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

• US 5,999,116 A
• Filed: 07/14/1998
• Issued: 12/07/1999
• 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:
  US09/114,921
• Time in Patent Office: 511 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 minimum of one signal source, said system comprising:

(a) a plurality of at least two fixed ground stations, each containing a means for receiving the signal transmissions from the mobile signal source, the receiving means being located very precisely at known coordinates (x₁,y₁,z₁) and (x₂,y₂,z₂), means for measuring precisely time of arrival of the source signal transmissions, means to decode the address contained in a source signal transmission, and means for time synchronizing said ground stations;

(b) a data communications link for transmitting time of arrival and associated source signal address from each time of arrival measuring/signal decoding means to a central data processor;

(c) a surveillance/identification processor for computing time difference of arrival using the time of arrival and associated source signal address data received from the ground station means, computes line of position when a signal sources transmissions is received by two receiving means, computes 2 dimensional multilateration position (x, y) when a signal source transmission is received by three receiving means, computes 3 dimensional multilateration position (x,y,z) when a signal source transmission is received by a minimum of four receiving means, provides identification of targets detected by any second surveillance system by correlating system measured time difference of arrival/source signal address to the second surveillance system target data, provides position aiding of any 2 dimensional and 3 dimensional position using system provided line of position from the source transmissions.

2. A method for determining the 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 the second surveillance system determined track position, the method comprising the steps of:

(a) measuring the time of arrival of source signal transmissions received at two fixed ground station means;

(b) decoding the signal source identifying address data contained in each source transmission;

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

(d) computing the predicted positions from position reports provided by a second surveillance system that correspond to the times that the system measured time difference of arrival were made;

(e) computing expected time difference of arrival s that correspond to the second surveillance source predicted position and the location of the system receiving means;

(f) defining an uncertainty window for each expected time difference of arrival;

(g) establishing correlation when a minimum of two system measured time difference of arrival s fall within a time uncertainty window;

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

3. A method for computing a 2 dimensional position from line of position to provide position aiding when a second surveillance systems fails to update a minimum of one track position, the method comprising the steps of:

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

(b) measuring time of arrivals for a source signal transmission received at two ground station means;

(c) decoding the address data contained in the source transmission;

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

(e) computing the line of position based on time difference of arrival measurements;

(f) correlating the source signal line of position to the second surveillance system position track by matching address associated to the line of position update to the identification of the track;

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

(g) computing a 2 dimensional position update by determining where the line of position intersects the center of the road;

(h) computing the track smoothed position using the 2 dimensional position update.