Set mode passive location in TOA/TDOA modes

• US 8,179,316 B2
• Filed: 12/13/2007
• Issued: 05/15/2012
• Est. Priority Date: 12/15/2006
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Allam, Sébastien, De Gramont, Emmanuel
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US12/519,324
• Publication Number:
  US 20100141529A1
• Time in Patent Office: 1,615 Days
• Field of Search: 342/387
• US Class Current: 342/387
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• 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
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

The present invention addresses the resolving of the problems associated with the passive location of targets in TOA (Time of Arrival) or TDOA (Time Difference of Arrivals) mode. The method of passively locating a target in TOA or TDOA mode implements a meshing (subdivision) into blocks of the space in which the location area is situated. The set of the blocks that form this mesh is analyzed iteratively. On each iteration, each block of interest is subdivided into smaller identical subblocks. A block of interest is, according to the invention, a block including at least one point belonging to the location area being sought for which the shape is to be determined. The iterative process is stopped when the size of the subblocks obtained on the current iteration corresponds to the desired resolution. The invention applies in particular to the 2D or 3D location systems that include TOA and TDOA modes or mixed modes.

Claims

1. A method of passively locating a target in TOA or TDOA mode comprising the steps of:

subdividing into blocks a space in which a location area is situated; and

iteratively performing on the blocks, until a predetermined criterion is obtained, the steps of;

searching within each block for a presence of at least one point belonging to the location area;

excluding from the blocks any blocks that do not contain a point that belongs to the location area;

resubdividing into subblocks any blocks that contain a point that belongs to the location area;

replacing the blocks by the subblocks,

wherein each iteration increases an accuracy of defining the location area, and the method further comprises the steps of;

forming a current selection from a first block that corresponds to an a priori search space;

forming a current list from the first block;

iteratively performing the steps of;

subdividing each block of a current list into a first, second, third, and fourth adjoining subblocks;

searching the first, second, third, and fourth subblocks for at least one point forming part of the location area, to produce searched subblocks;

selecting the searched subblocks having at least one point forming part of the location area, to produce selected subblocks;

updating the current list to obtain an updated list, by performing the steps of;

deleting blocks that have no selected subblocks; and

replacing blocks not deleted by the first, second, third, and fourth subblocks to form an updated current list,

wherein;

the iteratively performed steps comprise a test to compare a resolution of the blocks that constitute the updated current list; and

the iteratively performed steps stop when the resolution is greater than a desired resolution.

2. The method as claimed in claim 1, wherein in a TOA 2D single transmitter location mode, a subblock is selected if the subblock satisfies a criterion determined in accordance with the following relationship:

3. The method as claimed in claim 1, wherein in a TDOA 2D single secondary receiver location mode, a subblock is selected if the subblock satisfies a criterion determined in accordance with the following relationship:

4. The method as claimed in claim 1, wherein in a TOA 3D single transmitter location mode, a subblock is selected if the subblock satisfies a criterion determined in accordance with the following relationship:

5. The method as claimed in claim 1, wherein in a TDOA 3D single secondary receiver location mode, a subblock is selected if a point of the subblock satisfies a criterion determined in accordance with the following relationship:

6. The method as claimed in claim 1, wherein in a TOA multiple transmitters location mode or in a TDOA multiple secondary receivers location mode, a subblock is selected if the subblock satisfies a criterion determined in accordance with the following relationship;

7. The method as claimed in claim 1, wherein in a TOA multiple transmitters location mode or in TDOA multiple secondary receivers location mode, for a number N of transmitters or secondary receivers constituting the TOA or TDOA location system concerned, respectively, a subblock is selected if the subblock satisfies a criterion A determined in accordance with the following relationship:

8. The method as claimed in claim 6, wherein the method is used for the passive location of the target by a global system comprising individual single transmitter and single secondary receiver systems and operating in a mixed TOA/TDOA mode.

9. The method as claimed in claim 7, wherein the method is used for the passive location of the target by a global system comprising individual single transmitter and single secondary receiver systems and operating in a mixed TOA/TDOA mode.