Method and apparatus for improving the surveillance coverage and target identification in a radar based surveillance system

• US 6,211,811 B1
• Filed: 11/03/1999
• Issued: 04/03/2001
• Est. Priority Date: 07/14/1998
• Status: Expired due to Term

• Current Assignee: Omnipol as
• Original Assignee: Rannoch Corporation (General Dynamics Corporation)
• Inventors: Evers, Carl A.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/432,757
• Time in Patent Office: 517 Days
• Field of Search: 342/29, 342/31, 342/32, 342/33, 342/36, 342/37, 342/59, 342/450, 342/451, 342/453, 342/456, 342/463, 342/465
• US Class Current: 342/36
• CPC Class Codes: G01S 2013/916 Airport surface monitoring [ASDE]
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

The surveillance system provides a means to measure Time Difference of Arrival (TDOA) and decode identification of signal source transmissions. TDOA and identification information received from a minimum of two receiving means is used to supplement non-cooperative surveillance systems (e.g., primary radar, acoustic sensors) with target identification. The system uses a Line Of Position technique to determine position. The system can be implemented as a standalone multilateration surveillance system, which provides signal source position determination when reception is available from a minimum of two receiving means. The system provides position aiding when implemented to supplement non-cooperative surveillance systems.

Claims

1. A system for determining the line of position and identification of a mobile signal source, said system comprising:

at least two ground stations, each of said at least two ground stations comprising;

means for receiving signal transmissions from the mobile signal source, the means for receiving being located at known coordinates (x₁,y₁,z₁) and (x₂, y₂, z₂),

means for measuring time of arrival of the signal transmissions,

means for decoding an address contained in the signal transmission, and

means for time synchronizing said ground stations;

a data communications link, coupled to the at least two ground stations, for transmitting time of arrival and associated source signal address from each of the at least two ground stations; and

a surveillance/identification processor, coupled to the data communications link, for receiving the time of arrival and associated source signal address from each of the at least two ground stations from the data communications link and computing time difference of arrival using the time of arrival and associated source signal address data received from each of the at least two ground stations, computing line of position when a signal source transmissions are received by at least two ground stations, computing two-dimensional multilateration position (x,y) when a signal source transmission is received by at least three ground stations, computing three-dimensional multilateration position (x,y,z) when a signal source transmission is received by at least four ground stations, providing identification of targets detected by any second surveillance system by correlating system measured time difference of arrival/source signal address to second surveillance system target data, and providing position aiding of any two-dimensional and three-dimensional position using system provided line of position from the signal transmissions.

2. A method for determining identification of any second surveillance system target track with unknown identification by correlating system measured time difference of arrival and associated source signal address to a second surveillance system determined track position, the method comprising the steps of:

measuring time of arrival of source transmissions received at two ground stations;

decoding the signal source address from identifying address data contained in each source transmission;

computing the system measured time difference of arrival between two time of arrivals measured for each source transmission;

computing predicted positions from position reports provided by the second surveillance system corresponding to times when the system measured time difference of arrival were made;

computing expected time difference of arrivals corresponding to the predicted positions from position reports provided by the second surveillance system and the location of the ground stations;

defining a time uncertainty window for each expected time difference of arrival;

establishing a correlation when a minimum of two system time difference of arrivals fall with a time uncertainty window; and

Assigning the source signal address associated with the correlated time difference of arrival to the second surveillance system track number.

3. A method for establishing a two-dimensional position from a line of position to provide position aiding when a second surveillance system fails to update a minimum of one track position, the method comprising the steps of:

performing correlation of system measured time difference of arrival for source transmissions to the second surveillance system measured position track of a source;

measuring time of arrivals for a source transmission received at two ground stations;

decoding address data contained in the source transmission;

computing a system measured time difference of arrival between two time of arrivals measured for each source transmission;

computing a source line of position based on time difference of arrival measurements;

correlating the source line of position to the second surveillance system position track by matching an address associated to the line of position update to an identification of the track;

determining the road that the track is on by matching the track position to a road in a map database;

computing a two-dimensional position update by determining where the line of position intersects the center of the road; and

computing the track smoothed position using two-dimensional position update.

4. A system for determining the line of position and identification of a mobile signal source, said system comprising:

at least two ground stations, each of said at least two ground stations comprising;

means for receiving signal transmissions from the mobile signal source, the means for receiving being located known coordinates,

means for measuring time of arrival of the signal transmissions,

means for decoding an address contained in the signal transmission, and

means for time synchronizing said ground stations;

a data communications link, coupled to the at least two ground stations, for transmitting time of arrival and associated source signal address from each of the at least two ground stations; and

a processor, coupled to the data communications link, for receiving the time of arrival and associated source signal address from each of the at least two ground stations from the data communications link and computing time difference of arrival using the time of arrival and associated source signal address data received from each of the at least two ground stations.

5. The system of claim 4, wherein said processor computes line of position when a signal source transmissions are received by at least two ground stations.

6. The system of claim 5, wherein said processor computes two-dimensional multilateration position when a signal source transmission is received by at least three ground stations.

7. The system of claim 6, wherein said processor computes three-dimensional multilateration position when a signal source transmission is received by at least four ground stations.

8. The system of claim 7, wherein said processor computes identification of targets detected by any second surveillance system by correlating system measured time difference of arrival/source signal address to second surveillance system target data.

9. The system of claim 8, wherein said processor provides position aiding of any two-dimensional and three-dimensional position using system-provided line of position from the signal transmissions.