Patent ID: 6169958
Filing Date: 2001-01-02
Classification: G01S

Abstract:
A method using satellite signal transmission for determining the geographic location of a receiver on the earth's surface, comprising: receiving a first signal transmitted at a known frequency from a first satellite having a known orbital position; receiving a second signal transmitted at the same frequency as the first signal from a second satellite having a known orbital position; receiving a third signal transmitted at the same frequency as the first signal from a third satellite having a known orbital position; calculating measured distances .lambda..sup.1, .lambda..sup.2 and .lambda..sup.3 of the respective first, second and third satellites from the receiver based at least in part on the transmission time of the respective first, second and third signals; and calculating actual distances .rho..sup.1, .rho..sup.2 and .rho..sup.3 of the respective first, second and third satellites from the receiver based on the measured distances .lambda..sup.1, .lambda..sup.2 and .lambda..sup.3, according to the relationships ##EQU20## where F.sub.pp.sup.1, F.sub.pp.sup.2, and F.sub.pp.sup.3 are obliquity factors for the respective first, second and third satellites based on the respective angles .phi..sub.1, .phi..sub.2 and .phi..sub.3 they form with a plane tangent to the earth's surface at the geographic location of the receiver, with ##EQU21## where R.sub.e is the radius of the earth and H.sub.r is the height of maximum electron density in the ionosphere surrounding the earth's surface.