Patent ID: 6239721
Filing Date: 2001-05-29
Classification: G01S

Abstract:
A method for determining the location of a moving signal receiver, the method comprising the steps of:receiving primary location determination (LD) signals from two or more primary LD signal sources, whose locations are known, at a primary LD signal antenna and associated signal receiver;when sufficient primary LD signals are available, estimating the present location of the primary antenna;receiving secondary location determination (LD) signals from one or more secondary LD signal sources, whose locations are not necessarily known, at a secondary LD signal antenna at each of two or more spaced apart locations and estimating the location of each of the at least one secondary LD signal sources, using knowledge of the present location of the primary antenna; andwhen sufficient primary LD signals are unavailable to determine location of the primary antenna, analyzing the primary LD signals received and the secondary LD signals received and estimating the present location of at least one of the primary antenna and the secondary antenna.