Method and apparatus for registration and vector extraction of SAR images based on an anisotropic diffusion filtering algorithm

• US 7,929,802 B2
• Filed: 03/22/2007
• Issued: 04/19/2011
• Est. Priority Date: 03/22/2007
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Rahmes, Mark, Allen, Josef, Ganthier, Emile, Winter, Matthew, Kelley, Patrick
• Primary Examiner(s): Kassa, Yosef
• Application Number:
  US11/689,727
• Publication Number:
  US 20080232709A1
• Time in Patent Office: 1,489 Days
• Field of Search: 382/260, 382/274, 382/275, 382/282, 382/284, 382/291, 342/37, 342/73
• US Class Current: 382/294
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction

Abstract

A computer system for registering synthetic aperture radar (SAR) images includes a database for storing SAR images to be registered, and a processor for registering SAR images from the database. The registering includes selecting first and second SAR images to be registered, individually processing the selected first and second SAR images with an anisotropic diffusion algorithm, and registering the first and second SAR images after the processing. A shock filter is applied to the respective first and second processed SAR images before the registering. Elevation data is extracted based on the registered SAR images.

Claims

1. A computer-implemented method for registering synthetic aperture radar (SAR) images comprising:

selecting first and second SAR images to be registered;

individually processing the selected first and second SAR images with an anisotropic diffusion algorithm; and

registering the first and second SAR images after the processing.

2. A computer-implemented method according to claim 1 further comprising applying a shock filter to the respective first and second processed SAR images before the registering.

3. A computer-implemented method according to claim 1 further comprising extracting elevation data based on the registered SAR images.

4. A computer-implemented method according to claim 1 wherein the processing for each selected SAR image comprises:

determining noise in the SAR image;

selecting a noise threshold for the SAR image based on the determined noise; and

mathematically adjusting the anisotropic diffusion algorithm based on the selected noise threshold.

5. A computer-implemented method according to claim 4 wherein the anisotropic diffusion algorithm is based on a heat equation comprising a non-constant term;

and wherein mathematically adjusting the anisotropic diffusion algorithm comprises adjusting the non-constant term.

6. A computer-implemented method according to claim 5 wherein the non-constant term in the heat equation comprises a convection function.

7. A computer-implemented method according to claim 4 further comprising determining gradient values of each SAR image;

and wherein determining the noise is based on statistical analysis of the gradient values.

8. A computer-implemented method according to claim 7 wherein the statistical analysis is based on a standard deviation of the gradient values plus a constant.

9. A computer-implemented method according to claim 4 wherein determining the noise is based on a Fourier windowing scheme.

10. A computer-implemented method according to claim 4 wherein determining the noise is based on a wavelet decomposition.

11. A computer-implemented method according to claim 1 wherein the anisotropic diffusion algorithm is based on a second order linear partial differential equation.

12. A computer-implemented method according to claim 1 wherein the first and second SAR images comprise complex data.

13. A computer system for registering synthetic aperture radar (SAR) images comprising:

a database for storing SAR images to be registered; and

a processor for registering SAR images from said database, the registering comprising

selecting first and second SAR images to be registered,

individually processing the selected first and second SAR images with an anisotropic diffusion algorithm, and

registering the first and second SAR images after the processing.

14. A computer system according to claim 13 wherein said processor is configured for applying a shock filter to the respective first and second processed SAR images before the registering.

15. A computer system according to claim 13 wherein said processor is configured for extracting elevation data based on the registered SAR images.

16. A computer system according to claim 13 wherein the processing for each selected SAR image comprises:

determining noise in the SAR image;

selecting a noise threshold for the SAR image based on the determined noise; and

mathematically adjusting the anisotropic diffusion algorithm based on the selected noise threshold.

17. A computer system according to claim 16 wherein the anisotropic diffusion algorithm is based on a heat equation comprising a non-constant term;

and wherein mathematically adjusting the anisotropic diffusion algorithm comprises adjusting the non-constant term.

18. A computer system according to claim 17 wherein the non-constant term in the heat equation comprises a convection function.

19. A computer system according to claim 16 further comprising determining gradient values of each SAR image;

and wherein determining the noise is based on statistical analysis of the gradient values.

20. A computer system according to claim 19 wherein the statistical analysis is based on a standard deviation of the gradient values plus a constant.

21. A computer system according to claim 13 wherein the first and second SAR images comprise complex data.

22. A computer-implemented method for vector extraction in synthetic aperture radar (SAR) images comprising:

selecting a SAR image for vector extraction;

processing the selected SAR image with an anisotropic diffusion algorithm; and

extracting vector data based on the processed SAR image.

23. A computer-implemented method according to claim 22 further comprising applying a shock filter to the processed SAR image before the extracting.

24. A computer-implemented method according to claim 22 further comprising extracting road image data based on the extracted vector data.

25. A computer-implemented method according to claim 22 wherein the processing for the selected SAR image comprises:

determining noise in the SAR image;

selecting a noise threshold for the SAR image based on the determined noise; and

mathematically adjusting the anisotropic diffusion algorithm based on the selected noise threshold.

26. A computer-implemented method according to claim 25 wherein the anisotropic diffusion algorithm is based on a heat equation comprising a non-constant term;

and wherein mathematically adjusting the anisotropic diffusion algorithm comprises adjusting the non-constant term.

27. A computer-implemented method according to claim 26 wherein the non-constant term in the heat equation comprises a convection function.

28. A computer-implemented method according to claim 25 further comprising determining gradient values of the SAR image;

and wherein determining the noise is based on statistical analysis of the gradient values.

29. A computer-implemented method according to claim 28 wherein the statistical analysis is based on a standard deviation of the gradient values plus a constant.

30. A computer-implemented method according to claim 25 wherein determining the noise is based on a Fourier windowing scheme.

31. A computer-implemented method according to claim 25 wherein determining the noise is based on a wavelet decomposition.

32. A computer-implemented method according to claim 22 wherein the anisotropic diffusion algorithm is based on a second order linear partial differential equation.

33. A computer-implemented method according to claim 22 wherein the SAR image comprises complex data.

34. A computer system for performing vector extraction in synthetic aperture radar (SAR) images comprising:

a database for storing SAR images to be processed; and

a processor for extracting vector data on SAR images from said database, the extracting comprising

selecting a SAR image for vector extraction;

processing the selected SAR image with an anisotropic diffusion algorithm, and

extracting the vector data based on the processed SAR image.

35. A computer system according to claim 34 wherein said processor is configured for applying a shock filter to the processed SAR image before the extracting.

36. A computer system according to claim 34 wherein said processor is configured for extracting road image data based on the extracted vector data.

37. A computer system according to claim 34 wherein the processing for the selected SAR image comprises:

determining noise in the SAR image;

selecting a noise threshold for the SAR image based on the determined noise; and

mathematically adjusting the anisotropic diffusion algorithm based on the selected noise threshold.

38. A computer system according to claim 37 wherein the anisotropic diffusion algorithm is based on a heat equation comprising a non-constant term;

and wherein mathematically adjusting the anisotropic diffusion algorithm comprises adjusting the non-constant term.

39. A computer system according to claim 38 wherein the non-constant term in the heat equation comprises a convection function.

40. A computer system according to claim 37 further comprising determining gradient values of the SAR image;

and wherein determining the noise is based on statistical analysis of the gradient values.

41. A computer system according to claim 40 wherein the statistical analysis is based on a standard deviation of the gradient values plus a constant.

42. A computer system according to claim 39 wherein the SAR image comprises complex data.