Using GPS Time-Differenced Carrier Phase Observations to Calibrate LDV/INS Integrated Navigation Systems

A laser Doppler velocimeter (LDV) is usually integrated with an inertial navigation system (INS) to autonomously acquire a vehicle's position, velocity and attitude. The calibration process is trying to determine the scale factor of the LDV and the installation angles between LDV and INS. As a dead-reckoning system, the calibration accuracy affects the navigation performance of the LDV/INS integrated navigation system. This paper presents how to use time-differenced carrier phase (TDCP) observations instead of differenced GPS (DGPS) or precise point positioning (PPP) techniques to complete the calibration process. Differencing carrier phase observations between two GPS epochs can save the effort in ambiguity fixing and achieve centimeter relative positioning after outlier and cycle slip detection, which is suitable for LDV calibration. In order to finish the calibration within several minutes, an iteration scheme is implemented into the calibration for rapid convergence. The navigation experiment indicates that the horizontal position error of the LDV/INS integrated navigation system can achieve 26.6m/25.5km.