Apparatus, system and method for highlighting activity-induced change in multi-pass synthetic aperture radar imagery

• US 10,698,104 B1
• Filed: 03/27/2018
• Issued: 06/30/2020
• Est. Priority Date: 03/27/2018
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Inventors: Simonson, Katherine M., Perkins, David Nikolaus
• Primary Examiner(s): Diallo, Mamadou L
• Application Number:
  US15/936,806
• Time in Patent Office: 826 Days
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques
• CPC Class Codes: G01S 13/9027 Pattern recognition for feature extraction
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 13/9088 Circular SAR [CSAR, C-SAR]
• CPC Class Codes: G06T 2207/10044 Radar image
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: H01L 27/14831 Area CCD imagers

Abstract

Described herein are various technologies relating to constructing a differenced change product (DCP) image. A plurality of synthetic aperture radar (SAR) images of a scene are generated based upon radar signals directed towards and reflected off of the scene, and a plurality of coherence change detection (CCD) images of the scene are generated based upon the SAR images. The CCD images are registered with one another, and their pixel values re-scaled according to a monotonic mapping function. The DCP image is generated based upon a computed pixel-wise difference between a pair of the re-scaled CCD images. The DCP image identifies locations in the scene where human activity-induced change is likely to have occurred between a pair of SAR passes of the scene.

Claims

1. A system comprising:

a radar system, the radar system comprises a transmitter that is configured to emit radar signals and a receiver that is configured to detect radar signals;

at least one processor; and

memory that stores instructions that, when executed by the at least one processor, cause the at least one processor to perform acts comprising;

generating three synthetic aperature radar (SAR) images of a scene, the SAR images constructed based upon radar signals detected by the receiver of the radar system responsive to the radar signals being emitted by the transmitter towards the scene and reflecting off of the scene;

generating a first coherent change detection (CCD) image of the scene and a second CCD image of the scene based upon the three SAR images, wherein each CCD image is constructed based upon a respective pair of SAR images in the three SAR images, the CCD images comprising pixels that represent locations in the scene, and wherein pixel values of each of the CCD images are indicative of changes in the scene between the respective pair of SAR images used to construct the CCD image;

generating a differenced change product (DCP) image of the scene based upon the CCD images, the DCP image comprises pixels that represent locations in the scene, wherein each pixel in the DCP image is assigned a respective value based upon values assigned to pixels in the CCD images that represent the same location in the scene as the pixel, and further wherein a first pixel in the pixels of the DCP image that represents a first location in the scene is assigned a first value that indicates that change that has occurred at the first location in the scene is activity-induced change; and

causing the DCP image to be displayed on a display of an analyst.

2. The system of claim 1, the acts further comprising scaling pixel values in the CCD images according to a mapping function, wherein generating the DCP image is based upon the CCD images with the scaled pixel values.

3. The system of claim 2 wherein the mapping function comprises a monotonic continuous function.

4. The system of claim 3, wherein the monotonic continuous function is a nonlinear function.

5. The system of claim 3, wherein the monotonic continuous function is based on the incomplete beta function.

6. The system of claim 3, wherein the monotonic continuous function is a sigmoid function.

7. The system of claim 3, wherein the monotonic continuous function maps pixel values of the CCD images from a domain of zero to one into a range of zero to one.

8. The system of claim 1, wherein the first CCD image comprises a second pixel that represents the first location and the second CCD image comprises a third pixel that represents the first location, and wherein generating the DCP image comprises assigning the first value to the first pixel in the DCP image based upon a difference between a value of the second pixel and a value of the third pixel.

9. The system of claim 1, the acts further comprising:

prior to generating the DCP image, registering the first CCD image and the second CCD image to one another.

10. The system of claim 1, the acts further comprising:

prior to generating the CCD images, registering the three SAR images to one another.

11. The system of claim 1, wherein the first CCD image is representative of changes in the scene over a first window of time, the second CCD image is representative of changes in the scene over a second window of time, the second window of time subsequent to the first window of time, wherein the DCP image depicts only changes that occurred in the scene over the second window of time.

12. The system of claim 1, wherein the first CCD image is representative of changes in the scene over a first window of time, the second CCD image is representative of changes in the scene over a second window of time, the second window of time subsequent to the first window of time, wherein the DCP image depicts only changes that occurred in the scene over the first window of time.

13. The system of claim 1, the acts further comprising:

prior to generating the DCP image, selecting the first CCD image and the second CCD image from a larger collection of CCD images, wherein the first CCD image and the second CCD image are selected from the larger collection of CCD images based upon time windows assigned to CCD images in the larger collection of CCD images.

14. A method that facilitates indicating to an analyst that an anomalous alteration has been identified at a location in a scene, the method comprising:

emitting, from a radar system transmitter, radar signals towards the scene as an aircraft that includes the radar system transmitter passes by the scene;

detecting, with a radar system receiver, the radar signals that have reflected off of the scene;

repeating the acts of emitting and detecting for a plurality of passes by the scene;

generating a plurality of synthetic aperture radar (SAR) images of the scene for the plurality of passes by the scene;

generating two coherent change detection (CCD) images of the scene based upon the plurality of SAR images of the scene, wherein each CCD image is generated based upon a respective pair of SAR images in the plurality of SAR images, wherein further each CCD image is indicative of alterations in the scene between the pair of SAR images on which the CCD image is based;

generating a differenced change product (DCP) image based upon the two CCD images, the DCP image comprises pixels that represent locations in the scene, wherein each pixel in the DCP image is assigned a respective value based upon values assigned to pixels in the two CCD images that represent the same location in the scene as the pixel, and further wherein a first pixel in the DCP image that represents a first location in the scene is assigned a first value that indicates that an alteration that is depicted in one of the CCD images is an activity-induced alteration; and

causing the DCP image to be displayed on a display of an analyst.

15. The method of claim 14, further comprising scaling pixel values in the CCD images according to a mapping function, wherein generating the DCP image is based upon the CCD images with the scaled pixel values.

16. The method of claim 15, wherein the mapping function is a monotonically increasing continuous function.

17. The method of claim 16, wherein the mapping function is a sigmoid function.

18. The method of claim 14, wherein the first CCD image comprises a second pixel that represents the first location and the second CCD image comprises a third pixel that represents the first location, and wherein generating the DCP image comprises assigning the first value to the first pixel in the DCP image based upon a difference between a value of the second pixel and a value of the third pixel.

19. The method of claim 14, further comprising registering the SAR images to one another prior to generating the two CCD images of the scene.

20. A computer-readable storage medium comprising instructions that, when executed by a processor, cause the processor to perform acts comprising:

receiving a first coherent change detection (CCD) image of a scene and a second CCD image, each of the CCD images is based upon a respective pair of synthetic aperture radar (SAR) images of the scene, each of the CCD images is indicative of changes in the scene between two SAR passes of the scene;

remapping pixel values of the CCD images based upon a monotonic mapping function;

computing a pixel-wise difference between the CCD images subsequent to remapping the pixel values of the CCD images; and

generating a differenced change product (DCP) image responsive to computing the pixel-wise difference between the CCD images, wherein a pixel in the DCP image is representative of a first location in the scene, the pixel in the DCP image is assigned a value that is based upon a difference between a value of a second pixel in the first CCD image that is representative of the first location and a value of a third pixel in the second CCD image that is representative of the first location, the value of the pixel in the DCP image indicating that a change at the first location represented in at least one of the first CCD image or the second CCD image is an activity-induced change.