JP2005148906A - Shore line extraction device, shore line extraction method, computer-readable recording medium in which program is recorded, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shore line extraction device which extracts point data on a shore line from an aerial photograph and a satellite image, the shore line extraction device reducing a load on the production of a map and chart and eliminating the influence of a high-luminance sea area part such as a coral reef. <P>SOLUTION: A satellite photograph or the like is resolved into bands such as an R, G, and B at band resolution processing S20, and the value of a green band is compared with the value of a red band at an interband computation binarization processing S40. When the pixel value of the green band is larger, it is determined to be a candidate for a water surface area, and when the pixel value of the red band is larger, it is determined to be a candidate for a land area, and then a binary image is generated. The outline of a closed area in the binary image is traced at an outline trace S50, and the coordinates of the end of the image are removed at a redundancy point removal S60, and then the points of latitude and longitude are outputted at a shore line point output S70. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a shoreline extraction apparatus that extracts point data of a shoreline from aerial photographs and satellite images, and relates to a technique for reducing a load at the time of creating a map or a chart.

  Conventionally, in order to create a map, it has been necessary to conduct a geodetic survey on the spot, but in recent years, aerial photographs and satellite images have been used. In creating a map, in order to create a shoreline that is the boundary between land and sea, the coastline must be judged by hand from aerial photographs and satellite images, and each shoreline point must be designated.

  Also, since the brightness level is usually different between the sea and the land, the shoreline portion can be extracted by binarization. However, since binarized data is still raster data, it cannot be used as shoreline point data.

  In addition, in binarization, in areas where coral reefs are clustered, the brightness of the sea area may increase, so the sea and the land may not be well separated.

  FIG. 16 is a diagram illustrating an input image including a land area and a sea area. Since the brightness of the land area and the sea area is land area> sea area, the land area and the sea area can be separated by binarizing with a certain threshold value. However, in low-latitude areas where coral reefs are clustered, the brightness of the sea area is high, so simple binarization may not be able to separate the land area from the sea area well.

FIG. 17 is a diagram illustrating a binarized image. As shown in the figure, when the luminance is binarized when A≈B >> C, the land and the sea cannot be separated well.
JP-A-8-016777 JP-A-9-330418 JP 2000-132666 A JP 2001-066984 A JP 2002-251618 A

  The present invention has been made in order to eliminate the above-described drawbacks of the prior art, and the object of the present invention is to automatically extract shoreline points using aerial photographs and satellite images. It is to provide a device that reduces labor.

  In particular, an object is to obtain shoreline point data by using a technique for extracting a contour from a binarized image.

  Further, it is an object to remove the influence of a sea area portion having a high luminance such as a coral reef by performing a predetermined interband calculation during binarization processing.

The shoreline extraction apparatus according to the present invention is
(1) An image input unit for inputting a color image or a monochrome image including a water surface area and a land area taken from above altitude, or a color image or a monochrome image consisting of a water surface area or a land area. (2) Band decomposition unit that decomposes an input color image into two or more bands (3) Bands that calculate pixel values of two or more decomposed bands and binarize the calculation results to generate a binary image Inter-computation binarization unit (4) A contour tracking unit that performs contour tracking of a closed region in the generated binarized image and extracts coordinates constituting the contour.

The shoreline extraction apparatus according to the present invention is
(1) An image input unit for inputting an input image including a water surface region and a land region taken from above the altitude, or an input image consisting of a water surface region or a land region. A binarization unit for generating a binarized image by binarizing with respect to a predetermined threshold (3) Contour tracking of a closed region in the generated binarized image and extracting coordinates constituting the contour Contour tracking unit.

  Furthermore, it has a redundant point removing unit that excludes the coordinates of the straight line portion at the edge of the image from the extracted coordinates.

  Furthermore, it has a shoreline point output unit that converts the extracted coordinates into latitude and longitude, and outputs the converted latitude and longitude as shoreline points.

The band decomposition unit decomposes the input color image into at least a green band and a red band,
The interband calculation binarization unit compares the values of the green band and the red band for each pixel, and determines that the pixel value of the red band is a water surface area candidate when the pixel value of the green band is large. When the value is large, it is determined as a land area candidate.

The shoreline extraction method according to the present invention is:
(1) A step of inputting a color image or monochrome image including a water surface area and a land area photographed from above altitude, or a color image or monochrome image consisting of a water surface area or a land area (2) ) A step of decomposing the input color image into two or more bands (3) A step of calculating pixel values of the two or more decomposed bands and binarizing the calculation result to generate a binarized image (4) Generation A step of performing contour tracking of a closed region in the binarized image and extracting coordinates constituting the contour.

The shoreline extraction method according to the present invention is:
(1) Inputting an input image including a water surface area and a land area taken from above altitude, or an input image consisting of a water surface area or a land area (2) About luminance of the input image Step for generating a binarized image by binarizing with a predetermined threshold (3) Step for performing contour tracking of a closed region in the generated binarized image and extracting coordinates constituting the contour.

A computer-readable recording medium on which a program according to the present invention is recorded,
It is a computer-readable recording medium that records a program for causing a computer as a shoreline extraction device to execute the following processing. (1) Color including water surface area and land area photographed from above altitude Processing to input an image or monochrome image, or a color image or monochrome image consisting of a water surface area or land area (2) Processing to decompose an input color image into two or more bands (3) Pixels of two or more bands that have been decomposed A process of calculating a value and binarizing the calculation result to generate a binarized image (4) A process of performing contour tracking of a closed region in the generated binarized image and extracting coordinates constituting the contour.

A computer-readable recording medium on which a program according to the present invention is recorded,
(1) Input including water surface area and land area photographed from above the altitude Processing to input an image or an input image consisting of a water surface area or land area (2) Processing to generate a binarized image by binarizing the luminance of the input image with a predetermined threshold (3) Generated binarized image A process of tracing the contour of a closed area inside and extracting the coordinates constituting the contour.

The program according to the present invention is:
(1) A color image or a monochrome image including a water surface area and a land area photographed from above the altitude, or a water surface area or Procedure for inputting color image or monochrome image consisting of land area (2) Procedure for decomposing input color image into two or more bands (3) Calculate pixel values of two or more decomposed bands and calculate the result of 2 Procedure for binarizing and generating a binarized image (4) Procedure for performing contour tracking of a closed region in the generated binarized image and extracting coordinates constituting the contour.

The program according to the present invention is:
(1) From an input image including a water surface area and a land area taken from above altitude, or from a water surface area or a land area (2) A procedure for generating a binarized image by binarizing the luminance of the input image with a predetermined threshold (3) Contour tracking of a closed region in the generated binarized image A procedure for performing and extracting coordinates constituting the contour.

The shoreline extraction apparatus according to the present invention is
The shoreline extraction apparatus is characterized in that after extracting the contour coordinates, the shoreline determination is performed based on at least the area and the perimeter.

  In the present invention, since a technique for extracting a contour from a binarized image is used, shoreline point data can be obtained automatically. Furthermore, since predetermined band-to-band calculation is performed during the binarization process, it is possible to remove the influence of sea areas with high luminance such as coral reefs.

Embodiment 1 FIG.
Hereinafter, the present invention will be described based on embodiments shown in the drawings. FIG. 1 is a diagram showing a processing flow of the shoreline extraction apparatus.

  First, in S10, a monochrome or color (True, False) image is read by the image input unit. Next, in S20, in the case of a color image, the band decomposition processing unit decomposes each band (R (Red: red), G (Green: green), B (Blue: blue), NIR (near infrared)) in the case of a color image. . In S30, the binarization unit binarizes the input image with a predetermined threshold value to generate a binary image. Further, in S40, the interband calculation binarization processing unit performs binarization with the interband calculation and generates a binary image. In S50, the contour tracking unit performs contour tracking of a closed region (referred to as a figure) in the binary image, and extracts the coordinates constituting the contour. If the straight line portion at the end of the image is extracted as shoreline coordinates, the redundant point removal unit removes the coordinates at both ends in S60. Finally, in S70, the shoreline point output unit converts the extracted coordinates into latitude / longitude, and outputs the shoreline point. S50 uses any of the binarized images obtained by the processes of S30 and S40.

  Subsequently, details of the processing will be described. First, the interband calculation binarization (S40) will be described in detail. In this process, binarization processing with interband calculation is performed in order to remove a portion with high luminance in the sea area that affects binarization such as a coral reef area.

  FIG. 2 is a diagram showing a processing flow of inter-band calculation binarization. First, ratio image creation (G image / R image) is performed in S401. In this process, a ratio image based on the G image / R image is created. That is, for each pixel, a quotient obtained by dividing the G value by the R value is obtained, and an operation image (referred to as a ratio image) having the quotient value as the pixel value is generated.

FIG. 3 is a diagram showing an outline of comparative image creation. The characteristics of the object in the input image are shown below.
(1) The land area has higher R (red) band brightness than the G (green) band. (2) The coral reef area has higher G (green) band brightness than the R (red) band. By calculating R, it is possible to create an image in which the land portion has a luminance <1 and the other portions have a luminance> 1.

  In this calculation image, there may be a portion of luminance <1 in the sea portion as shown above. This is because this portion is removed in later processing. Further, an NIR (near infrared) image may be used instead of the R image. That is, a calculation image divided into an area where G / NIR> 1 and an area where G / NIR <1 is generated.

  In step S402, the ratio image is binarized. In this process, the ratio image is binarized with a predetermined threshold value, and land and other binary images are created. That is, an image divided into an area of G / R> 1 and an area of G / R <1 is generated with 1 as a threshold. FIG. 4 is a diagram showing an outline of binarization of the comparative image. Regardless of this example, a threshold other than 1 may be set.

  In step S403, the R image is binarized. In this process, the R image is binarized with a predetermined threshold value, and the sea and other binary images are created. Regardless of this example, an NIR image may be used instead of the R image. FIG. 5 is a diagram showing an outline of binarization of the R image.

  Next, a reverse image is created in S404. In this process, a reverse image of the binary image generated in S403 is created. FIG. 6 is a diagram showing an overview of creating a reverse image. In this example, black has a luminance of 0 and white has a luminance of 1. However, in the case of binarization in S403, if the lower luminance is binarized with luminance 1, this processing is not necessary.

  In step S405, a composite binary image is created (OR operation). In this process, the image generated in S402 and the image generated in S404 are ORed to create a composite binary image. FIG. 7 is a diagram showing an outline of creating a composite binary image. Here, black has a luminance of 0 and white has a luminance of 1.

  Noise that cannot be removed by the synthesis processing in S405 is removed using a known method (median filter or the like) (S406).

  Next, the contour tracking (S50) process will be described in detail. FIG. 8 is a diagram showing a processing flow of contour tracking.

  First, in step S501, binary figure contour tracking is performed. FIG. 9 is a diagram illustrating a binary image scanning method. When the binary image is scanned by the scanning method as shown in FIG. 9 and the starting point of the figure is found, one outline is traced. Thereafter, scanning is continued again to find the start point of the next figure. This operation is repeated to extract the coordinates of the contours of all graphics (including internal graphics) in the image and store them in a temporary array. Furthermore, the perimeter or area is also calculated. A specific tracking method, perimeter length, and area calculation are omitted because they are known techniques. FIG. 10 is a diagram illustrating contour coordinates after contour tracking.

  By the processing of the loop 1 in S502, a figure that is not valid as a shoreline is removed from the above-mentioned figures based on the perimeter and area. Therefore, the loop counter corresponds to the number of figures. Specifically, the circumference (or area) is determined in S502. That is, the perimeter (or area) calculated in S501 is compared with the set value. If it is smaller than the set value, all coordinates of the figure are deleted from the temporary array in which the coordinates of the figure are stored by deleting the coordinates in S504.

  The total number of data is reduced by thinning out the coordinates extracted pixel by pixel by the processing of loop 2 in S505. The loop counter corresponds to the number of figures. Therefore, the counter variable K is set to 1 in the counter variable initialization in S506.

  The coordinates thinned out for each figure are stored in the bank line array 1 by the processing of the loop 3 in S507. The step is a set thinning number (if 1 is not thinned), and the loop counter corresponds to the number of coordinates of the figure. In the coordinate storage of S508, the X coordinate of the temporary array (J) is stored in the X coordinate of the shoreline first array (K), and the Y coordinate of the temporary array (J) is stored in the Y coordinate of the shoreline second array (K). Is stored. Then, the counter variable is incremented (+1) by the counter increment of S509.

  Next, redundant point removal (S60) will be described in detail. In the processing by the contour tracking unit (S50), the edges of the image are also extracted in order to track all the contours of the binary graphic. However, since the edge of the image does not constitute a shoreline, detailed coordinate information is not necessary, and it is sufficient if each corner coordinate is present. Therefore, in this apparatus, the redundant point removal unit deletes the extra extracted points at the edge of the image. 11 and 12 show the contour coordinates before redundant point deletion and the contour coordinates after redundant point deletion.

  FIG. 13 to FIG. 15 are diagrams showing a processing flow for redundant point removal. First, the flag variable for redundant point removal is initialized by the flag variable initialization of S601. Set FLG to 0 and FLG_OLD to 0.

  In the process of loop 1 in S602, the edge portion of the image is removed from the coordinates of each figure. Therefore, the loop counter corresponds to the number of figures. Subsequently, the counter variable K is set to 1 in the counter variable initialization of S603.

Then, in loop 3 of S604, the coordinates of the first shoreline array are stored in the second shoreline array excluding the edge of the image. The loop counter corresponds to the number of coordinates of the figure. In the coordinate determination in S605, it is determined whether or not the X and Y coordinates are the edges of the image (up / down / left / right). If it is an edge, a value corresponding to the coordinates is set in the flag variable in the flag setting in S606.
X = 0 (left end) → FLG = 1
X = X size-1 (right end) → FLG = 2
Y = 0 (upper end) → FLG = 3
Y = Y size-1 (bottom) → FLG = 4
In the flag determination of S607, the values of FLG and FLG_OLD are compared. If FLG = FLG_OLD, it is a continuation of the end portion of the image, and if FLG ≠ FLG_OLD, it becomes the start coordinate of the end portion of the image.

  If it is the start coordinate of the edge portion of the image, the X coordinate of the shoreline first array (J) is set to the X coordinate of the shoreline second array (K) in the coordinate storage of S608, and the shoreline second The Y coordinate of the shoreline first array (J) is set to the Y coordinate of the array (K). Then, the counter variable is incremented (+1) by the counter increment of S609. Then, in the flag variable storage 6010, the current value is stored for the next flag determination. That is, the value of FLG is set in FLG_OLD.

  If it is determined in S605 that the X and Y coordinates are not the edge (up / down / left / right) of the image, the processing shown in FIG. 14 is performed. First, in the flag variable setting determination in S6011, it is determined whether or not a flag variable is set. If it is set, the previous coordinate is at the end of the image, so it is necessary to store the coordinate of J-1. Therefore, the last coordinate of the end of the image is stored in the coordinate storage of S6012. That is, the X coordinate of the shoreline first array (J-1) is set to the X coordinate of the shoreline second array (K), and the shoreline first array is set to the Y coordinate of the shoreline second array (K). The Y coordinate of (J-1) is set. Then, the counter variable is incremented (+1) by the counter increment of S6013, and the flag variable of S6014 is cleared. Set FLG to 0 and set FLG_OLD to 0.

  Then, in the coordinate storage of S6015, the X coordinate of the shoreline first array (J) is set to the X coordinate of the shoreline second array (K), and the shoreline first array is set to the Y coordinate of the shoreline second array (K). The Y coordinate of one array (J) is set, and the counter variable is incremented (+1) by the counter increment of S6016.

  The shoreline extraction device is a computer, and each element can execute processing by a program. Further, the program can be stored in a storage medium so that the computer can read the program from the storage medium.

  In the above example, R (red) and G (green) are compared when creating a ratio image. However, R (red) and B (blue) are compared, and B (blue) and G (green) are compared. It is also effective to compare the two. It is also effective to use NIR (near infrared) instead of R (red).

It is a figure which shows the processing flow of a shoreline extraction apparatus. It is a figure which shows the processing flow of the calculation between bands binarization. It is a figure which shows the outline | summary of comparative image preparation. It is a figure which shows the outline | summary of the binarization of a comparative image. It is a figure which shows the outline | summary of the binarization of R image. It is a figure which shows the outline | summary of reverse image creation. It is a figure which shows the outline | summary of synthetic | combination binary image preparation. It is a figure which shows the processing flow of outline tracking. It is a figure which shows the scanning system of a binary image. It is a figure which shows the outline coordinate after outline tracking. It is a figure which shows the outline coordinate before redundant point deletion. It is a figure which shows the outline coordinate after redundant point deletion. It is a figure which shows the processing flow (1/3) of redundant point removal. It is a figure which shows the processing flow (2/3) of redundant point removal. It is a figure which shows the processing flow (3/3) of redundant point removal. It is a figure which shows the input image containing a land area and a sea area. It is a figure which shows a binarized image.

Claims (12)

A shoreline extraction device characterized by having the following elements: (1) A color image or monochrome image including a water surface region and a land region taken from above altitude, or a color image or monochrome image consisting of a water surface region or a land region is input. An image input unit (2) A band decomposition unit that decomposes an input color image into two or more bands (3) A pixel value of two or more decomposed bands is calculated, and the calculation result is binarized to obtain a binary image (4) A contour tracking unit that performs contour tracking of a closed region in the generated binarized image and extracts coordinates constituting the contour. A shoreline extraction device characterized by having the following elements: (1) An image input unit (2) for inputting an input image including a water surface region and a land region taken from above altitude, or an input image consisting of a water surface region or a land region ) A binarization generating unit that generates a binarized image by binarizing the luminance of the input image with a predetermined threshold. (3) Performs contour tracking of a closed region in the generated binarized image to form a contour. A contour tracking unit for extracting coordinates to be performed.   The shoreline extraction device according to claim 1, further comprising a redundant point removal unit that excludes the coordinates of the straight line portion at the end of the image from the extracted coordinates.   The bank according to any one of claims 1 to 3, further comprising a shoreline point output unit that converts the extracted coordinates into latitude and longitude, and outputs the converted latitude and longitude as a shoreline point. Line extraction device. The band decomposition unit decomposes the input color image into at least a green band and a red band,
The interband calculation binarization unit compares the values of the green band and the red band for each pixel, and determines that the pixel value of the red band is a water surface area candidate when the pixel value of the green band is large. The shoreline extraction device according to claim 1, wherein the shoreline extraction device is determined to be a land area candidate when the area is large. A shoreline extraction method characterized by having the following elements: (1) A color image or monochrome image including a water surface area and a land area taken from above altitude, or a color image or monochrome image consisting of a water surface area or a land area is input. (2) A step of decomposing the input color image into two or more bands (3) A step of calculating pixel values of the two or more decomposed bands and binarizing the calculation result to generate a binarized image (4) A step of performing contour tracking of a closed region in the generated binarized image and extracting coordinates constituting the contour. A shoreline extraction method characterized by having the following elements: (1) Inputting an input image including a water surface area and a land area taken from above altitude, or an input image consisting of a water surface area or a land area (2) Input A step of generating a binarized image by binarizing the brightness of the image with a predetermined threshold (3) A step of tracing the contour of the closed region in the generated binarized image and extracting the coordinates constituting the contour . A computer-readable recording medium in which a computer for executing the following processing is recorded on a computer as a shoreline extraction device (1) a color image or monochrome image including a water surface area and a land area photographed from above altitude, or the water surface Processing to input color image or monochrome image consisting of area or land area (2) Processing to decompose input color image into two or more bands (3) Calculate pixel values of two or more decomposed bands, and result of calculation (4) Processing for tracing the contour of a closed region in the generated binarized image and extracting the coordinates constituting the contour. A computer-readable recording medium in which a computer for executing the following processing is recorded on a computer as a shoreline extraction device. (1) An input image including a water surface area and a land area taken from above altitude, or a water surface area or land. Processing for inputting an input image composed of regions (2) Processing for generating a binarized image by binarizing the luminance of the input image with a predetermined threshold (3) Outline of a closed region in the generated binarized image A process of tracking and extracting the coordinates that make up the contour. A program for causing a computer as a shoreline extraction device to execute the following procedure: (1) a color image or monochrome image including a water surface area and a land area taken from above altitude, or a color image consisting of a water surface area or a land area, or Procedure for inputting a monochrome image (2) Procedure for decomposing an input color image into two or more bands (3) A pixel value of two or more decomposed bands is calculated, and the calculation result is binarized to a binarized image (4) A procedure for performing contour tracking of a closed region in the generated binarized image and extracting coordinates constituting the contour. A program for causing a computer as a shoreline extraction device to execute the following procedure: (1) A procedure for inputting an input image including a water surface region and a land region taken from above altitude, or an input image consisting of a water surface region or a land region (2) Procedure for generating a binarized image by binarizing the luminance of the input image with a predetermined threshold (3) Coordinates that constitute the contour by tracing the contour of the closed region in the generated binarized image Procedure to extract.   The shoreline extraction apparatus according to claim 1, wherein the shoreline extraction apparatus performs shoreline determination based on at least an area and a perimeter after extracting contour coordinates.

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