JP2004093632A - Extraction method and system for topographic geometry, and program therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To create altitude distribution information expressing topographic geometry by eliminating affect of buildings, from altitude distribution information by stereo image processing of satellite photographs and aerial photographs or altitude distribution information by laser profiler mounted on an aircraft. <P>SOLUTION: This extraction system is provided with a processing altitude range setting part 231 setting the altitude range (the lower and upper limits of processing objects) for topograph extraction processing, a processing altitude setting part 232 setting altitude to be processed (processing altitude) in every repeated processing time within the range set by the setting part 231, a non-ground region detection part 233 detecting the non-ground region existing in the processing altitude plane in the altitude distribution information, and a non-ground region excluding part 234 eliminating affect of buildings and trees from the altitude distribution information, by changing the altitude values of the region in the altitude distribution information. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for extracting a terrain shape from given altitude distribution information, and in particular, a terrain shape extracting system, a terrain shape extracting method, and a terrain shape extracting method capable of extracting a terrain shape from altitude distribution information given as three-dimensional data. About the program.
[0002]
[Prior art]
Elevation distribution information is information that holds the elevation value of each point on the ground surface. For example, stereo image processing (stereo matching processing) from a plurality of images taken from the sky such as an aircraft or an artificial satellite, or a laser profiler It is acquired by a method of measuring the position and altitude at each point by irradiating a laser from an aircraft or a satellite using a satellite. Since such altitude distribution information is based on measurements from the sky, if there is a building or the like, it indicates the altitude value on the roof of the building, and if there is a feature such as a building, it necessarily represents the terrain itself. Do not mean. In the following description, the altitude distribution information refers to data expressed in a digital format having the altitude value corresponding to each point on the two-dimensional coordinates. Note that such altitude distribution information is also referred to as DEM (Digital Elevation Map). With respect to this DEM, a method of generating the DEM based on contour information obtained from a contour map issued by the Geospatial Information Authority of Japan is also known.
[0003]
By the way, when a land use plan is drafted, a building (a building that exists now or a building that may be constructed in the future) is displayed by computer graphics (CG), and based on topographical data when there is no building or tree. It reproduces the original terrain, and displays buildings etc. on it. When elevation distribution information is acquired from aerial photographs or satellite photographs by stereo image processing, or when elevation distribution information is acquired by laser measurement from the sky, the effects of features such as buildings are affected by these elevation distribution information. It is necessary to perform a process of extracting a terrain shape in which the influence of a building or the like has been removed from such elevation distribution information, and to create elevation distribution information as a numerical terrain model representing undulations of the terrain.
[0004]
A terrain shape extraction system that extracts a terrain shape from altitude distribution information is used for displaying three-dimensional graphics of a cityscape or the like, as a basic data for a survey of a terrain change, a simulation of a disaster or the like.
[0005]
An example of a conventional terrain shape generation system is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-129636 (Japanese Patent No. 2623449). The terrain model creation device described in Japanese Patent Application Laid-Open No. 8-129636 is a device that outputs a digitized terrain model using contour lines, and creates a contour line data storage unit for storing contour line data and initial terrain data. An initial terrain data creation program unit, a smoothing program unit for storing an operation program of an operator for smoothing the elevation value of the input terrain model along or near the water line, and a boundary for storing a program for setting boundary conditions. A condition setting program unit, a digitized terrain data storage unit for storing digitized terrain data generated by the device, and a control program unit for storing a control program for storing a control program such as an OS (operating system). Have. In this apparatus, an initial terrain is generated using contour data, and an operator for smoothing an elevation value along a flow line or its vicinity is applied to a terrain model. By repeating this smoothing process a specified number of times, a digitized terrain model is created and output.
[0006]
In addition, Naoko Kurizaki et al., "Creation of 3D City Model Using Aircraft Laser Measurement Points and Digital Images", 2000, Proceedings of the Geographic Information Systems Society of Japan, Vol. 9, pp. 235-238. A technique is disclosed in which three-dimensional ground surface data is acquired by a laser measurement device (laser profiler) obtained, and the terrain is extracted by noise processing and filtering. In this method, a height image is created from a laser measurement point, and a high-pass filter (high-frequency component passing filter) process is performed to mask a region of a structure or a tree. Furthermore, processing such as removing the mask for the area covered by the mask near the road, and removing the mask for the area covered by the mask that has a small elevation difference from the surrounding unmasked area I do. As a result of these processes, the unmasked area represents the terrain. In addition, for a masked area, the elevation is calculated by interpolating the laser points in the surrounding unmasked area to generate a terrain model. These filtering processes are based on a Fourier transform process on the image.
[0007]
Further, JP-A-2002-157576 discloses an example in which a DEM image obtained by stereo image processing is corrected using map information. In this publication, for example, it is disclosed that a smoothing process is performed on a portion determined as a road region in map information, and that an altitude is uniformly set to “0” for a portion determined as an ocean.
[0008]
JP-A-11-085012 discloses an example of a display method for displaying terrain data based on DEM data or the like.
[0009]
[Problems to be solved by the invention]
In the method described in Japanese Patent Application Laid-Open No. 8-129636, since the terrain data is created based on contour lines obtained by actual measurement, it is possible to create a terrain model of an area where contour data is not created. There is a problem that it cannot. Obtain contour data reflecting geographical changes due to recent land development etc. not only in areas (areas) where large-scale maps are not prepared, but also in areas where large-scale maps are generally prepared. Can be difficult to do. In addition, since the interval between contour lines is usually at least a few meters in altitude difference, it is not possible to extract a finer topographic shape by this method. In addition, operator selection and operator parameters require detailed information about the area, and it is difficult for a person who is not familiar with the area to judge whether the operator selection and parameter selection are appropriate. There is also a problem.
[0010]
On the other hand, with the method described in the above-mentioned Kurizaki et al. Article, it is extremely difficult to set a high-pass filter in a region where a cliff or a cliff where the terrain is rapidly changing or a building having a large bottom area exists. In other words, there is a problem in that the spatial frequency related to the change in elevation value is very high near a cliff or a cliff, and such a terrain is masked by the high-pass filter, and the terrain model becomes smooth. In addition, when a building with a large bottom area exists, a low-frequency high-pass filter must be used to remove the building, so that there is a possibility that undulations of the originally existing terrain may be removed. .
[0011]
Therefore, an object of the present invention is to provide a method for controlling the influence of a building or the like by using height information by stereo matching processing from a plurality of aerial photographs and height information measured by a laser profiler mounted on an aircraft even in an area without contour lines. It is an object of the present invention to provide a terrain shape extraction system capable of generating altitude distribution information representing the terrain by eliminating the terrain.
[0012]
Another object of the present invention is to provide a terrain shape extraction system capable of easily generating elevation distribution information representing terrain by setting simple parameters.
[0013]
Still another object of the present invention is to provide a terrain shape extraction system capable of generating altitude distribution information representing a terrain while maintaining a detailed shape of the terrain.
[0014]
Still another object of the present invention is to provide a terrain shape extraction system that can flexibly correspond to various regions and generate elevation distribution information representing terrain by using map information.
[0015]
[Means for Solving the Problems]
A terrain shape extraction method according to the present invention is a terrain shape extraction method for extracting a terrain shape from given altitude distribution information, wherein a non-ground surface detecting a non-ground area by analyzing the altitude distribution information based on a processing altitude. Area detection processing, and non-ground area removal processing for changing the altitude value of the detected non-ground area based on the processing altitude, and performing the non-ground area detection processing and the non-ground area removal processing for each processing elevation Or the elevation distribution information is divided into each area by analyzing the elevation distribution information based on the processing elevation, and a non-ground area for determining whether or not the divided area is a non-ground area. Detection processing, and a non-ground area removal processing of changing the elevation value of the area determined to be a non-ground area based on the processing altitude, and each of the non-ground area detection processing and the non-ground area removal processing Perform for each processing altitude And wherein the door.
[0016]
As a specific example, the terrain shape extraction method of the present invention is a terrain shape extraction method for extracting a terrain shape from given altitude distribution information, and performing an area distribution based on a set processing altitude as a reference. A second step of extracting a region whose elevation value exceeds the processing elevation in the information, a third step of determining whether the extracted region is a non-ground region based on characteristics of the extracted region, And a fourth step of changing the elevation value of each point in the area in the elevation distribution information when the area is determined to be an area.
[0017]
The present invention considers cutting altitude distribution information at a certain altitude plane, and buildings and trees having an altitude higher than the altitude plane on the ground at a position lower than the altitude plane are isolated small areas. Utilizes what will be detected as. Since the terrain shape changes globally compared to buildings and trees, for example, if an appropriate area threshold is determined, it can be determined that a region having an area equal to or less than the area threshold is a building or a tree. it can. As for an area determined to be a building or a tree (non-ground area), the altitude value is rewritten with the processing altitude at that time, so that the influence of the building or the tree can be removed as described later.
[0018]
In the present invention, in the first stage, the altitude distribution information is binarized based on the processing altitude, and the binarized altitude distribution information is regarded as a binary image. It is preferable to perform a labeling process on the image data and extract a region exceeding the processing altitude as a region independent of each other.
[0019]
Further, it is preferable that the processing from the first stage to the third stage is repeatedly executed so that the processing altitude sequentially changes between the minimum value and the maximum value. By repeatedly executing the processing altitude in small steps, the topographical shape can be more finely extracted.
[0020]
Further, in the present invention, it is preferable that a step of removing noise included in the given altitude distribution information is provided so that the first to third steps are performed on the altitude distribution information from which the noise has been removed. Further providing a step of aligning the distribution of each point in the given altitude distribution information at equal intervals in each coordinate axis direction on a two-dimensional coordinate plane, and a step of removing noise from the aligned altitude distribution information. Preferably, it is performed.
[0021]
Further, in the present invention, the topographical shape can be extracted more accurately by using the map information. For example, based on the result obtained by referring to the map information, it can be determined whether or not the extracted area is a non-ground area, and it is determined that the extracted area is a non-ground area in the elevation distribution information. The elevation value of each point in the area can be rewritten to the elevation value obtained by referring to the map information, the building shape polygon closest to the extracted area in the map information is searched, and the area of the extracted area And whether or not the extracted area is a non-ground area based on the ratio of the area of the searched building shape polygon.
[0022]
A terrain shape extraction system according to the present invention is a terrain shape extraction system for extracting a terrain shape from given altitude distribution information, and detects a non-ground area by analyzing the altitude distribution information based on a processing altitude. Area detecting means, and a non-ground area removing means for changing an altitude value of the detected non-ground area based on the processing altitude, wherein the non-ground area detecting means and the non-ground area removing means each have a processing altitude. The method is characterized in that the processing is performed for each area, or the elevation distribution information is divided into each area by analyzing the elevation distribution information based on the processing elevation, and it is determined whether or not the divided area is a non-ground area. Non-ground area detecting means, having a non-ground area removing means for changing the elevation value of the area determined to be a non-ground area based on the processing altitude, non-ground area detecting means and non-ground area removing means, Is each processing And performing the processing to high each.
[0023]
As a specific example, the terrain shape extraction system of the present invention is a terrain shape extraction system that extracts a terrain shape from given altitude distribution information, and performs an area distribution based on a set processing altitude as a reference. A non-ground area detecting means for extracting a region in which the elevation value exceeds the processing altitude in the information, and for each extracted region, determining whether or not the region is a non-ground region based on characteristics of the region; Non-ground area removing means for changing the elevation value of each point in the area in the elevation distribution information for the area determined to be present.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0025]
<< 1st Embodiment >>
The terrain shape extraction system according to the first embodiment of the present invention shown in FIG. 1 is roughly divided into a parameter input device 100 for inputting parameters required for processing, and altitude distribution information (DEM) including the influence of buildings and the like. The apparatus includes a DEM processing device 200 that processes and outputs altitude distribution information representing a terrain shape, a DEM storage device 300 that stores altitude distribution information to be processed, and a DEM output device 400 that outputs a processing result. Here, the DEM storage device 300 stores three-dimensional coordinate data representing the position and altitude of each point measured by a laser profiler mounted on an aircraft or satellite, or a plurality of images taken from the sky by an aircraft or satellite. Are stored as altitude distribution information.
[0026]
A DEM reading unit 210 that reads various types of elevation distribution information from the DEM storage device 300 and converts the information into aligned elevation distribution information (hereinafter, referred to as aligned elevation distribution information); A DEM correction unit 220 for performing correction such as noise removal on the aligned altitude distribution information, a terrain extracting unit 230 for generating aligned altitude distribution information representing a terrain shape from the corrected aligned altitude distribution information, , Are provided.
[0027]
Here, the altitude distribution information will be described. As described above, the elevation distribution information is digital data representing an elevation value at each point on two-dimensional coordinates (for example, rectangular coordinates in a plane) on the ground surface, and is an aerial photograph or a satellite photograph. This is obtained by stereo matching processing from the above or by laser measurement from above with a laser profiler. Here, the distribution of the points corresponding to the respective elevation data on the two-dimensional coordinate plane is not uniform especially in the case of the elevation distribution information acquired by the laser measurement. In the terrain shape extraction according to the present embodiment, since the area of the region is obtained as will be apparent from the following description, each point corresponding to each elevation data is placed on a two-dimensional coordinate plane so that the area can be easily calculated. It is preferable that they are arranged at equal intervals in the xy direction on the (xy plane). Therefore, by performing appropriate interpolation processing or the like, each data point in the elevation distribution information is arranged as grid points at equal intervals in the xy directions. Such altitude distribution information arranged as equally spaced grid points is referred to as aligned altitude distribution information.
[0028]
Since the aligned elevation distribution information is digital data having the elevation values of grid points arranged at equal intervals on a two-dimensional plane, the elevation values are read as pixel values. By normalizing the elevation value of each point according to the above, the image data can be regarded as digital image data of gray scale (black and white gradation). That is, the aligned elevation distribution information has the same data structure as the grayscale digital image, and is also called a DEM image. Therefore, in the present embodiment, the terrain shape is extracted by performing a process known in the field of image processing on the aligned elevation distribution information.
[0029]
Generally, the aligned elevation distribution information is generated corresponding to a rectangular area on the ground surface. Therefore, the number of grid points in the vertical and horizontal directions in the aligned altitude distribution information (the number of pixels in each of the vertical and horizontal directions when considered as a DEM image) is collectively called a DEM image size, and corresponds to the aligned altitude distribution information (DEM image). The area on the ground surface is called a DEM image area.
[0030]
Further, a region where it is considered that the altitude value of a building or a tree, not the altitude value of the ground or the water surface, is indicated in the altitude distribution information is referred to as a non-ground region.
[0031]
The terrain extraction unit 230 processes the elevation (processing altitude) which is to be processed in each iteration of the iterative processing, and a processing altitude range setting unit 231 which sets the range of the altitude for performing the terrain extraction processing (the lower and upper limits of the altitude to be processed). A processing elevation setting section 232 for setting within the elevation range set by the elevation range setting section 231, a non-ground area detection section 233 for detecting a non-ground area existing on the processing elevation surface in the aligned elevation distribution information; A non-ground area removing unit 234 that removes an influence of a building, a tree, or the like from the aligned elevation distribution information by changing the elevation value of the area in the aligned elevation distribution information when the ground area is detected; Have.
[0032]
Hereinafter, details of the terrain shape extraction system will be described.
[0033]
The parameter input device 100 specifies a geographical range (DEM image area) to be read when the DEM reading unit 210 reads the altitude distribution information from the DEM storage device 300, and DEM in the aligned altitude distribution information (DEM image) after the reading. The user inputs an image size, determines a DEM image correction method to be performed by the DEM image correction unit 220, sets a range of the processing altitude set by the processing altitude range setting unit 231, an amount of change, and the like. 233 is used to set an area threshold value used in 233. As will be described later, typically, a keyboard of a personal computer or the like is used as the parameter input device 100.
[0034]
The DEM reading unit 210 reads the altitude distribution information stored in the DEM storage device 300 after converting the altitude distribution information into aligned altitude distribution information. For example, considering that the altitude distribution information stored in the DEM storage device 300 is three-dimensional coordinate data measured by a laser profiler, the DEM reading unit 210 reads the DEM image area set by the parameter input device 100. Since the correspondence between the DEM image and the ground is determined from the DEM image and the DEM image size, the laser measurement points at positions corresponding to the respective grid points in the aligned elevation distribution information are read from the DEM storage device, and the elevation of the read laser measurement points is obtained. Let the value be the elevation value for that pixel. Here, when there is no laser measurement point corresponding to the grid point of the aligned elevation distribution information, the elevation value of the grid point can be calculated by interpolating using several points among the nearby measurement points. . Of course, if the altitude distribution information stored in the DEM storage device 300 is originally aligned altitude distribution information, the DEM reading unit 300 reads the aligned altitude distribution information as it is without performing further conversion. become.
[0035]
The DEM image correcting unit 220 applies the image processing technology by the DEM image correcting method designated by the parameter input device 100 and applies noise existing in the aligned elevation distribution information (DEM image) generated by the DEM reading unit 210. , Etc. The DEM image correcting unit 220 applies, for example, a smoothing filter or a median filter to reduce the sesame salt-like noise (noise that looks like sesame salt when viewed as an image) present in the aligned elevation distribution information. Can be removed.
[0036]
The DEM output device 400 outputs the aligned elevation distribution information representing the elevation of the terrain shape generated by the terrain extraction unit 230 on a display by visualization using CG technology, or converts the information into three-dimensional coordinate point data. It is converted and recorded on a recording medium such as a flexible disk, or recorded as a bitmap image on a storage medium.
[0037]
Next, the terrain extraction unit 230 will be described in more detail.
[0038]
The processing altitude range setting unit 231 sets the altitude range and the change amount input by the parameter input device 100 as the processing altitude range and the change amount. Alternatively, the processing elevation range setting unit 231 may check the elevation distribution in the aligned elevation distribution information corrected by the DEM image correction unit 220 and set the processing elevation range and the amount of change. For example, the elevation value of each point in the sorted elevation distribution information of the processing target is examined, the range from the highest value to the lowest value is set as the range of the elevation to be processed, and the range of the elevation determined in this way is input as a parameter. The quotient divided by the number of divisions set by the device 100 is defined as a change amount.
[0039]
The processing altitude setting unit 232 sequentially processes the altitude values from the lowest value to the highest value or from the highest value to the lowest value within the range according to the altitude range and the amount of change set by the processing altitude range setting unit 231. And set the processing altitude.
[0040]
Then, the non-ground area detection unit 233 generates binarized elevation distribution information by performing binarization processing on the aligned elevation distribution information at the processing altitude set by the processing altitude setting unit 232, and generates the binarized elevation distribution information. Area division is performed by performing labeling processing in the image processing technique on the elevation distribution information, and among the divided areas, an area having an area equal to or smaller than an area threshold set by the parameter input device 100 is detected as a non-ground area. . Then, the non-ground area removing unit 234 sets the elevation value of each point in the area extracted as the non-ground area among the points of the aligned elevation distribution information to the processing elevation setting unit 232 at that time. Rewrite to an altitude that is As the unit of the area threshold, the number of points (pixels) included in the area is simply used here. The labeling process is a well-known method in the field of image processing, which is also called a leveling process, and is described in, for example, Takeshi Aiin, Tomoharu Nagao, "Image Processing and Recognition", Shokodo, 1992, and the like.
[0041]
The binarized elevation distribution information has the same number of points as the aligned elevation distribution information, and each point has a value of “0” or “1”. As described above, the sorted altitude distribution information can be regarded as a grayscale image. However, the binarized altitude distribution information sets a processing altitude for a grayscale image corresponding to the aligned altitude distribution information. The image can be treated as a binary image generated by performing a binarization process using a value.
[0042]
Such processing by the non-ground area detecting unit 233 and the non-ground area removing unit 234 is performed each time the processing altitude setting unit 232 sequentially sets the processing altitude, and the processing altitude is set by the processing altitude range setting unit 231. When the distance falls outside the set range, the sorted elevation distribution information at that time is output to the DEM output device 400, and the DEM output device 400 outputs the sorted elevation information from which influences of buildings, trees, and the like have been removed. Output processing of distribution information (DEM image) is performed.
[0043]
FIG. 2A shows an example of sorted elevation distribution information. The small square areas in which the numbers are described respectively correspond to the pixels in the DEM image, that is, the points in the aligned elevation distribution information. Here, elevation values are shown for 8 × 8 grid points (pixels). Here, it is assumed that the processing altitude set by the processing altitude setting unit 232 is 50, and the area threshold in the non-ground area detection unit 233 is 4.
[0044]
When the binarization process is performed on the aligned elevation distribution information in FIG. 2A, binarized elevation distribution information (binary image) as shown in FIG. 2B is obtained. In FIG. 2B, a point (pixel) having an altitude higher than 50 is “1”, and a point having an altitude of 50 or less is “0”. FIG. 2C shows a result obtained by performing a labeling process on such binarized elevation distribution information and dividing the region. FIG. 2C shows that points (pixels) of the same character belong to the same area, and are shown to be divided into an area A, an area B, an area C, and an area D. Then, of the areas detected in this way, an area having an area equal to or smaller than the area threshold value (4 in this example) set by the parameter input device 100 is detected as a non-ground area. In FIG. 2C, the non-ground area is the area B.
[0045]
Next, the non-ground area removing unit 234 calculates the elevation of the point in the area detected as the non-ground area by the non-ground area detecting unit 233 among the points in the aligned elevation distribution information, by using the processing elevation setting unit 232. Set to the processing altitude at that time set in. In the example shown in FIG. 2C, since the area B is a non-ground area, the elevation value of a point (pixel) belonging to the area B is set to the processing elevation of 50, and as a result, the sorted elevation distribution information is The result is as shown in FIG.
[0046]
After all, in the example shown in FIG. 2, each point in the area B has an altitude value of 60, but since the point is detected as a non-ground area, the altitude value is rewritten to 50. Even if the above processing is repeated while changing the value of the processing altitude, the altitude value of each point around the area B is also 50, so that the area B is re-independent as an independent area. It is not detected, and after all, the altitude value of the part that was the area B remains at 50 and does not change.
[0047]
Here, a method of setting the area threshold will be described. The terrain shape extraction system of the present invention aims to extract the terrain shape using fewer parameters. Therefore, the area threshold is also determined whether the target area is a central commercial area in an urban area or a suburban house. The same value can be used regardless of whether it is a land, a rural area, or a mountain area. However, in general, large buildings tend to be constructed on flat terrain, and only small buildings on sloping terrain. , And the area of the selected area (multiplied by an appropriate coefficient) can be adopted as the area threshold. As will be described later, a configuration may be adopted in which the area threshold value is selected using map information.
[0048]
Next, the operation of the terrain shape extraction system shown in FIG. 1 will be described with reference to the flowchart in FIG.
[0049]
First, in step A1, the parameter input device 100 sets a DEM image size and a DEM image area required when the DEM capture unit 210 converts and captures elevation distribution information into aligned elevation distribution information, and sets a DEM image correction unit. 220 selects a correction processing method used when correcting the aligned altitude distribution information, sets parameters necessary for the correction processing, and a processing altitude range setting unit 231 to perform an altitude range and a variation amount for performing necessary processing. Is set, and the area threshold required by the non-ground area detection unit 233 is set. Then, the DEM reading unit 210 extracts elevation distribution information corresponding to the DEM image area set in step A1 from various elevation distribution information stored in the DEM storage device 300 (step A2), and specifies the designated DEM image. It is converted into size-aligned elevation distribution information and read (step A3). The DEM correction unit 220 performs a correction process, such as noise removal, on the read sorted altitude distribution information according to the processing method and parameters designated by the parameter input device 100 (step A4).
[0050]
Next, the processing altitude range setting unit 231 sets the altitude range and the amount of change set in step A1 as the altitude value range and the amount of change to be processed (step A5). At this time, the processing altitude range setting unit 231 checks the distribution of the altitude values in the sorted altitude distribution information, and may set the altitude range in which the processing is performed from the lowest value to the highest value, or the number of divisions set in step A1. The value obtained by dividing the range may be used as the change amount.
[0051]
The processing altitude setting unit 232 sets the altitude to be processed while sequentially changing the altitude from the highest or lowest altitude in the range set in step A5 (step A6). Here, it is assumed that the altitude value is sequentially set from the highest value to the lowest value of the altitude range set in step A5 by the change amount set in step A5. As described above, the altitude value set by the processing altitude setting unit 232 is called a processing altitude.
[0052]
The non-ground area detection unit 233 generates binarized elevation distribution information by performing binarization processing on the aligned elevation distribution information at the processing elevation set in step A6 (step A7). Labeling processing is performed on the binarized elevation distribution information to divide the area into areas (step A8). For example, binarized altitude distribution information is created by setting a region higher than the processing altitude to “1” and a region lower than the processing altitude to “0”. If adjacent pixels have the same value, they are considered to be the same region. Do. The non-ground area detecting unit 233 detects, as a non-ground area, an area whose area is equal to or smaller than the area threshold set in step A1 among the areas obtained in this manner (step A9).
[0053]
When the non-ground area is detected, the non-ground area removing unit 234 converts the elevation value of each point (pixel) of the aligned elevation distribution information corresponding to the detected non-ground area into the processing elevation at that time. It is changed (step A10).
[0054]
Subsequently, in step A11, it is checked whether or not the altitude value to be processed next (the processing altitude to be set by the processing altitude setting unit 232) is within the range set in step A5. Then, the process from step A6 to A11 is repeated, and if it is out of the range, the process proceeds to step A12.
[0055]
In step A12, the DEM output device 400 visualizes the aligned elevation distribution information from which the non-ground area has been removed in the terrain extracting unit 200 as described above, for example, by using the CG technique, and outputs the visualized information to a display or a three-dimensional display. The data is converted into coordinate point data and recorded on a recording medium such as a flexible disk, or recorded as a bitmap image on a storage medium. Thus, the terrain shape extraction processing is completed.
[0056]
Note that the binarization processing is performed in the processing described above because, in the field of image processing technology, labeling processing for region division is originally defined for a binary image. . If another area dividing method is used to extract a region above the processing elevation or below the processing elevation, the binarization processing is not necessarily required.
[0057]
FIG. 4 is a flowchart showing the above-described terrain shape extraction processing from an algorithm point of view. FIG. _L From the highest value H _U (B) shows the process when the processing altitude H is sequentially changed toward (b). _U From the lowest value H _L , The processing when the processing altitude H is sequentially changed is shown. The amount of change in the processing altitude between each repetition of the processing corresponding to steps A6 to A11 is ΔH.
[0058]
In the processing shown in FIG. 4A, first, as the initial setting, the processing altitude H is set to the minimum altitude H _L (Step B1), a region having an altitude higher than the processing altitude H is extracted from the sorted altitude distribution information using the image division technique (Step B2), and the area of the extracted region is equal to or smaller than the area threshold. Is detected as a non-ground area (step B3). Then, the altitude value of each point in the detected non-ground area is rewritten to the processing altitude H (step B4), and the processing altitude H is increased by ΔH (step B5). The processing altitude H increased by ΔH is the maximum altitude H _L It is determined whether or not H (H ≦ H) (step B6). _L If so, the process returns to step B2, and H> H _L If so, the process ends.
[0059]
As a process for extracting a region above the processing altitude H, various methods used for region division and region extraction in image processing technology are used in addition to a method combining binarization processing and labeling processing. be able to.
[0060]
In the process shown in FIG. 4B, first, as an initial setting, the processing altitude H is set to the maximum altitude H _U (Step B7), an area having an altitude higher than the processing altitude H is extracted from the aligned elevation distribution information using the image division technique (Step B8), and the area of the extracted area is equal to or smaller than the area threshold. Is detected as a non-ground area (step B9). Then, the altitude value of each point in the detected non-ground area is rewritten to the processing altitude H (step B10), and the processing altitude H is reduced by ΔH (step B11). The processing altitude H reduced by ΔH is the minimum altitude H _U It is determined whether or not it is above (step B12). _U If ≤H, the process returns to step B8 and H _U If> H, the process ends.
[0061]
The case where the processing altitude is sequentially increased from the lowest value to the highest value shown in FIG. 4A and the case where the processing altitude is sequentially reduced from the highest value to the lowest value shown in FIG. 4A, the area detected as the non-ground area is not detected and extracted again as the non-ground area after the altitude value is rewritten. On the other hand, in the case of FIG. 4B, even if the altitude value is rewritten, the area detected as the non-ground area may be repeatedly used until the altitude value is merged with the altitude of the surrounding area. The area is extracted and the altitude value is rewritten.
[0062]
In the terrain shape extraction system according to the first embodiment, the DEM processing device 200 causes a computer such as a personal computer to read a computer program (DEM processing program) for realizing the DEM processing device 200 and execute the program. It can also be realized by: FIG. 5 shows a terrain shape extraction system configured as described above.
[0063]
The terrain shape extraction system shown in FIG. 5 includes a parameter input device 100, a DEM processing device 200 provided as a personal computer, a DEM storage device 300, a DEM output device 400, and further includes a recording medium on which a DEM processing program 700 is recorded. . This recording medium may be a magnetic disk, a semiconductor memory, a CD-ROM, or other recording medium, and the DEM processing program 700 is read into the DEM processing device (personal computer) 200 by this recording medium. The DEM processing apparatus 200 shown in FIG. 5 executes the same processing as the DEM processing apparatus 200 in the terrain shape extraction system shown in FIG. 1 under the control of the DEM processing program. The DEM processing program can be read by a DEM processing device (personal computer) by means other than a recording medium. The DEM processing program is read into the DEM processing apparatus 200, for example, by downloading from a network.
[0064]
Next, an actual example of terrain shape extraction using the terrain shape extraction system of the first embodiment will be described. Here, a keyboard is provided as the parameter input device 100, a personal computer is provided as the DEM processing device 200, and a magnetic disk device is provided as the DEM storage device 300 and the DEM output device 400. The personal computer has a central processing unit (CPU) that functions as a DEM reading unit, a DEM image correcting unit, and a terrain extracting unit by executing a DEM processing program. Altitude distribution information is stored.
[0065]
Here, as shown in FIG. 6, a terrain composed of a sloping ground 500 and a building 510 built on the ground is considered, and two aerial photographs taken from different photographing positions are subjected to stereo image processing. It is assumed that the altitude distribution information thus generated is stored in the magnetic disk storage device.
[0066]
The elevation distribution information is read into the central processing unit, and as a result, aligned elevation distribution information (DEM image) having the DEM image size (width, height) specified by the parameter input device is generated. Thereafter, a noise component is removed by applying a median filter, a smoothing filter, and the like to the aligned elevation distribution information, and as a result, the aligned elevation distribution information shown in FIG. 7A is generated. In FIG. 7, the aligned elevation distribution information is represented as a grayscale image. Here, a darker (black) color corresponds to a lower altitude value, and a brighter (white) color corresponds to a higher altitude value. FIG. 8 is a cross-sectional view taken along the line AA ′ of FIG.
[0067]
From FIG. 8, the maximum elevation is H5 and the minimum elevation is H1 in the above-mentioned sorted elevation distribution information, so that the processing elevation range is from H1 to H5. Then, it is assumed that the change amount ΔH and the area threshold value T are set by the parameter input device. Here, it is assumed that the processing is performed while shifting the processing altitude H by ΔH from H5 to H1. Here, for the sake of explanation, the height obtained by dividing the maximum altitude H5 and the minimum altitude H1 into four is defined as a change amount ΔH, and as a result, the processing altitudes sequentially change to H5, H4, H3, H2, and H1. I have to.
[0068]
First, binarization processing is performed on the aligned elevation distribution information (FIG. 7A) with H5 as the processing elevation, and the binarized elevation distribution information (binary image) shown in FIG. 9A is obtained. Can be In FIG. 9, the area higher than the processing altitude is expressed in white, and the area lower than the processing altitude is expressed in gray. In FIG. 9A, the area A1 is detected. If T <A1, the area A1 is not a non-ground area, and thus the non-ground area removal processing is not performed.
That is, the altitude value in the sorted altitude distribution information is not rewritten.
[0069]
Next, when binarization processing is performed on the aligned elevation distribution information (FIG. 7A) at the processing altitude H4, binarized elevation distribution information shown in FIG. 9B is obtained. In FIG. 9B, areas B1, B2, and B3 are detected. If T <B1, T> B2, and T <B3, the non-ground area becomes B2. As a result, of the aligned elevation distribution information shown in FIG. 7A, the elevation values of points belonging to the area corresponding to the area B2 in FIG. 9B are rewritten to H4, and as a result, the aligned elevation distribution The information is as shown in FIG.
[0070]
Next, when the binarization processing is performed on the sorted elevation distribution information (FIG. 7B) at the processing altitude H3, the binarized elevation distribution information shown in FIG. 9C is obtained. In FIG. 9C, the areas C1, C2, and C3 are detected. If T <C1, T> C2, and T <C3, the non-ground area becomes the area C2. Here, the area C2 corresponds to the area B2 in FIG. 9B. As a result of the detection of the area C2 as a non-ground area, the altitude value of a point belonging to the area corresponding to the area C2 in the aligned elevation distribution information is rewritten as H3, and as a result, the aligned elevation distribution information is as shown in FIG. )become that way.
[0071]
Next, binarization processing is performed on the sorted altitude distribution information (FIG. 7C) at the height of the processing altitude H2, and the binarized altitude distribution information shown in FIG. 9D is obtained. In FIG. 9D, the areas D1 and D2 are detected, but if T <D1 and T <D2, the non-ground area removal processing is not performed.
[0072]
Similarly, when the binarization processing is performed on the aligned elevation distribution information at the processing altitude H1, the binarization elevation distribution information shown in FIG. 9E is obtained. In FIG. 9E, the area E1 is detected, but if T <E1, the area E1 is not a non-ground area, and thus the non-ground area removal processing is not performed.
[0073]
After all, the non-ground area is removed from the input aligned elevation distribution information (FIG. 7 (a)) by the above processing, and the aligned elevation distribution information (FIG. 7 (c)) is assumed to represent the terrain shape. Is generated. The aligned elevation distribution information in FIG. 7C is output to the DEM output device.
[0074]
In the above processing, it is apparent that by making the change amount (step value of the processing altitude) ΔH smaller, it is possible to more accurately generate the aligned elevation distribution information representing the terrain shape.
[0075]
Although the first embodiment of the present invention has been described above, according to this embodiment, regardless of the type of altitude distribution information, it is converted into aligned altitude distribution information, and only a small number of parameters are set. Non-ground areas can be automatically detected and removed. Therefore, the same processing can be applied regardless of the measurement location, regardless of the elevation distribution information obtained by measuring the urban area or the altitude distribution information obtained by measuring the mountainous area. It is possible to acquire aligned elevation distribution information representing a shape. Further, an operation for changing the altitude value is not performed on an area other than the area detected as the non-ground area. For this reason, it is possible to acquire aligned elevation distribution information (DEM image) representing the terrain while maintaining the detailed shape of the terrain detected as the ground area.
[0076]
<< 2nd Embodiment >>
The terrain shape extraction system according to the second embodiment of the present invention shown in FIG. 10 acquires map information in the terrain shape extraction system shown in FIG. 1 and can detect a non-ground area using this map area. It was made. The terrain shape extraction system shown in FIG. 10 is different from the terrain shape extraction system shown in FIG. 1 in that it has a map information processing device 600 including a map information reading unit 610 and a map information storage device 620. The difference is that the data is supplied from the reading unit 610 to the non-ground area detecting unit 233 and the non-ground area removing unit 234. In addition, the parameter input device 100 can specify the type of map information to be read to the map information reading unit 610.
[0077]
The map information storage device 620 stores polygon (polygon) information describing a block shape and a building shape, land attribute information at an arbitrary point or an arbitrary region, and the like.
[0078]
The land attribute information is a set of points, polygons, and vector information representing a place or an area, and information representing attributes of the point, polygon, or vector. For example, when representing a road, a polygon representing a road area and a character string such as "National highway XX" or an identifier for identifying a road are stored as a set.
[0079]
The map information reading unit 610 reads the type of map information specified by the parameter input device 100 from the map information storage device 620.
[0080]
In the terrain shape extraction system of the second embodiment, the non-ground area detection unit 233 or the non-ground area removal unit 234 performs processing using the map information read by the map information reading unit 610. Hereinafter, non-ground area detection using various types of map information will be described.
[0081]
When a building shape polygon is designated by the parameter input device 100 as the map information, the map information reading unit 610 reads the building shape polygon from the map information storage device 620.
[0082]
The non-ground area detection unit 233 performs area division by binarization processing and labeling processing on the aligned elevation distribution information, as in the case of the first embodiment. Further, the non-ground area detection unit 233 acquires a building shape polygon closest to each of the divided areas, and detects an area having an area smaller than the corresponding building shape polygon as a non-ground area. Alternatively, for each of the divided areas, the ratio of the area of the area to the area of the building-shaped polygon corresponding to the area is calculated, and (area of area) / (area of polygon) is a threshold value (for example, 1). If it is less than or equal to), the area is detected as a non-ground area. When the non-ground area is detected in this way, the non-ground area removing unit 234 calculates the elevation value of each point corresponding to the non-ground area as the processing altitude at that time, as in the first embodiment. By doing so, the non-ground area is removed.
[0083]
FIG. 11 is a diagram illustrating a process of acquiring a building shape polygon closest to an area on the binarized elevation distribution information. Since the building shape polygon can also be considered as a region in the map information, this process results in a process for obtaining the distance between the regions. Here, as shown in the figure, there are areas A to D, and the distance (L) between the area A and the other areas (areas B to D). _ab , L _ac , L _ad ). In FIG. 11A, the distance between the centers of gravity (indicated by ● in the figure) of each area is defined as the distance between the areas. FIG. 11B shows that the smallest distance between the side of one region and the side of the other region is set as the distance between these regions. Since the definition of the distance between the regions can be considered other than these, an appropriate method can be selected. When acquiring a building shape polygon closest to the area on the binarized elevation distribution information by these methods, it is preferable to consider mutual inclusion relations.
[0084]
As another example, when land attribute information is designated as map information by the parameter input device 100, the map information reading unit 610 reads the land attribute information from the map information storage device 620.
[0085]
The non-ground area detection unit 233 performs area division by binarization processing and labeling processing on the aligned elevation distribution information, as in the case of the first embodiment. Further, the non-ground area detecting unit 233 acquires land attribute information closest to each of the divided areas from the land attribute information read by the map information reading unit 610, and when the attribute of the area is a road, The area is detected as a non-ground area. The non-ground area removing unit 234 removes the non-ground area by setting the elevation value of each point corresponding to the non-ground area as the processing altitude at that time, as in the first embodiment. In general, roads are detected as non-ground areas because there are many street trees, telephone booths, telephone poles, etc. on roads. In order to remove it.
[0086]
If the land attribute information closest to the area is the sea, the non-ground area detecting unit 233 detects the area as a non-ground area, and the non-ground area removing unit 234 sets the altitude value of the area to 0 [ m]. If necessary, the altitude value of the area with respect to the sea surface may be made to match the standard of the altitude in the area. Here, the elevation value is forcibly set to 0 [m] for the sea part, for example, when the elevation value is obtained by stereo matching or the like, due to the influence of waves and light reflection, the elevation value is not necessarily correct on the sea surface. Is not always obtained.
[0087]
The above is an example of detecting a non-ground area exclusively using map information. However, the non-ground area detecting unit 233 specifies the area threshold set by the parameter input apparatus 100 and the area threshold specified by the parameter input apparatus 100. The non-ground area may be detected by using both of the map information.
[0088]
For example, when a building shape polygon is designated as map information by the parameter input device 100, the map information reading unit 610 reads the building shape polygon from the map information storage device 620. As in the case of the first embodiment, the non-ground area detecting unit 233 first determines, from each of the divided areas, an area smaller than the area threshold set by the parameter input device 100 (area A). To detect. Further, when the area of the area A is smaller than the area of the building-shaped polygon (polygon B) closest to the area A, the non-ground area detection unit 233 detects the area A as a non-ground area. After that, the non-ground area removing unit 234 removes the area A by rewriting the altitude value.
[0089]
In another example, when a building shape polygon is designated as map information by the parameter input device 100, the map information reading unit 610 reads the building shape polygon from the map information storage device 620. As in the case of the first embodiment, the non-ground area detecting unit 233 first determines, from among the divided areas, an area (area C) smaller than the area threshold set by the parameter input device 100. Among the large areas (area D), area C is detected as a non-ground area. Further, when the area of the area D is smaller than the closest building-shaped polygon (polygon E), the non-ground area detection unit 233 also detects the area D as a non-ground area. Thereafter, the non-ground area removing unit 234 removes the area C and the area D by rewriting the altitude value.
[0090]
Next, the operation of the terrain shape extraction system shown in FIG. 10 will be described with reference to the flowchart in FIG.
[0091]
First, in step C1, the type of map information to be used is designated by the parameter input device 100. At this time, similarly to the first embodiment, the selection of the correction processing method used when correcting the DEM image size and DEM image area, the aligned elevation distribution information, the parameters necessary for the correction processing, the range of the elevation and the amount of change Are also set. Also, an area threshold is set as needed.
[0092]
Next, similarly to steps A2 to A8 in the flowchart shown in FIG. 3, the elevation distribution information is extracted from the DEM storage device 300 (step C2), converted into aligned elevation distribution information (step C3), and aligned. Correction such as noise removal is performed on the altitude distribution information (step C4), a range of altitude to be processed is set (step C5), and a processing altitude is set within the altitude range (step C6), and step C6 is performed. The binarization processing is performed on the sorted elevation distribution information at the processing altitude set in the step (1) to generate binarized elevation distribution information (step C7), and the labeling processing is performed on the binarized elevation distribution information. (Step C8).
[0093]
Next, the map information reading unit 610 reads the designated type of map information from the map information storage device 620 and supplies it to at least one of the non-ground area detecting unit 233 and the non-ground area removing unit 234 (step C9). ). Thereafter, the non-ground area detection unit 233 determines whether each of the divided areas in the binarized elevation distribution information is a non-ground area (Step C10). At this time, as in the first embodiment, if the area of the area is equal to or smaller than the area threshold, the area may be determined to be a non-ground area. It may be used to determine whether or not the target area is a non-ground area, or may be determined to be a non-ground area by combining the determination based on the area threshold value and the determination based on the map information. . Here, the area threshold value itself may be changed according to the map information. For example, the building shape information closest to each area obtained in step C8 is read from the map information storage device 620, and the area of each building shape is set as the area threshold value of each area. The determination may be performed.
[0094]
When the non-ground area is detected, the non-ground area removing unit 234 removes the non-ground area by rewriting the elevation value of each point of the aligned elevation distribution information corresponding to the detected non-ground area. Is executed (step C11). In this case, similarly to the first embodiment, the altitude value may be rewritten at the processing altitude at that time, or when the altitude value is obtained from the map information, the altitude value may be rewritten with the altitude value based on the map information.
[0095]
Subsequently, in step C12, it is checked whether or not the altitude value to be processed next (the processing altitude to be set by the processing altitude setting unit 232) is within the range set in step C5. Then, the process from steps C6 to C12 is repeated, and if it is out of the range, the process proceeds to step C13. In step C13, the DEM output device 400 outputs or records the aligned elevation distribution information from which the non-ground area has been removed as described above, as in the first embodiment. Thus, the terrain shape extraction processing is completed.
[0096]
In the terrain shape extraction system according to the second embodiment described above, the DEM processing device 200 and the map information processing device 600 use a computer program (DEM processing program and map information processing program) for realizing the same. It can also be realized by causing a computer to read the program and executing the program. FIG. 13 shows a terrain shape extraction system configured as described above.
[0097]
The terrain shape extraction system shown in FIG. 13 includes a parameter input device 100, a DEM processing device 200 provided as a personal computer, a DEM storage device 300, a DEM output device 400, and a map information processing device 600, and further includes a DEM processing program and a map. There is provided a recording medium on which an information processing program (together, a program 700) is recorded. The recording medium may be a magnetic disk, a semiconductor memory, a CD-ROM, or another recording medium. The DEM processing program is read into the DEM processing device (personal computer) 200 by this recording medium, and the map information processing program is stored in the recording medium. The information is read into the map information processing device (personal computer) 600 by the medium. Here, the DEM processing apparatus 200 and the map information processing apparatus 600 are illustrated as being independent from each other, but both the DEM processing program and the map information processing program are executed on a single personal computer. The personal computer may function as both the DEM processing device 200 and the map information processing device 600. Further, the DEM processing program and the map information processing program can be read by a personal computer by means other than the recording medium. The DEM processing program and the map information processing program are read by a personal computer, for example, by downloading from a network. As a result, the personal computer functions as the DEM processing device 200 and the map information processing device 600.
[0098]
The DEM processing apparatus 200 shown in FIG. 13 executes the same processing as the DEM processing apparatus 200 in the terrain shape extraction system shown in FIG. 10 under the control of the DEM processing program. Similarly, the map information processing apparatus 600 shown in FIG. 13 executes the same processing as the map information processing apparatus 600 in the terrain shape extraction system shown in FIG. 10 under the control of the map information processing program.
[0099]
Next, an actual example of terrain shape extraction using the terrain shape extraction system of the second embodiment will be described. Here, a keyboard is provided as the parameter input device 100, a personal computer is provided as the DEM processing device 200 and the map information processing device 600, and a magnetic disk device is provided as the DEM storage device 300, the DEM output device 400, and the map information storage device 620. The personal computer has a central processing unit (CPU) that functions as a DEM reading unit, a DEM image correcting unit, a terrain extracting unit, and a map information reading unit by executing a DEM processing program. Stores altitude distribution information and map information to be processed. Here, as in the case of the first embodiment, the terrain shown in FIG. 6 will be considered.
[0100]
As in the case of the first embodiment, the elevation distribution information is read into the central processing unit, and as a result, an aligned elevation distribution of the DEM image size specified by the parameter input device is generated. Then, it is assumed that the noise component of the aligned elevation distribution information is removed, and as a result, the DEM image of FIG. 7A is generated. Here, as shown in FIG. 8, since the range of the altitude in the aligned elevation distribution information is H1 to H5, the range of the processed altitude is H1 to H5, and the change amount ΔH and the area threshold are set by the parameter input device. Set the value T.
[0101]
Next, similarly to the first embodiment, processing is performed while changing the processing altitude from the altitude H5 by ΔH. When the processing altitude is H4, the binarized altitude distribution information shown in FIG. 9B is obtained, and three areas B1, B2, and B3 are detected. Here, unlike the first embodiment, a case where T <B1, T <B2, and T <B3 is considered. It is also assumed that the building shape polygon closest to the area B2 read from the map information storage device is the building shape polygon 710 in FIG.
[0102]
When the area of the building shape polygon 710 is T ′ and T ′> B2, the non-ground area is B2, and the elevation value of the area corresponding to the area B2 in the aligned elevation distribution information is the processing altitude at that time. H4.
[0103]
Similarly, the building-shaped polygons close to the region B1 and the region B3 are the building-shaped polygon 710 and the building-shaped polygon 720 in FIG. 14, respectively, and the areas of the building-shaped polygons 710 and 720 are T ′ and T ″. At this time, if T ′ <B1, T ″ <B2, the areas B1 and B2 are not detected as non-ground areas. By performing the above processing for each ΔH from the processing altitude H5 in the range of H1 to H5, as a result, the aligned altitude distribution information as shown in FIG. 7C can be obtained.
[0104]
In the end, the above processing produces the aligned elevation distribution information (FIG. 7 (c)) from which the non-ground area has been removed from the aligned elevation distribution information including the influence of the building (FIG. 7 (a)). become. The aligned elevation distribution information (FIG. 7C) representing the terrain shape is output to the DEM output device.
[0105]
In the first embodiment, the non-ground area is detected using only the area threshold value input by the parameter input device 100. In the second embodiment, however, the processing target is determined by using the map information. Processing parameters can be set according to a certain area, and the accuracy of the non-ground area determination processing and the accuracy of the non-ground area removal processing are improved. Thus, according to the second embodiment, it is possible to generate the altitude distribution information representing the terrain with higher accuracy.
[0106]
【The invention's effect】
As described above, the present invention can detect and remove a non-ground area only by setting a small number of parameters such as an area threshold value and a processing altitude, and can easily obtain elevation distribution information representing terrain. There is an effect that it can be generated. In addition, since the processing that changes the altitude value is not performed on the area that is determined to be not the non-ground area, the altitude distribution information that excludes the influence of buildings etc. is generated while maintaining the detailed shape of the terrain. can do. Further, in the present invention, by using map information, it is possible to flexibly cope with various regions and to generate altitude distribution information representing the topography with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a terrain shape extraction system according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a terrain shape extraction process performed by the terrain shape extraction system according to the first embodiment.
FIG. 3 is a flowchart illustrating processing in the terrain shape extraction system according to the first embodiment.
FIG. 4 is a flowchart showing a terrain shape extraction process.
FIG. 5 is a block diagram showing another example of the terrain shape extraction system of the first embodiment.
FIG. 6 is a perspective view showing an example of terrain.
FIG. 7 is a diagram expressing aligned elevation distribution information corresponding to the terrain shown in FIG. 6 as a grayscale image.
FIG. 8 is a cross-sectional view expressing the terrain as a cross section taken along line AA ′ of FIG. 7;
FIG. 9 is a diagram showing binarized elevation distribution information.
FIG. 10 is a block diagram showing a configuration of a terrain shape extraction system according to a second embodiment of the present invention.
FIG. 11 is a diagram illustrating a process of obtaining a closest building shape polygon.
FIG. 12 is a flowchart illustrating a process in the terrain shape extraction system according to the second embodiment.
FIG. 13 is a block diagram showing another example of the terrain shape extraction system of the second embodiment.
FIG. 14 is a diagram showing an example of a building shape polygon in map information.
[Explanation of symbols]
100 Parameter input device
200 DEM processing equipment
210 DEM reading unit
220 DEM image correction unit
230 Terrain extraction unit
231 Processing altitude range setting unit
232 Processing altitude setting section
233 Non-ground area detection unit
234 Non-ground area removal unit
300 DEM storage device
400 DEM output device
600 Map information processing device
610 Map information readout unit
620 Map information storage device
700 programs

Claims (33)

A terrain shape extraction method for extracting a terrain shape from given altitude distribution information,
Non-ground area detection processing for detecting a non-ground area by analyzing the elevation distribution information based on the processing altitude,
A non-ground area removing process of changing the detected altitude value of the non-ground area based on the processing altitude,
A terrain shape extraction method, wherein the non-ground area detection processing and the non-ground area removal processing are performed for each processing elevation. A terrain shape extraction method for extracting a terrain shape from given altitude distribution information,
A non-ground area detection process of dividing the altitude distribution information into each area by analyzing the altitude distribution information based on the processing altitude, and determining whether the divided area is a non-ground area,
Non-ground area removal processing that changes the elevation value of the area determined to be a non-ground area based on the processing altitude,
A terrain shape extraction method, wherein the non-ground area detection processing and the non-ground area removal processing are performed for each processing elevation. A terrain shape extraction method for extracting a terrain shape from given altitude distribution information,
A first step of extracting a region whose altitude value exceeds the processing altitude in the altitude distribution information by performing region division based on the set processing altitude,
A second step of determining whether the extracted area is a non-ground area based on characteristics of the extracted area;
A third step of changing the elevation value of each point in the area in the elevation distribution information when it is determined that the area is a non-ground area;
And a terrain shape extraction method. 4. The terrain shape extraction method according to claim 3, wherein the processing from the first step to the third step is repeatedly performed so that the processing altitude sequentially changes between a minimum value and a maximum value. 5. The method according to claim 3, further comprising removing noise included in the given altitude distribution information, wherein the first to third steps are performed on the altitude distribution information from which the noise has been removed. The described terrain shape extraction method. Arranging the distribution of each point in the given altitude distribution information at equal intervals in the direction of each coordinate axis on a two-dimensional coordinate plane, and removing the noise from the aligned altitude distribution information. The terrain shape extraction method according to claim 5, wherein a step is performed. The terrain shape extraction according to any one of claims 3 to 6, wherein when the area of the extracted area is equal to or smaller than a predetermined area threshold, the extracted area is determined as a non-ground area. Method. The terrain shape extraction method according to any one of claims 3 to 7, wherein an altitude value of each point in an area determined as a non-ground area in the altitude distribution information is rewritten with the processing altitude. The terrain shape extraction method according to any one of claims 3 to 6, wherein it is determined whether or not the extracted area is a non-ground area based on a result obtained by referring to map information. The terrain shape extraction method according to claim 9, wherein the elevation value of each point in the area determined to be a non-ground area in the elevation distribution information is rewritten to an elevation value obtained by referring to the map information. Searching for the building shape polygon closest to the extracted region in the map information, based on the ratio of the area of the extracted region to the area of the searched building shape polygon, The terrain shape extraction method according to claim 9, wherein it is determined whether or not the area is an area. The first step includes binarizing the elevation distribution information based on the processing elevation, labeling the binarized elevation distribution information as a binary image, and labeling the binarized elevation distribution information. The terrain shape extraction method according to any one of claims 3 to 11, wherein a process is performed to extract a region exceeding the processing altitude as a region independent of each other. A terrain shape extraction system for extracting a terrain shape from given altitude distribution information,
Non-ground area detecting means for detecting a non-ground area by analyzing the elevation distribution information based on the processing altitude,
A non-ground area removing unit that changes an altitude value of the detected non-ground area based on the processing altitude,
A terrain shape extraction system, wherein the non-ground area detecting means and the non-ground area removing means perform processing at each processing altitude. A terrain shape extraction system for extracting a terrain shape from given altitude distribution information,
Non-ground area detecting means for analyzing the altitude distribution information based on the processing altitude to divide the altitude distribution information into each area, and determining whether the divided area is a non-ground area,
A non-ground area removing unit that changes an altitude value of an area determined to be a non-ground area based on the processing altitude,
A terrain shape extraction system, wherein the non-ground area detecting means and the non-ground area removing means perform processing for each processing altitude. A terrain shape extraction system for extracting a terrain shape from given altitude distribution information,
By performing area division on the basis of the set processing altitude, an area having an altitude value exceeding the processing altitude in the altitude distribution information is extracted, and for each of the extracted areas, the area is determined based on the characteristics of the area. Non-ground area detecting means for determining whether or not the area is a ground area;
Non-ground area removing means for changing the elevation value of each point in the area in the elevation distribution information for the area determined to be a non-ground area,
And a terrain shape extraction system. Processing altitude setting means for setting the processing altitude, processing altitude range setting means for setting the minimum and maximum values of the altitude and the amount of change in the processing altitude, between the minimum value and the maximum value The processing altitude setting means sets the processing altitude so that the processing altitude changes by the change amount, and for each processing altitude, the non-ground area detecting means extracts the area and determines whether the area is a non-ground area. The terrain shape extraction system according to claim 15, wherein the determination is performed, and the non-ground area removing unit changes the elevation value. The altitude distribution information from which the noise has been removed is provided to the non-ground area detecting means, further comprising DEM correction means for removing noise included in the given altitude distribution information. Terrain shape extraction system. A DEM storage device for storing the given elevation distribution information, and extracting elevation distribution information from the DEM storage device, and distributing the distribution of each point in the extracted elevation distribution information in the direction of each coordinate axis on a two-dimensional coordinate plane. 18. The terrain shape extraction system according to claim 17, further comprising: a DEM reading unit that supplies the DEM data to the DEM correction unit by aligning them at intervals. 19. The non-ground area detecting means, when the area of the extracted area is equal to or smaller than a predetermined area threshold, determines the extracted area as a non-ground area. A terrain shape extraction system according to claim 1. 20. The non-ground area removing unit according to claim 15, wherein the altitude value of each point in the area determined to be a non-ground area in the altitude distribution information is rewritten with the processing altitude. Terrain shape extraction system. A map information storage device for storing map information; and a map information readout unit for reading out the corresponding map information from the map information storage device, wherein the non-ground area detection unit is read out via the map information readout unit. The terrain shape extraction system according to any one of claims 15 to 18, wherein it is determined whether or not the extracted area is a non-ground area based on a result obtained by referring to the obtained map information. The non-ground area removing unit refers to the elevation information of each point in the area determined to be the non-ground area in the elevation distribution information, with reference to the map information read through the map information reading unit. 22. The terrain shape extraction system according to claim 21, wherein the terrain shape extraction system is rewritten with the obtained altitude value. The non-ground area detecting means searches for a building shape polygon closest to the extracted area in the map information, based on a ratio of an area of the extracted area to an area of the searched building shape polygon. 22. The terrain shape extraction system according to claim 21, wherein it is determined whether the extracted area is a non-ground area. On the computer,
Non-ground area detection processing for detecting a non-ground area by analyzing given altitude distribution information based on the processing altitude,
Non-ground area removal processing of changing the detected altitude value of the non-ground area based on the processing altitude,
A program for performing the non-ground area detection processing and the non-ground area removal processing for each processing altitude. On the computer,
Based on the processing altitude, the altitude distribution information is divided into each area by analyzing the given altitude distribution information, and the non-ground area detection processing for determining whether the divided area is a non-ground area,
Non-ground area removal processing of changing the elevation value of the area determined to be a non-ground area based on the processing altitude,
A program for performing the non-ground area detection processing and the non-ground area removal processing for each processing altitude. On the computer,
A first process of extracting a region whose altitude value exceeds the processing altitude in the altitude distribution information given by performing region division based on the set processing altitude,
A second process of determining whether or not the extracted region is a non-ground region based on characteristics of the extracted region;
A third process of changing the elevation value of each point in the area in the elevation distribution information when it is determined that the area is a non-ground area;
A program that executes The computer according to claim 26, wherein the computer is configured to repeatedly execute the processing from the first processing to the third processing so that the processing altitude sequentially changes between a minimum value and a maximum value. program. 27. The computer causes the computer to execute a process of removing noise included in the given altitude distribution information, and causes the computer to execute the first to third processes on the altitude distribution information from which the noise has been removed. Or the program according to 27. The computer further executes a process of aligning the distribution of each point in the given altitude distribution information at equal intervals in each coordinate axis direction on a two-dimensional coordinate plane, and for the aligned altitude distribution information. 29. The program according to claim 28, wherein the program causes the processing to remove the noise. 30. The second process according to claim 26, wherein the second process is a process of determining the extracted region as a non-ground region when the area of the extracted region is equal to or smaller than a predetermined area threshold. The program according to any one of the preceding claims. The said 3rd process is an altitude value of each point in the area | region determined as the non-ground area | region in the said altitude distribution information, Rewriting with the said process altitude. program. The said 2nd process is a process which determines whether the said extracted area | region is a non-ground area | region based on the result obtained with reference to map information. The program described in. The first processing binarizes the elevation distribution information based on the processing elevation, and treats the binarized elevation distribution information as a binary image to label the binarized elevation distribution information. The program according to any one of claims 26 to 32, wherein the program is a process of performing a process and extracting a region exceeding the processing altitude as a region independent of each other.

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