Topography change estimation apparatus and method for estimating topography change

Abstract

To provide a topography change estimation apparatus and a method for estimating a topography change that are capable of appropriately estimating changes in topography even in a steeply sloped area, thereby solving problems associated with existing techniques.SOLUTION: The present invention relates to a topography change estimation apparatus for estimating topography change using a plurality of measurement points obtained at two different times for the same target area, the apparatus including coordinate transformation means; topography model generation means; topography quantity calculation means; topography image creation means; and difference vector calculation means. Among these, coordinate transformation means is for transforming standard three-dimensional coordinates into inclined three-dimensional coordinates, and difference vector calculation means is for calculating, for each mesh, a difference vector by performing image matching between a first topography image and a second topography image.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technology for estimating changes in terrain over two periods of time, and more specifically to a terrain change estimation device that estimates changes in terrain by comparing terrain images that are created by imaging a terrain model based on terrain quantities, and a method for estimating changes in terrain using the same. [Background technology]

[0002] The topography that forms the earth's surface is constantly changing, albeit minutely, due to crustal movement. The rate of change is usually extremely slow, but major earthquakes and other events can cause rapid topography change, and in some cases, large-scale soil movement. Furthermore, when landslides begin to occur due to heavy rain or earthquakes, the earth's surface also begins to change accordingly, and ultimately the landslide can move large masses of soil, causing extensive damage to the surrounding area.

[0003] Japan has repeatedly suffered devastating damage from natural disasters, but by tracking and understanding changes in topography, it may be possible to prevent such disasters or mitigate the damage. Furthermore, once a disaster occurs, comparing the topography before and after the disaster makes it possible to identify the damaged areas, estimate the causes of the disaster, and determine the possibility of secondary disasters, which is also a very effective means of emergency response and recovery. In other words, understanding changes in topography between two periods is extremely useful.

[0004] For this reason, various techniques have been proposed for analyzing changes in terrain between two periods. For example, Patent Document 1 proposes a technique for creating a terrain image based on terrain quantities (such as slope and Laplacian value) for each mesh using a digital elevation model (DEM), a digital terrain model (DTM), or a digital surface model (DSM), and then comparing the terrain images from the two periods to obtain changes in terrain. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-266419 Summary of the Invention [Problem to be solved by the invention]

[0006] The invention disclosed in Patent Document 1 calculates the amount of terrain for each mesh based on a three-dimensional terrain model such as a DEM or DSM, and generates a terrain image by assigning color information (pixel values) corresponding to the amount of terrain, and as described above, one of its features is that it can grasp changes in terrain by comparing terrain images from two different periods. In other words, unlike conventional technology that simply calculates the difference in elevation between two periods at the same horizontal position, this is an extremely suitable invention that can grasp more realistic changes in terrain by comparing roughly similar terrain (i.e., terrain amounts) between two periods.

[0007] Because this technology is so suitable, the applicant of the present application has implemented the invention of Patent Document 1 on numerous occasions. However, problems have been identified as the technology has been implemented. DEMs and DSMs are generally generated from a cloud of measurement points acquired by airborne laser measurement or aerial photogrammetry. Each measurement point constituting the cloud of measurement points has three-dimensional coordinates, and these three-dimensional coordinates are typically set in a coordinate system consisting of two orthogonal axes (e.g., X-axis and Y-axis) set on a horizontal plane and a vertical axis (e.g., Z-axis). Therefore, DEMs and DSMs are generated as a model in which elevation is assigned to each mesh set on a horizontal plane; in other words, they are generated as a model orthogonally projected from above.

[0008] When the invention of Patent Document 1 is applied to flat or gently sloping terrain, extremely favorable results are obtained, but displacements that do not actually occur are sometimes detected in steeply sloping areas of the measurement area, especially at the base of steep slopes. Although steep slopes have a considerable area, they are modeled as an extremely narrow area because an orthographically projected DEM or DSM is used, which makes them prone to false detection.

[0009] The object of the present invention is to solve the problems associated with the prior art, that is, to provide a terrain change estimation device and a terrain change estimation method that can accurately estimate terrain changes even on steeply sloping terrain. [Means for solving the problem]

[0010] The present invention focuses on the fact that a coordinate system is changed according to the slope of the terrain, a three-dimensional terrain model is generated, and a difference vector is calculated based on changes in the terrain image created based on that three-dimensional terrain model, and is an invention based on an idea that has not been seen before.

[0011] The terrain change estimation device of the present invention estimates terrain changes using multiple measurement points obtained over two different periods over the same area. The device includes a coordinate conversion means, a terrain model generation means, a terrain quantity calculation means, a terrain image creation means, and a difference vector calculation means. The measurement points have "standard three-dimensional coordinates" set in a "standard coordinate system" consisting of two horizontal axes and a vertical axis. The coordinate conversion means converts the standard three-dimensional coordinates into "slope three-dimensional coordinates" set in a "slope coordinate system." The terrain model generation means generates a "first slope terrain model," a three-dimensional terrain model, based on the slope three-dimensional coordinates of the measurement points obtained over a first period, and generates a "second slope terrain model," a three-dimensional terrain model, based on the slope three-dimensional coordinates of the measurement points obtained over a second period. The terrain quantity calculation means calculates terrain quantities for each mesh constituting the first slope terrain model based on the first slope terrain model, and calculates terrain quantities for each mesh constituting the second slope terrain model based on the second slope terrain model. The terrain image creation means is a means for creating a "first terrain image" by imaging a first slope terrain model based on the terrain quantity, and a means for creating a second terrain image by imaging a second slope terrain model based on the terrain quantity. The difference vector calculation means is a means for calculating a difference vector for each mesh by comparing the first terrain image with the second terrain image. The slope coordinate system is set by two axes on an "inclined plane" inclined from the horizontal plane and one axis perpendicular to the inclined plane.

[0012] The terrain change estimation device of the present invention can also be configured to extract a portion of the first terrain image as a "partial search image" and compare it with the second terrain image. In this case, the difference vector calculation means compares the partial search image with the second terrain image to detect a portion of the second terrain image that corresponds to the partial search image, and then calculates a difference vector for each mesh.

[0013] The terrain change estimation device of the present invention may further include steep slope area extraction means. This steep slope area extraction means is means for extracting areas with slopes exceeding a predetermined slope threshold as "steep slope areas" from a "standard terrain model" generated based on standard three-dimensional coordinates of measurement points at a first time. In this case, the terrain model generation means generates a first slope terrain model and a second slope terrain model for the steep slope areas extracted by the steep slope area extraction means.

[0014] The topographic change estimation device of the present invention may further include a slope coordinate system setting means for setting a slope coordinate system for a steep slope region. The slope coordinate system setting means sets the slope coordinate system so that the area of ​​the slope plane in the steep slope region is maximized.

[0015] The terrain change estimation method of the present invention is a method for estimating terrain changes between two periods using the terrain change estimation device of the present invention, and includes a coordinate conversion step, a terrain model generation step, a terrain quantity calculation step, a terrain image creation step, and a difference vector calculation step. The coordinate conversion step converts standard three-dimensional coordinates into slope three-dimensional coordinates. The terrain model generation step generates a first slope terrain model and a second slope terrain model based on the slope three-dimensional coordinates for the first and second periods. The terrain quantity calculation step calculates terrain quantities for each mesh based on the first slope terrain model and the second slope terrain model. The terrain image creation step creates a first terrain image and a second terrain image based on the terrain quantities. The difference vector calculation step calculates a difference vector for each mesh by comparing the first terrain image with the second terrain image. [Effects of the Invention]

[0016] The terrain change estimation device and terrain change estimation method of the present invention have the following advantages. (1) It is possible to accurately estimate changes in topography even on steep slopes. (2) By applying an existing patented invention (the invention of Patent Document 1), it can be implemented at low cost without requiring significant technological improvements. (3) Of course, even on flat or gently sloping terrain, it is possible to accurately estimate changes in the terrain. [Brief explanation of the drawings]

[0017] [Figure 1] (a) is a model diagram showing a "standard coordinate system" consisting of two horizontal axes and a vertical axis, and (b) is a model diagram showing a "tilted coordinate system" consisting of two axes on an inclined plane and an axis perpendicular to them. [Figure 2] 1 is a block diagram showing the main configuration of a topographical change estimation device according to the present invention; [Figure 3] (a) is a model diagram explaining a partial search image, and (b) is a model diagram explaining a search range. [Figure 4] (a) A cross-sectional view showing a schematic representation of a steep slope area included in a standard terrain model, and (b) a cross-sectional view showing a schematic representation of the steep slope area with the maximum area of ​​the slope plane. [Figure 5] FIG. 2 is a flowchart showing the main processing flow of the topographic change estimation device of the present invention. [Figure 6] 1 is a flowchart showing the flow of main steps of a topographical change estimation method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] An example of an embodiment of a topographic change estimation device and a topographic change estimation method according to the present invention will be described with reference to the accompanying drawings.

[0019] 1.Definition Before describing the embodiments of the present invention, definitions of terms used herein will be provided.

[0020] (Standard and tilted coordinate systems) One of the technical features of the present invention is the estimation of topographical changes between two periods using multiple measurement points (hereinafter referred to as "measurement point clouds") acquired by airborne laser measurement or aerial photogrammetry. For convenience, one of the two different periods will be referred to as the "first period" and the other as the "second period." In other words, when the older of the two periods is referred to as the first period, the newer will be referred to as the second period, and when the newer of the two periods is referred to as the first period, the older will be referred to as the second period.

[0021] Each measurement point obtained by airborne laser measurement, etc., has three-dimensional coordinates. These three-dimensional coordinates are set in a coordinate system consisting of two axes (X-axis and Y-axis in the figure) placed on a horizontal plane and a vertical axis (Z-axis in the figure) as shown in Figure 1(a). For convenience, the coordinate system consisting of two horizontal axes and a vertical axis will be referred to as the "standard coordinate system," and the three-dimensional coordinates set in this standard coordinate system will be referred to as the "standard three-dimensional coordinates."

[0022] Another technical feature of the present invention is that standard three-dimensional coordinates are transformed to generate a terrain model (described later). Specifically, as shown in Figure 1(b), standard three-dimensional coordinates are transformed into a coordinate system consisting of two axes (X'-axis and Y'-axis in the figure) on a plane inclined from a horizontal plane (hereinafter referred to as the "inclined plane") and one axis (Z'-axis in the figure) perpendicular to the inclined plane. For convenience, the coordinate system shown in Figure 1(b) will be referred to as the "inclined coordinate system," the three-dimensional coordinates set in this inclined coordinate system will be referred to as the "inclined three-dimensional coordinates," and the angle of the inclined plane relative to the horizontal plane will be simply referred to as the "inclined three-dimensional coordinates." In other words, standard three-dimensional coordinates are transformed into inclined three-dimensional coordinates by coordinate transformation. Note that an inclined coordinate system can be a standard coordinate system simply inclined by the inclination angle, or a standard coordinate system inclined by the inclination angle and rotated around a vertical axis (Z'-axis in the figure).

[0023] (Standard terrain model and slope terrain model) As mentioned above, measurement point clouds can be used to create three-dimensional models (hereafter referred to as "terrain models") such as DEM (digital earth surface model), DTM (digital terrain model), and DSM (digital surface layer). Terrain models are composed of small areas (so-called meshes) obtained by dividing a planar area, and each mesh is assigned a height (elevation). Measurement point clouds obtained by airborne laser measurement, etc., are composed of random data (data that is irregularly arranged on a plane), so geometric calculations are often used to assign elevation to each mesh. Calculation methods include the TIN (triangulated irregular network) method, which calculates height using an irregular triangulation network formed from random data, the nearest neighbor method, which uses the nearest laser measurement point, the inverse distance weighting (IDW), the Kriging method, and the averaging method.

[0024] One of the technical features of the present invention is the generation of a terrain model based on tilted three-dimensional coordinates, which are obtained by transforming standard three-dimensional coordinates. In other words, a tilted terrain model is generated by setting multiple meshes on a tilted plane and assigning a height (Z' value in the figure) to each mesh. The meshes set on the tilted plane can be formed using orthogonal grids, non-orthogonal grids, or any other shape. For convenience, a terrain model generated based on standard three-dimensional coordinates (i.e., a general terrain model) will be referred to as the "standard terrain model," and a terrain model generated based on tilted three-dimensional coordinates (i.e., a tilted terrain model) will be referred to as the "tilted terrain model." Furthermore, a terrain model generated based on tilted three-dimensional coordinates for a first time period will be referred to as the "first tilted terrain model," and a terrain model generated based on tilted three-dimensional coordinates for a second time period will be referred to as the "second tilted terrain model."

[0025] (Topographic image) One of the technical features of the present invention is the generation of an image based on a slope terrain model. Specifically, an image is generated by assigning a value for image generation, such as color or shade (hereinafter referred to as a "pixel value") to each pixel. The pixel value assigned to each pixel is set according to a "terrain quantity" calculated for each mesh based on the slope terrain model. For convenience, the image generated using pixel values ​​according to this terrain quantity will be referred to as a "terrain image." Furthermore, the terrain image generated based on a first slope terrain model will be referred to as a "first terrain image," and the terrain image generated based on a second slope terrain model will be referred to as a "second terrain image."

[0026] Here, topographic quantities are indices that represent the characteristics of the terrain and are calculated based on representative points of the mesh or the original random data. Examples of topographic quantities include slope, elevation, Laplacian, aboveground opening, underground opening, or a combination of these. Here, slope is generally used to draw a slope map. A slope map indicates the degree of slope of the terrain; the greater the slope, the greater the slope value, and conversely, the gentler the slope, the smaller the slope value. Furthermore, Laplacian values ​​are generally used to draw a Laplacian diagram, which shows the rate of change in slope. This Laplacian diagram is characterized by being positive for concave terrain and negative for protruding terrain, with the absolute value increasing where the terrain changes significantly.

[0027] Aboveground and underground opening values ​​are generally used to draw opening maps. Among opening maps, aboveground opening maps represent the extent of the sky visible within a certain distance from a point of interest. The more a point protrudes from its surroundings, the greater the aboveground opening value. For example, mountain peaks and ridges show large aboveground opening values, resulting in the protruding mountain peaks and ridges being emphasized. On the other hand, underground opening maps, in contrast to aboveground opening maps, represent the extent of the underground within a certain distance when looking underground from the ground surface. The deeper a point penetrates underground, the greater the underground opening value. For example, depressions and valley bottoms show large underground opening values, resulting in the depressions and valleys being emphasized.

[0028] The pixels that make up a terrain image can be formed based on the meshes that make up the slope terrain model. For example, pixels can be formed by combining various meshes, such as one mesh per pixel, four meshes per pixel, or nine meshes per pixel. When a pixel is formed using multiple meshes, it is advisable to use multiple terrain quantities to determine a representative terrain quantity. In this case, a representative terrain quantity can be selected from the multiple terrain quantities (for example, the terrain quantity of the central mesh), or a statistical value such as the average, median, or mode can be calculated as the terrain quantity.

[0029] The pixel values ​​assigned to pixels represent brightness and color (hue, saturation, and lightness), and color models such as RGB, CMYK, NCS, and grayscale can be used. As mentioned above, pixel values ​​are set according to the terrain quantity, and can be arbitrarily set, for example, by defining the terrain quantity in descending order as red, orange, yellow, green, and blue, or by assigning 256 shades of gray to match the range of the terrain quantity, or by combining colors for elevation values ​​and brightness for slope values.

[0030] 2. Terrain change estimation device Next, an example of a terrain change estimation device of the present invention will be described with reference to the drawings. Note that the terrain change estimation method of the present invention is a method of estimating terrain change using the terrain change estimation device of the present invention, and therefore the terrain change estimation device of the present invention will be described first, followed by the terrain change estimation method of the present invention.

[0031] 2 is a block diagram showing the main components of a topographic change estimation device 100 of the present invention. As shown in this figure, the topographic change estimation device 100 of the present invention comprises coordinate conversion means 101, topographic model generation means 102, topographic quantity calculation means 103, topographic image creation means 104, and difference vector calculation means 105, and can also comprise steep slope area extraction means 106, slope coordinate system setting means 107, output means 108 such as a display or printer, and measurement point cloud storage means 109.

[0032] Each of the means constituting the terrain change estimation device 100 can be manufactured as a dedicated device, or a general-purpose computer device can be used. That is, the processing of the various means is performed by having the computer device execute calculations using a predetermined program. This computer device is equipped with a processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), memories such as ROM and RAM, and some also include input means such as a mouse and keyboard, and a display, and can be configured, for example, as a personal computer (PC) or server.

[0033] The measurement point cloud storage means 109 can use a storage device of a general-purpose computer (for example, a personal computer) or can be built in a database server. When built in a database server, it can be placed on a local network (LAN: Local Area Network) or can be a cloud server that stores data via the Internet.

[0034] Below, each of the main elements that make up the topographic change estimation device 100 of the present invention will be described in detail.

[0035] (Measurement point cloud storage means) The measurement point cloud storage means 109 is a means for storing measurement point clouds obtained by airborne laser measurement or aerial photogrammetry, and stores at least a measurement point cloud relating to a first period and a measurement point cloud relating to a second period.

[0036] (Coordinate conversion means) The coordinate conversion means 101 is a means for converting the standard three-dimensional coordinates of the measurement points of the measurement point cloud into tilted three-dimensional coordinates set in a tilted coordinate system. Of course, the coordinate conversion means 101 converts the measurement point cloud relating to a first time period into tilted three-dimensional coordinates, and also converts the measurement point cloud relating to a second time period into tilted three-dimensional coordinates. However, the same tilted coordinate system is used for the first time period and the second time period; in other words, the tilted three-dimensional coordinates relating to the first time period and the tilted three-dimensional coordinates relating to the second time period are coordinates set in the same tilted coordinate system.

[0037] (Terrain model generation means) The terrain model generating means 102 is a means for generating terrain models such as DEM (digital earth surface model), DTM (digital terrain model), and DSM (digital surface model) by using the measurement point cloud. Specifically, it generates a first slope terrain model based on the slope three-dimensional coordinates relating to a first time period, and generates a second slope terrain model based on the slope three-dimensional coordinates relating to a second time period. The terrain model generating means 102 can also generate a standard terrain model based on the standard three-dimensional coordinates relating to the first time period or the second time period.

[0038] (Means for calculating topographical quantities and creating topographical images) The terrain quantity calculation means 103 is a means for calculating the terrain quantity for each mesh based on a slope terrain model relating to a first time period, and for calculating the terrain quantity for each mesh based on a slope terrain model relating to a second time period. The terrain image creation means 104 is a means for generating a terrain image by assigning a pixel value corresponding to the terrain quantity to each pixel, and generates a first terrain image based on the terrain quantity according to the first slope terrain model, and generates a second terrain image based on the terrain quantity according to the second slope terrain model.

[0039] (Difference vector calculation means) The difference vector calculation means 105 is a means for calculating a "difference vector" for each mesh by comparing the first topographical image with the second topographical image. The procedure by which the difference vector calculation means 105 calculates the difference vector will be described in detail below.

[0040] The difference vector calculation means 105 first selects one of the first and second terrain images as a "search image" and selects the other as a "searched image." For convenience, an example will be described in which the first terrain image is the search image and the second terrain image is the searched image. Next, the difference vector calculation means 105 matches the meshes constituting the first slope terrain model with the meshes constituting the second slope terrain model by performing image matching between the first and second terrain images. At this time, the matching can be performed on the entire terrain image, or the terrain image can be divided into several parts and matching can be performed on each divided unit (hereinafter referred to as a "partial search image"). Specifically, a predetermined part, a partial search image, is extracted from the first terrain image, which is the search image, and the second terrain image, which is the searched image, is scanned with the partial search image to detect an area matching with the partial search image (hereinafter referred to as a "corresponding area").

[0041] FIG. 3 illustrates a situation in which a second topographical image (image to be searched) is searched for using a partial search image extracted from a first topographical image. (a) is a model diagram illustrating the partial search image, and (b) is a model diagram illustrating the search range. As shown in FIG. 3(a), the difference vector calculation means 105 extracts multiple partial search images from the first topographical image in regions of predetermined size and shape, and performs matching using each partial search image. In this process, the second topographical image is scanned, but it is also possible to scan only a specific area of ​​the second topographical image. This scanned area can be determined by extracting an image from the second topographical image that corresponds to the partial search image (hereinafter simply referred to as the "corresponding image"), and setting an area around the corresponding image by a predetermined width (buffer) as the search area (hereinafter referred to as the "search range"). By scanning only this search range, matching can be performed efficiently. When performing matching using partial search images, it is recommended to scan the partial search image by moving it pixel by pixel within the range of the second topographical image (or the search range).

[0042] When the first terrain image (or partial search image) is compared with the second terrain image, the meshes constituting the first slope terrain model are associated with the meshes constituting the second slope terrain model. Each mesh has a slope three-dimensional coordinate. The difference vector calculation means 105 calculates a three-dimensional vector, a "difference vector," for each mesh based on the slope three-dimensional coordinates of the meshes at the two corresponding times.

[0043] (Means for extracting steep slope areas and means for setting slope coordinate systems) The terrain change estimation device 100 of the present invention can be configured to generate a first slope terrain model and a second slope terrain model over the entire target range (hereinafter referred to as the "target range") and calculate a difference vector by matching the first terrain image with the second terrain image. Alternatively, it can be configured to calculate a difference vector using the first terrain image and the second terrain image for only a portion of the target range. As mentioned above, when the invention of Patent Document 1 is applied to flat or gently sloping terrain, extremely favorable results are obtained, but non-existent displacements may be detected in steeply sloping areas, particularly at the base of steep slopes. Therefore, steeply sloping areas (hereinafter simply referred to as "steep slope areas") are extracted from the target range, and then a difference vector using the first terrain image and the second terrain image is calculated for the steeply sloping areas.

[0044] In this case, the terrain model generating means 102 may generate a standard terrain model based on the standard 3D coordinates for the first time period (or the second time period), and the steep slope area extracting means 106 may extract steep slope areas from the standard terrain model. The steep slope area extracting means 106 may set a predetermined threshold (hereinafter referred to as the "slope threshold") and extract areas with slopes exceeding the slope threshold as steep slope areas. For example, in the standard terrain model shown in Figure 4(a), the sloped surfaces indicated by the thick lines exceed the slope threshold and are therefore extracted as steep slope areas, while the surfaces indicated by the thin lines do not exceed the slope threshold and are therefore not considered steep slope areas.

[0045] Furthermore, when a steep slope region is extracted by the steep slope region extraction means 106, it is preferable that the slope coordinate system setting means 107 set a slope terrain model (first slope terrain model or second slope terrain model) corresponding to the steep slope region. When a slope terrain model is set for the steep slope region, the slope coordinate system setting means 107 can set a slope coordinate system so that the area of ​​the slope plane corresponding to the steep slope region (i.e., the area of ​​the steep slope region projected onto the slope plane) is maximized. For example, in FIG. 4(b), the slope plane is set so that the area of ​​the steep slope region projected onto the slope plane is maximized. Note that the steep slope region projected onto the slope plane is a steep slope region that has the shape and slope of the standard terrain model. As described above, the same slope coordinate system is used in the first and second periods. Therefore, the slope coordinate system set by the steep slope region extraction means 106 using the steep slope region of the standard terrain model is used in common in the first and second periods.

[0046] (Processing flow) The main processing of the terrain change estimation device 100 will be explained in detail below with reference to Figure 5. Figure 5 is a flow diagram showing an example of the flow of the main processing of the terrain change estimation device 100, with the central column showing the processing to be performed, the left column showing what is necessary for that processing, and the right column showing what results from that processing.

[0047] To estimate terrain changes using the terrain change estimation device 100, first, the terrain quantity calculation means 103 generates a standard terrain model based on the measurement point cloud for the first time period read from the measurement point cloud storage means 109 (Step 201 in Fig. 5). Next, the steep slope area extraction means 106 extracts steep slope areas from the standard three-dimensional coordinates (Step 202 in Fig. 5), and the slope coordinate system setting means 107 sets a slope terrain model corresponding to the steep slope area (Step 203 in Fig. 5). The slope coordinate system set here is used in common for the first and second time periods in subsequent processing.

[0048] Once the tilt coordinate system is set, the coordinate conversion means 101 converts the standard three-dimensional coordinates into tilt three-dimensional coordinates (Step 204 in FIG. 5). Specifically, the coordinate conversion means 101 converts the standard three-dimensional coordinates of the measurement points for the first time period read from the measurement point cloud storage means 109 into tilt three-dimensional coordinates, and also converts the standard three-dimensional coordinates of the measurement points for the second time period read from the measurement point cloud storage means 109 into tilt three-dimensional coordinates. Then, the terrain model generation means 102 generates a first tilt terrain model based on the tilt three-dimensional coordinates for the first time period, and generates a second tilt terrain model based on the tilt three-dimensional coordinates for the second time period (Step 205 in FIG. 5).

[0049] Once the first slope terrain model and the second slope terrain model are generated, the terrain quantity calculation means 103 calculates the terrain quantity for each mesh based on the slope terrain model for the first time period, and calculates the terrain quantity for each mesh based on the slope terrain model for the second time period (Step 206 in Fig. 5). The terrain image creation means 104 generates a first terrain image based on the terrain quantity from the first slope terrain model, and generates a second terrain image based on the terrain quantity from the second slope terrain model (Step 207 in Fig. 5). The difference vector calculation means 105 then compares the first terrain image with the second terrain image to calculate a difference vector for each mesh (Step 208 in Fig. 5).

[0050] 3. Topographic change estimation method Next, the terrain change estimation method of the present invention will be explained with reference to Figure 6. The terrain change estimation method of the present invention is a method of estimating terrain change using the terrain change estimation device 100 explained up to this point, and therefore, we will avoid explanations that overlap with the content explained for the terrain change estimation device 100 and will mainly explain content that is unique to the terrain change estimation method of the present invention. In other words, content not described here is the same as that explained in "2. Terrain change estimation device", including "1. Definitions".

[0051] Figure 6 is a flow diagram showing the main steps of the terrain change estimation method of the present invention. To estimate terrain change using the terrain change estimation method of the present invention, first, a standard terrain model is generated based on the measurement point cloud at a first time point using the terrain change estimation device 100 (Step 301 in Figure 6). Next, steep slope area extraction means 106 is used to extract steep slope areas from the standard 3D coordinates (Step 302 in Figure 6), and a slope terrain model corresponding to the steep slope area is set using the slope coordinate system setting means 107 (Step 303 in Figure 6). Note that the slope coordinate system set here is used in common in the subsequent steps for both the first and second time points.

[0052] Once the tilt coordinate system is set, the coordinate conversion means 101 is used to convert the standard three-dimensional coordinates into tilt three-dimensional coordinates (Step 304 in FIG. 6). Specifically, the standard three-dimensional coordinates of the measurement points for the first time period read from the measurement point cloud storage means 109 are converted into tilt three-dimensional coordinates, and the standard three-dimensional coordinates of the measurement points for the second time period read from the measurement point cloud storage means 109 are converted into tilt three-dimensional coordinates. Then, the terrain model generation means 102 is used to generate a first tilt terrain model based on the tilt three-dimensional coordinates for the first time period, and to generate a second tilt terrain model based on the tilt three-dimensional coordinates for the second time period (Step 305 in FIG. 6).

[0053] After generating the first slope terrain model and the second slope terrain model, the terrain quantity calculation means 103 is used to calculate the terrain quantity for each mesh based on the slope terrain model for the first time period, and also calculate the terrain quantity for each mesh based on the slope terrain model for the second time period (Step 306 in Fig. 6).The terrain image creation means 104 is used to generate a first terrain image based on the terrain quantity from the first slope terrain model, and also generates a second terrain image based on the terrain quantity from the second slope terrain model (Step 307 in Fig. 6).Then, the difference vector calculation means 105 is used to compare the first terrain image with the second terrain image to calculate a difference vector for each mesh (Step 308 in Fig. 6). [Industrial Applicability]

[0054] The topographical change estimation device and topographical change estimation method of the present invention can grasp changes in the earth's surface due to crustal movement over time, topographical changes due to the activity of faults, topographical changes due to the activity of landslides, etc. If the present invention is to prevent natural disasters or reduce damage caused by natural disasters, it can be said that the present invention is not only applicable to industry but is also an invention that can be expected to make a great contribution to society. [Explanation of symbols]

[0055] 100 Topographical change estimation device of the present invention 101 (of the terrain change estimation device) coordinate conversion means 102 Terrain model generation means (of terrain change estimation device) 103 (of the terrain change estimation device) terrain quantity calculation means 104 Terrain image creation means (of terrain change estimation device) 105 (Topographical change estimation device) difference vector calculation means 106 (of the terrain change estimation device) steep slope area extraction means 107 (of the terrain change estimation device) slope coordinate system setting means 108 (of the terrain change estimation device) output means 109 (Topographical change estimation device) measurement point cloud storage means

Claims

1. A device for estimating topographical changes using multiple measurement points obtained over two periods over the same area, the measurement points have standard three-dimensional coordinates set in a standard coordinate system consisting of two horizontal axes and a vertical axis; a coordinate conversion means for converting the standard three-dimensional coordinates into tilted three-dimensional coordinates set in a tilted coordinate system; a terrain model generating means for generating a first slope terrain model, which is a three-dimensional terrain model, based on the slope three-dimensional coordinates of the measurement points at a first time, and generating a second slope terrain model, which is a three-dimensional terrain model, based on the slope three-dimensional coordinates of the measurement points at a second time; a terrain quantity calculation means for calculating a terrain quantity for each mesh constituting the first slope terrain model based on the first slope terrain model, and for calculating a terrain quantity for each mesh constituting the second slope terrain model based on the second slope terrain model; a terrain image creating means for creating a first terrain image by imaging the first slope terrain model based on the terrain quantity, and a second terrain image by imaging the second slope terrain model based on the terrain quantity; a difference vector calculation means for calculating a difference vector for each mesh by comparing the first topographical image with the second topographical image, The tilted coordinate system is set by two axes on a tilted plane tilted from a horizontal plane and one axis perpendicular to the tilted plane. A terrain change estimation device characterized by:

2. the difference vector calculation means extracts a part of the first topographical image as a partial search image, and compares the partial search image with the second topographical image to detect a part of the second topographical image corresponding to the partial search image, and then calculates the difference vector.

2. The topographical change estimation device according to claim 1.

3. a steep slope area extraction means for extracting, as a steep slope area, an area having a slope exceeding a predetermined slope threshold from a standard terrain model generated based on the standard three-dimensional coordinates of the measurement point at the first time; the terrain model generating means generates the first slope terrain model and the second slope terrain model for the steep slope area extracted by the steep slope area extracting means.

2. The topographical change estimation device according to claim 1.

4. further comprising an inclination coordinate system setting means for setting the inclination coordinate system for the steeply inclined region; the inclined coordinate system setting means sets the inclined coordinate system so that the area of ​​the inclined plane in the steeply inclined region is maximized.

4. The topographical change estimation device according to claim 3.

5. A method for estimating topographical changes using multiple measurement points obtained over two periods over the same area, comprising: the measurement points have standard three-dimensional coordinates set in a standard coordinate system consisting of two horizontal axes and a vertical axis; a coordinate conversion step of converting the standard three-dimensional coordinates into tilted three-dimensional coordinates set in a tilted coordinate system; a terrain model generation process for generating a first slope terrain model, which is a three-dimensional terrain model, based on the slope three-dimensional coordinates of the measurement points at a first time, and generating a second slope terrain model, which is a three-dimensional terrain model, based on the slope three-dimensional coordinates of the measurement points at a second time; a terrain quantity calculation step of calculating a terrain quantity for each mesh constituting the first slope terrain model based on the first slope terrain model, and calculating a terrain quantity for each mesh constituting the second slope terrain model based on the second slope terrain model; a terrain image creation step of creating a first terrain image by imaging the first slope terrain model and a second terrain image by imaging the second slope terrain model based on the terrain quantity; a difference vector calculation step of calculating a difference vector for each mesh by comparing the first topographical image with the second topographical image, The tilted coordinate system is set by two axes on a tilted plane tilted from a horizontal plane and one axis perpendicular to the tilted plane. A method for estimating topographical changes.

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