Vehicle position determination system and method

A method for improvingthe accuracy of terrestrial position estimates of a user antenna located at a vehicle, the method comprising the steps of:

• (1) obtaining a known position of a reference antenna;
• (2) receiving electromagnetic signals at said reference antenna from a constellation of satellites and responsively determining respective reference antenna pseudoranges;
• (3) computing an estimated position of said reference antenna using said reference antenna pseudoranges;
• (4) comparing said estimated position of said reference antenna with said known position of said reference antenna to derive a base residuals bias;
• (5) transmitting said base residuals bias and said reference antenna pseudoranges to the vehicle;
• (6) receiving electromagnetic signals at the user antenna, receiving said base residuals bias and said reference antenna pseudoranges at the vehicle, and computing future user pseudoranges as a function of said base residuals bias;
• (7) determining a position estimate of the vehicle as a function of said future user pseudoranges;
• (8) at the vehicle, determining another estimate of the position of the reference antenna as a function of the reference antenna pseudoranges;
• (9) determining an offset as a function of said another estimate of the position of the reference antenna and said known position of said reference antenna;
• (10) updating said position estimate of the vehicle as a function of said offset;
• and
• (11) repeating steps (8)-(10) until said offset is less than a predetermined threshold.

A method for estimating the terrestrial position of a vehicle (102), comprising:

• (1) receiving electromagnetic signals at a base station from a constellation of satellites and responsively determining a base spatial bias, a base clock bias, and base pseudoranges;
• (2) transmitting said base spatial bias, said base clock bias, and said base pseudoranges to the vehicle;
• (3) receiving electromagnetic signals at the vehicle from said constellation of satellites and responsively determining vehicle pseudoranges;
• (4) receiving said base spatial bias and said base clock bias at the vehicle and determining a position estimate of the vehicle as a function of said base spatial bias, said base clock bias, and said vehicle pseudoranges;
• (5) determining an estimate of the position of said base station at the vehicle as a function of said base pseudoranges;
• (6) determining an offset as a function of said estimate of the position of said base station and a known position of said base station;
• (7) updating said position estimate of the vehicle as a function of said offset;
• and
• (8) repeating steps (5)-(7) until said offset is less than a predetermined threshold.