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Method and apparatus for enhancing a global positioning system with terrain model

  • US 6,429,814 B1
  • Filed: 03/19/2001
  • Issued: 08/06/2002
  • Est. Priority Date: 11/17/2000
  • Status: Expired due to Term
First Claim
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1. A method for computing position comprising:

  • supplying pseudorange measurements that approximate the distance from a location to a plurality of global positioning system (GPS) satellites;

    supplying a terrain model; and

    computing a three-dimensional position of said location in response to said pseudorange measurements and said terrain model, wherein said computing step comprises;

    (a) determining an upper altitude bound and a lower altitude bound;

    (b) selecting a first altitude between said upper and lower altitude bounds;

    (c) determining from said pseudorange measurements a longitude and a latitude corresponding to said first altitude;

    (d) determining a second altitude using said terrain model at said longitude and latitude;

    (e) if said second altitude is above said first altitude, replacing said lower altitude limit with said first altitude, otherwise replacing said upper altitude bound with said first altitude; and

    (f) repeating steps (b), (c), (d), (e) and (f) until a difference between said upper and lower altitude bounds is within a predefined value.

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