科研之友
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摘要
Due to the disturbances along the signal path, it's inevitable that the loss of lock or data interruption interval of a few satellites reach to decades of seconds or even minutes. It will be difficult to recover data and evaluate cycle slips after a long gap in real time kinematic (RTK) positioning. A double-differenced (DD) velocity estimation method is proposed for the repair of cycle slip in RTK positioning, assuming available of fixed coordinate solutions for the previous epoch. We achieve the precise coordinate solution of the current epoch by using triple-differenced (TD) combinations. The dual-frequency observed minus computed (OMC) combinations are then calculated by using the observations and coordinate solutions. The differenced OMC values between two epochs are used to repair cycle slips. Two kinematic experiments carried out to evaluate the performance of the proposed method are for velocities less than 2 m s(-1) for a boat and about 10 m s(-1) for a vehicle. The averaged distance of boat and vehicle relative to the reference are about 11 km and 24.5 km, respectively. The experimental results of the boat case indicate that all cycle slips are corrected within 0.25 cycles even though sampling interval reaches to 120 s. The cycle slips fixing uncertainty is close to 0.3 cycles for a sampling interval of 30 s and 60 s vehicle experiments. As the sampling interval increases to 90 s and 120 s, the uncertainty rises to 0.35 cycles for the vehicle-dynamic vehicle experiment.
