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Tight optical integration (TOI) of images with GPS range measurements

  • US 9,726,765 B2
  • Filed: 07/20/2011
  • Issued: 08/08/2017
  • Est. Priority Date: 01/27/2009
  • Status: Active Grant
First Claim
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1. A method of determining a position of a user in 3D space utilizing an integrated navigation system including a GPS receiver and a camera located at the user position when a limited number of GPS signals are available, the method comprising:

  • capturing, by the camera, a camera image of a known marker through a focal point of the camera with optical measurements that extend from a position of the known marker within the camera image to the user position of the camera;

    determining two or more pseudoranges between a true user position and two or more GPS satellites with the integrated navigation system, wherein the two or more GPS satellites are insufficient to generate GPS measurements necessary to calculate a GPS standalone position;

    determining a marker unit vector from the optical measurements captured by at least one optic sensor associated with the camera that extends from the position within the camera image associated with the known marker through the focal point of the camera with the integrated navigation system, wherein unavailable GPS measurements necessary to calculate the GPS standalone position are replaced by the marker unit vector;

    converting, by the GPS receiver, the marker unit vector from a camera frame of reference to an earth frame of reference of GPS measurements by incorporating attitude information of the camera obtained from inertial measurements of the camera at the user position to transform a direction cosine of the marker unit vector in the camera frame of reference to the earth frame of reference;

    integrating, by the GPS receiver, the two or more pseudoranges and the marker unit vector into an ordinary least squares matrix with the integrated navigation system;

    generating a shortest vector starting from an estimated user position to a point on the marker unit vector, wherein the shortest vector is perpendicular to the marker unit vector at the point on the marker unit vector;

    converging, by the GPS receiver, a line joining the estimated user position and the marker and the two or more pseudoranges derived from the estimated user position to the point on the marker unit vector generated from the shortest vector being perpendicular to the marker unit vector;

    determining the position of the user in 3D space from the convergence of the line joining the estimated user position and the two or more pseudoranges derived from the estimated user position to the point on the marker unit vector generated from the shortest vector being perpendicular to the marker unit vector by solving the ordinary least squares matrix with the integrated navigation system so that the two or more pseudoranges are supplemented with the marker unit vector to overcome the unavailable GPS measurements to calculate the GPS standalone position.

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