponding to a change in terrain elevation near the reference elevation value in accordance with conditions such as an elevation distribution in a display area and a display magnification. The three-dimensional terrain display device according to claim 1, wherein a coloring function of a display color corresponding to the elevation value is determined. 7. The display color determining means includes a terrain display color storage means for storing a plurality of terrain display colors in advance corresponding to a location condition or a time condition, and 2. The display color of terrain shape data is determined based on the coloring function determined by the coloring function determining means, by reading the terrain display color from the terrain display color storage means in accordance with a temporal condition. Or the three-dimensional terrain display device according to 2. 8. The coordinate transformation means, wherein a perspective position is set at a predetermined relative position from the display reference point, and the perspective position is subjected to perspective projection transformation from the terrain shape data to a bird's-eye view using the viewpoint position as a projection center. The three-dimensional terrain display device according to claim 1 or 2, wherein: