Methods and systems for local principal axis rotation angle transform

• US 9,651,661 B2
• Filed: 04/09/2015
• Issued: 05/16/2017
• Est. Priority Date: 04/09/2014
• Status: Active Grant

• Current Assignee: SRC, Inc.
• Original Assignee: SRC, Inc.
• Inventors: Gonnella, James, Robinson, Michael
• Primary Examiner(s): Windrich, Marcus
• Application Number:
  US14/682,582
• Publication Number:
  US 20160041262A1
• Time in Patent Office: 768 Days
• Field of Search: 342 25 R- 25 F, 342191
• CPC Class Codes: G01S 13/9027 Pattern recognition for feature extraction
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

A method for processing synthetic aperture radar (SAR) data. The method includes the step of receiving SAR data that has been collected to provide a representation of a target scene, and dividing the data into a plurality of sub-blocks each having a plurality of pixels, each of the plurality of pixels having a coordinate and an amplitude. A transformation performed on each of the sub-blocks includes the steps of: (i) computing a mean coordinate; (ii) subtracting the mean coordinate from the pixel'"'"'s actual coordinate to arrive at a modified coordinate; (iii) multiplying the modified coordinate by the amplitude to arrive at an amplitude-modified coordinate; (iv) creating a covariance matrix using the amplitude-modified coordinates; (v) performing a singular value decomposition on the covariance matrix to arrive at a vector; and (vi) associating an angle with the calculated vector.

Claims

1. A method for processing synthetic aperture radar (SAR) data, the method comprising the steps of:

receiving a plurality of SAR data that has been collected to provide a representation of a target scene;

dividing, using a processor the collected SAR data for the target scene into a plurality of sub-blocks, each of the plurality of sub-blocks comprising a plurality of pixels, each of the plurality of pixels comprising a coordinate and an amplitude;

applying a local principal axis rotation transformation to each of the plurality of sub-blocks, the local principal axis rotation transformation comprising the steps of;

(i) computing, for a sub-block, a mean coordinate using the coordinates for the plurality of pixels in the sub-block;

(ii) subtracting, for each of the plurality of pixels in the sub-block, the mean coordinate from the pixel'"'"'s actual coordinate to arrive at a modified coordinate;

(iii) multiplying, for each of the plurality of pixels in the sub-block, the modified coordinate by the amplitude to arrive at an amplitude-modified coordinate;

(iv) creating a covariance matrix using the amplitude-modified coordinates;

(v) performing a singular value decomposition on the covariance matrix to arrive at a vector; and

(vi) associating an angle with the calculated vector.

2. The method of claim 1, further comprising the step of mapping the calculated angles on the target scene.

3. The method of claim 2, wherein each angle is associated with a color intensity.

4. The method of claim 1, wherein the target scene is a maritime scene.

5. The method of claim 1, wherein the SAR data is collected by airplane.

6. The method of claim 1, wherein the SAR data is collected by satellite.

7. The method of claim 1, wherein the step of providing a plurality of receiving SAR data comprises the steps of:

obtaining receiving SAR data for each of a plurality of target scenes; and

storing the receiving SAR data in memory for analysis.

8. A system for processing synthetic aperture radar (SAR) data, the system comprising:

a non-transitory memory comprising a plurality of receiving SAR data that has been collected to provide a representation of a target scene; and

a processor, the processor programmed to divide the collected SAR data for the target scene into a plurality of sub-blocks, each of the plurality of sub-blocks comprising a plurality of pixels, each of the plurality of pixels comprising a coordinate and an amplitude;

wherein the processor is further configured to apply a local principal axis rotation transformation to each of the plurality of sub-blocks, the local principal axis rotation transformation comprising the steps of;

(i) computing, for a sub-block, a mean coordinate using the coordinates for the plurality of pixels in the sub-block;

(ii) subtracting, for each of the plurality of pixels in the sub-block, the mean coordinate from the pixel'"'"'s actual coordinate to arrive at a modified coordinate;

(iii) multiplying, for each of the plurality of pixels in the sub-block, the modified coordinate by the amplitude to arrive at an amplitude-modified coordinate;

(iv) creating a covariance matrix using the amplitude-modified coordinates;

(v) performing a singular value decomposition on the covariance matrix to arrive at a vector; and

(vi) associating an angle with the calculated vector.

9. The system of claim 8, wherein the processor is further configured to map the calculated angles on the target scene.

10. The system of claim 9, wherein each angle is associated with a color intensity.

11. The system of claim 8, wherein the target scene is a maritime scene.

12. The system of claim 8, wherein the SAR data is collected by airplane.

13. The system of claim 8, wherein the SAR data is collected by satellite.

14. The system of claim 8, wherein the system further comprises:

a SAR radar configured to obtain a plurality of receiving SAR data for the target scene.

15. The system of claim 14, wherein the processor is further configured to receive the plurality of receiving SAR data for the target scene and store the data in the non-transitory memory.