JPH10269347A - Method for eliminating shade shadow element on geographic image, geographic image processor and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a geographic image processor which eliminates shadow elements from a geographic image including natural things, buildings, etc., and easily grasps changes among plural geographic images of the same place. SOLUTION: A geographic image processor 1 consists of an image processing part 2 and a shadow elimination processing part 3. The part 3 extracts a photographed date and time information and height information of buildings, etc., of a geographic image which is generated based on satellite image data from the satellite image data, separately calculates a sunshine direction, a sunshine angle and the width and length of a shadow from the extracted photographed data and time information and height information, also calculates an influenced area of a building, etc., about a shadow, specifies a shadow area by subtracting the calculated influenced area from a multiplication value of the width by the length of a shadow and eliminates pixels of the specified shadow area. Also, the part 2 generates differential information among plural geographic images that represent the same place from which shadows are removed and highlights the differential information on a displaying part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing technique using satellite image data, and more particularly, to a plurality of generations of satellite image data, that is, a plurality of satellite image data obtained by photographing the same point at different times and times. The present invention relates to a method of generating a geographic image from each of the satellite image data and removing a shadow image due to sunlight included in each geographic image to improve the accuracy of difference extraction between the images.

[0002]

2. Description of the Related Art Map data representing geographical information such as residential land, farmland, roads, rivers and the like, and arrangement information of buildings on the surface of the ground, is converted into a database, and necessary map data is appropriately displayed on a display unit as an image or printed. For example, a service system for providing a consumer is known. In such a service system, map data is generated by periodically acquiring aerial photographs, satellite photographs (hereinafter, aerial photographs, etc.), or survey result data on the ground surface, and the contents of the map data are changed with time. If it has changed, the operator has searched and corrected the corresponding map data from the database. In recent years, computerized pattern recognition of aerial photographs etc. and automatic generation of individual map data and detection of changes in the contents of multiple map data have been automated,
Attempts have been made to reduce the labor required for database maintenance work and to improve the accuracy of map data correction.

[0003]

In the case where map data is generated by performing pattern recognition on aerial photographs and the like, accuracy of pattern recognition and recognition processing time become problems. Further, the existence of shadows due to sunlight existing in aerial photographs and the like cannot be ignored. In other words, for example, a shadow due to sunlight is photographed near a high-rise building or a natural object having a height difference. The size (shape), direction, and density differ. For this reason, between images of a plurality of generations (a plurality of images obtained by shooting the same spot at different times and times), even when shooting the exact same geography, different images are obtained due to shadows. There was a problem of being recognized.

An object of the present invention is to provide a technique capable of removing a shadow component due to sunlight contained in a geographic image and improving the accuracy as map data when performing image processing by a computer. . Another object of the present invention is to provide a geographic image processing apparatus capable of quickly generating a geographic image to be used as a basis for map data and accurately and easily grasping a change portion between a plurality of geographic images at the same point. And a recording medium for realizing the geographic image processing device on a general-purpose computer device.

[0005]

According to a method of the present invention for solving the above-mentioned problems, constituent pixels of a geographic image generated based on satellite image data are binarized as necessary. Then, shooting date and time information of the geographic image and height information of an object such as a natural object or a building corresponding to the geographic image are acquired from the satellite image data, and the irradiation direction, irradiation angle, and presence of the sunlight on the object are obtained. Then, the width and length of the shadow generated by the above and the influence area of the object on the shadow are calculated. afterwards,
While determining the shadow area on the geographic image by subtracting the calculated influence area from the multiplication value of the width and the length of the shadow,
The pixels in the specified shadow area are deleted. Further, in order to prevent erroneous detection of the pixel distribution, the cloud amount information at the time of photographing included in the satellite image data is obtained and the density of the geographic image is predicted. Is corrected. Such processing is executed on a computer.

As shown in FIG. 1A, the satellite image data includes weather information at the time of photographing, such as positional information of a plurality of pixels 11, photographing date and time information, and cloud amount information. Each pixel 11 has a red component amount 11 as shown in FIG.
a, green component amount 11b, blue component amount 11c, and high-density information related to the geography of the shooting location, such as object height information 11n at the pixel. By doing so, it becomes easier to create map data than in the case where image processing of an aerial photograph is performed as in the related art. Further, in the artificial satellite, since the same spot is photographed in stereo by a camera in a plurality of directions, each pixel 11 includes height information of the spot. Therefore, the height information from the surface of the shooting point, the length, the size (shape), the direction, and the density of the shadow of the object at the shooting point can be calculated by using the geographic information. . Focusing on this point, the method of the present invention removes the shadow component due to sunlight from the geographic image.

Further, in order to solve the above-mentioned other problems, the present invention removes a shadow component due to sunlight from a geographic image to improve the detection accuracy of a difference between a plurality of geographic images at the same point. A geographic image processing device comprising the components is also provided. (1) Means for specifying a processing target range on a geographic image generated based on satellite image data. (2) The shooting date / time information of the geographic image within the specified processing target range and the height information of the object such as a natural object or a building corresponding to the image are extracted from the satellite image data, and the extracted shooting date / time information and height are extracted. From the information and the irradiation direction of sunlight to the object, the irradiation angle, the width of the shadow generated by the presence of the object,
And calculating the length of the shadow, calculating the area of influence of the object on the shadow, subtracting the calculated area of influence from the product of the width and length of the shadow, and calculating the shadow area on the geographic image. And means for deleting pixels in the specified shadow area. (3) Density correction means for extracting cloud amount information at the time of shooting from the satellite image data to predict the density of the geographic image, and correcting the density of the image when the predicted value is equal to or less than a predetermined reference value. (4) Difference information visualization means for generating difference information between a plurality of geographic images representing the same point from which the pixels in the shadow area have been removed, and visualizing the difference information.

The difference information visualizing means is configured to highlight the difference information on the geographic image.

A recording medium according to the present invention for solving the above-mentioned other problems is a computer-readable recording medium in which a program for causing a computer to execute the following processing is recorded. (A) a process of receiving satellite image data, (b) a process of generating a geographic image based on the received satellite image data, (c) shooting date and time information included in the satellite image data and the generated geographic image Acquire height information of an object such as a natural object or a building corresponding to the irradiation direction of sunlight to the object, the irradiation angle, the width and length of a shadow generated by the presence of the object, and the shadow (D) subtracting the calculated affected area from the product of the shadow width and its length to identify the shadow area on the geographic image; (e) A process of deleting the specified pixel of the shadow area.

[0010] The program also acquires cloud amount information at the time of photographing included in the satellite image data and predicts the density of the geographic image. When the predicted value is equal to or less than a predetermined reference value, the density of the image is determined. The computer may execute the correction process.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a configuration diagram showing an embodiment of the geographic image processing device of the present invention. The geographic image processing apparatus 1 includes, for example, an image processing unit 2, which is realized on an information processing apparatus such as a general-purpose workstation or a personal computer by reading a computer program and executing the computer program. And a shadow removal processing unit 3.
This computer program is usually incorporated in an internal storage device or an external storage device of the information processing apparatus, and is distributed integrally with the information processing apparatus. Recording media such as a CD-ROM (compact disk ROM) and F
D (flexible disk) or distributed through a machine-readable communication network, etc.
The information processing device may be installed in the information processing apparatus at the time of system construction and may be executed at any time.

The image processing unit 2 is connected with a data input device 4 composed of a pointing device and a keyboard and a storage device 5 composed of a large-capacity hard disk and the like, and also displays a CRT or the like for confirming the processing results and the like. The unit 6 is connected.

The storage device 5 stores satellite image data (raw data) in addition to the storage area of the computer program.
Storage area, a storage area for geographic image data (data on which a geographic image is based; hereinafter, when a geographic image is referred to, it also includes geographic image data), and an application to which noise pixels and required image processing have been performed A data storage area is formed. The application data is data processed so as to be used in the geographic image processing apparatus 1 and another image processing system.

As shown in FIG. 3, the image processing unit 2 includes a data conversion processing unit 21, a data input / output processing unit 22, a difference analysis processing unit 23, an image enhancement processing unit 24, a display control unit 25, and each of these units. And a main control unit 26 that controls the entire system.

The data conversion processing section 21 has a storage device 5 in advance.
The satellite image data (raw data) stored or acquired at any time is fetched, converted into a data format that can be processed by the geographic image processing apparatus 1, and binarized for convenience of post-processing. Generate data. The generated geographic image data is represented as a set of pixels. Pixels are x, y in two-dimensional coordinates
In the case of a binarized geographic image having the same number of components as the binary image, in the closed area, pixels having a pixel value of “1” including its edge, that is, colored pixels are continuous, and outside the closed area, the pixel value is Are "0" (that is, there is no colored pixel). Here, the pixel value is an identifier given to the pixel by the data conversion processing unit 21, where "0" is black and "1" is white. Binarization allows the image to be represented by a connected distribution of these pixel values, thus speeding up the subsequent processing. However, it is a matter of course that the present invention is not limited to only binarized images, and that the present invention can be realized by using a plurality of colored pixels as they are.

The generated geographic image data is stored in a storage device 5.
And sent to the shadow removal processing unit 3 as well. The data input / output processing unit 22 includes the shadow removal processing unit 3 and the storage device 5.
And input / output of the above-mentioned satellite image data (raw data) and geographic image data.

The difference analysis processing section 23 analyzes the distribution of pixel values among a plurality of generations of geographic images at the same point from which the shadow image has been removed by the shadow removal processing section 3 and detects a difference between the images. The image enhancement processing unit 24 highlights the analysis result of the difference analysis processing unit 23 on the display of the display unit 6. The display control unit 25 performs control for that. Examples of the mode of the highlight display include, for example, changing the color of the change on the geographic image, displaying the change, and blinking the display. The data to be highlighted is stored in the storage device 5 as application data. The application data is
The processing result data of the difference analysis processing unit 23 may be used.

The display control unit 25 performs display control for prompting the operator to input a processing target range on the geographic image, in addition to display control for the above-mentioned highlight display on the display unit 6.

As shown in FIG. 4, the shadow removal processing section 3 includes an image range specifying section 31, a shadow area specifying section 32, and a density correcting section 3.
3 and a pixel deletion unit 34.

The image range specifying unit 31 specifies, for example, an image range for performing a shadow removal process specified by the operator using the data input device (pointing device) 4 from the geographic image displayed on the display of the display unit 6. To identify. This can be achieved by a bitmap coordinate process corresponding to the display. The image range specifying unit 31 may be prepared as a function of the image processing unit 2.

The shadow area specifying section 32 specifies a shadow area of an object included in the geographic image. The principle of specifying the shadow area is as follows. Now, as shown in FIG. 5, it is assumed that two buildings at heights h1 and h2 from the ground surface are included in the geographic image. At this time, the irradiation direction of sunlight (sunshine direction) is known from the shooting date and time information, and the irradiation angles of sunlight (sunshine angles) θ1 and θ2 are known from the sunshine direction and the height information of each building. Length L of shadows behind each building due to sunlight
1 and L2 can be respectively calculated by the following equations.

L1 = h1 / tan θ1 L2 = h2 / tan θ2

Further, as shown in FIG. 6, the width of the shadow position can be calculated from the orthogonal projection length of the building figure to the vertical vector in the sunshine direction, and the contact points at both ends of the building figure and the shadow can be calculated. The influence area of the building on the shadow can be calculated from the integral value of the building figure on the side of the shadow with respect to the connecting vector. The size (shape) of the shadow due to each building can be calculated from the following equation.

Shadow size (shape) = shadow width × shadow length−
Influence area of building shape

Since the position information of the shadow is also clarified from the "shadow width", the shadow area on the geographic image can be specified by the expression representing the size of the shadow.

The density correcting section 33 extracts cloud amount information at the time of photographing from satellite image data and predicts image density (contrast). When the weather at the time of shooting is clear, the cloud amount is almost zero, and the predicted value of the image density is almost the maximum value, and the pixels constituting the image are sufficiently specified, but the image density decreases as the cloud amount increases Accordingly, the predicted value decreases accordingly. If the predicted value is reduced to a reference value, that is, a value at which pixel omission starts to occur, an error is likely to occur when calculating the shadow width and the area affected by the building graphic. Therefore, when the predicted value becomes equal to or smaller than the reference value, the density correction unit 33 corrects the image density to be higher. The correction process can be performed by, for example, a known image filtering process.

The pixel deleting section 34 deletes the pixels of the shadow area specified by the shadow area specifying section 32 from the corresponding area, sends the result to the image processing section 2 and causes the display section 6 to display the result. Also,
The geographic image from which the pixels in the shadow area have been deleted is sent to the image processing device 3.

Next, the operation of the geographic image processing apparatus 1 will be specifically described with reference to FIG. FIG. 7 mainly shows a processing procedure in the shadow removal processing unit 3. The geographic image processing apparatus 1 first displays a geographic image on the display unit 6.
(Step S101). When it is detected that a certain image range is designated by the pointing device (data input device 4) (step S102: Ye)
s), a processing target range on the geographic image is specified by the specified data (step S103). And
From the satellite image data, geographically related information about the image of the specified area, that is, the shooting date and time information, the height information,
Obtain and decode cloud amount information at the time of shooting (step S10)
4). Further, the image density is predicted from the cloud amount information, and if the predicted value is equal to or less than the reference value, the image density is corrected to be higher (step S105: No, step S106). If the image density has been corrected or the predicted value is equal to or greater than the reference value, the size and position of the shadow area are calculated (step S).
105: Yes, step S107). Thereafter, the pixels in the corresponding area are deleted (step S108), and the geographic image after the pixel deletion is output to the image processing unit 2 (step S10).
9). If there is a next processing target area, step S102
And the same processing is executed (step S11).
0: No). If there is no more processing target range, the processing ends (step S110: Yes). The geographic image from which the shadow has been removed by the above-described series of processing is used as a difference detection target between the images in the image processing unit 2.

[0029]

As is apparent from the above description, the shadow component removing method of the present invention uses the information included in the satellite image data to determine the shadow area on the geographic image generated based on the satellite image data. Since the pixels in the specified area are specified and deleted, there is an effect that a geographic image that can be used as highly accurate map data can be easily and quickly generated.

Further, the geographic image processing apparatus of the present invention detects and highlights a difference between geographic images from which a shadow component has been removed, so that a changed portion on the geographic image can be easily grasped, and a database can be obtained. This has the effect that labor saving of maintenance work is more thorough.

[Brief description of the drawings]

FIG. 1A is an explanatory diagram showing an example of the structure of satellite image data, and FIG. 1B is an explanatory diagram showing an example of the structure of pixels forming the satellite image data.

FIG. 2 is a configuration diagram of a geographic image processing apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram of an image processing unit according to the embodiment.

FIG. 4 is a block diagram of a shadow removal processing unit according to the embodiment;

FIG. 5 is an explanatory diagram showing a relationship between a sunshine direction, a sunshine angle, and a length of a shadow of a building.

FIG. 6 shows a sunshine direction, a shadow direction, and the like in a processing target area.
FIG. 4 is an explanatory diagram showing the relationship between the size of a shadow and a shadow.

FIG. 7 is a flowchart illustrating the operation of the geographic image processing apparatus according to the embodiment, in particular, the processing procedure of a shadow removal processing unit.

[Explanation of symbols]

 Reference Signs List 1 geographic image processing device 2 image processing unit 3 shadow removal processing unit 4 data input device 5 storage device 6 display unit 10 satellite image data 11 pixels 11a to 11n various information included in satellite image data 21 data conversion processing unit 22 data input / output Processing unit 23 Difference analysis processing unit 24 Image enhancement processing unit 25 Display control unit 26 Main control unit 31 Image range specification unit 32 Shadow area specification unit 33 Density correction unit 34 Pixel deletion unit

Claims (9)

[Claims] 1. A method for removing a shadow component caused by sunlight from a geographic image generated based on satellite image data, comprising: a photographing date and time information included in the satellite image data; a natural object corresponding to the geographic image; Obtain height information of an object such as a building, and irradiate the object with the sunlight in the irradiation direction, irradiation angle,
The width and length of the shadow generated by the presence of the object, and the affected area of the object for the shadow is calculated, and the calculated affected area is subtracted from the multiplication value of the width and the length of the shadow. A method of removing a shadow component on a geographic image, wherein the process of identifying a shadow region on the geographic image and deleting pixels of the identified shadow region is performed on a computer. 2. A process executed on the computer,
Acquiring a cloud amount information at the time of shooting included in the satellite image data, predicting the density of the geographic image, and correcting the density of the image when the predicted value is equal to or less than a predetermined reference value. 2. The method for removing shadow components according to claim 1. 3. The shadow component removing method according to claim 1, wherein the geographic image includes a set of binarized pixels. 4. A means for specifying a processing target range on a geographic image generated based on satellite image data, shooting date / time information of a geographic image within the specified processing target range, and a natural object or building corresponding to the image The height information of the object such as is extracted from the satellite image data, the direction of irradiation of sunlight to the object from the extracted shooting date and time information and the height information, the irradiation angle, the shadow generated by the presence of the object Calculate the width, and the length of the shadow, calculate the area of influence of the object on the shadow, subtract the calculated area of influence from the multiplied value of the width and length of the shadow on the geographic image. A geographic image processing apparatus comprising: means for specifying a shadow area; and means for deleting a pixel in the specified shadow area. 5. Density correction means for extracting cloud amount information at the time of photographing from the satellite image data to predict the density of the geographic image, and correcting the density of the geographic image when the predicted value is equal to or less than a predetermined reference value. The geographic image processing apparatus according to claim 4, comprising: 6. The image processing apparatus according to claim 1, further comprising: difference information visualizing means for generating difference information between a plurality of geographic images representing the same point from which the pixels in the shadow region have been removed, and visualizing the difference information. 6. The geographic image processing device according to 4 or 5. 7. The geographic image processing apparatus according to claim 6, wherein the difference information visualizing means is configured to highlight the difference information on the geographic image. 8. A process for receiving satellite image data, a process for generating a geographic image based on the received satellite image data, a photographing date and time information included in the satellite image data, and a natural object corresponding to the generated geographic image. And the height information of the object such as a building and the direction of irradiation of sunlight to the object, the irradiation angle, the width and length of the shadow generated by the presence of the object, and the object with respect to the shadow Calculating the affected area, subtracting the calculated affected area from the multiplied value of the shadow width and its length, and identifying the shadow area on the geographic image, deleting the identified pixel of the shadow area A computer-readable recording medium on which a program for causing a computer to execute a process is recorded. 9. The program acquires cloud amount information at the time of photographing included in the satellite image data, predicts the density of the geographic image, and determines the density of the image when the predicted value is equal to or less than a predetermined reference value. 9. The recording medium according to claim 8, wherein the computer is configured to execute a correction process.