JP3365313B2 - 3D terrain display device - Google Patents

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 which is loaded on a moving body or the like and stereoscopically displays a terrain shape based on terrain data, and more particularly, to a terrain near a display reference point viewed from the line of sight. The present invention relates to a three-dimensional terrain display device capable of determining the coordinate points of display terrain data according to the inclination of.

[0002]

2. Description of the Related Art As a conventional three-dimensional terrain display device, when three-dimensionally displaying the terrain near the target point from the terrain data corresponding to the target point, the altitude value is changed uniformly using only the altitude magnification as a parameter. What is highlighted is reported.

[0003]

However, in the conventional three-dimensional terrain display device, as shown in FIG. 9, when the display reference point exists on the downhill area, the display reference point is high behind the display reference point. Due to the effect of the altitude, the display reference point was hidden or the terrain in front of the display reference point was clogged and displayed. As a result, when the conventional three-dimensional terrain display device is applied to a navigation device, there is a problem that the display reference point is not displayed or the road near the display reference point is compressed and displayed, making it difficult to see.

The present invention has been made in view of the above,
It is therefore an object of the present invention to provide a stereoscopic terrain display device capable of easily displaying a stereoscopic terrain image in accordance with the terrain situation of a display target area.

[0005]

The invention according to claim 1 is
In order to solve the above problem, a display target area is determined based on the position of the display reference point and the direction of the area to be displayed, and the terrain shape is stereoscopically determined based on the terrain data including the position of the display target area and the elevation value. Is a three-dimensional terrain display device that generates display terrain data that is expressed in a three-dimensional manner, converts it into a three-dimensional terrain image, and draws it, based on the position of the display reference point and the terrain data specified in the display target area The reference altitude value determining means for determining the altitude value of, the altitude magnification determining means for determining the altitude magnification for highlighting the relief of the terrain, and the reference surface representing the tangent plane on the terrain of the display reference point, Display terrain that generates display terrain data so that the terrain shape in the area near the display reference point appears based on the distance from the reference plane and the elevation magnification for each point of the terrain data specified in the display target area And gist that a chromatography data generating means.

In order to solve the above-mentioned problems, the display terrain data generation means sets the reference plane at each point of the terrain data so that the corresponding point is far from the display reference point. The gist is to set the angle of the reference plane with respect to the horizontal plane as it becomes smaller.

In order to solve the above-mentioned problems, the display terrain data generating means in the area far from the display reference point directly multiplies the altitude value from the horizontal plane by the magnification to display the display terrain data. The gist is to generate.

In order to solve the above-mentioned problems, the display terrain data generation means converts the product of the distance from the reference plane and the altitude magnification into the altitude value, and the horizontal coordinate. The point is to change only the elevation value without changing the value.

[0009]

According to the invention of claim 1, the elevation value of the display reference point is determined based on the position of the display reference point and the terrain data specified in the display target area. The elevation magnification for highlighting the ups and downs of is determined. Here, the reference plane that represents the tangent plane on the terrain of the display reference point is defined, and for each point of the terrain data specified in the display target area, based on the distance from the reference plane and the elevation magnification, By generating the display terrain data so that the terrain shape of the near area appears, the three-dimensional terrain image can be displayed so that the terrain shape of the area near the display reference point appears. In addition, the terrain shape in front of the display reference point can be displayed without clogging. As a result, the three-dimensional topographic image can be displayed in an easy-to-see manner according to the topographical condition of the display target area.

According to the second aspect of the present invention, when the reference plane is set for each point of the topographical data, the angle of the reference plane with respect to the horizontal plane becomes smaller as the corresponding point becomes farther from the display reference point. By setting, it is possible to display at a point far from the display reference point without being affected by the inclination near the display reference point. As a result, it is possible to avoid the problem that, for example, a horizon that is far away is raised and displayed.

According to the third aspect of the present invention, in the area far from the display reference point, the display topography data is generated by directly multiplying the altitude value from the horizontal plane by the magnification, regardless of the reference plane, to thereby obtain the topography. Since it is not necessary to set a reference plane for each data point, it is possible to contribute to the saving of calculation amount.

According to the present invention of claim 4, the distance from the reference plane is multiplied by the altitude magnification to be converted into the altitude value, and only the altitude value is changed without changing the horizontal coordinate value. , Without distorting the perspective of each point of the terrain data,
It is possible to perform display in which the actual topographical shape and the sense of perspective match.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing a configuration of a three-dimensional terrain display device according to a first embodiment of the present invention.

In FIG. 1, the three-dimensional terrain display device is an external storage device 1 for storing terrain data consisting of elevation values corresponding to the latitude and longitude of the actual terrain, and the position of the moving body as a display reference point for the displayed area. And a display reference point positioning unit 3 for positioning, a calculation processing device 5 for performing a calculation process necessary for displaying a stereoscopic landform, and an image display unit 3 for displaying a stereoscopic landform image.
It is composed of 5 and.

Further, the arithmetic processing unit 5 determines the display target area based on the position and the direction of the display reference point measured by the display reference point positioning unit 3, and at the same time, determines the topographical data designated in this display target area. A display target area determination unit 11 that is read from the external storage device 1 and a reference elevation value determination that determines the elevation value of the display reference point based on the display reference point position output from the display reference point positioning unit 3 and the read topographical data. The unit 13, the altitude magnification determining unit 15 that determines the altitude magnification for emphasizing the relief of the terrain on the display, and the distance from the reference plane for each point of the read terrain data is multiplied by the altitude magnification. Display terrain data generation unit 2 for generating display terrain data so that the terrain shape in the area near the display reference point appears.
1, a coordinate conversion unit 31 that converts the displayed topographical data into an image coordinate system that forms a stereoscopic map image, and a drawing processing unit 33 that outputs the displayed topographical data as a stereoscopic map image to the image display unit 35. It is configured.

2 and 3 are flow charts for explaining the operation of the three-dimensional terrain display device according to the first embodiment of the present invention. Hereinafter, the operation of the three-dimensional terrain display device according to the present embodiment will be described with reference to FIG. 1 and the flowcharts shown in FIGS.

First, in step S10, the display target area determination section 11 determines the area to be displayed on the screen based on the position coordinates and the direction angle of the display reference point output from the display reference point positioning section 3. Generally, in order to display a three-dimensional shape on a two-dimensional screen, it is necessary to construct a three-dimensional shape model and project it on a screen coordinate system.

Therefore, a point on the terrain projected on a fixed point given in advance on the display screen is used as a display reference point, and a direction on the terrain corresponding to an upward direction on the screen is used as a direction angle. Decide in which direction to project.

For example, when the terrain display device is mounted on a vehicle to be applied to applications such as route guidance such as a navigation system, the terrain shape of the area around the current position of the host vehicle and its traveling direction can be seen. Display is required. In this case, a vehicle position measuring device that measures the current position and the traveling direction using a GPS receiver, a vehicle speed sensor, a gyro sensor, or the like can be used as the display reference point positioning unit 3.

For projection conversion, any method such as orthographic projection and perspective projection may be used, but it is necessary to determine in advance which one to use. When the perspective method is determined, the target area of the terrain projected on the display screen can be obtained using the given display reference point and direction angle.

For example, as shown in FIG. 4, a point at a distance B behind the viewpoint and a point above the altitude H with respect to the display reference point is the viewpoint as the projection center, and the direction of looking down at the ground at the line-of-sight depression angle θ is the projection axis ( If the perspective projection transformation of the line of sight is used, the display target area becomes a trapezoidal area. However, FIG. 4 is a projection diagram showing the relationship between the display reference point and the target area in the case of performing perspective projection. For simplicity, the elevation value Pz of the display reference point is shown.
Is virtually set, and the display target area is defined on this virtual plane.

Next, in step S20, the display target area determination unit 11 reads from the external storage device 1 the terrain data of the range that can sufficiently cover the display target area, which is obtained in step S10. However, this topographical data is such that the elevation value z of the point can be obtained in correspondence with the given point (x, y) on the two-dimensional position coordinates. Let y, z) be called points.

In step S30, the reference altitude value determining unit 1
3 obtains the elevation value Pz of the display reference point (hereinafter referred to as the reference elevation value). In general, the display reference point positioning unit 3 does not always output the elevation value of the display reference point, that is, the value z, so that the two-dimensional position coordinates (Px, Py) are calculated in step S10.
Then, the corresponding elevation value is obtained by applying the topographical data read in step S20.

In step S40, the altitude magnification determining unit 15
Generates an elevation magnification to be multiplied by the elevation value included in the original topographical data in order to emphasize the topographical relief on the display. The altitude magnification may be set in advance by the user, or an appropriate magnification may be automatically set based on the terrain data read in advance.

In step S50, the terrain display data generation unit 21 uses the read terrain data and the elevation magnification determined in step S40 to generate display terrain coordinates. Hereinafter, step S50 will be performed using the subroutine shown in FIG.
The detailed operation of will be described.

Turning to FIG. 3, in step S510, the terrain display data generator 21 determines the display reference plane.
Here, a method of determining the display reference plane will be described with reference to FIG. In FIG. 5A, if the line of sight is orthographically projected onto the plane z = Pz and the straight line forming the line-of-sight angle φ with the x-axis is the straight line e, the straight line l is a straight line that is orthogonal to the straight line e at the display reference point P. . The reference plane is a plane including the straight line l and forming an angle α with the plane z = Pz.

Here, FIG. 5 (b) is a side view of the diagram shown in FIG. 5 (a). The angle α shown in FIG. 5B is
The angle between the tangent plane at the display reference point of the actual topography and the horizontal plane, or an angle close to that.

In steps S520 and S530, points of the displayed topographical data (displayed topographical coordinates) are generated from the points forming the topographical data. In the present embodiment, a case will be described in which the points forming the topographical data are Q and the display topographical coordinates are generated for the point Q.

In step S520, the height h of the point Q from the reference plane is obtained. That is, when the point Q is viewed in the z-axis direction,
If it is above the reference plane, h = (distance from the point Q to the reference plane), and if point Q is below the reference plane, h =-(distance from the point Q to the reference plane) Ask.

In step S530, display topographical coordinates corresponding to the point Q are generated. 6 is a diagram showing an example of the method. First, set the point Q'so that the foot dropped on the reference plane is the same as that of the point Q and the height from the reference plane matches ((height h of the point Q from the reference plane) x elevation magnification). Ask.

In FIG. 6, an example in which the altitude magnification is 3 times is taken, and the point Q
Q'is shown as a point corresponding to. The displayed topographical coordinates of the point Q may be this Q ', or the value of the (x, y) coordinate of the point Q may be left as it is and the value of Q'only for the elevation value may be used. In addition, the value of the (x, y) coordinate of the point Q is unchanged,
The displayed topographical coordinates using only the elevation value Q'is shown as Q "in FIG.

In step S540, it is determined whether the display terrain coordinates have been generated for all the points forming the terrain data. When the generation of the display topographical coordinates is completed by this determination, the processing of step S50 is completed. on the other hand,
If the generation of the display topographical coordinates has not been completed by this determination, the process returns to step S520 and the series of processes described above is repeated. Note that from which point the display topographical coordinate point should be generated may be ordered, and in this case, it is possible to save the trouble of searching for the point to be generated next.

Returning to FIG. 2, in step S60, in order to display the three-dimensional terrain display shape on the two-dimensional screen, the coordinate conversion unit 31 performs perspective conversion to the screen coordinate system for each point of the displayed terrain data. To do. For example, as described above, perspective projection conversion is performed when the viewpoint is set rearward with respect to the display reference point.

In step S70, the drawing processor 33
The graphic (polygon) of each point of the display topographical data converted into the image coordinate system is drawn up to step S60 and output to the image display unit 35. Finally, in step S80, it is determined whether or not to continue the display process. If the display process is to be continued, the process returns to step S10 to repeat a series of processes. On the other hand, if it does not continue, the process ends.

(Second Embodiment) The configuration of the three-dimensional terrain display device according to the present embodiment is the same as that of the three-dimensional terrain display device according to the first embodiment shown in FIG. 1, and Since the flowchart for explaining the overall operation is the same as that shown in FIG. 2, its description is omitted.

In the second embodiment, the processing for changing the reference plane as described above for each point of the terrain data is performed.
This will be described with reference to FIG. 7. Note that FIG. 7 is a subroutine for explaining the detailed processing contents of step S50 shown in FIG.

In the subroutine shown in FIG. 7, step S
In the series of processing from 710 to S740, the terrain data
Display terrain coordinates are generated from each point that composes the data. Here, as in the case of the above-described first embodiment, a case will be described in which a point forming the terrain data is set as a point Q and display terrain coordinates are generated for the point Q.

First, in step S710, the distance d between the point Q and the display reference point is obtained. Here, the distance d is the plane z =
The distance between the point Q on Pz and the display reference point p. However, as a method of defining the distance d, as shown in FIG. 7, another method is to lower the straight line 1 passing through the display reference point on the plane z = Pz and perpendicular to the direction of the line of sight to the plane z = Pz of the point Q. A method is conceivable in which the distance to the foot of the vertical line is obtained and is set to d.

In step S720, the reference plane corresponding to the point Q is determined. As shown in FIG. 7A, the reference plane is a plane including the straight line 1 and intersecting with the line-of-sight direction at right angles, and the inclination α with respect to the horizontal plane changes depending on the value of d.

When the value of d is small and the point Q is close to the display reference point, the angle formed by the tangent plane of the display reference point and the horizontal plane is considered in consideration of the cross section of the terrain near the display reference point in the direction of the line of sight. Let the angle be α. Further, the angle α is set to be smaller as the value of d becomes larger, and the reference plane is set so that α = 0 at the coordinate points in the region far from the display reference point. In particular, the area is divided into two according to the value of d. As shown in FIG. 8, in the area M near the viewpoint, the reference plane m corresponding to the gradient of the display reference point p is used, and in the distant area N, the horizontal plane n is set. The method of using may be used. In this case, by saving the information of the reference plane m, it is possible to eliminate the trouble of recalculating the reference plane for each point.

In step S730, the height h of the point Q from the reference plane is obtained as in step S520 shown in FIG. In step S740, the display terrain coordinates corresponding to the point Q are generated as in step S530.

In step S750, it is determined whether the generation of the display terrain coordinates of all the points forming the terrain data has been completed. When the generation of the display topographical coordinates is completed by this determination, the processing of step S50 is completed. On the other hand, if the generation of the display topographical coordinates has not been completed by this determination, the process returns to step S710 and the series of processes described above is repeated.

FIG. 9 is a display example of a stereoscopic terrain image by a conventional stereoscopic terrain display device, and FIG. 10 is a display example of a stereoscopic terrain image by the stereoscopic terrain display device according to this embodiment corresponding to this area. is there.

The display reference point 150 in the conventional three-dimensional terrain image shown in FIG. 9 is actually on the other side of the hill 153 in front, but is displayed on the foreground for the sake of easy understanding of the position. In the conventional three-dimensional map image shown in FIG. 9, the display reference point 150 is hidden by emphasizing the front hill 153,
The road is compressed and displayed by emphasizing the downhill 155, and as a result, the road condition near the display reference point 150 is almost unknown.

On the other hand, in the display example of the three-dimensional terrain display device according to the present embodiment shown in FIG. 10, the road condition around the display reference point 60 can be well understood while emphasizing the undulations of the terrain. . Further, FIG. 11 is a graph showing the relationship between the distance from the display reference point and the elevation value in the cross section including the display reference points 50 and 60 in the line-of-sight direction in the same area as that shown in FIGS. 9 and 10. is there.

In the actual terrain graph shown in FIG. 11, the terrain data obtained from the read terrain data is displayed, and in the graph in which "Conventional example" is entered, the display generated when the conventional display method is used. In the graphs in which the terrain data is written as “first embodiment” and “second embodiment”, the three-dimensional shapes according to the first embodiment and the second embodiment of the present invention, respectively. The display terrain data generated by the terrain display device is used. The region where the distance from the display reference point is negative represents the region on the viewpoint side of the display reference point.

In the three-dimensional terrain display apparatus according to the first embodiment, from the graph shown in FIG. 11, the altitude value may be kept low at a position closer to the viewpoint than the display reference point, but the altitude is displayed in front of the display reference point. It can be seen that as the distance from the reference point increases, the emphasis is displayed far from the actual terrain shape, and in particular, it is emphasized that the terrain becomes higher than the actual terrain at a distant point.

On the other hand, in the three-dimensional terrain display apparatus according to the second embodiment, from the graph shown in FIG. 11, the altitude is kept low in front of the display reference point with respect to the viewpoint, and the conventional display is displayed far from the display reference point. It can be seen that the relief of the terrain is emphasized as well as the elevation value.

When the inclination of the reference plane is changed in accordance with the point at the time of highlighting, the perspective of display may be distorted as compared with the actual topography, as shown in FIG. In this figure, the elevation magnification is set to 4 times, but in actual terrain, a reversal phenomenon occurs in which the point a closer to the display reference point than the point b is displayed farther than the point b on the display.
However, as described above, the point obtained by multiplying the distance by the altitude magnification is not used as it is, but the coordinate value in the horizontal direction is not changed by using only the value of the altitude value as in Q ″ shown in FIG. If so, such distortion will not occur.

Further, in the first and second embodiments, the mode in which the three-dimensional map display device of the present invention is used in the navigation device has been described, and therefore the display reference point and the display target point for determining the display target area should be displayed. As the means for obtaining the direction of the area, the display reference point positioning unit that measures the position and direction of the moving body is used, but the display reference point may be specified by input.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a stereoscopic terrain display device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the three-dimensional terrain display device according to the first embodiment of the present invention.

FIG. 3 is a continuation of the flowchart showing a part of the operation of the three-dimensional terrain display device according to the first embodiment of the present invention.

FIG. 4 is a projection diagram showing a relationship between a display reference point and a target region when performing perspective projection.

FIG. 5 is a diagram showing a straight line 1 that passes through the reference plane and the display reference point and is perpendicular to the line-of-sight direction in order to explain the method for determining the reference plane.

FIG. 6 shows a point Q and two types of display terrain coordinates Q ′ · Q ″ generated from the point Q in order to explain a method of generating a display terrain coordinate corresponding to a point Q constituting terrain data. It is a figure.

FIG. 7 is a flowchart showing a part of the operation of the stereoscopic terrain display device according to the second embodiment of the present invention.

FIG. 8 is a diagram showing an example of a method of determining a reference plane, in which the reference plane is changed stepwise in a region close to the viewpoint and a region far from the viewpoint.

FIG. 9 is a diagram showing a display example of a stereoscopic terrain image by a conventional stereoscopic terrain display device.

FIG. 10 is a diagram showing a display example of a three-dimensional terrain display device according to a second embodiment of the present invention.

FIG. 11 is a graph showing a relationship between a distance from a display reference point and an altitude value in a cross section including the display reference point taken along the line of sight in the same area as shown in FIGS. 9 and 10.

FIG. 12 is a diagram showing an example in which a perspective display that differs from the actual topography is displayed by highlighting.

[Explanation of symbols]

1 External storage device 3 Display reference point positioning unit 5 Processor 11 Display target area determination unit 13 Standard elevation value determination unit 15 Altitude magnification determination unit 21 Display terrain data generator 31 Coordinate converter 33 Drawing processing unit 35 Image display section

Continuation of the front page (56) Reference JP-A-9-325692 (JP, A) JP-A-9-138136 (JP, A) JP-A-9-160487 (JP, A) JP-A-8-44996 (JP , A) JP-A-10-143066 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G09B 29/00-29/14 G01C 21/00-25/00

Claims (4)

(57) [Claims] 1. A display target area is determined based on a position of a display reference point and a direction of an area to be displayed, and a terrain shape is three-dimensionally determined based on terrain data including the position of the display target area and an elevation value. Generate display terrain data to represent,
A three-dimensional terrain display device that converts and draws a three-dimensional terrain image, and determines a reference elevation value that determines an elevation value of a display reference point based on the position of the display reference point and the terrain data specified in the display target area. Means, an altitude magnification determining means for determining an altitude magnification for highlighting the undulations of the terrain, and a reference plane representing a tangent plane on the terrain of the display reference point,
Generating display terrain data that generates display terrain data such that the terrain shape in the area near the display reference point appears based on the distance from the reference plane and the elevation magnification for each point of the terrain data specified in the display target area A three-dimensional terrain display device comprising means. 2. The display terrain data generation means, when setting the reference plane at each point of terrain data,
The three-dimensional terrain display device according to claim 1, wherein an angle of the reference plane with respect to the horizontal plane becomes smaller as the corresponding point becomes farther from the display reference point. 3. The display terrain data generating means generates display terrain data by directly multiplying an altitude value from a horizontal plane by a magnification factor in a region far from the display reference point. 3D terrain display device. 4. The display terrain data generating means converts a value obtained by multiplying a distance from the reference plane by an altitude magnification into an altitude value, and changes only the altitude value without changing a horizontal coordinate value. The three-dimensional terrain display device according to any one of claims 1 to 3.