JP6922445B2 - Radar image processing device and radar image processing device method and radar image processing device program - Google Patents

Description

The present invention relates to a technique for interfering with a synthetic aperture radar image.

Synthetic aperture radar (abbreviated as Synthetic Amplitude Radar, SAR) irradiates the ground surface with microwaves while flying objects such as artificial satellites and aircraft move, receives echoes reflected from the ground surface, and processes the signals. Generates a SAR image with amplitude and phase in the pixels. In SAR, by artificially "synthesizing" the "aperture", a radar image equivalent to that of an antenna having a large aperture can be obtained. Furthermore, in SAR, the elevation information of the ground surface is extracted by interfering two SAR images observed from different positions, and the displacement of the ground surface (how much the ground has moved) is calculated by taking the difference between the two observation data. Interference processing techniques such as measurement are used. Interference images obtained by interfering with SAR images are used for disaster monitoring, harbor monitoring, volcano monitoring, etc. that involve displacement of the ground surface because they can capture minute displacements of the ground surface.

Techniques for improving the accuracy of interference images are disclosed in Patent Documents 1, 2 and 3. In Patent Document 1, the accuracy of altitude measurement is improved by selecting SAR images obtained by two satellites having an appropriate distance (baseline length) between satellites and performing interference processing. Further, in Patent Document 2, a plurality of coherence (ease of interference) and scattering intensity (intensity of microwaves emitted from a satellite antenna being scattered by an object and returning toward the antenna) are obtained from the SAR image to be observed. Calculate the characteristic value of. Further, the extraction accuracy is improved by determining the method of discriminating the displacement of the observation target using the characteristic value according to the observation target and extracting the displacement region in the observation target by the determined discrimination method.

Further, in Patent Document 3, the displacement of an urban area or a landslide region is calculated by interfering with a large number of SAR images. At this time, the noise component is suppressed by extracting only the pixels having high coherence called the PS point (Persistent Scatterer), and the accuracy of measurement is improved. Furthermore, by interfering a large number of SAR images, changes in the phase component over time can be analyzed, and the displacement velocity (displacement tendency in a certain period) can be measured with high accuracy.

JP-A-2007-256134 Japanese Unexamined Patent Publication No. 2008-46107 U.S. Pat. No. 6,583,751

However, since the techniques of Patent Documents 1 and 2 obtain an interference image by interfering two SAR images, only an interference image limited to the difference information between the two SAR images can be obtained. There is a limit to improving the accuracy of extracting changes. On the other hand, the technique of Patent Document 3 is effective in improving the accuracy of extracting changes because it is possible to use difference information between a large number of three or more SAR images. However, when a large number of images interfere with each other, the accuracy deteriorates due to a low coherence image being mixed in the large number of images required, and when selecting a high coherence image, a large number of images are used. There is a problem such as complexity due to having to select.

The present invention has been made in view of the above problems, and an object of the present invention is to easily select an image having high coherence when interfering with a SAR image by satisfying a number required for the coherence processing. , To provide a radar image processing apparatus.

The radar image processing apparatus of the present invention includes a data input means for inputting data including a radar image and predetermined data associated with the acquisition of the radar image, and a predetermined index that affects the interference processing of the radar image based on the data. An index calculation means for calculating the above, an image selection means for selecting the radar image satisfying the number required for the interference processing based on the index, and an interference processing means for performing the interference processing of the selected radar image. Has.

In the radar image processing method of the present invention, a predetermined index that affects the interference processing of the radar image is calculated based on the data including the radar image and the predetermined data associated with the acquisition of the radar image, and the index is used as the basis for calculating the predetermined index. The radar images satisfying the number required for the interference processing are selected, and the interference processing of the selected radar images is performed.

The radar image processing program of the present invention calculates a predetermined index that affects the interference processing of the radar image based on the data including the radar image and the predetermined data associated with the acquisition of the radar image, and the process based on the index. The computer is made to execute the process of selecting the radar images satisfying the number required for the interference process and the process of performing the interference process of the selected radar images.

According to the present invention, it is possible to provide a radar image processing apparatus capable of easily selecting an image having high coherence when interfering with a SAR image by satisfying a number required for the interference processing.

It is a block diagram which shows the structure of the radar image processing apparatus of 1st Embodiment of this invention. It is a block diagram which shows the structure of the radar image processing apparatus of the 2nd Embodiment of this invention. It is a flowchart which shows the operation of the radar image processing apparatus of 2nd Embodiment of this invention. It is a figure which shows the structure of the master image and the slave image by the radar image processing apparatus of the 2nd Embodiment of this invention. It is a figure which shows the relationship between the magnitude of an index by the radar image processing apparatus of the 2nd Embodiment of this invention, and coherence.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, the scope of the invention is not limited to the following.
(First Embodiment)
FIG. 1 is a block diagram showing a configuration of a radar image processing device according to the first embodiment of the present invention. The radar image processing device 1 of the present embodiment affects the interference processing of the radar image based on the data input means 11 for inputting the data including the radar image and the predetermined data associated with the acquisition of the radar image, and the data. It has an index calculation means 12 for calculating a predetermined index. Further, it has an image selection means 13 for selecting the radar images satisfying the number required for the interference processing based on the index, and an interference processing means 14 for performing the interference processing of the selected radar images.

According to the radar image processing device 1 of the present embodiment, the index calculation means 12 can calculate a predetermined index that affects the interference processing based on the data input by the data input means 11. Further, the image selection means 13 can select radar images satisfying the number required for the interference processing based on a predetermined index affecting the interference processing. Therefore, even when interfering with a large number of three or more SAR images, the image selection means 13 selects radar images that satisfy the number required for the interference processing, so that the images are accurate without relying on human experience. It is possible to easily and easily select images having high coherence by satisfying the number required for coherence processing.

As described above, according to the present embodiment, there is provided a radar image processing apparatus capable of easily selecting an image having high coherence when interfering with a SAR image by satisfying the number required for the interference processing. be able to.
(Second embodiment)
FIG. 2 is a block diagram showing a configuration of a radar image processing device 2 according to a second embodiment of the present invention. The radar image processing device 2 includes a data input unit 21, an index calculation unit 22, an image selection unit 23, and an interference processing unit 24.

The data input unit 21 irradiates the ground surface with microwaves while a flying object such as an artificial satellite or an aircraft moves, receives the microwave reflected on the ground surface, and processes the signal to process the received microwaves. SAR image data having amplitude and phase as pixel data is input. Further, one or more of the orbit data of the flying object, the meteorological data, and the time data at the time of acquiring the SAR image is input.

The index calculation unit 22 calculates a predetermined index that affects the interference processing of the SAR image based on the data input to the data input unit 21. The index includes one or more of the coherence, focus, signal-to-noise ratio (Signal-Noise Ratio, SNR), baseline length, rainfall, and observation time interval of the SAR image.

The image selection unit 23 selects SAR images that satisfy the number required for interference processing of SAR images based on the index calculated by the index calculation unit 22. The image selection unit 23 selects the SAR image based on the threshold value for the index. When the number of selected SAR images is insufficient for the interference processing, the image selection unit 23 adjusts the threshold value for selecting the SAR image and selects the SAR image again. The image selection unit 23 repeats the adjustment of the threshold value and the selection of the SAR image based on the adjusted threshold value until the number of SAR images satisfies the number required for the interference processing.

The interference processing unit 24 performs interference processing on the SAR image selected by the image selection unit 23, generates an interference image, and outputs the interference image. The interference processing unit 24 can improve the displacement extraction accuracy by performing interference processing on a large number of three or more SAR images.

The radar image processing device 2 can also have a data storage unit, which is omitted in FIG. The data storage unit includes data input to the data input unit 21, an index calculated by the index calculation unit 22, thresholds and threshold adjustment information for selecting a SAR image by the image selection unit 23, and an image selection unit. Information on the SAR image selected by the 23 and the interference image generated by the interference processing unit 24 can be stored.

The radar image processing device 2 can be an information processing device (computer) such as a PC (Personal Computer) or a server. Information processing equipment includes CPU (Central Processing Unit), which is an arithmetic resource, memory and HDD (Hard Disk Drive), which are storage resources, communication boards and input interfaces, which are communication resources, and keyboards and mice, which are input resources. It is equipped with a touch panel and display resources such as a display and a printer. By operating a predetermined program on the CPU and using these components, each part constituting the radar image processing device 2 can be realized.

That is, the data input unit 21 is realized by a communication unit that receives SAR image data and various data transmitted from a satellite or an aircraft, an input interface for inputting the data, and the like. The index calculation unit 22, the image selection unit 23, and the interference processing unit 24 are realized by operating a predetermined program on the CPU. Further, the interference processing unit 24 may have a display, a printer, or the like for displaying the generated interference image. Further, the data storage unit is realized by a memory, an HDD, or the like.

FIG. 3 is a flowchart showing the operation of the radar image processing device 2 of the present embodiment. This flowchart is started by starting a program that executes an operation of performing interference processing of the SAR image shown in FIG. 3 on a computer.

First, in step S01, the data input unit 21 includes SAR image data having the amplitude and phase of the microwave reflected on the ground surface as pixel data acquired by the projectile, and orbital data and meteorological data when the SAR image is acquired. And one or more of the time data and. The data at the time of acquiring the SAR image is not limited to the orbit data, the meteorological data, and the time data.

Next, in steps S02-a to f, the index calculation unit 22 calculates a predetermined index that affects the interference processing of the SAR image based on the data input to the data input unit 21. Indicators include one or more of the coherence and focus of SAR images, SNR, baseline length, rainfall and observation day intervals. The index is not limited to coherence, focus, SNR, baseline length, rainfall, and observation day interval.

Indicators such as focus, SNR, and rainfall can be calculated for each SAR image. On the other hand, indexes such as coherence, baseline length, and observation day interval can be calculated from the relationship between the two SAR images. As shown in FIG. 4, the two SAR images may be composed of a reference master image and a slave image subordinate to the master image (1 to N: N are positive integers). .. Each index can be calculated from the relationship between the master image and the slave image. The configuration of the two SAR images is not limited to the configuration of the master image and the slave image shown in FIG.

As for the composition of the master image and the slave image, for example, the first acquired SAR image can be used as the master image, and the second and subsequent acquired SAR images can be used as the slave image. Further, when a natural disaster such as an earthquake or an eruption occurs, the SAR image before the occurrence can be used as a master image and the SAR image after the occurrence can be used as a slave image. The composition of the master image and the slave image is not limited to the above.

In the calculation of coherence (step S02-a), the index calculation unit 22 compares the phases of the pixels corresponding to each other in the master image and the slave image. Then, the coherence of the master image and the slave image is calculated by calculating the ratio of the number of pixels having different phases to the total number of pixels. The coherence shows the correlation between the master image and the slave image to be interfered with, and becomes 1 when the master image and the slave image completely match, and becomes 0 as the difference between the two increases. It can be said that the closer the coherence is to 1, the better the coherence of the SAR image.

In the focus calculation (step S02-b), the index calculation unit 22 calculates the diameter at which the point object under observation is displayed in the SAR image. The image in the SAR image of a point object takes the form of a sinc function and is displayed as a small circle. At that time, if the SAR image is out of focus, it is displayed with a blur corresponding to the out of focus. If the SAR image is out of focus and the blur progresses, the diameter of the circle becomes large or distorted. Therefore, by calculating the diameter of the image of the point object, it is possible to evaluate the blurring of the SAR image and the defocusing. The diameter at which the point object is displayed in the SAR image can be calculated from the number of pixels for displaying the point object. The smaller the diameter, the better the focus, and it can be said that the SAR image has good coherence.

In the calculation of the SNR (step S02-c), the index calculation unit 22 calculates the ratio of the signal to the noise for each pixel of the SAR image. If the signal is noisy, the SNR will show a small value. Therefore, it can be said that the larger the SNR, the better the coherence of the SAR image.

In the calculation of the baseline length (step S02-d), the index calculation unit 22 calculates the distance between the projectiles when the master image and the slave image are acquired from the orbital data of the projectiles. Since the position of the projectile is specified by the orbit data, the distance between the projectiles can be calculated based on the position of the projectile when the master image and the slave image are acquired respectively. The baseline length represents the distance between the flying objects when two SAR images are acquired, and it can be said that the closer the distance is, the better the coherence is in the SAR image.

In the calculation of rainfall (step S02-e), the index calculation unit 22 calculates the rainfall when the SAR image is acquired based on the meteorological data when the SAR image is acquired. The rainfall can be, for example, the amount of precipitation per hour at the time and place where the SAR image is acquired. Rainfall is an index for evaluating factors that affect radio waves, such as clouds and water content in the atmosphere. The magnitude of the effect of rainfall also depends on the frequency of radio waves. It can be said that the smaller the amount of rainfall, the better the coherence of the SAR image.

In the calculation of the observation day interval (step S02-f), the index calculation unit 22 acquires the number of days of the acquisition interval of the master image and the slave image based on the time data when the SAR image is acquired, and each SAR image. It is calculated by taking the difference between the date and time. The closer the observation date is, the less the change in conditions such as climate between the SAR and the observation target is likely to occur, and it can be said that the SAR image has good coherence. On the contrary, as the interval between the observation days increases, the change in the condition between the SAR and the observation target tends to be large, and it can be said that the SAR image causes deterioration of coherence.

Next, in step S03, the image selection unit 23 selects a SAR image having good coherence based on the threshold value provided for each index calculated by the index calculation unit 22.

FIG. 5 is a diagram showing the relationship between the magnitude of the index and the coherence. By setting a threshold value for each index in advance, it is possible to select a SAR image that meets the conditions above or below the threshold value. For example, when the index is coherence, a combination of SAR images (master image and slave image) having coherence equal to or higher than the threshold value is selected. Further, in the case of the diameter of the point object representing the focus, a SAR image having a diameter equal to or less than the threshold value is selected.

The image selection unit 23 may select a SAR image that satisfies all of the indicators of FIG. 5, or may select a SAR image that satisfies at least one of the indicators of FIG. good. At this time, the selection may be made according to the index having the greatest influence on the coherence.

Further, when the SAR image is composed of the master image and the slave image shown in FIG. 4, the image selection unit 23 selects the master image. Since the master image serves as a reference for the slave image to be interfered with, the image selection unit 23 may preferentially select from the SAR images.

For the threshold value, for example, it is examined how much the threshold value should be set to obtain a desired interference image from each index obtained from the SAR image accumulated in the past and the accompanying orbital data, meteorological data, and time data. By doing so, it can be set in advance. Further, the threshold value may be updated by feeding back the processing result while actually executing the interference processing.

Next, in step S04, the image selection unit 23 determines whether or not the number of SAR images selected in step S03 satisfies the number of SAR images for performing interference processing. If the number is satisfied (YES in S04), the process proceeds to step S06, and the interference processing unit 24 performs interference processing on the selected SAR image.

When the selected SAR images do not satisfy the number, that is, when the number is insufficient (NO in S04), the image selection unit 23 adjusts the threshold value so that the number of selected SAR images increases (step S05). ). The amount of threshold adjustment can be set in advance. Further, when adjusting the threshold value, for example, the threshold values of each index may be shifted by a predetermined amount, and the threshold values of one or more indexes may be predetermined in order from the index having a large influence on coherence. You may shift by the amount. The method of adjusting the threshold value is not limited to the above.

The image selection unit 23 reselects a SAR image having good coherence based on the reset threshold value (step S03). Further, the image selection unit 23 again determines whether or not the number of reselected SAR images satisfies the number of SAR images for performing interference processing (step S04). If the number is satisfied (YES in S04), the process proceeds to step S06. If the number is not satisfied (NO in S04), the threshold value is adjusted again (step S05). The image selection unit 23 repeats steps S03 to S05 until the number of selected SAR images satisfies the number of SAR images for performing interference processing.

When the number of selected SAR images greatly exceeds the number of SAR images for performing interference processing, the image selection unit 23 can adjust the threshold value so as to reduce the number of SAR images to be selected. Then, by reselecting the SAR images based on the adjusted threshold value, the number of SAR images may approach the number of SAR images for performing the interference process. In this case, since a SAR image having higher coherence is selected, it is effective in improving the accuracy by the coherence processing.

In step S06, the interference processing unit 24 performs interference processing of the SAR image selected by the image selection unit 23, and ends. In the case of the configuration of the master image and the slave image shown in FIG. 4, the interference processing unit 24 can generate an interference image by taking the difference between the master image and the slave image. Further, the individual interference images may be superposed to form a single interference image.

According to the radar image processing device 2 of the present embodiment, the index calculation unit 22 can calculate a predetermined index that affects the interference processing based on the data input by the data input unit 21. Further, the image selection unit 23 can select radar images satisfying the number required for the interference processing based on a predetermined index affecting the interference processing. Therefore, even when interfering with a large number of three or more SAR images, the image selection unit 23 selects radar images that satisfy the number required for the interference processing, so that it is accurate without relying on human experience. It is possible to easily and easily select images having high coherence by satisfying the number required for coherence processing.

As described above, according to the present embodiment, there is provided a radar image processing apparatus capable of easily selecting an image having high coherence when interfering with a SAR image by satisfying the number required for the interference processing. be able to.

Although the invention of the present application has been described above with reference to the embodiment, the invention of the present application is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made within the scope of the present invention in terms of the structure and details of the present invention.

In addition, some or all of the above embodiments may be described as in the following appendix, but are not limited to the following.
(Appendix 1)
A data input means for inputting data including a radar image and predetermined data associated with the acquisition of the radar image, and
An index calculation means for calculating a predetermined index that affects the interference processing of the radar image based on the data, and
An image selection means for selecting the radar image satisfying the number required for the interference processing based on the index, and
A radar image processing apparatus comprising an interference processing means for performing the interference processing of the selected radar image.
(Appendix 2)
The radar image processing device according to Appendix 1, wherein the image selection means selects the radar image based on a threshold value for the index.
(Appendix 3)
The radar image processing device according to Appendix 2, wherein the image selection means adjusts the threshold value and repeats the selection of the radar image when the selected radar images are insufficient for the number required for the interference processing.
(Appendix 4)
The radar image processing apparatus according to item 1 of Appendix 1 to 3, wherein the predetermined data includes one or more of track data, meteorological data, and time data at the time of acquiring the radar image.
(Appendix 5)
The radar image processing apparatus according to item 1 of Appendix 1 to 4, wherein the index includes one or more of the coherence, focus, SNR, baseline length, rainfall, and observation time interval of the radar image.
(Appendix 6)
The radar image processing apparatus according to item 1 of Appendix 1 to 5, which has a storage means for storing the data.
(Appendix 7)
A predetermined index that affects the interference processing of the radar image is calculated based on the data including the radar image and the predetermined data associated with the acquisition of the radar image.
Based on the index, the radar images satisfying the number required for the interference processing are selected, and the radar images are selected.
A radar image processing method that performs the interference processing of the selected radar image.
(Appendix 8)
The radar image processing method according to Appendix 7, wherein the radar image is selected based on a threshold value for the index.
(Appendix 9)
The radar image processing method according to Appendix 8, wherein when the selected radar images are insufficient in the number required for the interference processing, the threshold value is adjusted and the selection of the radar images is repeated.
(Appendix 10)
The radar image processing method according to item 1 of Appendix 7 to 9, wherein the predetermined data includes one or more of track data, meteorological data, and time data at the time of acquiring the radar image.
(Appendix 11)
The radar image processing method according to item 1 of Appendix 7 to 10, wherein the index includes one or more of the coherence, focus, SNR, baseline length, rainfall, and observation time interval of the radar image.
(Appendix 12)
The radar image processing method according to item 1 of Appendix 7 to 11, which stores the data.
(Appendix 13)
A process of calculating a predetermined index that affects the interference process of the radar image based on the data including the radar image and the predetermined data associated with the acquisition of the radar image, and
A process of selecting the radar image satisfying the number required for the interference process based on the index, and a process of selecting the radar image.
A radar image processing program that causes a computer to execute a process of performing the interference process of the selected radar image.
(Appendix 14)
The radar image processing program according to Appendix 13, which causes the computer to execute a process of selecting the radar image based on a threshold value for the index.
(Appendix 15)
The radar image processing program according to Appendix 14, wherein when the selected radar images are insufficient in the number required for the interference processing, the computer is made to execute a process of adjusting the threshold value and repeating the selection of the radar images.
(Appendix 16)
The radar image processing program according to item 1 of Appendix 13 to 15, wherein the predetermined data includes one or more of track data, meteorological data, and time data at the time of acquiring the radar image.
(Appendix 17)
The radar image processing program according to item 1 of Appendix 13 to 16, wherein the index includes one or more of the coherence, focus, SNR, baseline length, rainfall, and observation time interval of the radar image.
(Appendix 18)
The radar image processing program according to item 1 of Appendix 13 to 17, which causes the computer to execute the process of storing the data.

1, 2 Radar image processing device 11 Data input means 12 Index calculation means 13 Image selection means 14 Interference processing means 21 Data input unit 22 Index calculation unit 23 Image selection unit 24 Interference processing unit

Claims (6)

A data input means for inputting data including a radar image and predetermined data associated with the acquisition of the radar image, and
An index calculation means for calculating a predetermined index that affects the interference processing of the radar image based on the data, and
An image selection means for selecting the radar image satisfying the number required for the interference processing based on the threshold value for the index, and
It has an interference processing means that performs the interference processing of the selected radar image.
Wherein the image selecting means, when the radar image selected is insufficient to the required number on the interference processing, to repeat the selection of the radar image by adjusting the threshold value
Les over da image processing apparatus. Wherein the predetermined data, when obtaining the radar image, orbit data, weather data, including one or more of time data, according to claim 1 Symbol placement of radar image processing apparatus. The radar image processing apparatus according to claim 1 or 2 , wherein the index includes one or more of the coherence, focus, SNR, baseline length, rainfall, and observation time interval of the radar image. Wherein the data comprises a storage means for storing, radar image processing apparatus according one of among claims 1 to 3. A predetermined index that affects the interference processing of the radar image is calculated based on the data including the radar image and the predetermined data associated with the acquisition of the radar image.
The radar images satisfying the number required for the interference processing are selected based on the threshold value for the index, and the radar images are selected.
The interference processing of the selected radar image is performed, and the interference processing is performed.
If the selected said radar image is insufficient to the required number on the interference processing, to repeat the selection of the radar image by adjusting the threshold value
Les over da image processing method. A process of calculating a predetermined index that affects the interference process of the radar image based on the data including the radar image and the predetermined data associated with the acquisition of the radar image, and
A process of selecting the radar image satisfying the number required for the interference process based on the threshold value for the index, and a process of selecting the radar image.
The process of performing the interference process of the selected radar image and the process of performing the interference process.
A radar image processing program that causes a computer to perform a process of adjusting the threshold value and repeating the selection of the radar image when the selected radar image is insufficient for the number required for the interference process.

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