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Airborne surveillance method and system

  • US 5,075,694 A
  • Filed: 12/14/1989
  • Issued: 12/24/1991
  • Est. Priority Date: 05/18/1987
  • Status: Expired due to Fees
First Claim
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1. In an environment having only a single rotating interrogation signal source within sensing range, a method of locating the position of at least one target object carrying an interrogation signal responsive transponder from an observer object located remotely from the rotating interrogation signal source comprising:

  • a) determining the direction of said interrogation signal source by direction finding on said interrogation signal to develop source direction data;

    b) determining the direction to a said target object by direction finding on a transponder signal produced by said transponder to develop target direction data; and

    c) assembling additional available data relevant to relative positions of said objects and/or said interrogation signal source;

    d) estimating the error of each of said source direction data, target direction data, and additional available data to develop data value error estimates;

    e) developing a present position estimate of said target object and an associated position error estimate from said data values and data value error estimates; and

    f) developing a present position value of said target aircraft by using a past position value of the position of said target aircraft to modify the present position estimate including varying the degree of modification based on the position error estimate to optimize the developed position value without use of an observer aircraft active interrogation source.

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