Patent Document ID: 20020021241
Application ID: 09875066
Patent Flag: 0

Claim One:
1. A method of extrapolating the value of a navigation parameter (e.g., &phgr; B k or &ggr; B k ) from a global positioning satellite as measured by a base receiver, said navigation parameter being transmitted to a rover receiver over a communication link in a sequence of consecutively provided frames, each frame comprising the measured value of the navigation parameter made for a specific time moment t k as designated by a clock in the base receiver, the start of each frame occurring at a time interval T k from the start of the previous frame, the navigation parameter being extrapolated according to an extrapolation form comprising a constant, plus one or more terms which are a function of time, and one or more corresponding scaling parameters for scaling the terms, the values of said constant and scaling parameters being generated by said method, said method comprising the steps of: (a) transmitting in each frame a measured value of the navigation parameter, a representation of the specific time moment t k as designated by a clock in the base receiver at which the value was measured, and a weight factor K k representative of the estimated quality of measured value of said frame; (b) measuring the signal-to-noise ratio of the communication link during the time each frame is received by the rover; (c) storing a plurality M r of the most recent consecutive frames in a memory of the rover, and further storing for each stored frame an indication representative of the signal-to-noise ratio of the communication link during the receipt of the corresponding stored frame; (d) generating a quality indication associated with each stored frame of whether the measured value of a frame is satisfactory or unsatisfactory, said quality indication being generated as satisfactory unless one or more unsatisfactory conditions occurs, said quality indication being generated as unsatisfactory when the signal-to-noise ratio of the communication link falls below a first threshold value during the reception of the frame; (e) selecting, after each frame is received and stored, a subset of a number n s of the most recent frames from said set M r of stored frames which have satisfactory quality indications; (f) computing the values of the constant and scaling parameters of the extrapolation form from at least one selected subset of n s frames by an application of a least squares method which accounts for the weighting factors; and (g) generating an extrapolated value of the navigation parameter frame from the extrapolation form for one or more time moments occurring after the time moment of the last received frame.