GPS/IRS global position determination method and apparatus with integrity loss provisions

  • US 5,923,286 A
  • Filed: 10/23/1996
  • Issued: 07/13/1999
  • Est. Priority Date: 10/23/1996
  • Status: Expired due to Term
First Claim
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1. A combined inertial reference system and a satellite positioning system for determining user position comprising:

  • an inertial reference system employing inertial sensors for providing IRS position and inertial reference information, including IRS velocity information, derived from output information from said inertial sensors;

    a satellite positioning system receiver for providing a GPS position solution including a resultant GPS position and resultant GPS velocity information derived form satellite information from signals transmitted from a plurality of satellites;

    validation means responsive to at least the number of said plurality of satellites transmitting said satellite information signals for indicating a non-availability time period when said number is below that which is required to provide at least one integrity limit value associated with the accuracy of said GPS solution, as opposed to an integrity time period when said number is sufficient to provide said at least one integrity limit value;

    error estimator means for determining velocity and acceleration error estimates associated with said IRS inertial information as a function of said IRS velocity information and said resultant GPS velocity information;

    coast position estimator means for determining a first estimated position of the user'"'"'s position during said non-availability time period as function of said velocity and acceleration error estimates occurring at the beginning of said non-availability time period, the elapsed time accumulated since the beginning of said non-availability time period, and the IRS position.

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