Research On Precise Point Positioning Ambiguity Resolution Algorithm And Performance Evaluation

Precise point positioning has been widely used in various fields such as disaster monitoring,precise agriculture,transportation,etc.,due to its advantages of simple positioning method,wide operating range,and the ability to achieve high-precision positioning on global scale.However,precise point positioning usually requires a long convergence time to achieve highprecision positioning;When the observation signal is interrupted or lost,it needs to converge again,which seriously affects the promotion and application of precise point positioning.The paper focuses on methods and strategies to shorten the convergence time and improve positioning accuracy.It researches on the selection of ambiguity subsets and proposes a method for selecting ambiguity subsets that takes elevation,signal-to-noise ratio(SNR)and ambiguity variance into account;Two algorithms for NL ambiguity resolution are compared and analyzed;The performance of BDS-3/GPS real-time precise point positioning is analyzed and researched,and based on this,the ambiguity resolution and positioning performance are verified in actual measurement environments.The main research content and achievements of the paper are as follows:(1)Compared and analyzed the convergence time and positioning accuracy in static and kinematic modes for two NL ambiguity resolution algorithms named LAMBDA and BIE.The results show that: During the convergence process,the stability of LAMBDA solution is higher,while the convergence speed of BIE algorithm is faster;After convergence,the positioning accuracy of BIE algorithm is a little bit better than that of LAMBDA algorithm;Finally,the applicability and characteristics of the two algorithms are summarized and summarized.(2)An improved ambiguity subset selection method is proposed,in which the elevation,signal-to-noise ratio(SNR)and ambiguity variance are combined as the indicator for ambiguity subset selection to improve the fixed rate,time to first fixed,convergence time and positioning accuracy.The experimental results show that: compared to the full ambiguity resolution(FAR)and the partial ambiguity resolution(PAR)based on the elevation method,the improvement of fixed rate,time to first fixed and convergence time of the proposed method are 9.65% and2.56%,6.86% and 3.43%,15.57% and 5.13% respectively in the static mode.When the fixed rate of the three methods is almost the same,the improvement of positioning accuracy is 4.74%and 5.39% respectively.For the kinematic mode,compared to the FAR and the PAR based on the elevation,the improvement of fixed rate,time to first fixed of the proposed are 22.75% and0.92%,12.44% and 0.44%,respectively.When the fixed rate of the three methods is similar,the positioning accuracy is improved by 3.50% and 4.89%,respectively.(3)Analyze the impact of combining BDS-3 satellites on the real-time PPP positioning performance of the ionospheric free combination model,and use the BDS-3/GPS to verify the positioning performance of the improved ambiguity resolution strategy in actual measurement environments.The experimental results are as follows: Combining BDS-3 satellite can significantly accelerate convergence speed and improve positioning accuracy,and this improvement is more significant in kinematic mode.The of PPP-AR technology can accelerate convergence and improve accuracy,and the improvement effect is more significant in BDS-3/GPS system.