Patent ID: 7019689
Filing Date: 2006-03-28
Classification: G01S

Abstract:
1. A navigation-satellite receiver system, comprising: a GPS radio frequency (GPS-RF) stage and digital signal processor (DSP) for navigation fixes; a network client for connecting to a network source and for obtaining GPS navigation data for the DSP whenever direct GPS satellite transmissions received by the GPS-RF are determined to be too weak to be directly demodulated of such GPS navigation data, or GPS navigation data are determined to be too old to be useful; a timer connected to the DSP and able to maintain a time-base count when the DSP is powered-down; a calibrator for comparing GPS system time to a count in the timer for later use in reconstructing GPS system time; a position and time uncertainty calculator disposed in the DSP for determining if such uncertainties exceed particular limits; and a navigation calculator disposed in the DSP for using said time-base count when the DSP is powered-up to produce a fix without first obtaining GPS navigation data from said network source if said uncertainties do not exceed said particular limits; wherein, a time-consuming or non-available request from a server for GPS navigation data can be avoided when the position uncertainty does not exceed a particular threshold.