System and method for central association and tracking in passive coherent location applications

• US 6,710,743 B2
• Filed: 05/02/2002
• Issued: 03/23/2004
• Est. Priority Date: 05/04/2001
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Baker, Gregory, Benner, Robert H., Rucker, Jon
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US10/136,441
• Publication Number:
  US 20030085840A1
• Time in Patent Office: 691 Days
• Field of Search: 342/450, 342/451, 342/453
• US Class Current: 342/453
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 7/285 Receivers
• CPC Class Codes: G01S 7/4004 of parts of a radar system

Abstract

A system and method for central association and tracking for PCL applications is disclosed. Detection reports are received at a target tracking processing system. The detection reports include measurements correlating to line tracks associated with target echoes in earlier processing operations. In addition, other information, such as parameters and observables, are received by the target track processing system. The target track processing system performs a line track association function and a track filtering function on the line tracks according to the measurements within the detection reports. These operations also predict and estimate target parameters for tracking. Target parameters are extrapolated from the propagated and updated target tracks, and fed to a display for a user, or back into the PCL system for further processing.

Claims

1. A method for associating a line track with a target for a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

receiving a detection report at least partly derived from said comparison data, said detection report having said line track corresponding to said target;

computing a target state using measurements of said line track;

computing a state covariance using said measurement of said line track;

scoring said line track according to said target state and said state covariance; and

assigning said line track to a target track according to said scoring.

2. The method of claim 1, further comprising filtering said target track by computing corrections to said target state and state covariance.

3. The method of claim 2, further comprising updating said target state and state covariance using measurements from said detection report.

4. The method of claim 2, further comprising performing validity checks on said target track.

5. The method of claim 1, further comprising extrapolating target data from said target track and said detection report.

6. The method of claim 5, further comprising extrapolating an updated state vector and a propagated state vector from said target track and said detection report.

7. The method of claim 1, further comprising performing a modulation line test on said line track.

8. The method of claim 1, further comprising placing said detection report in a buffer.

9. The method of claim 1, further comprising initializing said target track.

10. A method for associating and tracking target data within a passive coherent location system, said target data including measurements from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

computing a target state and a state covariance from said measurements, said measurements at least partly comprising said comparison data from said direct and reflected signals;

assigning a line track correlating said target data to a target track according to said target state and said state covariance;

initializing said target track;

initializing a filter according to said target state and said state covariance;

tracking said target track with said filter; and

extrapolating said target data from said target track.

11. The method of claim 10, further comprising applying at least one gate to said line track.

12. The method of claim 10, further comprising scoring said line track according to said measurements.

13. The method of claim 12, further comprising using a nonlinear least squares batch estimator for said scoring.

14. The method of claim 12, further comprising calculating residuals and partial derivatives for said measurements.

15. The method of claim 12, wherein said assigning occurs according to said scoring.

16. The method of claim 10, further comprising computing corrections to said target state and state covariance.

17. The method of claim 16, further comprising updating said target state and said state covariance with said corrections.

18. The method of claim 10, further comprising receiving a detection report including said measurements and said line track.

19. The method of claim 10, further comprising receiving parameters for a receiver and an illuminator to be used in initializing said target track.

20. The method of claim 10, further comprising outputting said target data to a display.

21. A method for associating a line track to a target track for target tracking operations within a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

determining a candidate association combination for said line track;

applying at least one gate to said candidate association combination;

estimating a target state for said line track;

estimating a state covariance for said line track;

computing a score for said candidate association combination according to said target state and said state covariance; and

assigning said line track to a target track according to said score.

22. The method of claim 21, further comprising initializing said target track.

23. The method of claim 21, wherein said estimating includes using a nonlinear least squares estimator.

24. The method of claim 23, further comprising seeding said nonlinear least squares estimator.

25. The method of claim 21, further comprising performing a modulation line test on said line track.

26. The method of claim 21, further comprising buffering said line track.

27. The method of claim 21, further comprising indicating said line track is available for line track association.

28. The method of claim 21, further comprising removing said line track from a list of unassigned line tracks after said assigning.

29. The method of claim 21, further comprising identifying multiple illuminators for said line track.

30. The method of claim 29, further comprising performing an illuminator hypothesis for said line track according to parameters from said multiple illuminators.

31. The method of claim 21, further comprising applying post-scoring gates to said score.

32. A method for filtering a target track correlating with a detection report having measurements associated with a target within a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

computing corrections for a target state and state covariance for said detection report, said detection report at least partly derived from said comparison data;

updating said target state and said state covariance with said corrections; and

propagating said target track with said updated target state and said updated state covariance.

33. The method for claim 32, further comprising editing said target track.

34. The method of claim 32, further comprising adding weighting factors to said measurements.

35. The method of claim 32, further comprising performing at least one validity check on said updated target track.

36. The method of claim 35, further comprising removing said target track when said target track fails said at least one validity check.

37. A system for estimating target parameters for a target in a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

detection reports comprising measurements at least partly derived from said comparison data;

a line track association function to associate a line track correlating to said detection reports to a target track;

a track filtering function to propagate said target track according to said measurements; and

a target extrapolation function to calculate said target parameters from said target track and said measurements.

38. The system of claim 37, wherein said line track association function generates a state vector and a covariance matrix for said line track.

39. The system of claim 38, wherein said track filtering function propagates said state vector and said covariance matrix.

40. The system of claim 39, wherein said target data extrapolation function extrapolates said target parameters from said propagated state vector and said propagated covariance matrix.

41. The system of claim 37, wherein said line track association function scores said line track.

42. The system of claim 41, wherein said line track association function assigns said line track to said target track according to said score.

43. The system of claim 41, further comprising a nonlinear least squares batch estimator to generate said score.

44. The system of claim 37, further comprising an output including said target parameters.

45. The system of claim 44, wherein said output is transmitted to a display.

46. The system of claim 37, wherein said track filtering function includes a Kalman filter.

47. A system for associating a line track to a target track in a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver and wherein said line track correlates to at least one detection report, comprising:

a nonlinear least squares batch estimator to compute a target state and state covariance for measurements from said at least one detection report at least partly derived from said comparison data and to score a candidate associate combination for said line track; and

a line track assignment function to assign said line track according to said score for said candidate associate combination.

48. The system of claim 47, wherein said target track is initialized.

49. The system of claim 47, further comprising an initialization check function to validate said target track according to said score.

50. The system of claim 47, further comprising pre-scoring gates applied to said at least one detection report.

51. The system of claim 47, further comprising post-scoring gates applied to said score.

52. The system of claim 47, further comprising a buffer to queue said at least one detection report.

53. The system of claim 52, wherein said buffer is a first in, first out buffer.

54. The system of claim 47, wherein said target state and said state covariance is communicated to a track filtering function.

55. A system for track filtering a target track in a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver and wherein said target track is associated with a line track from at least one detection report, comprising:

a filter to compute corrections to a target state and state covariance to update said target track using a means for computing measurement residuals and partial derivatives of measurements from said at least one detection report; and

a validity checker to check said updated target track using a velocity magnitude component and an acceleration magnitude component.

56. The system of claim 55, further comprising an outlier editor to test said measurements from said at least one detection report, wherein said outlier editing function discards said target track if said test is failed.

57. The system of claim 55, further comprising weighting factors within said filter for said measurements.

58. The system of claim 55, further comprising a dissociation function to resolve a target track composed of multiple line tracks, including said line track.

59. The system of claim 55, further comprising a coasting target association function to coast said target track for a specified period of time.

60. A system for associating a line track for a target for a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

means for receiving a detection report, at least partly derived from said comparison data, said detection report having said line track corresponding to said target;

means for computing a target state and state covariance for measurements of said line track;

means for scoring said line track according to said target state and said state covariance; and

means for assigning said line track to a target track according to said scoring.

61. A system for associating and tracking target data within a passive coherent location system, said target data including measurements from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

means for computing a target state and state covariance from said measurements, said measurements at least partly comprising comparison data from said direct and reflected signals;

means for assigning a line track correlating to said target data to a target track according to said target state and said state covariance;

means for initializing said target track;

means for initializing a filter according to said target state and said state covariance;

means for tracking said target track with said filter; and

means for extrapolating said target data from said target track.

62. A system for associating a line track to a target track for target tracking operations within a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

means for determining a candidate association combination for said line track;

means for applying at least one gate to said candidate association combination;

means for estimating a target state and a state covariance for said line track;

means for computing a score for said candidate association combination according to said target state and said state covariance; and

means for assigning said line track to a target track according to said score.

63. A system for filtering a target track correlating with a detection report having measurements associated with a target within a passive coherent location system, wherein said passive coherent location system uses comparison data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, comprising:

means for computing corrections for a target state and state covariance for said detection report, said detection report at least partly derived from said comparison data;

means for updating said target state and said state covariance with said corrections; and

means for propagating said target track with said updated target state and said updated state covariance.

64. A computer program product comprising a computer useable medium having computer readable code embodied therein for associating a line track for a target for a passive coherent location system, wherein said passive coherent location system uses at least one of time-difference-of-arrival (TDOA) and frequency-difference-of-arrival (FDOA) data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, and the computer program product adapted when run on a computer to execute steps, including:

receiving a detection report at least partly derived from said data, said detection report having said line track corresponding to said target;

computing a target state and state covariance for measurements of said line track;

scoring said line track according to said target state and said state covariance; and

assigning said line track to a target track according to said scoring.

65. A computer program product comprising a computer useable medium having computer readable code embodied therein for associating and tracking target data within a passive coherent location system, said target data including measurements from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver said target data including measurements, the computer program product adapted when run on a computer to execute steps, including:

computing a target state and state covariance from said measurements said measurements at least partly comprising at least one of TDOA and FDOA data;

assigning a line track correlating to said target data to a target track according to said target state and said state covariance;

initializing said target track;

initializing a filter according to said target state and said state covariance;

tracking said target track with said filter; and

extrapolating said target data from said target track.

66. A computer program product comprising a computer useable medium having computer readable code embodied therein for associating a line track to a target track for target tracking operations within a passive coherent location system, wherein said passive coherent location system uses at least one of TDOA and FDOA data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, the computer program product adapted when run on a computer to execute steps, including:

determining a candidate association combination for said line track;

applying at least one gate to said candidate association combination;

estimating a target state and a state covariance for said line track;

computing a score for said candidate association combination according to said target state and said state covariance; and

assigning said line track to a target track according to said score.

67. A computer program product comprising a computer useable medium having computer readable code embodied therein for filtering a target track correlating with a detection report having measurements associated with a target within a passive coherent location system, wherein said passive coherent location system uses at least one of TDOA and FDOA data from a direct and a reflected signal emitted from one or more transmitters geographically separated from a receiver, the computer program product adapted when run on a computer to execute steps, including:

computing corrections for a target state and state covariance for said detection report, said detection report being at least partly derived from said data;

updating said target state and said state covariance with said corrections; and

propagating said target track with said updated target state and said updated state covariance.