Method and system for calibrating group delay errors in a combined GPS and GLONASS receiver

摘要

A combined GPS and GLONASS receiver receives GPS signals and GLONASS signals. A calibration signal is generated utilizing the received GPS signals and/or the received GLONASS signals to offset group delay errors in the received GLONASS signals. The generated calibration signal is filtered through Kalman filters to estimate group delay variations in the received GLONASS signals. The estimated group error delay variations are combined with the received GLONASS signals to calibrate the received GLONASS signals by offsetting the estimated group error delay variations. When GPS signals are not available for use, the combined GPS and GLONASS receiver obtains group delay errors stored or in the received GLONASS signals to estimate calibration coefficients. The estimate calibration coefficients are updated utilizing received GPS and/or GLONASS signals. The updated estimated calibration coefficients are stored before turning off the combined GPS and GLONASS receiver to expedite calibrating of GLONASS signals received upon turning on.