Patent ID: 8676490
Filing Date: 2014-03-18
Classification: G01C

Abstract:
1. A computer implemented method for determining the position of a movable platform, said method comprising the steps of: measuring the azimuth and elevation of a plurality of stars from said platform, and using the measured azimuth and elevation of said stars to determine the orientation of said platform in an Earth-Centered Earth-Fixed coordinate frame; determining a series of platform coordinates of at least the azimuth and elevation of a satellite from said platform, and converting said series of azimuth and elevation determinations of said satellite in the platform coordinates to corresponding coordinates in an inertial frame fixed in time; determining from said corresponding coordinates a best-fit ellipse in said inertial frame fixed in time; determining, in said inertial frame fixed in time, vectors extending from said platform frame to foci of said ellipse; converting said vectors extending from said platform frame to said foci of said ellipse to said Earth-Centered Earth-Fixed coordinate frame, and identifying a vector extending from said platform frame to a focus lying at the gravitational center of the Earth to thereby establish the position of said platform.