Multi-platform geolocation method and system

• US 6,407,703 B1
• Filed: 08/07/2000
• Issued: 06/18/2002
• Est. Priority Date: 08/07/2000
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Reichert, Robert S., Kallaus, Richard A., Minter, Thomas C.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/633,382
• Time in Patent Office: 680 Days
• Field of Search: 342/450, 342/457, 342/462, 342/465
• US Class Current: 342/450
• CPC Class Codes: G01S 2205/03 Airborne
• CPC Class Codes: G01S 5/0249 Determining position using measurements made by a non-stationary device other than the device whose position is being determined

Abstract

A method for determining the geolocation of an emitter using sensors located at a single or multiple platforms is disclosed. Generally, the method includes the steps of receiving a first measurement set relative to a first emitter, the first measurement set including angle of arrival, time difference of arrival and/or terrain height/altitude measurements, receiving a first location guess or estimate for the first emitter, and determining at least a second location estimate using at least one of a batch least squares analysis and a Kalman filter analysis.

Claims

1. A method for locating a first emitter comprising the steps of:

receiving at a first platform and a second platform at a first point in time a first signal from the first emitter;

determining at least one of a first angle of arrival and a first time of arrival of the first signal at the first platform at the first point in time;

determining at least one of a second angle of arrival and a second time of arrival of the first signal at the second platform at the first point in time;

receiving a first altitude estimate for the first emitter, wherein the first altitude estimate is an estimate of an altitude of the first emitter in relation to a predetermined altitude reference;

determining a first location estimate of the first emitter using said first altitude estimate for the first emitter and at least one of the first angle of arrival and the first time of arrival of the first signal at the first platform at the first point in time and said at least one of the second angle of arrival and the second time of arrival of the first signal at the second platform at the first point in time.

2. A method as claimed in claim 1, wherein said first altitude estimate is independent of said first and second angles of arrival.

3. A method as claimed in claim 1, wherein said receiving the first altitude estimate comprises the step of:

determining a coarse location estimate of the first emitter;

retrieving the first altitude estimate from a terrain database based on the first course location estimate.

4. A method as claimed in claim 1, further comprising the steps of:

receiving at the first and second platforms a second signal from the first emitter, the second signal different from the first signal;

determining at least one of a first angle of arrival and a first time of arrival of the second signal at the first platform;

determining at least one of a second angle of arrival and a second time of arrival of the second signal at the second platform;

determining a second location estimate of the first emitter using said at least one of the first angle of arrival and the first time of arrival of the second signal at the first platform, said at least one of the second angle of arrival and the second time of arrival of the second signal at the second platform and said first location estimate.

5. A method as claimed in claim 1, wherein said determining said first location estimate step comprises performing one of a least squares analysis and a Kalman filter analysis using said at least one of the first angle of arrival and the first time of arrival of the first signal at the first platform and said at least one of the second angle of arrival and the second time of arrival of the first signal at the second platform.

6. A method as claimed in claim 1, further comprising the step of:

receiving an initial location estimate for the first emitter.

7. A method as claimed in claim 6, wherein said determining said first location estimate step further comprises using said initial location estimate.

8. A method as claimed in claim 6, wherein said receiving said initial location estimate step comprises performing one of the steps of:

determining said initial location from a first intersection of said first and second angles of arrival of said first signal at the first and second platforms, respectively, the first platform being remote from the second platform;

determining said initial location from a second intersection of said first angle of arrival and a third angle of arrival of said first signal at the first platform and a third platform, respectively, the first platform being remote from the third platform;

determining said initial location from a third intersection of said third angle of arrival and a fourth angle of arrival of said first signal at the third platform and a fourth platform, respectively; and

determining said initial location from first and second azimuths of first and second angles of arrival of said first signal at the third platform at first and second times, respectively.

9. A method as claimed in claim 6, wherein said receiving said initial location estimate step comprises performing one of the steps of:

determining said initial location from a first intersection of said first angle of arrival and a second angle of arrival of said first signal at the first and second platforms;

determining said initial location from a second intersection of a first angle of arrival and a second angle of arrival of said first signal at a third platform; and

determining said initial location from a third intersection of a third and a fourth angle of arrival of said first signal at the third and a fourth platform.

10. A method as claimed in claim 6, wherein said receiving said initial location estimate comprises performing one of the steps of:

determining said initial location from a first intersection of a first pointing direction with a ground surface, said first pointing direction corresponding to a first azimuth and a first elevation of said first angle of arrival of said first signal at the first platform; and

determining said initial location from a second intersection of a second pointing direction with the ground surface, said second pointing direction corresponding to a first azimuth and a first elevation of a third angle of arrival of said first signal at a third platform.

11. A method as claimed in claim 10, wherein, said predetermined altitide reference is sea level.

12. A method for locating a first emitter comprising the steps of:

receiving an initial location estimate of the first emitter;

receiving a first altitude estimate of the first emitter, wherein the first altitude estimate is an estimate of an altitude of the first emitter above sea level in relation to a predetermined altitude reference;

receiving at a first platform and a second platform at a first point in time a first signal from the first emitter;

determining a first time difference of arrival of the first signal at the first and second platforms at the first point in time;

determining a first location estimate of the first emitter using said first time difference of arrival of the first signal at the first and second platforms at the first point in time, said inital location of the first emitter and said first altitude estimate of the first emitter.

13. A method as claimed in claim 12, further comprising the steps of:

receiving at least one of the first and second platforms a first angle of arrival and a second angle of arrival of the first signal from the first emitter.

14. A method as claimed in claim 13, wherein said first and second angles of arrival are received at the first and second platforms, respectively, wherein said first and second angles of arrival are used in said determining said first location estimate step.

15. A method as claimed in claim 13, wherein said receiving said initial location estimate comprises the step of:

determining said initial location estimate using said first and second angles of arrival of the first signal from the first emitter.

16. A method as claimed in claim 12, wherein said determining said first location estimate comprises performing one of a least squares analysis and a Kalman filter analysis using said first time difference of arrival of the first signal at the first and second platforms, said initial location of the first emitter and said first altitude estimate of the first emitter.

17. A method as claimed in claim 12, wherein said determining said first location estimate comprises performing a least squares analysis using said first time difference of arrival of the first signal at the first and second platforms, said initial location of the first emitter and said first altitude estimate of the first emitter, said method further comprising the steps of:

receiving at two of the first platform, the second platform, a third platform and a fourth platform a second signal from the first emitter;

determining a second time difference of arrival of the second signal at said two of the first, second, third and fourth platforms; and

determining a second location estimate of the first emitter, said determining said second location step comprising the step of performing a Kalman filter analysis using at least one of said first location estimate, said second time difference of arrival of the second signal at said two of the first, second, third and fourth platforms, said initial location of the first emitter and said first altitude estimate of the first emitter.

18. A method as claimed in claim 17, further comprising the step of determining a first location uncertainty, wherein said performing said Kalman filter step further includes using said first location uncertainty.

19. A method as claimed in claim 12, further comprising:

retrieving said first altitude estimate from a terrain database based on the first location estimate.

20. A method as claimed in claim 12, wherein said predetermined altitude reference is sea level.