SET MODE PASSIVE LOCATION IN TOA/TDOA MODES

US 20100141529A1
Filed: 12/13/2007
Published: 06/10/2010
Est. Priority Date: 12/15/2006
Status: Active Grant

First Claim

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

subdiving 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.

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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.

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12 Claims

1. A method of passively locating a target in TOA or TDOA mode comprising the steps of:
- subdiving 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.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- - 2. The method as claimed in claim 1, further comprising an initial step of forming an initial selection from a first block that corresponds to an a priori search space.
  - 3. The method as claimed in claim 1, wherein the predetermined criterion comprises a desired resolution provided by the subblocks.
  - 4. The method as claimed in claim 1, further comprising 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 subblock;
      
      searching 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,
5. The method as claimed in claim 4, 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:
- $0 \in J ([X^{j}]) with J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[a]}^{2}} + \frac{{[y^{j}]}^{2}}{{[b]}^{2}} - 1],$ wherein;
  
  a=R_b/2;
  
  b=√
  
  {square root over (a²−
  
  L²/4)};
  
  L is a length from a transmitter to a receiver;
  
  R_bis a sum of a length from the transmitter to the target, and a length from the target to the receiver;
  
  x^jand y^jare Cartesian coordinates of a subblock j, for a frame of reference centered on a middle of a line segment linking the source and the receiver; and
  
  [X^j] is a j-th subblock of block [X].
6. The method as claimed in claim 4, 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:
- $0 \in J ([X^{j}]) with J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[c]}^{2}} - \frac{{[y^{j}]}^{2}}{{[d]}^{2}} - 1],$ wherein;
  
  c=R_d1/2;
  
  d=√
  
  {square root over (L²/4−
  
  c²)};
  
  L is a length from a first receiver to a second receiver;
  
  R_d1is a difference between a length from the transmitter to the second receiver, and a length from the transmitter to the first receiver;
  
  x^jand y^jare Cartesian coordinates of a subblock j, for a frame of reference centered on a middle of a line segment linking the first receiver and the second receiver; and
  
  [X^j] is a j-th subblock of block [X].
7. The method as claimed in claim 4, 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:
- $0 \in J ([X^{j}]) with J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[a]}^{2}} + \frac{{[y^{j}]}^{2}}{{[b]}^{2}} + \frac{{[z^{j}]}^{2}}{{[b]}^{2}} - 1]$ wherein;
  
  a=R_b/2;
  
  b=√
  
  {square root over (a²−
  
  L²/4)};
  
  L is a length from a transmitter to a receiver;
  
  R_bis a sum of a length from the transmitter to the target, and a length from the target to the receiver;
  
  x^j, y^jand z^jare Cartesian coordinates of a subblock j, for a frame of reference centered on a middle of a line segment linking the source and the receiver; and
  
  [X^j] is a j-th subblock of block [X].
8. The method as claimed in claim 4, 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:
- $0 \in J ([X^{j}]) with J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[c]}^{2}} - \frac{{[y^{j}]}^{2}}{{[d]}^{2}} - \frac{{[z^{j}]}^{2}}{[d^{2}]} - 1],$ wherein;
  
  c=R_d1/2;
  
  d=√
  
  {square root over (L²/4−
  
  c²)};
  
  L is a length from a first receiver to a second receiver;
  
  R_d1is a difference between a length from the transmitter to the second receiver, and a length from the transmitter to the first receiver;
  
  x^j, y^jand z^jare Cartesian coordinates of a subblock j, for a frame of reference centered on a middle of a line segment linking the first receiver and the second receiver; and
  
  [X^j] is a j-th subblock of block [X].
9. The method as claimed in claim 4, 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;
- $A = \sum_{j = 1}^{N} a_{j} = N$ wherein;
  
  N is a number of transmitters or secondary receivers that constitute the TOA or TDOA location system concerned, respectively; and
  
  the terms a_jare determined in accordance with the following relationships;
  
  $a_{1} = {\begin{matrix} 1 if 0 \in J_{1} ([X]) \\ 0 else; \end{matrix} a_{2} = {\begin{matrix} 1 if 0 \in J_{2} ([X]) \\ 0 else; \end{matrix} \dots a_{N} = {\begin{matrix} 1 if 0 \in J_{N} ([X]) \\ 0 else, \end{matrix}$ wherein;
  
  for each individual single transmitter or single secondary receiver system, a quantity J_j([X]) is determined in accordance with the following relationships;
  
  $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[a]}^{2}} + \frac{{[y^{j}]}^{2}}{{[b]}^{2}} - 1] in^{``} TOA 2 D^{″} mode;$ $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[a]}^{2}} + \frac{{[y^{j}]}^{2}}{{[b]}^{2}} + \frac{{[z^{j}]}^{2}}{{[b]}^{2}} - 1] in^{``} TOA 3 D^{″} mode;$ $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[c]}^{2}} - \frac{{[y^{j}]}^{2}}{{[d]}^{2}} - 1] in^{``} TDOA 2 D^{″} mode;$ $and$ $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[c]}^{2}} - \frac{{[y^{j}]}^{2}}{{[d]}^{2}} - \frac{{[z^{j}]}^{2}}{{[d]}^{2}} - 1] in^{``} TDOA 3 D^{″} mode,$ wherein;
  
  a=R_b/2;
  
  b=√
  
  {square root over (a²−
  
  L_TOA²/4)};
  
  c=R_d1/2;
  
  d=√
  
  {square root over (L_TDOA²/4−
  
  c²)};
  
  L_TOAis a length from a transmitter to a first receiver;
  
  L_TDOAis a length from a first receiver to a second receiver;
  
  R_bis a sum of a length from the transmitter to the target, and a length from the target to the receiver;
  
  R_d1is a difference between a length from the transmitter to the second receiver, and a length from the transmitter to the first receiver;
  
  x^j, y^jand z^jare Cartesian coordinates of a subblock j, for a frame of reference centered on a middle of a line segment linking the source and the receiver in TOA mode, or for a frame of reference centered on a middle of a line segment linking the first receiver and the second receiver in TDOA mode, respectively; and
  
  [X^j] is a j-th subblock of block [X].
10. The method as claimed in claim 4, 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:
- $A = \sum_{j = 1}^{N} a_{j} \geq M$ wherein;
  
  M is a pre-determined number, less than N, of transmitters or secondary receivers constituting the TOA or TDOA location system concerned, respectively; and
  
  the terms a_jare determined in accordance with the following relationships;
  
  $a_{1} = {\begin{matrix} 1 if 0 \in J_{1} ([X]) \\ 0 else; \end{matrix} a_{2} = {\begin{matrix} 1 if 0 \in J_{2} ([X]) \\ 0 else; \end{matrix} \dots a_{N} = {\begin{matrix} 1 if 0 \in J_{N} ([X]) \\ 0 else, \end{matrix}$ wherein;
  
  for each individual single transmitter or single secondary receiver system, a quantity J_j([X]) is determined in accordance with the following relationships;
  
  $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[a]}^{2}} + \frac{{[y^{j}]}^{2}}{{[b]}^{2}} - 1] in^{``} TOA 2 D^{″} mode;$ $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[a]}^{2}} + \frac{{[y^{j}]}^{2}}{{[b]}^{2}} + \frac{{[z^{j}]}^{2}}{{[b]}^{2}} - 1] in^{``} TOA 3 D^{″} mode;$ $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[c]}^{2}} - \frac{{[y^{j}]}^{2}}{{[d]}^{2}} - 1] in^{``} TDOA 2 D^{″} mode;$ $and$ $J ([X^{j}]) = [\frac{{[x^{j}]}^{2}}{{[c]}^{2}} - \frac{{[y^{j}]}^{2}}{{[d]}^{2}} - \frac{{[z^{j}]}^{2}}{{[d]}^{2}} - 1] in^{``} TDOA 3 D^{″} mode,$ wherein;
  
  a=R_b/2;
  
  b=√
  
  {square root over (a²−
  
  L_TOA²/4)};
  
  c=R_d1/2;
  
  d=√
  
  {square root over (L_TDOA²/4−
  
  c²)};
  
  L_TOAis a length from a transmitter to a first receiver;
  
  L_TDOAis a length from a first receiver to a second receiver;
  
  R_bis a sum of a length from the transmitter to the target, and a length from the target to the receiver;
  
  R_d1is a difference between a length from the transmitter to the second receiver, and a length from the transmitter to the first receiver;
  
  x^j, y^jand z^jare Cartesian coordinates of a subblock j, for a frame of reference centered on a middle of a line segment linking the source and the receiver in TOA mode, or for a frame of reference centered on a middle of a line segment linking the first receiver and the second receiver in TDOA mode, respectively; and
  
  [X^j] is a j-th subblock of block [X].
11. The method as claimed in claim 9, 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.
12. The method as claimed in claim 10, 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.

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Current Assignee
Thales SA
Original Assignee
Thales SA
Inventors
Allam, Sebastien, De Gramont, Emmanuel

Granted Patent

US 8,179,316 B2
Time in Patent Office

Days
Field of Search
US Class Current

342/387
CPC Class Codes

G01S 5/06   Position of source determin...

G01S 5/10   Position of receiver fixed ...

G01S 5/14   Determining absolute distan...

SET MODE PASSIVE LOCATION IN TOA/TDOA MODES

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SET MODE PASSIVE LOCATION IN TOA/TDOA MODES

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