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Precise inverse differential corrections for location determination

  • US 5,825,328 A
  • Filed: 05/29/1997
  • Issued: 10/20/1998
  • Est. Priority Date: 01/11/1997
  • Status: Expired due to Fees
First Claim
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1. A method for determining location fix coordinates with enhanced accuracy for a mobile user location determination station, the method comprising the steps of:

  • (1) receiving location determination (LD) signals from a selected constellation of J LD signal sources with known locations at a selected location, and measuring a pseudorange value associated with each of the J LD signals received at approximately a selected signal observation time, where J is an integer satisfying J≧

    2;

    (2) computing location fix coordinate values for the selected observation time from the pseudorange values measured at the selected location, using an exact, invertible transformation between a set of J pseudorange values and a corresponding set of J location fix coordinates;

    (3) forming a location fix signal that includes the J location fix coordinates for the selected location computed using the selected location pseudorange values, the signal observation time, and an indicium that represents the selected constellation of sources of LD signals whose pseudorange values are measured at the selected location, and transmitting the location fix signal to a selected LD signal processing station;

    (4) receiving the location fix signal at the selected LD signal processing station, and computing pseudorange values for the selected location at the selected observation time from the information contained in the location fix signal;

    (5) receiving LD signals from the selected constellation of LD signal sources at a reference station having a known location at approximately the selected observation time, and measuring a pseudorange value associated with an LD signal received from each of the LD signal sources in the selected constellation at the reference station;

    (6) determining a pseudorange correction for each of the J pseudorange values measured at the reference station, based on the known locations of the LD signal sources and the known location of the reference station; and

    (7) computing a selected location corrected pseudorange value for the selected location at the selected LD signal processing station as a sum of a selected location pseudorange value, for an LD signal received at the selected location from an LD signal source, plus the reference station pseudorange correction for the LD signal received from the same LD signal source, for each of the J LD signal sources.

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