Patent ID: 6121923
Filing Date: 2000-09-19
Classification: G01S,H04B

Abstract:
A method for determining position fix by interpreting a plurality of broadcasted GPS signals comprising the steps of:receiving the plurality of broadcasted GPS signals and providing a digitized signal dependent thereon;determining local time;determining a capture start time dependent on the determined local time;receiving a reference code phase delay, a reference Doppler shift, a reference elevation angle, and a reference azimuth angle for each of a plurality of satellites from a fixed position reference site;identifying a first satellite of the plurality of satellites;identifying a reduced code replica search space for the first satellite dependent on the determined local time, and the received reference code phase delay, reference Doppler shift, reference elevation angle, reference azimuth angle, each associated with the first satellite;capturing a second portion of the digitized signal into a memory commencing coincident with the determined capture start time;extracting the second portion of the digitized signal from the memory and correlating the extracted signal to the reduced code replica search space and determining an off-line code phase delay for the first satellite dependent thereon;identifying a further reduced code replica search space for a second satellite dependent on the determined off-line code phase delay for the first satellite, the determined local time, and the received reference code phase delay, reference Doppler shift, reference elevation angle, reference azimuth angle, each associated with the second satellite; andextracting the second portion of the digitized signal from the memory and correlating the extracted signal to the further reduced code replica search space and determining an off-line code phase delay for the second satellite dependent thereon.