Locating an object of interest using back tracked-rays derived from multipath signals

• US 7,212,160 B2
• Filed: 02/17/2004
• Issued: 05/01/2007
• Est. Priority Date: 02/17/2004
• Status: Active Grant

• Current Assignee: Polytechnic University (New York University)
• Original Assignee: Polytechnic University (New York University)
• Inventors: Sugla, Binay, Bertoni, Henry
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): MULL, FRED H
• Application Number:
  US10/780,139
• Publication Number:
  US 20050179591A1
• Time in Patent Office: 1,169 Days
• Field of Search: 342/453
• US Class Current: 342/453
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial

Abstract

Multipath signals (rays) emanating from an object of interest are processed to locate the object. Multipath signals may be accepted, screened, and associated with a specific object by an observer. Information (time, amplitude, and angle information) may be recorded for each ray. A set of incoming rays associated with a signal from an object are traced back toward the emanating object generating traceback ray segments. Candidate crossings of ray traceback segments are tested for time and/or amplitude consistency with ray information, and candidate crossings with inconsistent amplitude and/or time information may be eliminated from consideration. If there is only one candidate crossing remaining, it may be used to define the object location. Otherwise, the remaining crossings may be grouped, each grouping with a crossing cardinality, and location. Multiple crossings of multiple rays may be grouped into clusters with a cluster cardinality and diameter. The location may then be determined using crossing cardinality, cluster cardinality, and/or cluster diameter.

Claims

1. A method for locating an object of interest, the method comprising:

a) accepting at an observation point, signals emanating from the object;

b) determining, for each of the accepted signals, a direction of arrival;

c) determining at least two trace-back rays from the observation point using solely the direction of arrival of signals and topographical information;

d) determining at least one candidate location at crossings of two or more trace-back rays;

e) determining a set of final candidate locations from the determined candidate locations; and

f) determining the location of the object of interest using the set of final candidate locations, wherein the act of determining the location of the object of interest using the set of final candidate locations includes

i) defining an area of accuracy including at least one candidate location from the set of final candidate locations, and

ii) determining the location of the object of interest using the defined area of accuracy,

wherein at least two areas of accuracy are defined, and

wherein the act of determining the location of the object of interest uses a cardinality of each of the areas of accuracy.

2. The method of claim 1 wherein the area of accuracy is a circle of accuracy.

3. A method for locating an object of interest, the method comprising:

a) accepting at an observation point, signals emanating from the object;

b) determining, for each of the accepted signals, a direction of arrival;

c) determining at least two trace-back rays from the observation point using solely the direction of arrival of signals and topographical information;

d) determining at least one candidate location at crossings of two or more trace-back rays;

e) determining a set of final candidate locations from the determined candidate locations; and

f) determining the location of the object of interest using the set of final candidate locations, wherein the act of determining the location of the object of interest using the set of final candidate locations includes

i) defining an area of accuracy including at least one candidate location from the set of final candidate locations, and

ii) determining the location of the object of interest using the defined area of accuracy,

wherein at least two areas of accuracy are defined, and

wherein the act of determining the location of the object of interest includes

A) defining at least one cluster, each cluster including locations of each of at least two areas of accuracy, and

B) determining the location of the object of interest using the at least one cluster.

4. The method of claim 3 wherein the act of determining the location of the object of interest uses a location of the at least one cluster.

5. The method of claim 3 wherein at least two clusters are defined, each of the at least two clusters having an associated diameter and

wherein the act of determining the location of the object of interest uses the diameter of each of the at least two clusters.

6. The method of claim 3 wherein at least two clusters are defined, each of the at least two clusters having an associated cluster cardinality, and

wherein the act of determining the location of the object of interest uses the cluster cardinality of each of the at least two clusters.

7. The method of claim 3 wherein at least two clusters are defined, each of the at least two clusters having both an associated diameter and an associated cluster cardinality, and

wherein the act of determining the location of the object of interest uses the cluster cardinality and the diameter of each of the at least two clusters.

8. The method of claim 3 wherein at least two clusters are defined, each of the at least two clusters having

associated areas of accuracy, each of the associated areas of accuracy having a cardinality,

an associated diameter, and

an associated cluster cardinality, and

wherein the act of determining the location of the object of interest uses

the cardinalities of the areas of accuracy associated with each of the at least two clusters,

the diameters associated with each of the at least two clusters, and

the cluster cardinalities associated with each of the at least two clusters.

9. A method for locating an object of interest, the method comprising:

a) accepting at an observation point, signals emanating from the object;

b) determining, for each of the accepted signals, a direction of arrival;

c) determining at least two trace-back rays from the observation point using solely the direction of arrival of signals and topographical information;

d) determining at least one candidate location at crossings of two or more trace-back rays;

e) determining a set of final candidate locations from the determined candidate locations; and

f) determining the location of the object of interest using the set of final candidate locations,

wherein the act of determining the location of the object of interest using the set of final candidate locations includes

i) defining a volume of accuracy including at least one candidate location from the set of final candidate locations, and

ii) determining the location of the object of interest using the defined volume of accuracy.

10. The method of claim 9 wherein the volume of accuracy is a sphere of accuracy.

11. The method of claim 9 wherein at least two volumes of accuracy are defined, and

wherein the act of determining the location of the object of interest uses a cardinality of each of the volumes of accuracy.

12. The method of claim 9 wherein at least two volumes of accuracy are defined, and

wherein the act of determining the location of the object of interest includes

A) defining at least one cluster, each cluster including locations of each of at least two volumes of accuracy, and

B) determining the location of the object of interest using the at least one cluster.

13. The method of claim 12 wherein the act of determining the location of the object of interest uses a location of the at least one cluster.

14. The method of claim 12 wherein at least two clusters are defined, each of the at least two clusters having an associated diameter and

wherein the act of determining the location of the object of interest uses the diameter of each of the at least two clusters.

15. The method of claim 12 wherein at least two clusters are defined, each of the at least two clusters having an associated cluster cardinality, and

wherein the act of determining the location of the object of interest uses the cluster cardinality of each of the at least two clusters.

16. The method of claim 12 wherein at least two clusters are defined, each of the at least two clusters having both an associated diameter and an associated cluster cardinality, and

wherein the act of determining the location of the object of interest uses the cluster cardinality and the diameter of each of the at least two clusters.

17. The method of claim 12 wherein at least two clusters are defined, each of the at least two clusters having

associated volumes of accuracy, each of the associated volumes of accuracy having a cardinality,

an associated diameter, and

an associated cluster cardinality, and

wherein the act of determining the location of the object of interest uses

the cardinalities of the volumes of accuracy associated with each of the at least two clusters,

the diameters associated with each of the at least two clusters, and

the cluster cardinalities associated with each of the at least two clusters.

18. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signals using a physical characteristic of the signals.

19. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signals using a bandpass frequency filter.

20. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signals using a signal amplitude threshold.

21. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signals using a signal-to-noise threshold.

22. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signals using an angle of arrival threshold.

23. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signals using a relative time of arrival threshold.

24. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signal using information carried by the signals.

25. The method of claim 9 wherein the act of accepting at an observation point, signals emanating from the object, includes screening the signal using a unique identifier carried by the signals and associated with the object.

26. The method of claim 9 wherein the act accepting at an observation point, signals emanating from the object, includes screening the signal using both (A) a physical characteristic of the signals, and (B) information carried by the signals.

27. The method of claim 9 further comprising determining, for each of the accepted signals, (A) an associated time of arrival, and (B) an amplitude.

28. The method of claim 9 wherein the topographical information includes sources of signal reflection.

29. The method of claim 9 wherein the topographical information includes sources of signal diffraction.

30. The method of claim 9 wherein the topographical information includes building surfaces.

31. The method of claim 9 wherein the topographical information includes signal attenuation information.

32. The method of claim 9 wherein the act of determining a set of final candidate locations from the determined candidate locations includes eliminating at least some of the candidate locations using times of arrival associated with the signals from which trace-back rays were determined.

33. The method of claim 32 wherein a candidate location is eliminated if the times of arrival are inconsistent with expected times of arrival.

34. The method of claim 33 wherein a time of arrival is determined to be inconsistent with an expected time of arrival if they differ by more than a threshold difference.

35. The method of claim 9 wherein the act of determining a set of final candidate locations from the determined candidate locations includes eliminating at least some of the candidate locations using amplitudes associated with the signals from which trace-back rays were determined.

36. The method of claim 35 wherein a candidate location is eliminated if the amplitudes are inconsistent with expected amplitudes.

37. The method of claim 35 wherein an amplitude is determined to be inconsistent with an expected amplitude if they differ by more than a threshold difference.

38. The method of claim 9 wherein the act of determining a set of final candidate locations from the determined candidate locations includes eliminating at least some of the candidate locations using both times of arrival and amplitudes associated with the signals from which trace-back rays were determined.

39. The method of claim 9 wherein the act of determining a set of final candidate locations from the determined candidate locations includes

i) determining if times of arrival of each of the accepted signals are inconsistent with expected times of arrival;

ii) if it was determined that the times of arrival are inconsistent with expected times of arrival, then excluding the candidate location from the set of final candidate locations; and

iii) if it was determined that the times of arrival are not inconsistent with expected times of arrival, then

A) determining if amplitudes of each of the accepted signals are inconsistent with expected amplitudes, and

B) if it was determined that the amplitudes are inconsistent with expected amplitudes, then excluding the candidate location from the set of final candidate locations.

40. Apparatus for locating an object of interest, the apparatus comprising:

a) means for accepting at an observation point, signals emanating from the object;

b) means for determining, for each of the accepted signals, a direction of arrival;

c) means for determining at least two trace-back rays from the observation point using solely the direction of arrival of signals and topographical information;

d) means for determining at least one candidate location at crossings of two or more trace-back rays;

e) means for determining a set of final candidate locations from the determined candidate locations; and

f) means for determining the location of the object of interest using the set of final candidate locations, wherein the means for determining the location of the object of interest using the set of final candidate locations include

i) means for defining an area of accuracy including at least one candidate location from the set of final candidate locations, and

ii) means for determining the location of the object of interest using the defined area of accuracy,

wherein at least two areas of accuracy are defined, and

wherein the means for determining the location of the object of interest use a cardinality of each of the areas of accuracy.

41. Apparatus for locating an object of interest, the apparatus comprising:

a) means for accepting at an observation point, signals emanating from the object;

b) means for determining, for each of the accepted signals, a direction of arrival;

c) means for determining at least two trace-back rays from the observation point using solely the direction of arrival of signals and topographical information;

d) means for determining at least one candidate location at crossings of two or more trace-back rays;

e) means for determining a set of final candidate locations from the determined candidate locations; and

f) means for determining the location of the object of interest using the set of final candidate locations, wherein the means for determining the location of the object of interest using the set of final candidate locations include

i) means for defining an area of accuracy including at least one candidate location from the set of final candidate locations, and

ii) means for determining the location of the object of interest using the defined area of accuracy,

wherein at least two areas of accuracy are defined, and

wherein the means for determining the location of the object of interest include

A) means for defining at least one cluster, each cluster including locations of each of at least two areas of accuracy, and

B) means for determining the location of the object of interest using the at least one cluster.

42. Apparatus for locating an object of interest, the apparatus comprising:

a) means for accepting at an observation point, signals emanating from the object;

b) means for determining, for each of the accepted signals, a direction of arrival;

c) means for determining at least two trace-back rays from the observation point using solely the direction of arrival of signals and topographical information;

d) means for determining at least one candidate location at crossings of two or more trace-back rays;

e) means for determining a set of final candidate locations from the determined candidate locations; and

f) means for determining the location of the object of interest using the set of final candidate locations, wherein the means for determining the location of the object of interest using the set of final candidate locations include

i) means for defining a volume of accuracy including at least one candidate location from the set of final candidate locations, and

ii) means for determining the location of the object of interest using the defined volume of accuracy.