Middle-Lon- Range Differential Positioning Using TripleFrequency BeiDou Satellite System

Based on the unique advantages of Beidou triple frequency, we use the real measured data to study the performance of differential positioning in middle long baseline and conduct the resolution of triple ambiguity with stepwise method, and resolve the B3 narrow ambiguity with the aid of wide lane ambiguity and ionosphericfree combination. Then using the observation epoch selecting strategy the paper presents that combining the construction of the kalman filter innovation vector using the B3 narrow lane ambiguity in adjoin epoch with the filter divergence condition, it is easy to analyze the impact of narrow lane ambiguity error on the filter performance using the RMS of inner product of kalman filter innovation vector. Finally, we get the centimeterlevel differential positioning accuracy in middlelong baseline and shorten the time to firstfixed solution effectively and improve the fix rate that has a practical significance on promoting BeiDou highprecision positioning.