Multi target tracking initiation with passive angle measurements

US 6,292,136 B1
Filed: 09/14/1999
Issued: 09/18/2001
Est. Priority Date: 02/27/1997
Status: Expired due to Term

First Claim

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1. A track initiation method for multi target tracking by means of at least two passive sensors, comprising the steps of:

creating strobe tracks for each of the at least two sensors, where said strobe tracks are filtered sets of strobes, belonging to the same target;

calculating strobe track crosses, including a step of calculating 2nd order strobe track crosses;

selecting a strobe track cross as a probable target; and

creating a target track, wherein said step of calculating 2nd order strobe track crosses comprises, for every pair of two said strobe tracks from different said sensors, the steps of;

calculating a distance between said strobe tracks;

rejecting the strobe track combination as a potential strobe track cross if the distance is larger than a predetermined value;

calculating a closest point on each strobe track corresponding to said distance between said strobe tracks;

calculating a cross-to-sensor distance between each closest point and each respective sensor;

rejecting the strobe track combination as a potential strobe track cross if at least one of the cross-to-sensor distances exceeds a range of a corresponding said sensor; and

calculating position and position uncertainty for strobe track crosses of the remaining strobe tracks combinations.

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Abstract

The present invention is in general related to tracking of multiple targets by means of measurements by various sensors. In particular the invention provides procedures for track initiation during multiple target tracking by means of measurements from passive sensors. The invention defines a quality measure for each tentative new target, by which the tentative targets are sorted and selected. The calculation of the parameters of possible targets and their covariance are preferably performed in a recursive manner. The track initiation comprises the steps of creating strobe tracks, calculating strobe track crosses, selecting a strobe track cross as a probable target and creating a target track.

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13 Claims

1. A track initiation method for multi target tracking by means of at least two passive sensors, comprising the steps of:
- creating strobe tracks for each of the at least two sensors, where said strobe tracks are filtered sets of strobes, belonging to the same target;
  
  calculating strobe track crosses, including a step of calculating 2nd order strobe track crosses;
  
  selecting a strobe track cross as a probable target; and
  
  creating a target track, wherein said step of calculating 2nd order strobe track crosses comprises, for every pair of two said strobe tracks from different said sensors, the steps of;
  
  calculating a distance between said strobe tracks;
  
  rejecting the strobe track combination as a potential strobe track cross if the distance is larger than a predetermined value;
  
  calculating a closest point on each strobe track corresponding to said distance between said strobe tracks;
  
  calculating a cross-to-sensor distance between each closest point and each respective sensor;
  
  rejecting the strobe track combination as a potential strobe track cross if at least one of the cross-to-sensor distances exceeds a range of a corresponding said sensor; and
  
  calculating position and position uncertainty for strobe track crosses of the remaining strobe tracks combinations.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- - 2. A track initiation method according to claim 1, wherein the step of calculating strobe tracks crosses, following said step of calculating 2nd order strobe track crosses, further comprises a step of calculating strobe track crosses of order n, wherein n>
    - 2, and wherein each said calculation of strobe track crosses of order n>
      
      2 is based on strobe track crosses of order n−
      
      1.
  - 3. A track initiation method according to claim 2, wherein said step of calculating strobe tracks crosses of order n, where n>
    - 2, further comprises steps of;
4. A track initiation method according to claim 1, wherein, if at least one strobe track is a 2D strobe track, said step of calculating position and position uncertainty is performed according to $X = (\sum$
- i=1n
  
  Pi-1)-1
  
  (∑
  
  i=1n
  
  Pi-1
  
  Fi),
  
  P=(∑
  
  i=1n
  
  Pi-1)-1where
5. A track initiation method according to claim 1, wherein said distance between the strobe tracks (l₁,l₂) is computed according to $Dist$
- (l1,l2)=Δ
  
  PwhereΔ
  
  =(F₁−
  
  F₂)·
  
  e₀, P=(P_θ
  
  θ
  
  ,1(e₀·
  
  e_θ
  
  ,1)²+P_φ
  
  φ
  
  ,1(e₀·
  
  e_φ
  
  ,1)²)d₁²+(P_θ
  
  θ
  
  ,2(e₀·
  
  e_θ
  
  ,2)²+P_φ
  
  φ
  
  ,2(e₀·
  
  e_φ
  
  ,2)²)d₂²l_i(d)=e_r,id+F_i, d>
  
  0, i=1,2, (d₁,d₂)=arg_d₁_,d₂_>
  
  0min (e_r,1d₁+F₁−
  
  e_r,2d₂−
  
  F₂)², F_irepresenting the foot point vectors of the respective sensors.
6. A track initiation method according to claim 3, wherein said distance between strobe track crosses is computed according to
7. A track initiation method according to claim 1, wherein said step of selecting a strobe track cross as a probable target comprises the steps of:
- calculating a cross quality value for each strobe track cross using the probability density functions of the strobe tracks contributing to the strobe track cross;
  
  sorting strobe track crosses into a list in order by the cross quality value; and
  
  selecting at least one said strobe track cross from the list.
8. A track initiation method according to claim 7, wherein said cross quality value calculation uses the order of the strobe track cross.
9. A track initiation method according to claim 8, wherein said cross quality value is calculated by $X$
- 
  
  Q
  
  (X)=∏
  
  k=1
  
  …
  
  
  
  
  
  n
  
  
  
  X
  
  
  
  Q
  
  (S
  
  
  
  Tk,ik),where $X Q (S T_{k, i_{k}}) = \frac{f_{k} (X) P (X)}{\sum_{X^{'} \in S T_{k, i_{k}}} f_{k} (X^{'}) P (X^{'}) + ρ (S T_{k, i_{k}}) P (S T_{k, i_{k}})},$ X=X_i₁_,i₂_{. . . i}_na strobe track cross of order n, formed from strobe tracks {ST_k,i_k}_{k=1 . . . n}.
10. A track initiation method according to claim 7, wherein said step of selecting a strobe track cross as a probable target further comprises the steps of:
- removing those strobe track crosses, which are formed by at least one strobe track that is used for forming the selected strobe track cross, from the sorted list; and
  
  repeating the selection of strobe track crosses as probable targets until the sorted list is empty.
11. A track initiation method according to claim 7, wherein said step of selecting a strobe track cross as a probable target further comprises the step of determining if a selected strobe track cross should give rise to an automatic creation of a new target track, based on at least one of the cross quality value and the order of the strobe track cross.
12. A track initiation method according to claim 1, wherein said step of creating a target track comprises the step of calculating a target track state vector and its covariance matrix in a global tracking coordinate system.
13. A track initiation method according to claim 12, wherein said step of calculating a target track state vector and its covariance matrix is performed in a Cartesian coordinate system according to $(x, \dot{x}),$
- 
  
  (Px
  
  
  
  xPx
  
  x.Px
  
  x.Px.
  
  x.),where $x = {(\sum_{i = 1}^{n} P_{i}^{- 1})}^{- 1} (\sum_{i = 1}^{n} P_{i}^{- 1} F_{i}), \dot{x} = {(\sum_{i = 1}^{n} P_{i}^{- 1})}^{- 1} (\sum_{i = 1}^{n} P_{i}^{- 1} m_{i}), m_{i} = d_{i} ({\dot{θ}}_{i} \cos (ϕ_{i}) e_{θ, i} + {\dot{ϕ}}_{i} e_{ϕ, i}), P_{x x} = {(\sum_{k = 1}^{n} P_{k}^{- 1})}^{- 1}, P_{\dot{x} \dot{x}} = {(\sum_{k = 1}^{n} P_{k}^{- 1})}^{- 1} (\sum_{k = 1}^{n} P_{k}^{- 1} V_{k} P_{k}^{- 1}) {(\sum_{k = 1}^{n} P_{k}^{- 1})}^{- 1}, P_{x \dot{x}} = {(\sum_{k = 1}^{n} P_{k}^{- 1})}^{- 1} (\sum_{k = 1}^{n} P_{k}^{- 1} M_{k} P_{k}^{- 1}) {(\sum_{k = 1}^{n} P_{k}^{- 1})}^{- 1},$ with $P^{- 1} V P^{- 1} \approx (\frac{P_{\dot{θ} \dot{θ}}}{P_{θθ}^{2} \cos^{2} (ϕ)} e_{θ} \otimes e_{θ} + \frac{P_{\dot{ϕ} \dot{ϕ}}}{P_{ϕϕ}^{2}} e_{ϕ} \otimes e_{ϕ}) d^{- 2}, P^{- 1} M P^{- 1} \approx (\frac{P_{θ \dot{θ}}}{P_{θθ}^{2} \cos^{2} (ϕ)} e_{θ} \otimes e_{θ} + \frac{P_{ϕ \dot{ϕ}}}{P_{ϕϕ}^{2}} e_{ϕ} \otimes e_{ϕ}) d^{- 2} .$

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Current Assignee
Saab AB
Original Assignee
Saab AB
Inventors
Egnell, Henrik
Primary Examiner(s)
Issing, Gregory C.

Application Number

US09/355,503
Time in Patent Office

735 Days
Field of Search

342/126, 342/160, 342/432, 342/162, 342/189, 342/90
US Class Current

342/432
CPC Class Codes

G01S 3/043   Receivers

G01S 3/74   Multi-channel systems speci...

G01S 5/04   Position of source determin...

Multi target tracking initiation with passive angle measurements

First Claim

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Abstract

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13 Claims

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Multi target tracking initiation with passive angle measurements

First Claim

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