Method and system for elliptical-based surveillance

• US 20070040734A1
• Filed: 05/08/2006
• Published: 02/22/2007
• Est. Priority Date: 03/05/1999
• Status: Active Grant

• Current Assignee: Omnipol as
• Original Assignee: ERA Systems Corporation (General Dynamics Corporation)
• Inventors: Breen, Thomas, Evers, Carl, Xie, Yue
• Granted Patent: US 7,477,193 B2
• Time in Patent Office: Days
• US Class Current: 342/126
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 2013/916 Airport surface monitoring [ASDE]
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations

Abstract

A method and system are provided for performing elliptical-based and hybrid surveillance, performing false target detection and resolution, and performing integrity monitoring using one or more receiving and transmitting elements time synchronized to a common precision time reference, and a central workstation. Antennas for transmitting and receiving elements are located at known positions separated from one another. At a given time, one of the transmitting elements transmits an interrogation signal to one or more targets, which respond to the interrogation with a reply transmission, received by one or more receiving elements. The central workstation calculates each target'"'"'s ellipse of position with respect to each receiving element, using the interrogator element time of interrogation measurement and each receiving element'"'"'s time of arrival measurement for the corresponding reply transmission, and then fuses the elliptical line of positions for each receiving element to compute target positions or augment passive surveillance position. At a scheduled time, the one or more transmitting elements transmit a reference signal to the receiving elements(s). The central workstation uses each of the receiving elements time stamped signals to perform integrity monitoring.

Claims

1. A target position locating system for generating position data for a plurality of targets, the system comprising:

one or more transmitters for transmitting a transmit signal to a target at a transmit signal Time of Transmission (TOT) for each transmitted signal;

one or more system receivers for receiving a target return signal corresponding to each transmit signal and measuring target return signal Time of Arrival (TOA);

a processor for synchronizing a transmit signal TOT and a target return signal TOA measurements to a system precision time reference and correlating a target return signal TOA to a corresponding transmit signal TOT, calculating the Round Trip Delay Time (RTDT) for each correlated transmit signal TOT and return signal TOA, and calculating the target'"'"'s Ellipse of Position (EOP) for each RTDT.

2. The target position locating system of claim 1, wherein the processor further calculates two-dimensional (x,y) target position using the RTDT and EOP data.

3. The target position locating system of claim 1, wherein the processor further calculates three-dimensional (x,y,z) target position using the RTDT and EOP data.

4. The target position locating system of claim 1, wherein the processor further detects false targets using one or more RTDT and EOPs.

5. The target position locating system of claim 1, further comprising:

one or more transmit signal receivers for receiving the transmit signal from the one or more transmitters and determining the transmit signal Time of Transmission (TOT) for each transmitted signal;

wherein the TOT is determined by measuring TOA of the transmit signal from one or more transmit signal receivers and subtracting the known transmission time between a corresponding transmitter and each transmit signal receiver.

6. The target position locating system of claim 5, wherein the transmit signal receivers are precision time synchronized to a common system reference time and have line-of-sight with at least one of one or more transmitters.

7. The target position locating system of claim 6, wherein one or more of satellite-based timing, precision clocks, and reference transmissions are used to synchronize the one or more transmitters.

8. The target position locating system of claim 1, wherein the processor precisely schedules transmit signal TOT and coordinate this schedule with each transmitter.

9. The target position locating system of claim 8, wherein the transmitters and return signal receivers are precision time synchronized to a common system reference time.

10. The target position locating system of claim 1, wherein the return signal receivers are precision time synchronized to a common system reference time.

11. The target position locating system of claim 1, wherein antennas for the one or more return signal receivers and antennas for the one or more the transmitters are separated by a fixed distance at survey positions.

12. The target position locating system of claim 1, wherein target position is calculated from two or more EOPs.

13. A target position locating system for generating position data for a plurality of targets, the system comprising:

one or more transmitters for transmitting a transmit signal to a target and determining the transmit signal Time of Transmission (TOT) for each transmitted signal;

one or more system receivers for receiving a target return signal corresponding to each transmit signal and measuring target return signal Time of Arrival (TOA);

a processor for synchronizing a transmit signal TOT and a target return signal TOA measurements to a system precision time reference, correlating return signal TOA measurements of a return signal received at two or more receivers, calculating Time Difference of Arrival (TDOA) for all combinations of receiver pairs of correlated return signal TOA measurements, and calculating a Line of Position (LOP) for each TDOA for the target.

14. The target position locating system of claim 13, wherein the processor calculates two-dimensional (x,y) target position using the TDOA and LOP data.

15. The target position locating system of claim 13, wherein the processor calculates three-dimensional (x,y,z) target position using the TDOA and LOP data.

16. The target position locating system of claim 13, wherein the processor further detects false targets using one or more TDOA and LOPs.

17. The target position locating system of claim 13, further comprising:

one or more transmit signal receivers for receiving the transmit signal from the one or more transmitters and determining the transmit signal Time of Transmission (TOT) for each transmitted signal;

wherein the TOT is determined by measuring TOA of the transmit signal from one or more transmit signal receivers and subtracting the known transmission time between a corresponding transmitter and each transmit signal receiver.

18. The target position locating system of claim 13, wherein the transmit signal receivers are precision time synchronized to a common system reference time and have line-of-sight with at least one of one or more transmitters.

19. The target position locating system of claim 18, wherein one or more of satellite-based timing, precision clocks, and reference transmissions are used to synchronize the one or more transmitters.

20. The target position locating system of claim 13, wherein the processor precisely schedules transmit signal TOT and coordinate this schedule with each transmitter.

21. The target position locating system of claim 20, wherein the transmitters and return signal receivers are precision time synchronized to a common system reference time.

22. The target position locating system of claim 13, wherein the return signal receivers are precision time synchronized to a common system reference time.

23. The target position locating system of claim 13, wherein antennas for the one or more return signal receivers and antennas for the one or more the transmitters are separated by a fixed distance at survey positions.

24. The target position locating system of claim 13, wherein target position is calculated from one or more EOP and one or more LOP.

25. A target position locating system for generating position data for a plurality of targets, the system comprising:

one or more transmitters for transmitting a transmit signal to a target and determining the transmit signal Time of Transmission (TOT) for each transmitted signal;

one or more system receivers for receiving a target return signal corresponding to each transmit signal and measuring target return signal Time of Arrival (TOA);

a processor for synchronizing a transmit signal TOT and a target return signal TOA measurements to a system precision time reference and correlating a target return signal TOA to a corresponding transmit signal TOT, calculating the Round Trip Delay Time (RTDT) for each correlated transmit signal TOT and return signal TOA, calculating the target'"'"'s Ellipse of Position (EOP) for each RTDT, correlating return signal TOA measurements of a return signal received at two or more receivers, calculating Time Difference of Arrival (TDOA) for all combinations of receiver pairs of correlated return signal TOA measurements, and calculating a Line of Position (LOP) for each TDOA for the target.

26. The target position locating system of claim 25, wherein the processor calculates two-dimensional (x,y) target position using position using RTDT, TDOA, EOP and LOP data.

27. The target position locating system of claim 25, wherein the processor calculates three-dimensional (x,y,z) target position using position using RTDT, TDOA, EOP and LOP data.

28. The target position locating system of claim 25, wherein the processor further detects false targets using one or more RTDT and EOPs.

29. The target position locating system of claim 25, wherein the processor further detects false targets using one or more TDOA and LOPs.

30. The target position locating system of claim 25, further comprising:

one or more transmit signal receivers for receiving the transmit signal from the one or more transmitters and determining the transmit signal Time of Transmission (TOT) for each transmitted signal;

wherein the TOT is determined by measuring TOA of the transmit signal from one or more transmit signal receivers and subtracting the known transmission time between a corresponding transmitter and each transmit signal receiver.

31. The target position locating system of claim 30, wherein the transmit signal receivers are precision time synchronized to a common system reference time and have line-of-sight with at least one of one or more transmitters.

32. The target position locating system of claim 31, wherein one or more of satellite-based timing, precision clocks, and reference transmissions are used to synchronize the one or more transmitters.

33. The target position locating system of claim 25, wherein the processor precisely schedules transmit signal TOT and coordinate this schedule with each transmitter.

34. The target position locating system of claim 33, wherein the transmitters and return signal receivers are precision time synchronized to a common system reference time.

35. The target position locating system of claim 25, wherein the return signal receivers are precision time synchronized to a common system reference time.

36. The target position locating system of claim 25, wherein antennas for the one or more return signal receivers and antennas for the one or more the transmitters are separated by a fixed distance at survey positions.

37. The target position locating system of claim 25, wherein target position is calculated from two or more EOPs.

38. The target position locating system of claim 25, wherein target position is calculated from one or more EOP and one or more LOP.

39. An integrity monitoring system for verifying the surveillance integrity of a target position locating system, the integrity monitoring system comprising:

a synchronizer for synchronizing all integrity transmitter sites to the integrity monitor systems common system precision time reference;

a transmitter for transmitting an integrity signal transmission having a time of transmission (TOT) from one or more integrity transmitter sites to a target position locating system;

a processor for precisely controlling the TOT for two or more integrity transmitter sites, such that the target position locating system will receive an integrity transmissions from each integrity transmitter site and compute an integrity “

ghost”

target position, communicating with the target position locating system and obtaining target position locating system computed TOA and target position data for the integrity “

ghost”

target and targets of opportunity, and calculating target position location system errors in TOA measurement and computed position of the integrity “

ghost”

target.

40. The integrity monitoring system of claim 39, wherein the processor calculates target position location system errors in TOA measurement and computed position for targets of opportunity that are being tracked by the target position location system.

41. The integrity monitoring system of claim 39, wherein the address field of the integrity signal data transmission is set to a common integrity “

ghost”

target address for all integrity transmitter sites.

42. The integrity monitoring system of claim 39, wherein the integrity transmissions have a fixed format and transmission characteristics such that the target position locating system can receive, decode and measure TOA of the integrity transmission.

43. The integrity monitoring system of claim 42, wherein integrity transmitter sites are located to have line-of-sight with one or more target position locating system receiving elements.

44. The integrity monitoring system of claim 39, wherein the integrity “

ghost”

target is used to integrity verify target position locating system receiving elements that have line-of-sight with integrity transmitter sites.

45. The integrity monitoring system of claim 39, wherein the processor computes the position of targets of opportunity using TOA measurements provided by the target position locating system from integrity verified receivers that have been verified by the integrity “

ghost”

transmission, computes the expected target of opportunity TOA values for unverified receivers that decoded and measured TOA data for a target of opportunity, measures error in expected TOA and measured TOA of the unverified receivers.

46. A precision time synchronized transmitter system for generating time correlated return signal for a plurality of targets, the system comprising:

means for transmitting a transmit signal to a target from one or more system transmitter sites;

means for determining the transmit signal Time of Transmission (TOT) for each transmitted signal;

means for receiving at one or more system receiver sites, the target return signal that corresponds to each transmit signal;

means for synchronizing the transmit signal TOT to a common system precision time reference;

means for communicating TOT and transmission content data to a target position locating system; and

means for time scheduling of transmit signal Time of Transmission (TOT) and setting transmission type and transmission content data from a position locating system.

47. The precision time synchronized transmitter system of claim 46, wherein two or more system transmitter sites perform signal transmissions that are coordinated between the sites and sequenced with precise timing.

48. The means precision time synchronizing of claim 47, wherein satellite-based timing or precision clocks or reference transmissions are used to synchronize transmitter sites.

49. The precision time synchronized transmitter system of claim 46, wherein time scheduling of transmit signal Time of Transmission (TOT) and setting transmission type and transmission content data from a position locating system is communicated to the precision time synchronized transmitter system from an external system source.

50. A target position locating system for generating position data for a plurality of targets, the system comprising:

means for receiving at one or more system receiver sites, a target signal from the target corresponding to a transmit signal from the target;

means for measuring target signal Time of Arrival (TOA);

means for decoding target signal data transmissions;

means for synchronizing target signal TOA measurements to a satellite based time reference;

means for correlating return signal TOA measurements of a return signal received at two or more sites;

means for calculating the Time Difference of Arrival (TDOA) for all combinations of receive site pairs of correlated return signal TOA measurements; and

means for calculating the target'"'"'s Line of Position (LOP) for each TDOA;

51. The target position locating system of claim 50, further comprising:

means for calculating the two-dimensional (x,y) and three-dimensional (x,y,z) target position using the TDOA.

52. The target position locating system of claim 50, further comprising:

means for communicating target signal TOA and decoded data transmissions to other surveillance systems.

53. The target position locating system of claim 50, further comprising:

means for receiving and processing target signal TOA and decoded data transmissions from other surveillance systems.

54. The target position locating system of claim 50, wherein the target signal TOA and decoded data transmissions are formatted in a standardized message format.

55. The target position locating system of claim 50, wherein the system receiver sites use satellite network to generate a periodic synchronization timing pulse for defining the start of a TOA measurement period.

56. The target position locating system of claim 50, wherein the system receiver sites uses satellite network to generate the time reference data for each synchronization timing pulse.