JP5587677B2 - Topographic relief image generation method and topographic relief image generation apparatus - Google Patents

Description

  The present invention interprets relatively large undulations and relatively small irregularities (micro terrain) such as ridges and valleys based on 3D terrain data including altitude such as digital elevation model data (DEM: Digital Elevation Model). The present invention relates to a terrain undulation image generation method and a terrain undulation image generation apparatus that generate easily visualized terrain undulation images.

  In recent years, high-density digital elevation data has been obtained by advancing terrain surveying technology using aerial laser surveying and satellites. The numerical elevation data indicates the coordinates of an arbitrary position, and the coordinates of each point are composed of X, Y, and Z coordinate information. In particular, data whose horizontal plane positions (X and Y) are regular intervals (mesh) are referred to as mesh data.

  Conventionally, contour maps, stage charts, shading maps, etc. are known as methods for expressing topographic relief on a plane and outputting them to a display or a paper map. As a result, accurate terrain interpretation and understanding were hindered.

Further, for example, a combination of a stepped shade map and a contour map, and a combination of an elevation stepped color and an inclination section are also known.
In Patent Document 1, based on DEM data, red gradation is displayed according to the maximum gradient so that the deeper the gradient is, the red brightness is displayed according to the degree of rise and fall representing the degree of unevenness. A gradation processing system for generating an inclined reddish stereoscopic image in which the ridge is white and the valley bottom is black is disclosed. Moreover, in this patent document 1, a reddish three-dimensional image is synthesized by synthesizing a composite image of a gray scale corresponding to the ground opening and a gray scale corresponding to the underground opening, and a red image corresponding to the degree of inclination. A configuration for generating is also disclosed.

  Further, Patent Document 2 discloses a terrain data of a concave portion in which a concavo-convex portion is detected and a cold color is given to the concave portion, a terrain data of a convex portion in which a warm color is given to the convex portion, and a terrain of the flat portion. Create shaded terrain data that combines the data. A 3D image that creates a 3D image by mixing this shaded terrain data with another base image (for example, a shadow image, a color gradation image, a contour map image, and a gradient image) that expresses the same terrain at an appropriate mixing ratio. A creation device is disclosed. In this stereoscopic image, ridges and valleys are highlighted.

  Furthermore, in Patent Document 3, a color elevation slope map is created by transparently synthesizing an altitude step chart (color elevation map) assigned to hue, etc., from numerical elevation data and a gray scale slope map to which a darker density is assigned as the slope is larger. A method for creating a color elevation slope map is disclosed. The altitude chromatic diagram was assigned a blue-red hue according to the altitude. Patent Document 3 also discloses the synthesis of a color elevation map and a Laplacian map. Note that the color range from blue (low altitude) to red (high altitude) is set for the step color corresponding to the altitude in the color elevation map, and the color range corresponding to the slope change rate in the Laplacian map is blue (concave) to The red (convex) color range was set.

  In Patent Document 4, based on the altitude data, the hue determination unit generates hueed elevation data, the luminance determination unit generates sunlight reflection intensity data, and the unevenness correction unit generates correction data of fine unevenness information. . Further, the saturation determination unit determines the saturation data based on the processing result of the unevenness correction unit. A topographic map creation method is disclosed in which the image synthesis unit synthesizes hued elevation data, sunlight reflection intensity data, and saturation data to generate image data of the target ground surface.

International Publication No. 2004/042675 (Patent No. 3670274) (for example, paragraphs [0050] [0051], [0095]-[0108], etc., FIG. 11, FIG. 19, FIG. 20, etc.) Japanese Patent Laying-Open No. 2006-72857 (Patent No. 4379264) (for example, paragraphs [0014]-[0017] of the specification, FIG. 1) Japanese Unexamined Patent Application Publication No. 2007-48185 (for example, paragraphs [0036] [0042] [0047] [0055] [0064] in the specification) Japanese Unexamined Patent Application Publication No. 2008-242298 (eg, paragraphs [0014]-[0018] [0027] [0033] of the specification, FIG. 1, FIG. 5, etc.)

However, in the reddish three-dimensional image in Patent Document 1, there is a problem in that the valley is shaded and the valley is dark and difficult to read.
Further, in the stereoscopic image in Patent Document 2, it is easy to read the ridge and valley, but when the color gradation image is mixed as a base image, for example, the color of the gradation image and the color of the uneven portion are similar colors. There was a problem that ridges and valleys were difficult to read. In addition, since the concave portion, the convex portion, and the flat portion are only expressed in three gradations (three gradations), it is difficult to read the degree of the concave portion or the convex portion. In addition, it is necessary to change the setting of the spatial frequency and generate the terrain data of the recess separately so that the expression can be distinguished from the narrow recess and the large depression.

  Furthermore, in Patent Document 3, although the altitude and the slope are easy to read in the color elevation slope map, it is difficult to read the ridges and valleys. In addition, if a composite map of a color elevation map and a Laplacian map is used, it is easy to read ridges and valleys. However, this composite map has a problem that the slope is difficult to read. Note that the color range corresponding to the altitude in the color elevation map and the color scale corresponding to the slope change rate in the Laplacian map are both similar color ranges from blue (low elevation, concave) to red (high elevation, convex). Therefore, there is also a problem that it is relatively difficult to discriminate the altitude and the degree of unevenness (ridge valley degree).

  Further, according to Patent Document 4, since the method of emphasizing the color of the unevenness by performing a correction that greatly changes the elevation of the unevenness, there is a problem that the color expressing the unevenness is displayed in a color different from the actual altitude. It was.

  The present invention has been made paying attention to the above-mentioned problems, and its purpose is based on the three-dimensional terrain data including the elevation of the terrain, and relatively small undulations of terrain, relatively small ridges and valleys, etc. An object of the present invention is to provide a terrain undulation image generation method and a terrain undulation image generation apparatus capable of generating a terrain undulation image that makes it easy to interpret unevenness and the slope of the terrain.

In order to achieve the above object, the present invention is a terrain relief image generation method by a terrain relief image generation device that generates a terrain relief image based on three-dimensional terrain data including elevation , Elevation step color processing procedure for generating elevation step color data by performing step color processing for assigning a color corresponding to the altitude of the point to each point serving as a pixel based on the inputted three-dimensional terrain data, and unevenness degree calculating means The unevenness degree calculating procedure for calculating the unevenness degree of the terrain at each point based on the three-dimensional terrain data, and the color corresponding to the unevenness degree at each point by the unevenness degree gradation processing means. and asperity Dan'irodori procedure for generating the asperity Dan'irodori data by Dan'irodori treatment for imparting, by the inclination calculating means, inclined for calculating the inclination in the each point on the basis of the three-dimensional topography data And degree calculation procedure, the shadow generation means, and shading generation step of generating a shadow data by performing shading treatment for imparting shadow in accordance with the inclination of each said point on said each point, by combining the processing means, the altitude A composition processing procedure for generating stepped terrain data by combining stepped data, the unevenness degree stepped data and the shadow data, and an output means for outputting a terrain relief image based on the stepped terrain data by output means In the above-described altitude gradation processing procedure, the altitude gradation data is generated by assigning a color according to the altitude according to a first color range set between the minimum value and the maximum value of the altitude. In the unevenness degree gradation processing procedure, the unevenness degree gradation data is obtained by assigning a color according to the unevenness degree according to a second color range set between the minimum value and the maximum value of the unevenness degree. Generating the first color The surrounding color and the second color range are different from each other in the set color range, the color corresponding to each minimum value of the altitude and the degree of unevenness is a cold color different from each other, and the warm color corresponding to the maximum value is different from each other. The gist is to be set .

According to this invention, the step color corresponding to the altitude is given, the step color corresponding to the unevenness degree is given, and the shading corresponding to the inclination is given. Therefore, based on the three-dimensional terrain data including the altitude, it is possible to generate a terrain undulation image that allows easy interpretation of relatively large undulations of terrain, relatively small irregularities (fine terrain) such as ridges and valleys, and the degree of inclination. In addition, the step color corresponding to the altitude and the step color corresponding to the degree of unevenness are the first color range and the second color range which are different from each other in the color range in which the minimum value is set to a different cold color and the maximum value is set to a different warm color. Are applied according to the color range. Therefore, it is easy to discriminate relatively large undulations and relatively small irregularities (fine terrain) from the applied color.

In the invention described in claim 2, in terrain relief image generation method according to claim 1, in the asperity algorithm, for each of the points in the three-dimensional topography data, and ground angle in a plurality of directions from the point The underground angle is obtained, and the ridge valley degree as the degree of unevenness is calculated based on the ground opening that is the average of the ground angles and the underground opening that is the average of the underground angles.

  According to the present invention, the ground angle and the underground angle are respectively determined in a plurality of directions from the point of interest (target point), and the ground opening that is the average of the ground angle and the underground opening that is the average of the underground angle are obtained. The terrain quantity parameter calculated based on the ridge valley degree is used as the unevenness degree, and the stage color corresponding to the ridge valley degree is applied. Therefore, it becomes easier to interpret fine terrain such as ridges and valleys more appropriately.

According to a third aspect of the present invention, in the terrain relief image generating method according to the first or second aspect , in the inclination calculation procedure, the x-direction inclination and the y-direction at each point based on the three-dimensional terrain data. The inclination is calculated, and the inclination is calculated by synthesizing the x-direction inclination and the y-direction inclination.

  According to this configuration, since the gradient is calculated by combining the gradient in the x direction and the gradient in the y direction, an appropriate gradient can be acquired regardless of the direction of the inclined surface. Therefore, an appropriate shadow according to the inclination can be given.

The invention according to claim 4 is a terrain undulation image generation method by a terrain undulation image generation device that generates a terrain undulation image based on three-dimensional terrain data including an elevation, wherein the terrain undulation image generation device inputs the The elevation gradation processing procedure for generating elevation gradation data by performing a gradation processing that gives a color corresponding to the elevation of the point to each point that becomes a pixel based on the three-dimensional terrain data, and the unevenness degree calculating means, The unevenness degree calculation procedure for calculating the unevenness degree of the topography at each point based on the three-dimensional landform data and the unevenness degree gradation processing means give each point a color according to the unevenness degree at each point. An unevenness degree gradation processing procedure for generating unevenness gradation data by performing gradation processing, and an inclination calculation procedure for calculating an inclination at each point based on the three-dimensional terrain data by an inclination calculation means A shadow generation procedure for generating shadow data by performing a shadow process for applying a shadow corresponding to the slope at each point to each point by the shadow generation means; and A composition processing procedure for synthesizing the unevenness gradation data and the shadow data to generate gradation terrain data; and an output procedure for outputting a terrain relief image based on the gradation terrain data by output means. In the synthesis processing procedure, three-dimensional color coordinates obtained by adding the color information acquired in the synthesis processing procedure to the three-dimensional spatial coordinate points corresponding to the points in the three-dimensional terrain data are displayed in three dimensions. The stepwise terrain data having six or more dimensions including three-dimensional color coordinates and three-component color coordinates are generated. In the output procedure, the spatial coordinate points of the stepwise terrain data are copied to an output surface in a specified viewing direction. Generating the terrain relief image by giving color coordinates corresponding to the spatial coordinates in the pixel to the point as a pixel as a pixel value.

  According to this configuration, a terrain undulation image is generated by using a point obtained by mapping a spatial coordinate point of terrain terrain data on an output surface in a specified viewing direction as a pixel and giving a color coordinate corresponding to the pixel as a pixel value. The Therefore, it is possible to generate a terrain relief image corresponding to the designated visual field direction relatively simply by changing the mapping direction according to the designated visual field direction. For example, rendering processing can be made unnecessary.

The invention according to claim 5 is a terrain undulation image generating device that generates a terrain undulation image based on three-dimensional terrain data including altitude, and is applied to each point serving as a pixel based on the input three-dimensional terrain data. Elevation stage color processing means for generating elevation stage color data by performing stage color processing to give colors according to the altitude of the point, and unevenness for calculating the degree of unevenness of the topography at each point based on the three-dimensional topographic data Degree calculation means, unevenness degree gradation processing means for generating unevenness degree gradation data by performing gradation processing for imparting a color corresponding to the degree of unevenness at each point to each point, and the three-dimensional landform data An inclination calculating means for calculating the inclination at each point based on the above, and a shadow generating means for generating shadow data by applying a shadow process according to the inclination at each point to each of the points , The altitude stage Data, the concavo-convex degree gradation data, and the shadow data are combined to generate gradation terrain data; and output means for outputting a terrain relief image based on the gradation terrain data, The elevation stage color processing means generates the elevation stage color data by assigning a color according to the elevation according to a first color range set between the minimum value and the maximum value of the elevation, and the unevenness level stage. A saturation processing unit configured to generate the concavo-convex degree gradation data by assigning a color corresponding to the concavo-convex degree according to a second color range set between the minimum value and the maximum value of the concavo-convex degree; And the second color range are different from each other in the set color range, and the colors corresponding to the minimum values of the altitude and the unevenness are different from each other in the cold colors and the colors corresponding to the maximum values. Summary that it is set to warm color To.
The invention according to claim 6 is a terrain undulation image generating device that generates a terrain undulation image based on three-dimensional terrain data including altitude, wherein each point serving as a pixel is applied to each point based on the input three-dimensional terrain data. Elevation stage color processing means for generating elevation stage color data by performing stage color processing to give colors according to the altitude of the point, and unevenness for calculating the degree of unevenness of the topography at each point based on the three-dimensional topographic data Degree calculation means, unevenness degree gradation processing means for generating unevenness degree gradation data by performing gradation processing for imparting a color corresponding to the degree of unevenness at each point to each point, and the three-dimensional landform data An inclination calculating means for calculating the inclination at each point based on the above, and a shadow generating means for generating shadow data by applying a shadow process according to the inclination at each point to each of the points , The altitude stage Wherein the data and the asperity Dan'irodori data shading data and combined to a provided a synthesis processing means for generating Dan'irodori terrain data, and output means for outputting the terrain relief image based on the Dan'irodori terrain data, and the The synthesis processing means adds the color information acquired by the synthesis processing means to the three-dimensional space coordinate points corresponding to the respective points in the three-dimensional terrain data with three-component color coordinates, thereby obtaining a three-dimensional space. The stepped terrain data having six or more dimensions including coordinates and three-component color coordinates is generated, and the output means is a point obtained by mapping a spatial coordinate point of the tiered landform data to an output surface in a specified viewing direction. The gist is to generate the topographic relief image by giving the pixel a color coordinate corresponding to the spatial coordinate as a pixel value . According to this invention, it is possible to obtain the same effect as that of the invention according to the above-described terrain relief image generation method.

  According to the present invention, based on the three-dimensional terrain data including the altitude, it is possible to generate a terrain undulation image that allows easy interpretation of the relatively large undulations of the terrain, relatively small irregularities such as ridges and valleys, and the degree of inclination. An excellent effect is obtained.

The block diagram which shows the function structure of a map production | generation apparatus. The schematic diagram explaining the method of an aerial laser surveying. The graph explaining the ground angle and underground angle in a target point. (A) Explanatory drawing of ground opening degree (PHI) L, (b) is explanatory drawing of underground opening degree (PSI) L. (A), (b) Explanatory drawing which shows the ground opening degree (PHI) L and underground opening degree (PSI) L in a convex part and a recessed part. The graph which shows the relationship between ridge valley degree (alpha), ground opening degree (PHI) L, and underground opening degree (PSI) L. The schematic diagram which shows the altitude of eight surrounding vicinity of the target point used for calculation of inclination | tilt degree (theta). (A) Elevation color conversion table T1, (b) ridge valley degree color conversion table T2. The processing flowchart of a map production | generation apparatus. The figure which shows the altitude stage color image C1. The figure which shows a ridge valley degree stage image C2. The figure which shows the 1st synthesized image G1. The figure which shows inclination shadow image G (theta). The figure which shows the 2nd synthetic | combination image G2 (stepped terrain image G). The figure which shows the step topography image GP. The figure which shows the topographical relief image of a top view. The figure which shows the topographical relief image of a bird's-eye view.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
FIG. 1 is a block diagram illustrating a functional configuration of a map generation apparatus that is an example of a terrain relief image generation apparatus. A map generation apparatus 100 shown in FIG. 1 is constructed by installing a terrain relief image generation program in a main body 10 of a personal computer PC. The map generation apparatus 100 is connected to an input unit 11 including a communication interface (for example, a USB port, a LAN port, etc.) and an optical disk reader, and an input operation unit 12 including a keyboard and a mouse. Three-dimensional landform data (digital elevation model data) DEM (X, Y, Z) is input to the map generation device 100 through the input unit 11. The map generation apparatus 100 is graded according to the altitude Z and the ridge valley degree based on the three-dimensional terrain data DEM (X, Y, Z) (DEM: Digital Elevation Model), and has a slope. The topographic relief image data G (R, G, B) shaded according to is generated. A topographic relief image (three-dimensional topographic map) based on the topographic relief image data G generated by the map generation device 100 is displayed on the monitor 14 via the display driver 13 in the main body 10 or via the print driver 15 in the main body 10. Then, it is printed on paper by the printer 16.

  The three-dimensional terrain data DEM (X, Y, Z) is acquired by using, for example, an aviation laser survey as shown in FIG. As shown in FIG. 2, an aircraft 202 equipped with a laser surveying instrument 201 performs a laser scan that emits a laser to the ground while flying over the topographic survey target area, and measures the reflected pulse to obtain the aviation laser survey data. get. The aircraft 202 acquires the latitude / longitude of the current survey position based on the GPS signal received from the GPS satellite 203 and the altitude Z based on the measurement value of the reflected laser at that time, and the altitude is associated with the latitude / longitude. Get aerial laser survey data. From this aviation laser survey data, features such as buildings, trees, vehicles, etc. that do not represent topographical shapes are separated, and modeled and generated from TIN (Triangle Irregular Network), etc. By reading the altitude Z of the intersection of the distance (for example, a predetermined value within a range of 0.1 m to 50 m) mesh, the three-dimensional terrain data DEM (X, Y, Z) is generated. Of course, the three-dimensional terrain data DEM (X, Y, Z) can also be obtained from aerial photogrammetry, satellite imagery, radar measurement, or the like.

  Details of the map generation apparatus 100 shown in FIG. 1 will be described below. The map generation apparatus 100 includes a control unit 21, an input buffer 22, a first stage saturation calculation unit 23 that is an example of an elevation stage saturation processing unit, a ridge valley degree calculation unit 24 that is an example of a ridge valley degree calculation unit, and a ridge valley degree. The second stage saturation calculation unit 25, the gradient degree calculation unit 26, the shadow calculation unit 27, the synthesis processing unit 28, the polygon processing unit 29, and the image generation unit 30 are provided as an example of the stage color processing means.

  The control unit 21 controls the entire map generation apparatus 100 and gives necessary instructions to the units 22 to 30. The input buffer 22 stores three-dimensional terrain data DEM (X, Y, Z) from the input unit 11 and various setting values set by the user by operating the input operation unit 12. Each of the units 22 to 28 has a stage color process (first processing) for assigning a color corresponding to the altitude Z to each coordinate point (X, Y, Z) constituting the three-dimensional landform data DEM (X, Y, Z). ), A stage color process (second stage color process) for imparting a color according to the ridge valley degree α, and a shadow process for giving a shadow according to the slope (tilt angle) θ. Then, the synthesis processing unit 28 weights the processing results of the first stage color process, the second stage color process, and the shadow process as necessary to synthesize the three-dimensional space coordinates (X, Y). , Z) and color values (R, G, B), a point (X, Y, Z, R, G, B) expressed in a total of six dimensions is generated. Further, when the synthesis processing unit 28 generates 6-dimensional points (X, Y, Z, R, G, B) corresponding to all the points of the three-dimensional terrain data DEM (X, Y, Z), the 6-dimensional data is generated. The terrain terrain data G (X, Y, Z, R, G, B) composed of 6-dimensional mesh data expressed by a set of points is generated.

  The first stage color calculation unit 23 includes a first conversion table creation unit 31 for creating an elevation color conversion table T1 (see FIG. 8A) for converting the elevation value Z into a color. With reference to the elevation color conversion table T1 created by the table creation unit 31, a color corresponding to the elevation value Z of each point is acquired. The point data representing the color is input to the synthesis processing unit 28 as elevation stage color data C1 (R, G, B).

The ridge valley degree calculation unit 24 calculates the ridge valley degree α from the spatial coordinates (X, Y, Z) of the target point (a point that becomes a pixel). A detailed calculation method of the ridge valley degree α will be described later.
The second stage color calculation unit 25 includes a second conversion table creation unit 32 for creating a ridge valley degree color conversion table T2 (see FIG. 8B) for converting the ridge valley degree α into a color. With reference to the ridge valley degree color conversion table T2 created by the second conversion table creation unit 32, a color corresponding to the altitude value Z of each point is acquired. The point data representing the color is input to the composition processing unit 28 as ridge valley degree color data C2 (R, G, B).

The inclination calculating unit 26 calculates the inclination θ (inclination angle) from the spatial coordinates (X, Y, Z) of the target point. A detailed calculation method of the inclination degree θ will be described later.
The shadow calculation unit 27 uses a gradient shadow conversion table (not shown) for converting the gradient θ to a shadow (brightness) or a calculation formula for gradient shadow conversion, and a shadow value corresponding to the gradient θ. To get. The point data representing the shadow is input to the composition processing unit 28 as the shadow data Gθ.

  The synthesis processing unit 28 performs color synthesis of the altitude stage color data C1 (R, G, B) and the ridge valley degree stage color data C2 (R, G, B) to generate first synthesized data G1. And a shadow composition processing unit 34 that synthesizes the first synthesized data G1 and the shadow data Gθ to generate the second synthesized data G2. The color synthesis by the color synthesis processing unit 33 is performed by, for example, weighted synthesis (weighted average). Further, the shadow composition processing unit 34 multiplies the first composite data G1 (R1, G1, B1) by the shadow value Gθ (= 0 to 1.0) of the shadow data, thereby obtaining the second composite data G2 (R2 , G2, B2) = (R1 · Gθ, G1 · Gθ, B1 · Gθ).

  The second synthesized data G2 is accumulated in the buffer 35, and when the processing is completed for all points of the three-dimensional terrain data DEM (X, Y, Z), the synthesis processing unit 28 stores the second synthesized data G2 stored in the buffer 35. The staged landform data G (X, Y, Z, R, G, B) expressed as a collection of points (R2, G2, B2) is output to the polygon processing unit 29.

  The polygon processing unit 29 changes the color of the pixel in the water part polygon specified based on the water part polygon data PD in the staged terrain data G (X, Y, Z, R, G, B) to blue, The stepped landform data GP (X, Y, Z, R, G, B) in which water surfaces such as ponds, swamps, rivers, and the sea are colored in blue is output to the image generation unit 30. Here, the water part polygon data PD is created from the three-dimensional terrain data DEM (X, Y, Z) or other materials, and designates a region recognized by the operator as a water part as a polygon (polygon). It is data.

  The image generation unit 30 generates terrain relief image data G (R, G, B) obtained by viewing the stepped terrain data GP (X, Y, Z, R, G, B) from the viewing direction specified by the user. . For example, a terrain undulation image (plan view) when the viewing direction is from directly above, or a terrain undulation image (bird's eye view) when obliquely upward is generated. The topographic relief image is displayed on the monitor 14 or printed on paper by the printer 16 according to the output method selected by the user.

  Next, according to the processing flow shown in FIG. 9, the details of the terrain relief image generation method by the map generation device 100 will be described. In the following description, a specific calculation method of the ridge valley degree α and the inclination degree θ will also be described.

  The processing flow of this embodiment includes a table generation process and a relief image generation process. The undulation image generation process is roughly divided into three processes. That is, the undulating image generation process includes a first stage color process for obtaining a color according to the altitude value Z of the target point, a second stage color process for obtaining a color according to the ridge valley degree α of the target point, and the gradient at the target point. and a shadow process for obtaining a shadow corresponding to θ.

First, table generation processing for creating the conversion tables T1 and T2 will be described.
In step S10, the altitude Z of all points of the three-dimensional landform data DEM (X, Y, Z) is acquired. As can be seen from the step color setting of the altitude color conversion table T1 shown in FIG. 8A, the low altitude is green (strictly, the minimum value is light blue-green), and the high altitude is brown (strictly, the maximum value is dark brown) ).

  In step S20, an altitude color conversion table T1 is created based on the minimum altitude value Zmin and the maximum value Zmax. A color table (right part of FIG. 8A) that is color-coded into a plurality of gradations (22 gradations in this example) whose color gradually changes in the color range of green (light green blue) to brown (dark brown) is previously stored. It is prepared. The altitude range from the minimum value Zmin to the maximum value Zmax is divided into a plurality of levels (for example, 22 levels) equal to the color table and the number of gradations. Assign each tone color. Therefore, even if the altitude ranges of the target areas (display areas) are different, it is possible to perform gradation processing with the minimum altitude being green and the maximum altitude being brown. For this reason, comparatively large undulations are easy to read by the green to brown stage colors. This stage color is easy to grasp, similar to the expression of a general map book, and it is possible to capture accurate topographic relief while giving a natural impression.

In step S30, data (X, Y, Z) of points within a set distance with respect to the target point (target point) is acquired.
In step S40, the ridge valley degree α is calculated based on the data (X, Y, Z) of the points within the set distance from the target point. Here, the calculation method of the ridge valley degree α will be described with reference to FIGS. The ridge valley degree α is a topographic amount representing the degree of unevenness calculated from the average angle between the ground opening and the underground opening.

FIG. 3 is a graph for explaining the ground angle obtained when calculating the ground opening and the underground angle obtained when calculating the underground opening.
The ground opening is a terrain quantity parameter that represents the degree to which each mesh protrudes from the ground compared to the surrounding area. The ground opening represents the size of the sky that can be seen within a set distance L from the point of interest (target point), and generally the point that protrudes from the surroundings has a larger value. The ground opening shows a large value at the summit and ridge and a small value at the depression and valley bottom, and the protruding summit and ridge are emphasized.

  The underground opening is a terrain quantity parameter that expresses the degree to which each mesh protrudes underground compared to the surrounding area. The underground opening represents the size of the underground in the range of the set distance L when the underground is looked over from the ground surface, and the value of the underground opening is generally larger at the point where the underground is difficult. The underground opening shows a large value at the depression and valley bottom, and a small value at the mountain top and ridge, and the depression and valley are emphasized.

  When obtaining the ground opening and the underground opening, first, the ground angle Φ1 and the underground angle Φ2 shown in FIG. 3 are respectively calculated. As shown in FIG. 3, the grid point elevation Z is searched in eight directions from the target point (however, only one search direction is shown in FIG. 3), and the target point Pj and the elevation point are within the set distance L in each search direction. The minimum value of the angle formed by the line segment connecting the two and the shaft portion extending from the target point Pj to the high altitude side on the z axis (elevation axis) is obtained as the ground angle Φ1. As a result, eight ground angles Φ1 in eight directions are calculated. Similarly, as shown in FIG. 3, the elevation Z of the grid point is searched in eight directions from the target point, and a line segment connecting the target point Pj and the elevation point within the set distance L in each search direction, and the z axis ( The minimum value of the angle formed by the shaft portion extending from the target point Pj of the altitude axis to the lower altitude side is obtained as the underground angle Φ2. As a result, eight underground angles Φ2 in eight directions are calculated. In the present embodiment, in the case of terrain mesh data of about 0.5 m to 5.0 m, the set distance L is set to 25 m as an example. Of course, the set distance L is preferably set to a value several to several tens of times depending on the mesh size, and other distances such as 5 m, 10 m, and 50 m may be set. Further, the set distance L may be set by the number of meshes. Further, the search direction from the target point is not limited to eight directions, and may be further subdivided into four directions or 16 directions or 32 directions.

  Next, the average of the ground angles Φ1 in the eight directions is calculated to obtain the ground opening ΦL shown in FIG. Further, the average of the underground angles Φ2 in the eight directions is calculated to determine the underground opening ΨL shown in FIG. 4A shows an example of the ground opening ΦL of a concave portion such as a valley or a depression, and FIG. 4B shows an example of the underground opening ψL of a convex portion such as a ridge. Actually, as shown in FIGS. 5 (a) and 5 (b), the ground opening ΦL and the underground opening ψL are obtained for the concave portion and the convex portion, respectively.

  For the convex portion shown in FIG. 5A and the concave portion shown in FIG. 5B, a conical surface defined by the ground opening ΦL (ground conical surface) and a conical surface defined by the underground opening ψL ( Underground conical surface). 5 (a) and 5 (b), the angle from the horizontal plane passing through the target point Pj to the lower side (positive) to the ground conical surface (hereinafter referred to as “ground opening angle”) (= ΦL−90), and the horizontal plane To the underground conical surface (hereinafter referred to as “underground opening angle”) (= 90−ΨL).

FIG. 6 is an example of the convex portion as shown in FIG. 5A, and shows the ground opening angle (= −90 + ΦL) from the horizontal plane and the underground opening angle (= 90−ΨL) from the horizontal plane to the underground conical surface. . In the present embodiment, the average (= ((− 90 + ΦL) + (90−ΨL)) / 2 of the ground opening angle (= −90 + ΦL) and the underground opening angle (= 90−ΨL) from the horizontal plane to the underground conical surface. ) Is defined as the ridge valley degree α. By the ridge valley degree α, the unevenness degree can be expressed by one index that takes into account the topographic amount of both the ground opening ΦL and the underground opening ΨL. Accordingly, the ridge valley degree α is given by the following equation using the ground opening ΦL and the underground opening ΨL.
Cone valley degree α = (ΦL−ΨL) / 2 (1)
In the convex portion shown in FIG. 5 (a), since the ground opening ΦL has a relatively large value and the underground opening ψL has a small value, the ridge valley degree α is positive (α> 0). On the other hand, in the recess shown in FIG. 5 (b), the ground opening ΦL has a relatively small value and the underground opening ψL has a large value, so the ridge valley degree α is negative (α <0). Thus, the ridge valley degree α is determined as a value in the range of the minimum value αmin (<0) to the maximum value αmax (> 0).

  In step S50, the ridge valley degree color conversion table T2 is created based on the minimum value αmin and the maximum value αmax of the ridge valley degree. A color table (right side portion in the conversion table T2 in FIG. 8B) is prepared in advance that is color-coded into a plurality of gradations (22 gradations in this example) whose color gradually changes in the range from blue to red. The ridge valley degree range of the minimum value αmin to the maximum value αmax of the ridge valley degree is divided into a plurality of stages (for example, 22 stages) of the same number as the color table, and each of the ridge valley degrees of the minimum value αmin to the maximum value αmax is blue to red. Assign each color. Therefore, according to the ridge valley degree α, the valley (concave portion) is colored in blue, and the ridge (convex portion) is red in color. This stage color makes it easy to read even relatively small uneven portions (micro terrain). Thus, the table generation processing is completed by creating the conversion tables T1 and T2 shown in FIGS.

  The first color range for the stage color set in each conversion table T1 shown in FIG. 8A is “green to brown”, and is set in each conversion table T2 shown in FIG. 8B. The second color range for the tan color is “blue to red”. The first color range and the second color range are common in that the minimum value side is “cold color” and the maximum value side is “warm color”, but the specific color of the cold color (green and blue) And the specific colors of warm colors (brown and red) are different from each other.

  In the present embodiment, “cold color” refers to a color in which at least one of the color components red (R), green (G), and blue (B) is larger than the red component. At least one of G> R and B> R is established). “Warm color” refers to a color in which the red component of the color components red (R), green (G), and blue (B) is larger than the green and blue components (R> G and R>). B).

  A green color is assigned to a low altitude region, and a brown color is assigned to a high altitude region. In addition, the valley is given to the blue color, and the ridge is given to the red color. Since the color given for the stage color display is different between the altitude Z and the ridge valley degree α, relatively large undulations and relatively small irregularities (micro-topography) such as ridges and valleys are represented by the color of the stage color. Easy to distinguish from differences. In addition, the low altitude flat land is green, the high altitude mountain peaks are brown, and the familiar colors used for general map books are used. The second color range where the valley is set to blue and the ridge is set to red is different from the first color range set for elevation, making the ridge and valley easy to read. . It should be noted that the minimum color in the first color range and the second color range may be green and the other may be blue. For example, opposite colors are used for altitude and ridge valley degree. May be.

  Next, the green-brown color corresponding to the altitude Z obtained by using the conversion tables T1 and T2 and the shadow table, the ridge valley degree, for all target points of the three-dimensional terrain data DEM (X, Y, Z). The blue-red color corresponding to α and the black-white shadow corresponding to the gradient θ are synthesized and applied to generate stepped landform data G (X, Y, Z, R, G, B, Z). The undulation image generation process (S60 to S170) will be described.

  In step S60, a target point Pj (where j = 1, 2, 3,... N (n is the total number of points in the display area in the DEM)) is set. All points (points to be pixels) constituting the three-dimensional terrain data DEM (X, Y, Z) are set as target points one by one in order. In the following target point color generation processing (S70 to S150), color information (R, G, B) is obtained by performing first-stage saturation processing, second-stage saturation processing, shadow processing, and composition processing on the target point. Is granted.

First, in step S70, the altitude value Z of the target point is acquired. In step S80, a color (elevation step color value) (Rz, Gz, Bz) corresponding to the altitude value Z is calculated with reference to the altitude color conversion table T1 (FIG. 8A). With reference to the altitude color conversion table T1 (FIG. 8A), it is determined which tone belongs to a plurality of tones (22 tones), and the lower limit values of the altitude and the color in the tone range to which the tone belongs ( First boundary values) Z1, (R1, G1, B1) and respective upper limit values (second boundary values) Z2, (R2, G2, B2) are acquired. Then, by calculating a weighted average for each RGB component according to the following calculation formula so that the color according to the altitude is smooth, the altitude stage color data C1 (Rz) indicating the colors of green to brown according to the altitude Z , Gz, Bz).
Rz = R2 + (R1-R2). (Z-Z2) / (Z1-Z2) (2)
Gz = G2 + (G1-G2). (Z-Z2) / (Z1-Z2) (3)
Bz = B2 + (B1-B2). (Z-Z2) / (Z1-Z2) (4)
The altitude stage color image C1 shown in FIG. 10 is a color display of all points obtained by assigning the elevation stage color data C1 (Rz, Gz, Bz) to the spatial coordinates (X, Y, Z) as pixels. As shown in the elevation gradation image C1 in FIG. 10, in this display area, light blue green to brown are graded according to the elevation Z, and relatively large undulations can be interpreted from the difference in the graded color. .

In step S90, the ridge valley degree α of the target point is acquired. In step S100, a color (ridge valley degree chromatic value) (Rα, Gα, Bα) corresponding to the ridge valley degree α is calculated with reference to the ridge valley degree color conversion table T2 (FIG. 8B). By referring to the ridge valley degree color conversion table T2 (FIG. 8B), it is determined which of the plurality of gradations (22 gradations) belongs to, and the ridge valley degree α and the color in the gradation range to which it belongs. Each lower limit value (first boundary value) α1, (R1, G1, B1) and each upper limit value (second boundary value) α2, (R2, G2, B2) are acquired. And the ridge valley which shows the color of blue-red according to ridge valley degree alpha by calculating a weighted average for every RGB component according to the following formula so that the color according to ridge valley degree alpha may become smooth The degree color data C2 (Rα, Gα, Bα) is calculated.
Rα = R2 + (R1−R2) · (α−α2) / (α1−α2) (5)
Gα = G2 + (G1−G2) · (α−α2) / (α1−α2) (6)
Bα = B2 + (B1−B2) · (α−α2) / (α1−α2) (7)
The ridge valley degree stage color image C2 shown in FIG. 11 is a color display of all points obtained by assigning the ridge valley degree stage color data C2 (Rα, Gα, Bα) to the spatial coordinates (X, Y, Z) as pixels. It is. As shown in the ridge valley degree stepped image C2 in FIG. 11, the display area is stepped from blue to red in blue green to yellow according to the ridge valley degree α, and the ridge is determined from the difference in the stepped colors. It is possible to interpret relatively small irregularities such as ridges and valleys.

In step S110, a weighted average (weighted average) of the altitude stage color data C1 and the ridge valley degree stage color data C2 is calculated to generate first synthesized data G1. The first composite data G1 (Rzα, Gzα, Bzα) is calculated according to the following calculation formula.
Rzα = (w1 · Rz + w2 · Rα) / (w1 + w2) (8)
Gzα = (w1 · Gz + w2 · Gα) / (w1 + w2) (9)
Bzα = (w1 · Bz + w2 · Bα) / (w1 + w2) (10)
Here, w1 is a weighting coefficient of the altitude stage color, and w2 is a weighting coefficient of the ridge valley degree stage color. A first composite image G1 shown in FIG. 12 is a color display of all the points obtained by assigning the first composite data G1 (Rzα, Gzα, Bzα) to the spatial coordinates (X, Y, Z) as pixels. This first composite image G1 shows an example in which the weight coefficient w1 = 0.5 for the altitude stage color and the weight coefficient w2 = 0.5 for the degree ridge valley degree color. According to the combination of the color ranges (green to brown) (blue to red) set in the conversion tables T1 and T2, it is possible to distinguish between the stage color due to the altitude Z and the level color due to the ridge valley degree α. Appropriate weighting factors w1 and w2 can be set.

  In the display area of the first composite image G1, the step color of the green to brown range corresponding to the altitude Z and the step color of the blue to red range corresponding to the ridge valley degree α are color-synthesized, and the flat ground is thin. The green, high altitude part is a teacup and the brown ridge extends into a vein, the next highest altitude is yellow tea and the deep yellow ridge extends into a vein, and the vein The valley that extends to is expressed in blue-green. In the first composite image G1, it is possible to interpret both relatively large undulations and relatively small irregularities due to the difference in the colors that have been staged.

In step S120, data (X, Y, Z) of eight points near the target point are acquired. In step S130, the inclination θ is calculated using data (X, Y, Z) of eight points in the vicinity of the target point. FIG. 7 shows eight elevation values located near the periphery of the target point. First, the slope Sx in the x direction and the slope Sy in the y direction are calculated by the following equations using the elevation values Z1 to Z8 at the eight neighboring points around the target point.
Sx = ((Z1 + Z4 + Z6) − (Z3 + Z5 + Z8)) / 6 / Msize (11)
Sy = ((Z1 + Z2 + Z3)-(Z6 + Z7 + Z8)) / 6 / Msize (12)
Here, Msize is the mesh size (size (length) of one pixel per side). Next, using the inclination degree Sx in the x direction and the inclination degree Sy in the y direction, the inclination (inclination angle) θ is calculated by the following equation.
Inclination θ = arctan (√ (Sx · Sx + Sy · Sy) (13)
As described above, in this embodiment, the inclination θ is calculated by combining the inclination Sx in the x direction and the inclination Sy in the y direction. By using this inclination degree θ, the inclination angles in the eight surrounding directions are appropriately smoothed compared to the method of applying the shadow using the maximum inclination angle among the eight inclination angles around the target point Pj. A natural shading according to is given. Of course, a value obtained by dividing the difference in elevation average of each of the three points on both sides in the x direction by “mesh size Msize”, such as “(Z1 + Z4 + Z6) / 3− (Z3 + Z5 + Z8) / 3”. You may use for. Note that the equation θ = √ (Sx · Sx + Sy · Sy) can also be used as the inclination θ.

  In step S140, the shadow Gθ is calculated from the inclination θ. A shade Gθ corresponding to the gradient θ is obtained by referring to a gradient shade conversion table (gray scale table) prepared in advance with the maximum gradient being “black” and the minimum gradient being “white”. In this example, the shadow Gθ is calculated as a value within the range of 0 to 1.0. An inclined shadow image Gθ shown in FIG. 13 is displayed in gray scale with all the points where the shadow Gθ is assigned to the spatial coordinates (X, Y, Z) as pixels. In the display area of the gradient shadow image Gθ, a shadow corresponding to the gradient θ is represented, and a region with a large gradient is represented with a gray color (low lightness) and a region with a small gradient is represented with a light color (high lightness) grayscale. Yes. For example, ridges, valleys, and plains that extend in a vein shape are expressed in light gray (light gray), and the slope between the ridge and the valley is expressed in dark gray (dark gray) corresponding to the inclination.

In step S150, the first composite data G1 and the shadow Gθ are multiplied to generate second composite data G2. The second combined data G2 (Rzαθ, Gzαθ, Bzαθ) is calculated according to the following calculation formula.
Rzαθ = Rzα · Gθ (14)
Gzαθ = Gzα · Gθ (15)
Bzαθ = Bzα · Gθ (16)
The second composite image G2 shown in FIG. 14 is a color display of all the points obtained by assigning the second composite data G2 (Rzαθ, Gzαθ, Bzαθ) to the spatial coordinates (X, Y, Z) as pixels. In the display area of the second composite image G2, the stage colors in the range of green to brown according to the altitude Z, the stage colors in the range of blue to red according to the ridge valley degree α, and the shade according to the inclination degree θ. And the color is light green, the flat area is light green, the high altitude part is dark brown, the light brown and the ridge part extends in a vein shape, the yellow tea ridge part in the next highest altitude part in a vein shape The valleys that extend and further extend like a vein are expressed in blue-green. On both sides of the ridge, the slope with a large slope is represented by a dark gray color mixture, and the slope with a small slope is represented by a light gray color mixture. Therefore, in the second composite image G2, it is possible to interpret both relatively large undulations and relatively small irregularities due to the difference in the staged colors, and it is also possible to interpret the magnitude of the inclination from the shadow. The second composite data G2 (Rzαθ, Gzαθ, Bzαθ) is 6-dimensional data (X, Y, Z, Rzαθ, Gzαθ) that combines the spatial coordinates and the color values together with the spatial coordinates (X, Y, Z). , Bzαθ) is stored in the buffer 35.

  In this way, when the processing of S70 to S150 is completed for one target point, and two types of gradations and shadows are combined and applied to the target point, it is determined in step S160 whether the processing has been completed for all points. . If there are still coordinate points to be processed before all points have been processed, the next point number is incremented by 1 (j = j + 1) in step S170, and the next target point Pj is set in step S60. . Hereinafter, similarly, when the processing of S70 to S150 is repeated for each target point and the processing is finished for all coordinate points, it is determined that the processing of all points is finished in S160. At this time, the buffer 35 stores the second composite data G2 (X, Y, Z, Rzαθ, Gzαθ, Bzαθ) of all points.

  In step S180, stepped terrain data G (X, Y, Z, R, G, B) is generated. That is, the collection of all the points of the second composite data G2 (X, Y, Z, Rzαθ, Gzαθ, Bzαθ) stored in the buffer 35 is the stepped terrain data G (X, Y, Z, R, G, B). ). This staged terrain data G (X, Y, Z, R, G, B) is 6-dimensional numerical data including spatial coordinate values and color values as components, and each point is a spatial coordinate point and a pixel. Function. If each point of the stepped terrain data G (X, Y, Z, R, G, B) is expressed in color as a pixel, the stepped terrain data G is a collection of the second synthesized data G2. Same image.

  In step S190, water part polygon data PD (a closed polygonal surface separately represented by an X, Y coordinate sequence) is obtained, and water is obtained from the stepped terrain data G (X, Y, Z, R, G, B). The color within the polygon defined by the partial polygon data PD is changed to generate stepped landform data GP (X, Y, Z, R, G, B). The polygon processing unit 29 performs this polygon processing. As a result of this polygon processing, the color values (R, G, B) of all points (pixels) existing in the water part polygon set in the water surface area such as a pond, swamp, river, sea, etc. are blue values, for example. Changed to The staged landform image GP shown in FIG. 15 is a color representation of each point of the staged landform data GP (X, Y, Z, R, G, B) as a pixel.

  In step S200, terrain undulation image data G (R, G, B) from a specified direction is generated based on the stepped terrain data GP (X, Y, Z, R, G, B). The terrain relief image data G (R, G, B) is generated by the image generation unit 30. For example, in the case of a plan view in which the designated direction view is from directly above, the stepped landform data GP (X, Y, Z, R, G, B) is designated as the output surface (display surface) when viewed from the z direction. By mapping each point (pixel) in the area and giving a pixel value (R, G, B) corresponding to each mapping point on the output surface, the topographic relief image data G (R, G, B) in plan view ) Is generated. As a result, based on the generated topographic relief image data G (R, G, B), a topographic relief image in plan view (z direction view) shown in FIG. 16 is output (displayed or printed). Further, when the designated direction view is an oblique direction, the stepped terrain data GP (X, Y, Z, R, G, B) is displayed on the output surface (display surface) when viewed obliquely with respect to the z direction. By mapping each point (pixel) in the designated area and giving the corresponding pixel value (R, G, B) to each mapping point (pixel) on the output surface, the terrain relief image data G viewed from an oblique direction (R, G, B) is generated. As a result, the topographic relief image (bird's eye view) shown in FIG. 17 is output (displayed or printed) based on the generated topographic relief image data G (R, G, B).

  Conventionally, when generating a bird's-eye view based on three-dimensional terrain data DEM (X, Y, Z), a method has been adopted in which a terrain surface is first generated and then a color is added to the terrain surface by rendering processing. The display speed is slowed down by a heavy rendering process. On the other hand, in this embodiment, three-dimensional information is maintained in the stepped terrain data GP generated by adding the color values (R, G, B) to the three-dimensional coordinates (X, Y, Z). Therefore, image data such as a bird's-eye view can be generated at a relatively high speed simply by changing the direction (viewing direction) when mapping the terraced terrain data GP onto the output surface (display surface). As a result, a three-dimensional image such as a bird's eye view can be displayed at a relatively high speed.

  In FIG. 9, the processes of S10, S20, S70, and S80 correspond to the altitude step color processing procedure, the processes of S30 and S40 correspond to the unevenness degree calculation procedure, and the processes of S50, S90, and S100 further correspond to the unevenness degree. This corresponds to the step color processing procedure. In addition, the processing in S120 and S130 corresponds to a gradient calculation procedure, the processing in S140 corresponds to a shadow generation procedure, and the processing in S110, S150, and S180 corresponds to a synthesis processing procedure. Further, the process of S200 corresponds to an output procedure.

As described above in detail, according to this embodiment, the following effects can be obtained.
(1) Elevation dansai and ridge valley degree dansai (uneven degree dansai) make it easy to interpret relatively large undulations by altitude dansai. It becomes easy to read small irregularities (micro terrain).

  (2) Since the shadow emphasizing the fine topography is created from the inclination θ, there is no dependency on the light incident direction of the shadow which becomes a problem when the shadow is applied assuming the oblique incident light. Thus, it is possible to avoid the problem that the valley is dark in the red three-dimensional map due to the shade according to the degree of unevenness (the degree of rise and fall). By superimposing shadows based on the inclination degree θ on the ridge valley degree stepwise image, the ridges and valleys that are difficult to distinguish only by light and dark can be read more clearly. Further, according to the inclination degree θ, it is possible to give a stereoscopic effect by increasing the lightness of the gently inclined portion and decreasing the lightness of the steeply inclined portion.

  (3) Elevation stage color is emphasized by coloring the first color range “green (minimum elevation Zmin) to brown (maximum elevation Zmax)” according to the elevation value Z. The second color range “blue (minimum value αmin) to red (maximum value αmax)” corresponding to the valley degree α is emphasized and expressed. Set the color range in which the first color range and the second color range are different (that is, the minimum color and the maximum color of the parameters (elevation Z, ridge valley degree α) are different from each other), and the minimum value of both parameters Are set to be different cold colors and maximum values are different warm colors. Therefore, even if the altitude stage color and the ridge valley degree stage color are combined and displayed, it is easier to interpret a relatively large undulation and a relatively small unevenness (fine landform) in the interpretation.

  (4) In the method of displaying gradation in red brightness according to the degree of floating and sinking as in the reddish stereoscopic image in Patent Document 1, an image in which convex portions such as ridges expand and concave portions such as valleys contract (valleys) Taniuchi is dark and difficult to see. However, according to the present embodiment, unevenness such as ridges and valleys are highlighted with a stepped color in the blue to red color range according to the ridge valley degree α, so that convex portions such as ridges expand, It is possible to avoid the image where the concave portion is contracted.

  (5) The terraced landform data GP is generated by adding color information (R, G, B) as additional information of the three-dimensional coordinates (X, Y, Z), and the three-dimensional coordinates (X, Y, Z). ). For this reason, a three-dimensional terrain relief image can be created by viewing the spatially three-dimensional terraced terrain data GP from an oblique direction. Usually, a surface is generated from three-dimensional data, and then rendering processing is generally performed to express a terrain relief image, resulting in a slow display speed. However, according to the present embodiment, the processing for displaying the colored points in the three-dimensional terrain data is sufficient, so that the terrain relief image can be generated at high speed.

  (6) Although the conventional topographic image has many monochromatic and red to blue gradations, this embodiment can express the topographic relief image with green to brown and a familiar color tone that is close to that of a general map book. In addition, large undulations are emphasized with green-brown gradations, and micro-terrain such as irregularities is emphasized with blue-red gradations, so the notes (red, blue, black) on the composite color are in the background. The effect of being easy to read without melting is also obtained. Further, by coloring the water part using a separately created water part polygon (or water part attribute), it is possible to provide a terrain relief image that is more familiar than a map book.

  (7) In the unevenness degree calculation procedure (S30, S40), the ground angle Φ1 and the underground angle Φ2 are obtained for each target point in the three-dimensional terrain data DEM in a plurality of directions (for example, eight directions) from the target point. Based on the ground opening ΦL, which is the average of the angle Φ1, and the underground opening ΨL, which is the average of the underground angle Φ2, the ridge valley degree α is calculated as an example of the unevenness by the formula α = (ΦL−ΨL) / 2. To do. From the ground opening ΦL that can represent convex parts such as ridges and the underground opening ΨL that can represent concave parts such as valleys, the ridge valley degree α is obtained as one terrain quantity parameter that can express the degree of unevenness, and the ridge valley degree α Since the color determined from the conversion table T2 is applied according to the above, the fine terrain can be expressed in a stepwise manner.

  (8) In the gradient calculation procedure (S120, S130), the x-direction gradient Sx and the y-direction gradient calculated by the equations (11) and (12), respectively, using the elevations Z of the eight neighboring points around the target point. Sy is synthesized by equation (13) to determine the inclination θ. Therefore, it is possible to employ the degree of inclination θ in which the inclination angles in the eight directions from the target point are appropriately smoothed. As a result, it is possible to give a natural shadow according to the slope θ that is moderately smoothed.

  (9) The weighted average (weighted average) of the altitude stage color data C1 and the ridge valley degree stage color data C2 is calculated by the formulas (8) to (10) to generate the first synthesized data G1. Therefore, by adjusting the weighting by the coefficients w1 and w2, the staged landform data GP can be generated under the condition that it is easy to read relatively large undulations and relatively small unevenness.

The said embodiment is not limited above, It can also change into the following aspects.
The color range of the conversion tables T1 and T2 is not limited to the above embodiment, and an appropriate color range can be set. For example, the color ranges used in the conversion tables T1 and T2 may be interchanged. Furthermore, for at least one of the conversion tables T1 and T2, a color range in which the minimum value side of the altitude Z or the ridge valley degree α is a warm color and the maximum value side is a cool color may be set. Moreover, it is good also as the same color range to be used using the same conversion table for elevation and for ridge valley degree.

  ・ A method was adopted in which the first stage saturation process according to the altitude Z, the second stage saturation process according to the ridge valley degree α, the shading process according to the inclination degree and the synthesis process were repeated for each target point until the end of all points. However, instead of this, a method of proceeding to the next processing after finishing the processing of all points can also be adopted.

-You may change the calculation formula which calculates | requires inclination suitably. A calculation formula for obtaining the maximum inclination angle may be used.
-The formula for obtaining the ridge valley degree α may be changed as appropriate. Further, the search direction is not limited to eight directions, and may be four directions, sixteen directions, or thirty-two directions.

  -The unevenness degree is not limited to the ridge valley degree α. Laplacian may be used as the degree of unevenness. Furthermore, the average curvature defined as the average of the maximum value and the minimum value of all geodesic curves passing through a certain point on the curve (the shortest distance curve connecting two points on the curved surface) may be used as the unevenness degree. Good.

  The 3D terrain data may be TIN (triangulated irregular network). Furthermore, an ortho image, DTM (Digital Terrain Model), and DSM (Digital Surface Model) may be used.

  ・ The terraced terrain data is not limited to 6-dimensional data. It may be 7-dimensional or more data including other information. Alternatively, it may be three-dimensional terraced landform data GP (R, G, B) in which the three-dimensional space coordinates (X, Y, Z) are eliminated. In this case, the staged terrain data generation process is performed for each designated visual field direction.

  DESCRIPTION OF SYMBOLS 10 ... Main body, 11 ... Input part, 12 ... Input operation part, 13 ... Display driver, 14 ... Monitor, 15 ... Print driver, 16 ... Printer, 21 ... Control part, 22 ... Input buffer, 23 ... Elevation stage color processing means A first stage saturation calculation unit, which is an example of 24, a ridge valley degree calculation unit which is an example of the degree of unevenness calculation means, 25 ... a second stage saturation calculation part which is an example of the degree of unevenness stage color processing means, 26 ... an inclination degree An inclination calculating unit as an example of a calculating unit, 27... A shadow calculating unit as an example of a shadow generating unit, 28... A combining processing unit as an example of a combining processing unit, 29. An image generation unit, 31 ... first conversion table creation unit, 32 ... second conversion table creation unit, 33 ... color synthesis processing unit, 34 ... shadow synthesis processing unit, 35 ... buffer, 100 ... example of terrain relief image generation device A map generator, PC ... -Sonal computer, DEM (X, Y, Z) ... 3D terrain data, Z ... Elevation, Φ1 ... Ground angle, Φ2 ... Underground angle, ΦL ... Ground opening, ΨL ... Underground opening, α ... Example of unevenness Ridge valley degree, Sx: inclination in x direction, Sy: inclination in y direction, θ: inclination, T1: high color conversion table, T2: ridge valley color conversion table, Zmin: minimum altitude, Zmax: Maximum value of altitude, αmin: minimum value of ridge valley degree, αmax: maximum value of ridge valley degree, Pj: target point (point of interest) C1: altitude stage color data, C2: unevenness level color data Ridge valley level data, Gθ ... shadow data (shadow), G1 ... first composite data, G2 ... second composite data, G (X, Y, Z, R, G, B) ... step topography data (water Part polygon color before), GP (X, Y, Z, R, G, B)... Terrain data (after water part polygon color assignment), G ( , G, B) ... terrain relief image data.

Claims (6)

A terrain undulation image generation method by a terrain undulation image generation device that generates a terrain undulation image based on three-dimensional terrain data including altitude,
Elevation stage chrominance processing that generates elevation stage chromatic data by performing stage grading processing that assigns a color according to the elevation of the point to each point that becomes a pixel based on the input three-dimensional terrain data by the elevation stage chromatic processing means Procedure and
The unevenness degree calculating means calculates the unevenness degree of the terrain at each point based on the three-dimensional terrain data by the unevenness degree calculating means ,
An unevenness degree gradation processing procedure for generating unevenness degree gradation data by performing a gradation process that imparts a color corresponding to the unevenness degree for each point to each point by the unevenness degree gradation processing means ;
An inclination calculation procedure for calculating an inclination at each point based on the three-dimensional terrain data by an inclination calculation means ;
A shadow generation procedure for generating shadow data by performing a shadow process for applying a shadow according to the slope at each point to each point by a shadow generation unit ;
A synthesis processing procedure for synthesizing the elevation gradation data, the unevenness degree gradation data, and the shadow data to generate gradation terrain data by a combination processing means;
An output procedure for outputting a terrain relief image based on the stepped terrain data by output means ;
Equipped with a,
In the altitude stage color processing procedure, the altitude stage color data is generated by giving a color according to the altitude according to a first color range set between the minimum value and the maximum value of the altitude,
In the unevenness degree gradation processing procedure, the unevenness degree gradation data is generated by assigning a color according to the unevenness degree according to a second color range set between the minimum value and the maximum value of the unevenness degree. ,
The first color range and the second color range are different from each other in the set color ranges, and the colors corresponding to the minimum values of the altitude and the unevenness are the cold colors and the colors corresponding to the maximum values. The terrain relief image generating method is characterized in that are set to different warm colors . In the unevenness degree calculation procedure, for each point in the three-dimensional terrain data, a ground angle and a underground angle are obtained in a plurality of directions from the point, respectively, and the ground opening that is an average of the ground angle and the underground angle The terrain relief image generating method according to claim 1, wherein the ridge valley degree as the degree of unevenness is calculated based on an underground opening that is an average of the terrain. In the inclination calculation procedure, an x-direction inclination and a y-direction inclination at each point are calculated based on the three-dimensional terrain data, and the x-direction inclination and the y-direction inclination are combined to generate the inclination. The method according to claim 1 or 2, wherein the degree is calculated. A terrain undulation image generation method by a terrain undulation image generation device that generates a terrain undulation image based on three-dimensional terrain data including altitude,
Elevation stage chrominance processing that generates elevation stage chromatic data by performing stage grading processing that assigns a color according to the elevation of the point to each point that becomes a pixel based on the input three-dimensional terrain data by the elevation stage chromatic processing means Procedure and
The unevenness degree calculating means calculates the unevenness degree of the terrain at each point based on the three-dimensional terrain data by the unevenness degree calculating means,
An unevenness degree gradation processing procedure for generating unevenness degree gradation data by performing a gradation process that imparts a color corresponding to the unevenness degree for each point to each point by the unevenness degree gradation processing means;
An inclination calculation procedure for calculating an inclination at each point based on the three-dimensional terrain data by an inclination calculation means;
A shadow generation procedure for generating shadow data by performing a shadow process for applying a shadow according to the slope at each point to each point by a shadow generation unit;
A synthesis processing procedure for synthesizing the elevation gradation data, the unevenness degree gradation data, and the shadow data to generate gradation terrain data by a combination processing means;
An output procedure for outputting a terrain relief image based on the stepped terrain data by output means;
With
In the synthesis processing procedure, three-dimensional color coordinates are added to the three-dimensional spatial coordinate points corresponding to the points in the three-dimensional terrain data by adding the color information acquired in the synthesis processing procedure to three-dimensional color coordinates. Generate the above-mentioned terraced terrain data including six or more dimensions including spatial coordinates and three-component color coordinates,
In the output procedure, a point obtained by mapping a spatial coordinate point of the staged terrain data to an output surface in a specified viewing direction is used as a pixel, and a color coordinate corresponding to the spatial coordinate is given to the pixel as a pixel value. A method for generating a terrain undulation image, characterized by generating an undulation image. A topographic relief image generating device that generates a topographic relief image based on three-dimensional topography data including elevation,
Elevation stage color processing means for generating altitude stage color data by performing stage color processing for assigning a color according to the altitude of the point to each point that becomes a pixel based on the input three-dimensional terrain data,
Concavity and convexity calculation means for calculating the concavo-convex degree of the terrain at each point based on the three-dimensional terrain data,
Concave degree degree step color processing means for performing step color processing for assigning a color according to the degree of unevenness for each point to each point to generate uneven degree step color data,
Inclination degree calculating means for calculating the inclination degree at each point based on the three-dimensional terrain data;
A shadow generation means for generating shadow data by performing a shadow process to give a shadow according to the inclination of each point to each point;
A synthesizing processing means for synthesizing the altitude gradation data, the unevenness degree gradation data and the shadow data to generate gradation terrain data;
Output means for outputting a terrain relief image based on the staged terrain data;
With
The elevation stage color processing means generates the elevation stage color data by giving a color according to the elevation according to a first color range set between the minimum value and the maximum value of the elevation,
The unevenness level gradation processing unit generates the unevenness level gradation data by assigning a color corresponding to the unevenness degree according to a second color range set between the minimum value and the maximum value of the unevenness level. ,
The first color range and the second color range are different from each other in the set color ranges, and the colors corresponding to the minimum values of the altitude and the unevenness are the cold colors and the colors corresponding to the maximum values. Is set to a warm color different from each other. A topographic relief image generating device that generates a topographic relief image based on three-dimensional topography data including elevation,
Elevation stage color processing means for generating altitude stage color data by performing stage color processing for assigning a color according to the altitude of the point to each point that becomes a pixel based on the input three-dimensional terrain data,
Concavity and convexity calculation means for calculating the unevenness of the terrain at each point based on the three-dimensional terrain data,
Concave degree degree step color processing means for performing step color processing for assigning a color according to the degree of unevenness for each point to each point to generate uneven degree step color data,
Inclination degree calculating means for calculating the inclination degree at each point based on the three-dimensional terrain data;
A shadow generation means for generating shadow data by performing a shadow process to give a shadow according to the inclination of each point to each point;
A synthesizing processing means for synthesizing the altitude gradation data, the unevenness degree gradation data and the shadow data to generate gradation terrain data;
Output means for outputting a terrain relief image based on the staged terrain data;
Equipped with a,
The synthesis processing means adds three-dimensional color coordinates to the three-dimensional spatial coordinate points corresponding to the respective points in the three-dimensional terrain data, thereby adding three-dimensional color coordinates. Generate the above-mentioned terraced terrain data including six or more dimensions including spatial coordinates and three-component color coordinates,
The output means gives the pixel as a pixel value a color coordinate corresponding to the spatial coordinate, with a point obtained by mapping the spatial coordinate point of the staged terrain data on an output surface in a specified viewing direction as a pixel. A terrain undulation image generating apparatus characterized by generating a undulation image.