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Geolocation method and apparatus for satellite based telecommunications system

  • US 6,020,847 A
  • Filed: 04/25/1996
  • Issued: 02/01/2000
  • Est. Priority Date: 04/25/1996
  • Status: Expired due to Fees
First Claim
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1. A method for determining a geolocation of a user terminal in a satellite based telecommunications system which passes communications signals along assigned channels between a user terminal, a satellite, and an associated earth station, said method comprising the steps of:

  • receiving a telecommunications signal over an assigned channel from a user terminal at an earth station;

    determining a timing error offset representative of motion of said user terminal relative to said earth station and based on said telecommunications signal;

    combining said timing error offset with a round trip propagation delay representing round trip propagation time of an RF signal through said user terminal, a satellite, and said earth station to obtain an updated round trip propagation delay through said user terminal, said satellite, and said earth station;

    removing an earth station-to-satellite round trip delay from said updated round trip propagation delay, thereby determining a satellite-to-mobile terminal round trip propagation delay;

    determining a range solution line based on said satellite-to-mobile terminal round trip propagation delay;

    determining a Doppler solution line based on said telecommunications signal;

    determining geographic points of intersection of said range and Doppler solution lines; and

    outputting one of said geographic points of intersection as a geolocation of the user terminal.

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