JP6334281B2 - Forest phase analysis apparatus, forest phase analysis method and program - Google Patents

Description

  The present invention relates to a forest facies analysis apparatus, a forest facies analysis method, and a program for extracting a forest change region from an image obtained by photographing a forest from the sky and an existing forest facies division map at a different time from the image.

  Remote sensing from the sky by aircraft or the like can grasp the situation on the ground over a wide range, and is used to detect forest changes due to felling, wind damage, etc., and to create a forest fauna classification map. Incidentally, in Japan, forest planning and management is generally carried out in units of several years, and in response to this, forest surveys and forest fauna classification maps are also updated every few years.

  Conventionally, human detection of forest changes and updates of forest phase classification maps using existing forest phase classification maps and newly acquired high-resolution image data such as aerial photographs are basically carried out by visual interpretation. However, since a large amount of time is required for visual interpretation over a wide area, more efficient methods for detecting forest changes and updating the forest fauna classification map are required.

  As a conventional technique for automatically interpreting forest changes, there is known a method for comparing a forest phase map created from an image of a new year with an existing forest phase map. In addition, regarding the technology for automatically generating a forest fauna map from an image of forests, the image is divided into regions to generate forest fauna compartments that are a plurality of small regions with similar characteristics, and forest fauna compartments for each forest fauna compartment. Methods for classification are being studied.

JP 2008-046837 A JP 2011-024471 A

  In the automatic detection of forest changes, when automatically generating a forest phase map for the new year to be compared with the existing forest phase map, forest phase classification is performed using teacher data acquired from images of forests. Conventionally, when acquiring teacher data, a human selects a region corresponding to each forest phase, and the teacher data of each forest phase is extracted from the region. For this reason, the creation of forest facies map has not been fully automated, and the detection of forest changes has not been sufficiently efficient and automated.

  In addition, the acquisition of the teacher data regarding the above-mentioned forestry is performed from a part of the image due to the human workload. Here, even in the same forest phase, the characteristics vary within the image. For this reason, misclassification is likely to occur in the forest fauna map generated using the teacher data obtained from a part of the image. For this reason, there is a problem that erroneous detection is likely to occur when forest change detection is directly performed using the automatically generated forest phase classification map.

  The present invention has been made to solve the above-mentioned problems, and automatically detects a forest change region with high accuracy using an existing forest fauna map and high-resolution images such as aerial photographs. It is an object of the present invention to provide a forest facies analysis apparatus, a forest facies analysis method, and a program that enable automatic generation of forest facies division maps.

  (1) The forest fauna analysis apparatus according to the present invention corresponds to each forest fauna area in the known forest fauna division map in the first period of the target area including the forest, and the target area is viewed from the sky in the second period. Statistical distribution creating means for setting a region of interest in the captured original image and obtaining a statistical distribution for image feature information extracted for each predetermined element region in the region of interest of each forest phase; Change area detection means for detecting an outlier in the statistical distribution and detecting the element area that gives the outlier as a change area in which the forest phase has changed between the first period in the attention area. .

  (2) In the forest fauna analysis apparatus described in (1) above, further, the forest fauna segmentation diagram that generates the forest fauna segmentation diagram of the second time period by reflecting the change region in the forest fauna segmentation diagram of the first time period. It can also be set as the structure which has a production | generation means.

  (3) In the forest fauna analysis apparatus described in the above (1) or (2), the target area is further divided into a plurality of regions based on the similarity of one or more types of partition feature quantities of the original image. A forest fauna compartment generating means for generating and outputting the forest fauna compartment may be provided, and the element area in the statistical distribution creating means and the change area detecting means may be the forest fauna compartment.

  (4) In the forest fauna analysis apparatus described in (3) above, image degradation means for generating a degraded image in which the resolution is reduced from the original image using a region composed of a plurality of adjacent pixels of the original image as a pixel. An initial compartment means for dividing the degraded image into a plurality of regions based on the similarity of the one or a plurality of types of feature values, and creating a forest fauna compartment; and an adjacent forest fauna compartment Are combined on the basis of the similarity of the one or a plurality of types of the feature values for the partition to generate a new forest fauna partition once or a plurality of times, and the forest fauna partition of the forest in the target area is obtained. And subsequent partition means for outputting, the succeeding partition means performs at least one sequential partition processing on the partition feature amount of the original image, or each of the sections of the original image and the degraded image. It can be configured to perform, based on the use feature amount.

  (5) In the forest fauna analyzing apparatus described in (3) or (4), the forest fauna analyzing apparatus includes texture information extracting means for extracting texture information from the original image, and the statistical distribution creating means is output from the forest fauna section generating means. The statistical distribution can be obtained by using the texture information extracted from the forest stand sections as the feature information.

  (6) The forest fauna analysis apparatus according to (5), further including spectrum information extraction means for extracting spectrum information from the original image, wherein the statistical distribution creation means is the forest fauna output from the forest fauna section generation means. The statistical distribution can be obtained by using the texture information and the spectrum information extracted from the section as the feature information.

  (7) In the forest fauna analysis apparatus according to (3) or (4), the forest fauna analyzing apparatus includes a spectrum information extracting unit that extracts spectrum information from the original image, and the statistical distribution creating unit outputs from the forest fauna section generating unit. The statistical distribution can be obtained using the spectrum information extracted from each forest fauna section as the feature information.

  (8) The forest fauna analysis method according to the present invention corresponds to each forest fauna area in the known forest fauna division map in the first period of the target area including the forest, and the target area from the sky in the second period. A statistical distribution creating step for obtaining a statistical distribution for the feature information of the image extracted for each predetermined element area in the attention area of each forestry phase by setting an attention area in the captured original image; and in each of the attention areas A change area detection step of detecting an outlier in the statistical distribution and detecting the element area that gives the outlier as a change area in which the forest phase has changed between the first period and the attention area. .

  (9) A program according to the present invention is a program for causing a computer to perform a forest facies analysis in a target area including a forest, and the computer is used to identify a known forest facies classification in a first period of the target area including a forest. Corresponding to the area of each forest fauna in the figure, the target area is set in the original image taken from the sky in the second period, and extracted for each predetermined element area in the attention area of each forest fauna Statistical distribution creating means for obtaining a statistical distribution for the feature information of the image to be detected, and an outlier in the statistical distribution in each region of interest is detected, and the element region that gives the outlier is the first region in the region of interest It is made to function as a change area detection means for detecting as a change area in which the forest phase has changed between the two times.

  According to the present invention, it is possible to automatically detect a forest change region with high accuracy by using an existing forest phase map and a high-resolution image such as an aerial photograph, and thus automatic generation of a forest phase map. Is possible.

It is a block diagram which shows the structure of the outline of the forest facies analysis system which is the 1st Embodiment of this invention. It is explanatory drawing which shows the example of a sunshine / shade distribution pattern. It is explanatory drawing which shows the example of a sunny / shade boundary pattern. It is explanatory drawing which shows the example of a LBP image. It is an image which shows the example of the ortho image before a normalization process. 6 is an image obtained by normalizing the image of FIG. It is a schematic data flow figure in the forest facies analysis system which is an embodiment of the present invention. It is a general | schematic flowchart explaining the production | generation process of the forest fauna compartment by a forest fauna compartment production | generation part. It is an image which shows the example of the forest fauna division produced | generated from the low-resolution image in the first hierarchy of a hierarchical area | region division process. It is an image which shows the example of the forest fauna division produced | generated in the middle hierarchy of the hierarchical area | region division process. It is an image which shows the example of the forest fauna division produced | generated in the hierarchy after the hierarchy shown in FIG. It is a general | schematic flowchart explaining the extraction process of the feature information data by a texture analysis part and a spectrum analysis part. It is a schematic diagram of the statistical distribution regarding an attention area. It is a block diagram which shows the structure of the outline of the forest facies analysis system which is the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of a forest facies analysis system 2 according to the first embodiment. The system includes an arithmetic processing device 4, a storage device 6, an input device 8, and an output device 10. As the arithmetic processing unit 4, it is possible to make dedicated hardware for performing the processing of this system. However, in this embodiment, the arithmetic processing unit 4 is constructed using a computer and a program executed on the computer. Is done.

  The arithmetic processing unit 4 is composed of a CPU (Central Processing Unit) of a computer, and will be described later with reference to a forest phase section generation unit 20, a texture analysis unit 22, a spectrum analysis unit 24, a statistical distribution creation unit 26, a change region detection unit 28, and a forest phase division diagram. It functions as the generation unit 30.

  The storage device 6 is a memory device such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The storage device 6 stores various programs executed by the arithmetic processing device 4 and various data necessary for processing of the present system, and inputs / outputs such information to / from the arithmetic processing device 4. For example, the storage device 6 stores in advance ortho image data 40, forest facies section map data 42, spectral conditions 44 and geometric conditions 46 relating to forest facies sections.

  The ortho image data 40 is generated based on an aerial photograph image taken from an aircraft or the like. In this system, the ortho image data 40 is high-resolution image data used as an original image obtained by photographing a target area including a forest from the sky. For example, three components of red (R), green (G), and blue (B) are used. Or a four-band multispectral image composed of four components obtained by adding the near infrared (NIR) to the three-band multispectral image.

  The forest phase map data 42 is data representing an existing forest phase map for the target area shown in the ortho image data 40. The forest fauna division map data 42 represents forest fauna sections that are elemental areas obtained by dividing the target area into regions and forest faunas in the sections. Here, it is assumed that the forest phase classification map data 42 relates to the time T1, while the ortho image data 40 relates to the time T2 different from the time T1. Although the anteroposterior relationship between T1 and T2 is arbitrary, in the example shown in the present embodiment, T1 is assumed to precede T2.

  The spectral condition 44 and the geometric condition 46 are conditions that should be satisfied by the forest section that is an object region generated by dividing the original image into regions. The spectrum condition 44 defines a condition relating to a spectral feature amount extracted from the color, density, and brightness of the pixel group constituting the forest fauna compartment. For example, a statistical quantity such as an average value or standard deviation of each color (band) can be used as the spectral feature quantity. On the other hand, the geometric condition 46 defines a condition related to a shape (Shape) which is a geometric feature amount of the forest fauna section. For example, the shape is represented by parameters such as compactness and smoothness.

  The input device 8 is a keyboard, a mouse, or the like, and is used for a user to operate the system.

  The output device 10 is a display, a printer, or the like, and is used to display a forest stand section or a forest stand division map (forest stand map) generated by the present system to a user by screen display, printing, or the like. Moreover, you may output as data so that the data regarding forest facies division and forest facies classification can be used in other systems.

  The forest phase section generation unit 20 performs a region division process on the ortho image data 40 in a hierarchical manner to generate forest phase sections. The forest phase section generation unit 20 includes a low resolution image generation unit 70, an initial partition section 72, and a subsequent partition section 74.

  The low-resolution image generation unit 70 is an image deterioration unit that generates a low-resolution image (degraded image) in which the resolution is lowered by performing a gradation process on the high-resolution ortho-image data 40, and the pixels of the low-resolution image are ortho-images. This corresponds to a region composed of a plurality of adjacent pixels in the data 40. Here, for easy discrimination, the pixels of the ortho image data 40 are expressed as original pixels, and the pixels of the low resolution image are expressed as enlarged pixels. For example, the low-resolution image can be generated by down-sampling the ortho-image data 40 at a uniform sampling density, and the pixel value of the enlarged pixel is representative of a plurality of original pixels in the corresponding region in the ortho-image data 40. Can be set to a value. For example, the low-resolution image generation unit 70 performs smoothing processing on the original image by convolution using a predetermined filter, and the pixel value of the enlarged pixel is subjected to smoothing processing at the original pixel at a predetermined position in the enlarged pixel. Can be set to the pixel value. In a general image, the luminance value of a pixel that is close to the target pixel often becomes closer to the luminance value of the target pixel, and the difference from the luminance value of the target pixel often increases as the distance from the target pixel increases. Considering these properties, a Gaussian filter that smoothes an image using a two-dimensional Gaussian distribution is known so that the weight when calculating an average value increases as it is closer to the target pixel, and the weight decreases as it is further away. It has been. This Gaussian filter can be employed for the smoothing process when obtaining the pixel value of the enlarged pixel. As a simpler method, for example, the pixel value of the enlarged pixel can be defined by an average value, a median value, or the like of the pixel values of a plurality of original pixels corresponding thereto.

  The initial partition unit 72 performs processing of the first hierarchy of hierarchical area division processing. Specifically, one or both of the spectral feature quantity and the geometric feature quantity of the image are set as the feature values for partitioning, and the initial partition unit 72 uses the low resolution image generated by the low resolution image generation unit 70 as the feature value for partitioning. Based on the similarity, it is divided into a plurality of regions, and primary forest fauna sections are generated. For example, the initial partition unit 72 determines whether or not a region composed of a plurality of adjacent enlarged pixels is a primary forest phase compartment, similarity of spectral feature amounts (spectral conditions) of pixel values of these enlarged pixels, and It is determined based on the similarity (geometric condition) of the geometric feature amount for the region obtained by combining these enlarged pixels.

  The succeeding partition unit 74 performs processing after the second layer of the hierarchical area division processing. Specifically, the succeeding partition unit 74 performs a sequential partition process once or a plurality of times by combining adjacent forest fauna partitions to generate a new forest fauna partition. Sequential parcel processing is based on the similarity of their spectral features for a plurality of adjacent low-order forest fauna compartments and the similarity of geometric features for higher-order forest fauna compartments obtained by combining them. Decide whether or not to join these lower forest fauna compartments.

  In the present embodiment, the subsequent partitioning unit 74 performs the sequential partitioning process between the low resolution image and the high resolution image (original image) in the forest phase partitioning that are the result of the region division processing of the low resolution image generated by the initial partitioning unit 72. Region segmentation processing is performed using both or only high-resolution images. From the low-resolution image, the spectral feature amount for the enlarged pixel group included in the forest phase section is obtained as the spectral feature amount of the pixel value used for determining whether or not the forest phase section can be combined. On the other hand, from the high-resolution image, a spectral feature amount for the original pixel group included in the forest phase section is obtained as a spectral feature amount of the pixel value used for determining whether or not the forest phase section can be combined. The subsequent partitioning unit 74 performs at least one sequential partitioning process based on the spectral feature amount of the pixel value of the high resolution image or the spectral feature amount of the pixel value of each of the high resolution image and the low resolution image. It can also be set as the structure which is. That is, when the subsequent partitioning unit 74 performs a plurality of sequential partitioning processes, a part of the number of times may extract a spectral feature amount from only the pixel values of the low resolution image, and perform the region partitioning process based thereon. .

  For example, a technique based on region merging can be used for image region segmentation. In this method, whether or not two adjacent objects existing in an image to be subjected to image region division processing are integrated depends on the heterogeneity of a new object generated after integration and the heterogeneity of an object before integration. Is determined by evaluating the change between. Incidentally, the object is a pixel of a low-resolution image in the process in the initial partition unit 72, and the object is a forest phase partition that has already been generated in the process in the subsequent partition unit 74.

Specifically, the object heterogeneity change Δh due to region merging is calculated from the spectral heterogeneity change Δh _p and the shape heterogeneity change Δh _t before and after merging by the following equation.

Here, w _p is a spectral heterogeneity weight, and w _t is a shape heterogeneity weight.

The change in spectral heterogeneity Δh _p before and after merging is calculated by the following equation using the standard deviation of the pixel values in the object before and after merging in each band of the target image.

Here, N is the number of bands of the image, w _i is the weight of band i, n _ab is the number of pixels of the new object after merging, n _a and n _b are the number of pixels of the two objects before merging, σ _{i, ab} Is the standard deviation in band i of the object after merging, and σ _{i, a} , σ _{i, b} is the standard deviation in band i of the two objects before merging.

The change Delta] h _t in shape heterogeneity around merging is defined by the following equation in two criteria of compactness and smooth ness.

Here, Δh _c is a change in compactness before and after merging, Δh _s is a change in smoothness before and after merging, w _c is a weight for compactness, and w _s is a weight for smoothness.

The object compactness criterion is calculated from the object perimeter and area, while the smoothness criterion is calculated from the object perimeter and the bounding box diameter (major axis). Specifically, Δh _c and Δh _s are defined by the following equations.

Here, l _ab is the perimeter of the object after merging, l _a and l _b are the perimeter of the two objects before merging, s _ab is the area of the object after merging, and s _a and s _b are the two before the merging. The area of one object, b _ab is the diameter of the bounding box of the object after merging, b _a , b _b are the diameters of the bounding box of the two objects before merging, n _ab is the number of pixels of the new object after merging, n _a , _Nb is the number of pixels of the two objects before merging.

  When the change Δh of the object heterogeneity before and after merging does not exceed the set threshold value, the region merging process is performed, and when it exceeds the threshold value, the region merging process is stopped. The set threshold value is called a scale parameter, and represents the size of an object generated by the image division process. The larger the scale parameter, the more objects are merged, and the size of the object that is finally generated by area division increases.

As shown in the equation (1), the contribution ratio of each of the spectral feature quantity and the geometric feature quantity to the judgment of the combination of the enlarged pixels in the initial partition section 72 or the judgment of the combination of the lower order forest fauna sections in the subsequent partition section 74 is a weight. It can be adjusted by w _p and w _c . Here, one or both of the initial partition unit 72 and the subsequent partition unit 74 may be configured to perform determination based on the similarity of the spectral feature amount without using the geometric condition in the determination of the forest phase partition generation.

  The texture analysis unit 22 is a texture information extraction unit that extracts texture information from the ortho image data 40. The texture analysis unit 22 includes a sunshine / shade distribution pattern information extraction unit 80, a sunshine / shade boundary pattern information extraction unit 82, and an LBP image information extraction unit 84.

  The sun / shade distribution pattern information extraction unit 80 binarizes the ortho image data 40 to extract the sun / shade distribution pattern in which the sun and the shade are distinguished as texture information. FIG. 2 is an explanatory diagram showing an example of the sunny / shade distribution pattern. FIGS. 2A to 2D are examples of a cedar forest, a cypress forest, a broadleaf forest, and a non-forest, respectively. Of the two images arranged on the left and right, the left side is the ortho image data 40, and the right side is the sunshine / shade distribution pattern. is there. In the sunshine / shade distribution pattern, the white area is sunshine and the black area is shade. Incidentally, the threshold for binarization here is determined by Otsu's method.

  The sun / shade boundary pattern information extraction unit 82 binarizes the luminance gradient in the ortho image data 40 and extracts the sun / shade boundary pattern in which the boundary region between the sun and the shade appears as texture information. FIG. 3 is an explanatory diagram showing an example of a sunny / shade boundary pattern. FIGS. 3A to 3D are examples of cedar forest, cypress forest, broadleaf forest, and non-forest, respectively, as in FIG. 2. Of the two images arranged side by side, the left side is ortho image data 40 and the right side is Hinata. / Shade boundary pattern. In the sun / shade boundary pattern, the white area is an area where the luminance gradient is greater than or equal to the threshold value, and the black area is an area where the brightness gradient is less than the threshold value. Again, the threshold is determined by Otsu's method. From the Hinata / Shade boundary pattern, the spatial frequency of switching between the Hinata and the Shade can be read.

  The LBP image information extraction unit 84 extracts an LBP (Local Binary Pattern) image obtained from the ortho image data 40 using a local binary pattern operator as texture information. FIG. 4 is an explanatory diagram showing an example of an LBP image. 4A to 4D are examples of a cedar forest, a cypress forest, a broad-leaved forest, and a non-forest, respectively, as in FIG. 2 and FIG. The right side is an LBP image. The LBP image reflects the detailed pattern structure pattern of the original image and has a characteristic that it is not easily affected by the contrast of the image.

  The texture analysis unit 22 calculates statistics such as an average value and a standard deviation as the feature values of the extracted sunny / shade distribution pattern, sunny / shade boundary pattern, and LBP image.

  The spectrum analysis unit 24 is a spectrum information extraction unit that extracts spectrum information from the ortho image data 40. In the present embodiment, the spectrum analysis unit 24 performs a normalization process represented by the following expression on the 4-band multispectral image of R, G, B, and NIR, and normalizes the components R ′, G ′, and B ′. A spectral feature amount is extracted from the image consisting of. Further, the spectrum analysis unit 24 extracts a spectrum feature amount only from the sunny area in each forest phase section based on the sunny / shade distribution pattern information.

  5 and 6 are images showing an example of normalization processing for the ortho image data 40. FIG. 5 shows an original image, that is, an ortho image before normalization processing, and FIG. 6 shows the ortho image data 40 corresponding to FIG. It is an image obtained by normalization processing. Although FIGS. 5 and 6 are displayed in gray scale, FIG. 5 is originally an RGB composite color image, and FIG. 6 is an R′G′B ′ composite color image. For example, due to the difference in the size of the near-infrared component according to the difference in the tree species or the like, a difference in hue or the like occurs between the original image and the normalized image. The difference between the original image and the normalized image in FIG. 5 and FIG. 6 can be read because the change in shading in the image is different between the two images.

  In addition, the spectrum analysis part 24 can also be set as the structure which extracts a spectrum feature-value without performing a normalization process, or the structure which extracts the spectrum feature-value in the whole each forest fauna division including a shade.

  The statistical distribution creation unit 26 corresponds to the region of each forest phase in the known forest phase map at time T1 given as the forest phase map data 42, and focuses on the original image at time T2 given in the ortho image data 40. And a statistical distribution is obtained for the feature information of the image extracted for each predetermined element region in the attention region of each forest phase.

  The feature information is texture information and spectrum information extracted from the original image by the texture analysis unit 22 and the spectrum analysis unit 24. In the present embodiment, corresponding to using texture information as feature information of an image for which a statistical distribution is obtained, for example, a forest fauna section generated for an original image is set as an element region. In addition, when only the spectrum information is used as the feature information of the image for obtaining the statistical distribution, the pixel can be used as the element region.

  For example, a region of interest related to a cedar forest is set in the original image corresponding to a set of forest facies sections of a cedar forest in the forest fauna division map at the time T1. The region of interest is the same or approximately the same region as a region composed of a set of cedar forest facies sections in the forest facies section diagram at time T1. Specifically, a set of forest phase sections generated for the original image that are present at a position corresponding to the cedar forest area at time T1 can be set as an attention area regarding the cedar forest. Here, when a certain forest fauna section of the original image straddles a plurality of forest fauna areas at the time T1, for example, the forest fauna section has the most overlap with the forest fauna section among the forest fading areas at the time T1. It can be included in the attention area of the forest fauna corresponding to the larger one. In addition, weighting can be performed according to the ratio of the overlapping area and reflected in the statistical distribution.

  As a statistical distribution, a frequency distribution is obtained using a feature amount representing texture information and spectrum information as image feature information as variables. There may be only one type of variable or a plurality of variables. The frequency may be simply the number of elemental areas, or in the case of using forest stand sections as element areas, values weighted according to the area of forest stand sections may be integrated.

  The change area detection unit 28 detects an outlier in the statistical distribution in each attention area, and detects an element area that gives the outlier as a change area in which the forest phase has changed between the time T1 in the attention area. Outliers are values that deviate significantly from other values in statistics. Here, as already mentioned, the forest phase map is usually updated every few years. That is, the interval between the time T1 and the time T2 is basically about several years. The forest phase analysis system 2 efficiently performs a wide range of forest phase analysis using the ortho image data 40 taken by an aircraft or the like, and a large-scale forest phase change within a short period of about several years in the wide target area. There is not much that happens. That is, normally, it can be expected that the area where the forest fauna changes between time T1 and time T2 is a small part of the wide target area, and in each attention area set for the original image of time T2, It is possible to perform a statistical analysis on the assumption that most of the unchanged areas where the forest fauna does not change from the time T1 when the existing forest fauna classification map is obtained. Therefore, the change area detection unit 28 assumes a probability density function of a predetermined form for the unchanged area in the statistical distribution obtained for the attention area corresponding to a certain forest aspect, and is a sample that is greatly deviated from the probability density function. It is determined that a certain element region is a region different from the forest type, that is, a change region.

  The statistical distribution in the attention area corresponding to a certain forest fauna basically reflects the feature information in all the forest fauna compartments that have that forest fauna in the target area, and is affected by variations in feature information in the forest fauna compartments that share the forest fauna. Hateful. Therefore, a change area with high reliability can be obtained by determining the change area based on the statistical distribution.

  The forest phase map generation unit 30 reflects the change region in the forest phase map of time T1 and generates the forest phase map of time T2. Specifically, the forest fauna division map generation unit 30 cuts forest parcel sections that are determined to be changed areas in the attention area in the original image at the time T2 set corresponding to each forest fauna in the forest fauna division map at the time T1. The remaining forest facies section, which is a non-change area, is classified as a forest facies corresponding to the region of interest, and a forest facies division map at time T2 is generated. Incidentally, the interval between the times T1 and T2 is a period of several years. The period is relatively short in terms of the growth of the forest, and there is basically no change in the forest fauna such as changing from a cedar forest to a cypress forest during the period, so the change area is classified as non-forest here. For example, the feature information about the texture and spectrum is stored in advance in the storage device 6 for each forest fauna, and using this, it is determined which forest fauna the change region has, and the forest fauna of the change region. May be determined.

  FIG. 7 is a schematic data flow diagram in the forest facies analysis system 2. Hereinafter, the processing of the forest facies analysis system 2 will be described with reference to FIG.

  The forest phase section generation unit 20 generates forest phase section data 100 at the time T2 from the ortho image data 40 at the time T2. FIG. 8 is a schematic flow diagram illustrating the forest fauna compartment generation process by the forest fauna compartment generator 20. The forest phase section generation unit 20 generates a low resolution image from the ortho image data 40 by the low resolution image generation unit 70 (S10). Further, the forest facies section generation unit 20 hierarchically divides the forest fauna section obtained by dividing the low resolution image into regions, and generates a forest fauna section corresponding to a region composed of a uniform forest fauna (S20). The area dividing process S20 is performed by the initial partition unit 72 and the subsequent partition unit 74. The region division processing is started from the low resolution image, and the division processing using the pixel values of the enlarged pixels constituting the low resolution image is first performed at least once, and thereafter, the original pixel and the enlarged pixels constituting the ortho image data 40 Alternatively, the partition process using the pixel value of only the original pixel is performed at least once. Specifically, the initial partition unit 72 divides the low-resolution image into regions and generates a forest stand partition with a small scale (S22). The succeeding section 74 uses the low resolution image and the high resolution image together, and generates a forest fauna section having a larger scale by combining the forest fauna sections (S24).

  The region division process is performed so as to satisfy the spectrum condition 44 and the geometric condition 46. At that time, the specific gravity between the spectral condition 44 and the geometric condition 46, that is, the degree to which each contributes to the region division can be adjusted.

Here, the conditions at the time of generating the forest fauna division may be different for each layer of the region division processing. That is, Δh, which is a scale parameter, is generated when the initial enlarged pixels are combined to generate an initial forest fauna section, or when lower order forest fauna sections are combined to generate a higher order forest fauna section. It is set to allow the scale of the forest fauna compartment to gradually increase. Due to the increase of Δh, regarding the spectral condition 44, the similarity criterion (Δh _p ) for the similarity of spectral features for a plurality of enlarged pixels or forestry sections to be combined is relaxed as the region division processing becomes higher. Also, the geometric feature similarity criterion (Δh _t ) is relaxed with respect to the geometric condition 46, and as the region segmentation process becomes higher, forest facies sections with more complex shapes or larger areas are allowed. Bonding is promoted. On the other hand, since it is sufficient that the coupling is relaxed comprehensively in the spectral condition 44 and the geometric condition 46, the geometric condition 46 is changed in a direction to suppress the coupling to some extent while the coupling is relaxed by the spectral condition 44, and the simpler. It is also possible to set conditions that encourage the generation of forest-shaped sections of various shapes. For example, such adjustment is possible by changing the weights w _p and w _t in equation (1). Specifically, w _p is decreased, while w _t is increased and Δh _p is changed to Δh. This can be realized by making it difficult to contribute and making Δh _t easily contribute to Δh.

  Now, as already mentioned, in high resolution images, there are large variations in pixel values even within the same forest fauna due to the difference between the sun and shade of the forest, and it has been difficult to distinguish and accurately separate adjacent forest fauna. There was a problem that there was. On the other hand, the forest phase analysis system 2 reduces the resolution of the original image and performs at least the first one of the hierarchical region segmentation processes on the low resolution image. When the image is reduced in resolution, the variation in pixel values within the same forest phase is smoothed and alleviated, so the partition processing based on the low-resolution image is less affected by the difference in pixel values between the sun and the shade, and adjacent It is easy to distinguish different forest fauna. It should be noted that the effect can be expected to be higher when the partition processing at a low resolution is performed at an earlier stage of a plurality of hierarchical partition processing.

  On the other hand, information on the high resolution image is obtained in the final forest fauna compartment by performing the compartment processing using both the low resolution image and the high resolution image or only the high resolution image in the hierarchical compartment processing. Can be reflected.

  9 to 11 are images showing examples of processing of the forest fauna compartment generating unit 20, and the boundaries of the forest fauna compartments are drawn with black lines in the aerial photograph images of the same forest. FIG. 9 shows a result of processing by the initial partition unit 72, and shows an initial forest phase partition generated using a low resolution image. 10 and 11 show the results of processing by the subsequent partition unit 74, and the image of FIG. 11 shows the result of the region dividing process of higher floors than the image of FIG. That is, area division is performed hierarchically in the order of FIG. 9, FIG. 10, and FIG. Here, as described above, the forest stand section is generated by using both the low resolution image and the high resolution image. Specifically, in the case where the three layers shown in FIGS. 9 to 11 are all layers of the region dividing process for generating the forest fauna compartment, the forest fauna compartment of FIG. 9 is generated using the low resolution image, and FIG. 11 are generated using both the low-resolution image and the high-resolution image in the forest-facing zone, which are the processing results of the preceding region division, or only the high-resolution image. And the forest fauna compartment of FIG. 11 becomes the forest fauna compartment finally extracted.

  The forest block data 100 finally extracted from the target area by the processing of the forest block section generation unit 20 described above is used by the texture analysis unit 22, the spectrum analysis unit 24, and the forest phase division map generation unit 30.

  Now, the description returns to FIG. The texture analysis unit 22 and the spectrum analysis unit 24 extract the image feature information data 102 for each forest phase section at the time T2 from the ortho image data 40 and the forest phase section data 100. FIG. 12 is a schematic flowchart for explaining the feature information data 102 extraction processing by the texture analysis unit 22 and the spectrum analysis unit 24.

  The forest phase analysis system 2 extracts texture information from the ortho image data 40 by the texture analysis unit 22 (S40, S50, S60). Specifically, the texture analysis unit 22 extracts the sun / shade distribution pattern by the sun / shade distribution pattern information extraction unit 80 (S40), and extracts the sun / shade boundary pattern by the sun / shade boundary pattern information extraction unit 82. (S50) Further, the LBP image information extraction unit 84 extracts an LBP image in which a detailed pattern structure pattern in the original image appears (S60), and obtains texture information.

  Further, the forest phase analysis system 2 normalizes the ortho image data 40 by the spectrum analysis unit 24, and extracts spectral feature information from the normalized image (S70). Further, the spectrum analysis unit 24 uses the sunny / shade distribution pattern extracted by the sunny / shade distribution pattern information extracting unit 80 to extract spectral feature information only from the sunny part where the forest spectral features can be satisfactorily displayed (S80). .

  Then, the texture analysis unit 22 and the spectrum analysis unit 24 acquire image feature information for each forest phase section extracted by the forest phase section generation unit 20 (S90), and generate feature information data 102. This feature information data 102 is used by the statistical distribution creation unit 26.

  Returning again to FIG. The statistical distribution creation unit 26 uses the feature map data 42 for the forest phase at the time T1 and the feature information data 102 for the image for each forest phase at the time T2 to generate an image of each region of interest set for each forest phase in the original image at the time T2. Find the statistical distribution of feature information. Based on the statistical distribution data 104 output from the statistical distribution creation unit 26, the change region detection unit 28 generates change region data 106 indicating the change region included in each region of interest.

  FIG. 13 is a schematic diagram of a statistical distribution related to a region of interest corresponding to one forest phase. The horizontal axis corresponds to a variable represented by the feature amount X related to feature information, and the vertical axis corresponds to the frequency Y. Here, for convenience of illustration, the statistical distribution 108 is a one-dimensional distribution having one variable, but the statistical distribution creating unit 26 may obtain a multi-dimensional statistical distribution having a plurality of variables. For example, the variables are the forest fauna corresponding to the attention area by the user, and the forest fauna corresponding to the forest change that is expected to occur between the times T1 and T2 in the attention area, specifically the felling or wind damage damage. It is set to a single feature value or a combination of a plurality of feature values suitable for discriminating. Each feature information calculated by the texture analysis unit 22 and the spectrum analysis unit 24 described above is suitable for the discrimination, and a statistical distribution variable can be defined by some or all of the plurality of types of feature information. .

The statistical distribution of feature values for element regions (forest stand sections, pixels, etc.) with common forest phases is basically a distribution that accumulates near the average value to form a peak. For example, a normal distribution is assumed. be able to. As already described, it can be assumed that the number of change areas in which the forest fauna changes from the time T1 in the target area is smaller than the area that does not change. Therefore, the statistical distribution 108 for each region of interest approximates the distribution of feature values of the forest fauna corresponding to the region of interest. That is, there is a high probability that the element region of the forest fauna has a feature quantity near the maximum peak in the statistical distribution 108. On the other hand, the feature quantity X as a variable of the statistical distribution is set to facilitate discrimination of the presence or absence of changes in the forest fauna as described above, and the element region in which the forest fauna has changed is a range away from the peak in the statistical distribution 108 (for example, FIG. 13 can be expected to have a feature value belonging to the range R _E ). Therefore, the change area detection unit 28 detects an element area that is an outlier in the statistical distribution 108 obtained for the attention area corresponding to a certain forest phase, and outputs information indicating the element area as the change area data 106. For example, the forest fauna compartment generating unit 20 defines an identifier (ID) for identifying the created forest fauna compartment, and the forest fauna compartment data 100 and the feature information data 102 are information on the forest fauna compartment associated with the ID and feature information, respectively. The The change area detection unit 28 can extract, for example, the ID as the change area data 106.

  The change region detection unit 28 uses, for example, a hypothesis test that verifies whether the statistical distribution of the region of interest corresponding to a certain forest phase conforms to the distribution assumed for the feature information of the forest phase, and samples that cause the hypothesis to be rejected And make it an outlier.

For example, a chi-square (χ ² ) test can be used when the statistical distribution of feature values of each forest phase is a normal distribution. The change area detection unit 28 calculates the χ ² value by using the average value of the statistical information of the attention area as the estimated value of the average value of the normal distribution to be followed by the feature information of the forest fauna. When the χ ² value is in the rejection area at a predetermined significance level (for example, 1%) in the χ ² distribution, the sample set consisting of feature information observed in the region of interest has the largest variance. Recalculate χ ² values for the remaining set. This operation is repeated until the χ ² value falls within the acceptance range. The change region detection unit 28 detects the sample removed from the original sample set by this processing as an outlier, and detects it as a change region.

  In addition, the detection of an outlier can also be performed using other well-known test methods, such as a Smirnov-Grubbs test.

  The forest fauna section map generation unit 30 determines, for each forest fauna section given by the forest fauna section data 100, which forest fauna the target area belongs to based on the forest fauna section map data 42 at the time T <b> 1, and further based on the change area data 106. It is then determined whether or not the region of interest is a change region. As a result, the forest fauna of each forest fauna section at time T2 is determined, and a forest fauna map (forest fauna map data 110) for time T2 is generated.

  Note that texture information other than the above three types can also be used. For example, an image texture extracted by wavelet analysis can be used. Specifically, the forest phase can be determined using the high-frequency component information extracted by the wavelet analysis as texture information together with the spectral feature information of the image.

  In the present embodiment, the ortho image data 40 is an aerial photograph, but the present invention can also be applied to forest facies analysis using other high resolution images such as satellite photographs. In the present embodiment, an ortho image is described as an example, but it is not always necessary to use an ortho image, and an image taken from the sky can be used as appropriate.

[Second Embodiment]
In the forest phase analysis system of the second embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, differences between the forest facies analysis system 200 of the second embodiment and the forest facies analysis system 2 of the first embodiment will be described.

  FIG. 14 is a block diagram showing a schematic configuration of a forest facies analysis system 200 according to the second embodiment. The difference between the forest facies analysis system 200 and the forest facies analysis system 2 is in what conditions the forest facies division is performed. In the first embodiment, the forest facies section generation unit 20 generates a forest facies section by performing region division processing so as to satisfy the spectrum condition 44 for the spectral feature quantity and the geometric condition 46 for the geometric feature quantity. On the other hand, in the forest analysis system 200 of the second embodiment, the object before and after the region merging, that is, the color, shape, texture, and area of the pixel of the degraded image or the forest phase partition are used as the feature amount for the partition, and the colors for these Region division processing is performed so as to satisfy the condition 202, the shape condition 204, the texture condition 206, and the area condition 208, and forest stand sections are generated.

  The color condition 202, the shape condition 204, the texture condition 206, and the area condition 208 are conditions that must be satisfied by a forest section that is an object region generated by dividing an ortho image (ortho image data 40). The color condition 202 defines a condition regarding the pixel value of the ortho image in the forest block. Incidentally, “color” in “color condition” means a pixel value of an ortho image and is used in a broader sense than spectral information composed of RGB information. Specifically, the “color” here corresponds to the spectral feature amount of the first embodiment, and for example, the pixel value of a multispectral image including NIR information can also be included in the color concept here. The shape condition 204 defines a condition regarding the shape of the forest fauna compartment. The texture condition 206 defines a condition related to the image texture of the forest fauna section. The image texture is evaluated by the texture feature amount. The area condition 208 defines a condition relating to the area of the forest land section. In addition, the shape and area of the forest fauna compartment are geometric feature quantities of the forest fauna compartment.

  The initial partition unit 72 determines whether or not a region composed of a plurality of pixels adjacent to each other is a primary forest phase partition, the similarity of pixel values of these pixels, the similarity of the image texture of the region, the shape of the region, It is determined based on the similarity of geometric features such as area. Here, the similarity of the pixel values between the regions to be combined or between the regions before and after the combination can be determined based on a feature amount such as a statistic such as an average value of the pixel values.

  The subsequent partition unit 74 performs sequential partition processing as in the first embodiment. In the present embodiment, the sequential partition processing is performed on the plurality of low-order forest facies partitions adjacent to each other, the color condition 202 regarding the similarity of pixel values in them, and the shape condition on the higher-order forest tract partitions obtained by combining them. Based on 204, texture condition 206 and area condition 208, it is determined whether or not to combine these lower-order forest fauna sections.

Similar to the first embodiment, a method based on region merging is used for image region division. In this embodiment, the change in object heterogeneity Δh due to region merging includes a change in color heterogeneity Δh _color before and after merging, a change in shape heterogeneity Δh _shape , a change in _texture heterogeneity Δh _texture , The area heterogeneity change _Δhaera is calculated by the following equation.

Here, w _color is the weight of the heterogeneity of the color, w _shape is the weight of the heterogeneity of the shape, w _texture is the weight of the heterogeneity of the texture, and w _area is the weight of the heterogeneity of the area.

The change in _color heterogeneity Δh _color before and after merging, the change in shape heterogeneity Δh _shape , the change in texture heterogeneity Δh _texture , and the change in area heterogeneity _Δhaera are calculated by the following equations, for example.

Here, n _ab is the number of pixels of the new object after merging, and n _a and n _b are the number of pixels of the two objects before merging. CI _ab is the color information index (for example, pixel value) of the object after merging, CI _a and CI _b are the color information indices of the two objects before merging, and SI _ab is the shape information index of the object after merging (for example, , Smoothness), SI _a and SI _b are the shape information indices of the two objects before merging, TI _ab is the texture information index of the object after merging (for example, the standard deviation value of the pixel value), and TI _a and TI _b are The texture information index of the two objects before merging, AI _ab is the area information index (for example, area value) of the object after merging, and AI _a and AI _b are the area information indices of the two objects before merging.

As shown in the equation (6), each of the color condition, the shape condition, the texture condition, and the area condition contributes to the determination of the combination of pixels in the initial partition section 72 or the determination of the combination of low-order forest facies sections in the subsequent partition section 74. The ratio can be adjusted by weights w _color , w _shape, w _texture, w _area . Here, one or both of the initial partition unit 72 and the subsequent partition unit 74 are configured based on any one or a combination of a color condition, a shape condition, a texture condition, and an area condition in the generation determination of the forest block section. It can also be.

  2,200 Forest phase analysis system, 4 arithmetic processing device, 6 storage device, 8 input device, 10 output device, 20 forest phase section generation unit, 22 texture analysis unit, 24 spectrum analysis unit, 26 statistical distribution creation unit, 28 change area detection , 30 Forest phase division map generation unit, 40 Ortho image data, 42 Time phase T1 forest phase map data, 44 Spectral conditions, 46 Geometric conditions, 70 Low resolution image generation unit, 72 Initial partition unit, 74 Subsequent partition unit, 80 Hyuga / Shade distribution pattern information extraction unit, 82 Hinata / shade boundary pattern information extraction unit, 84 LBP image information extraction unit, 100 forest phase section data, 102 feature information data, 104 statistical distribution data, 106 change area data, 110 forest phase at time T2 Section map data, 202 color conditions, 204 shape conditions, 206 texture conditions, 208 Area condition.

Claims (9)

Corresponding to the area of each forest fauna in the known forest fauna division map in the first period of the target area including the forest, the target area is set to the original image taken from the sky in the second period, Statistical distribution creating means for obtaining a statistical distribution for the feature information of the image extracted for each predetermined element region in the attention region of each forest phase;
For each region of interest, the statistical distribution of the original image is compared with the statistical distribution assumed for the feature information in the region of the forest fauna corresponding to the region of interest in the forest fauna division map, detecting outliers in the statistical distribution of in the region of interest, the change area where the said element region for applying the outlier between said second timing and the first timing in the attention area forest physiognomy has changed Change area detection means for detecting as,
A forest phase analysis apparatus characterized by comprising: In the forest phase analysis apparatus according to claim 1,
A forest facies analysis apparatus comprising forest facies segment map generation means for generating the forest facies segment map of the second time period by reflecting the change region as a non-forest in the forest fauna segment map of the first period. In the forest fauna analysis apparatus according to claim 1 or 2,
A forest fauna compartment generating means for generating and outputting the forest fauna compartment of the forest by dividing the target area into a plurality of regions based on the similarity of one or more kinds of compartment features of the original image;
The element region in the statistical distribution creation means and the change region detection means is the forest fauna compartment;
Forest phase analysis device characterized by In the forest phase analysis apparatus according to claim 3,
From the original image, having an image deterioration means for generating a deteriorated image in which the resolution is reduced with a region composed of a plurality of adjacent pixels of the original image as a pixel,
The forest fauna compartment generating means includes:
An initial partition means for dividing the degraded image into a plurality of regions based on the similarity of the one or more types of the feature values for the partition, and generating a forest fauna partition;
The adjacent forest fauna compartments are combined based on the similarity of the one or more types of the feature values for the compartments to generate a new forest fauna compartment once or multiple times, and the forest in the target area Subsequent compartment means for outputting the forest fauna compartment,
Have
The subsequent partition means performs at least one sequential partition processing based on the partition feature of the original image or the partition feature of each of the original image and the degraded image;
Forest phase analysis device characterized by In the forest fauna analysis apparatus according to claim 3 or claim 4,
Texture information extracting means for extracting texture information from the original image;
The statistical distribution creating means obtains the statistical distribution using the texture information extracted from each forest fauna compartment output from the forest fauna compartment generating means as the feature information;
Forest phase analysis device characterized by In the forest phase analysis apparatus according to claim 5,
Spectral information extracting means for extracting spectral information from the original image;
The statistical distribution creating means obtains the statistical distribution using the texture information and the spectrum information extracted from each forest fauna compartment output from the forest fauna compartment generating means as the feature information,
Forest phase analysis device characterized by In the forest fauna analysis apparatus according to claim 3 or claim 4,
Spectral information extracting means for extracting spectral information from the original image;
The statistical distribution creating means obtains the statistical distribution using the spectral information extracted from each forest fauna compartment output from the forest fauna compartment generating means as the feature information;
Forest phase analysis device characterized by Corresponding to the area of each forest fauna in the known forest fauna division map in the first period of the target area including the forest, the target area is set to the original image taken from the sky in the second period, A statistical distribution creating step for obtaining a statistical distribution for feature information of an image extracted for each predetermined element region in the attention region of each forest phase;
For each region of interest, the statistical distribution of the original image is compared with the statistical distribution assumed for the feature information in the region of the forest fauna corresponding to the region of interest in the forest fauna division map, detecting outliers in the statistical distribution of in the region of interest, the change area where the said element region for applying the outlier between said second timing and the first timing in the attention area forest physiognomy has changed A change area detection step to detect as,
The forest phase analysis method characterized by having. A program for causing a computer to perform forest fauna analysis in a target area including forests,
Corresponding to the area of each forest fauna in the known forest fauna division map in the first period of the target area including the forest, the target area is set to the original image taken from the sky in the second period, A statistical distribution creating means for obtaining a statistical distribution for the feature information of the image extracted for each predetermined element region in the target region of each forest phase; and
For each region of interest, the statistical distribution of the original image is compared with the statistical distribution assumed for the feature information in the region of the forest fauna corresponding to the region of interest in the forest fauna division map, detecting outliers in the statistical distribution of in the region of interest, the change area where the said element region for applying the outlier between said second timing and the first timing in the attention area forest physiognomy has changed Change area detection means for detecting,
A program characterized by functioning as

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