Ambiguity Resolution And Cycle Slips Detection In High Precision Positioning

With the emergence of global navigation system and positioning technology,people are increasingly inseparable from high-precision positioning.The pseudo-range of meter-level positioning accuracy generated by satellite can no longer meet people's needs.Carrier phase measurements with centimeter-level positioning accuracy are gradually favored by people,so as to achieve high-precision positioning.The utilization of carrier phase observation has far-reaching popularization significance for high-precision positioning.Integer ambiguity resolution and cycle slip detection and repair are the two core technologies to achieve high-precision positioning.Therefore,it is necessary to quickly solve the ambiguity and accurately detect and repair cycle slip.The main contributions of this paper are as follow:(1)In complex geomorphological environment,the intensity of BDS signal is weak.With the increase of baseline length,ionospheric delay and measurement noise will seriously affect the ambiguity resolution of narrow lanes.Firstly,the ambiguity of two ultra-wide lanes is fixed by using BDS/Galileo carrier phase combination observation with geometric –free model and geometric model respectively.Then the effect of fixed BDS/Galileo multi-frequency medium-long baseline narrow lane ambiguity based on the improved geometric ionospheric model of TCAR algorithm is analyzed.The experimental results show that in the B2,B3 and E1,E5 a modes,the fixed error of the BDS/Galileo combined observation ambiguity is small at the medium and long baseline.(2)In view of the shortcomings of TurboEdit method in cycle slip detection and repair of carrier phase observations,an improved un-difference TurboEdit method considering satellite altitude angle is proposed.For the MW combination,an adaptive sliding window model is designed.The step size of sliding window varies with the altitude angle of satellite.For the GF combination,a weighting factor which varies with the sampling interval and the satellite altitude angle is added to reduce the false cycle slip.The carrier phase observations are repaired by combining the two methods.The experimental results show that the improved un-difference TurboEdit method considering satellite altitude angle can reduce the error caused by low altitude angle,which lays a foundation for ambiguity resolution and subsequent processing.(3)In order to weaken the influence of noise,from the perspective of Bayesian statistics,an INS-assisted cycle slip detection and repair method for BDS based on compressed sensing is proposed.Firstly,the tight combination positioning model of BDS and INS is established by Kalman filter.Then,a sparse cycle slip detection model based on compressed sensing is constructed.Finally,the cycle slip value is reconstructed according to Bayesian theory of statistical method,and the cycle slip is further repaired.The experimental results show that the proposed algorithm can effectively reduce the error rate of BDS cycle slip repair and improve the positioning accuracy.