Patent ID: 6417802
Filing Date: 2002-07-09
Classification: G01S

Abstract:
A method for adjusting the phase and frequency of a received GPS signal in an inertial-GPS navigation system comprising an inertial measurement unit (IMU) and a GPS receiver, the GPS receiver having an input port for inputting a delta-phase at delta-time intervals into a received satellite signal, the GPS receiver having an output port for outputting a carrier phase error, the carrier phase error being the difference between the actual phase of the received GPS signal and a reference value, the GPS receiver having an output port for outputting a pseudorange associated with the received GPS signal, the IMU having an output port for outputting acceleration and angular velocity of the IMU, the delta-phase being the sum of at least two delta-phase components, the method comprising the step:(a) determining a Kalman delta-phase component, a plurality of candidate Kalman delta-phase components being obtained by performing a first set of more than one Kalman filter processes, the inputs to each first-set Kalman filter process including the carrier phase error and a position vector associated with the IMU, a candidate Kalman delta-phase component being produced as an output of each first-set Kalman filter process, the Kalman delta-phase component being determined from a candidate Kalman delta-phase components selected from the plurality of candidate Kalman delta-phase components by applying a predetermined Kalman delta-phase component selection rule; (b) determining an IMU delta-phase component from the IMU outputs and a direction-cosine matrix that translates the body coordinates of the IMU into the navigation coordinates of the inertial-GPS navigation system.