Research On Integrated Positioning Of PPP With Fixed Ambiguity And INS

With the development of GNSS,PPP has attracted more and more attention.PPP with fix ambiguity and combined positioning of PPP/INS have broad application prospects.The main contents include: implementation of high-precision GPS PPP positioning algorithm,bidirectional filtering algorithm for PPP,modified ambiguity fixing and quality control methods,fixed ambiguity PPP/INS integrated navigation and so on.This paper implements the algorithm using C language on the visual studio2017 platform to realize the method of PPP with fixed ambiguity under GPS and INS.The main research contents and results are as follows:(1)Positioning algorithm of PPP with float solution and PPP with fixed solution are realized.The correction model of GPS error: correction model of tropospheric delay and ionospheric delay,are used to correct the corresponding GPS errors,so as to achieve high-precision positioning algorithm of PPP with float solution.The positioning algorithm of PPP with fixed solution is realized by using the integer phase clock to fix ambiguity of PPP and using the FCBs to fix ambiguity of PPP.The experimental results show that algorithm implemented for of PPP with float solution and PPP with fixed solution have higher positioning accuracy and quicker convergence speed.Positioning accuracy of algorithm for PPP with fixed solution under static mode reaches centimeter(about 0.02m).Positioning accuracy of algorithm for PPP with fixed solution under dynamic mode reaches decimeter(about 0.1m).(2)A bidirectional filtering algorithm for PPP is proposed to realize positioning of PPP with bidirectional filtering.The influence of different satellite altitude drag angle on positioning of PPP is analyzed.The influence on positioning of PPP is analyzed by using different satellite altitude drag angle.The experimental results show that the bidirectional filtering algorithm applied to PPP can effectively improve the positioning accuracy,which can achieve millimeter level positioning under static mode and achieve centimeter level positioning under dynamic mode.(3)The algorithm of partial ambiguity fixing and quality control is realized.Algorithm of the partial ambiguity fixing is improved by introduction of position precision control factor.Algorithm of quality control for fixed wide-lane ambiguity is also improved by modified formula of success rate.The experimental results show that the improved algorithm of partial ambiguity fixing can enhance fixed success rate and reliability of positioning.Improved algorithm of quality control for fixed wide-lane ambiguity is better than the original,which has a higher success rate for fixing wide-lane ambiguity and can efficiently control the influence of pseudorandom probability.(4)The algorithm of fixed ambiguity PPP/INS integrated navigation is realized.The model,state equation and observation equation of the GPS/INS combination are studied.Experimental results show that positioning accuracy of fixed ambiguity PPP/INS can reach decimeter level(about 0.1M),which can meet the requirements of dynamic positioning for vehicle and ship.Under the Semi-Cutoff environment,the fixed ambiguity PPP/INS combination without GPS satellite in short time(5S)can maintain higher positioning accuracy in vehicle experiment.Under the cutoff environment,GPS satellite is unlocked for long time(about 300s),the GPS PPP is unable to complete the positioning and combination of ambiguity fixed PPP/INS can provide more reliable positioning service(about 5 m).