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Direct geolocation from TDOA, FDOA and AGL

  • US 9,625,566 B2
  • Filed: 05/21/2014
  • Issued: 04/18/2017
  • Est. Priority Date: 05/21/2014
  • Status: Active Grant
First Claim
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1. A method for estimating a location of a stationary emitter located on the Earth surface, the method comprising:

  • collecting data during a plurality of time periods, the data including Time Difference of Arrival (TDOA) and Frequency Difference of Arrival (FDOA) measurements of a radar pulse sent from a stationary emitter located on the Earth surface and received by at least two antennas on an aircraft, and altitude measurements of the aircraft above the Earth surface;

    for each of the plurality of time periods, estimating a location of the stationary emitter based on the TDOA, FDOA, and altitude measurements associated with a respective time period, the result being an estimated location of the stationary emitter associated with the respective time period, the estimated location of the stationary emitter including a candidate longitude and a candidate latitude of the stationary emitter;

    averaging the estimated locations associated with the plurality of time periods forming an averaged estimated location of the stationary emitter, the averaged estimated location including an average of the candidate longitudes and an average of the candidate latitudes of the stationary emitter; and

    providing the averaged estimated location of the stationary emitter,wherein estimating includes calculating two solutions for each of the estimated locations,wherein averaging includes maintaining a first averaged estimated location and a second averaged estimated location, each being a running average of the solutions calculated for the estimated locations, and associating each of the solutions with either the first or second averaged estimated location based on proximity of each of the solutions to either the first or second averaged estimated location, andwherein providing includes selecting either the first or second averaged estimated location having a range to the aircraft closest in value to a computed range from the aircraft to the stationary emitter.

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