SYSTEM AND METHOD FOR PROCESSING RADAR IMAGERY

• US 20110299733A1
• Filed: 11/04/2009
• Published: 12/08/2011
• Est. Priority Date: 12/18/2008
• Status: Active Grant

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Jahangir, Mohammed, Kealey, Paul Graham, Moate, Christopher Paul, Hill, Robert David
• Granted Patent: US 8,805,005 B2
• Time in Patent Office: Days
• US Class Current: 382/103
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques
• 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

Abstract

The present invention relates to a system and method for processing imagery, such as may be derived from a coherent imaging system e.g. a synthetic aperture radar (SAR). The system processes sequences of SAR images of a region taken in at least two different passes and generates Coherent Change Detection (CCD) base images from corresponding images of each pass. A reference image is formed from one or more of the CCD base images images, and an incoherent change detection image formed by comparison between a given CCD base image and the reference image. The technique is able to detect targets from tracks left in soft ground, or from shadow areas caused by vehicles, and so does not rely on a reflection directly from the target itself. The technique may be implemented on data recorded in real time, or may be done in post-processing on a suitable computer system.

Claims

1. A method of detecting movement parameters of a ground based target by processing first and a second temporal sequences of returns from a Synthetic Aperture system, each sequence collected during separate imaging passes, the returns comprising a plurality of synthetic aperture base images of a region comprising the steps of:

i) pairing an image in the second temporal sequence with a corresponding primary image from the first temporal sequence, aligning the images if required and forming a coherent change detection (CCD) image, and repeating for each pair to produce a plurality of CCD base images;

ii) forming a reference image from one or more of the CCD base images;

iii) forming an “

incoherent change detection”

image by normalising the reference image with a suitably aligned, predetermined CCD base image from the sequence.

2. A method as claimed in claim 1 wherein the returns are from a synthetic aperture radar system.

3. A method as claimed in claim 1 wherein steps ii) and iii) are repeated for successive CCD base images, to form a sequence of incoherent change detection images.

4. A method as claimed in claim 3 wherein the sequence of incoherent change detection images is provided as an input to an automatic target detection algorithm.

5. A method as claimed in claim 1 wherein the reference image is formed by temporally filtering two or more of the CCD base images.

6. A method as claimed in claim 1 wherein the reference image comprises one of the CCD images.

7. A method as claimed in claim 1 wherein the incoherent change detection image comprises a ratio of two CCD base images.

9. A method as claimed in claim 1 wherein one or more incoherent change detection images are analysed to detect the shadow of the target in the imagery.

10. A method as claimed in claim 9 wherein a target is detected by producing one or more focused images by manipulating phases of the temporal returns according to motion parameters estimated from the track of a target.

13. A method as claimed in claim 9 wherein a radar cross section (RCS) value of the detected target is estimated from its focused image.

25. A computer program adapted to implement the method as claimed in claim 1 on a computer system, and further adapted, when run on the computer system, to produce image data comprising an incoherent change detection image.

8. (canceled)

11. (canceled)

12. (canceled)

14. A processing system for the detection of movement parameters of a target, the processing system processing returns from a Synthetic Aperture system, comprising a processor adapted to receive data from the synthetic aperture system, the data comprising image information from two independent imaging passes of the same scene, the image information comprising a plurality of synthetic aperture images from each pass of the scene, the processing system comprising a processor adapted to process the data in the form of synthetic aperture images from the two independent imaging passes and, pairing primary and repeat pass images for the same geometries, to produce a coherent change detection (CCD) image for each pairing, so generating a plurality of CCD base images;

wherein;

the processor is adapted to form a reference image from one or more of the CCD base images, the one or more CCD base images being suitably spatially aligned with respect to each other; and

the processor is further adapted to normalise the reference image with a given CCD base image to form an associated incoherent change detection image, the given CCD base image being suitably aligned with the reference image.

15. A processing system as claimed in claim 14 wherein the system forms part of a synthetic aperture radar system.

16. A processing system as claimed in claim 14 wherein the system is adapted to process data previously generated by a synthetic aperture system.

17. A processing system as claimed in claim 14 wherein the processor is adapted to produce a plurality of incoherent change detection images from a succession of CCD base images.

18. A processing system as claimed in claim 17 wherein the processor is adapted to process the plurality of incoherent change detection images to automatically detect moving targets in the scene.

19. A processing system as claimed in claim 14 wherein the reference image comprises one of the CCD images.

20. A processing system as claimed in claim 14 wherein the processor is adapted to form the reference image(s) by temporally filtering two or more of the CCD base images.

21. A processing system as claimed in claim 14 wherein the processor is adapted to form the incoherent change image(s) by calculating a ratio of two CCD base images.

22. A processing system as claimed in claim 14 wherein the processor is adapted to analyse one or more incoherent change detection images to detect a track left by the target on the ground.

23. A processing system as claimed in claim 22 wherein the processor is adapted to locate a target by producing one or more focused images by manipulating phases of the temporal returns according to motion parameters estimated from the track of a target.

24. A processing system as claimed in 23 wherein the processing system is adapted to obtained focused images based upon a shadow of a moving target.