Research And Implementation On Single Point Precise Positioning Of Multi GNSS

With the development and maturity of technology of GNSS(global satellite navigation system)positioning by single receiver,the accuracy request of satellite positioning is more and more strict,which is widely used.Because of its independence and flexibility,precise point positioning(PPP)attracts the attention of scholars,and its application in navigation and aviation is more and more popular.Multi-GNSS provides more observables,which can not only locate accurately but also converge rapidly when used in PPP,so it becomes a trend.In order to achieve the requirements of precise positioning,more accurate observation values must be used,and the noise of carrier phase is relatively small compared with the pseudo range.But in order to get accurate carrier phase,cycle-slip detection and repair is the key step.The quality of repairing cycle-slip directly affects the positioning effect.Based on the current situation,this paper studies the PPP of multi-GNSS,and realizes the PPP of dual-frequency ionosphere-free combination.In order to solve the problem that small cycle-slips are difficult to be detected and the low precision of existing detection methods,this paper proposes the improvement and innovation of methods of cycle-slip detection and repair for dual frequency observation.This paper contains following contents and innovations:1.Some methods of cycle-slip detection and repair are studied,and their advantages and disadvantages are analyzed.In view of the difference between the advantages and disadvantages of STPIR(second-order,time-difference phase ionospheric residual)and the Doppler integration method,a method of combining the above two methods is proposed to realize the complementary advantages.2.It is well-known that the MW(Melbourn-Wübbena combination)method generally remains a large cycle-slip detection error.To address this problem,we propose a novel method that effectively detects the cycle-slip with reconstruction Doppler integral algorithm.The proposed method has the same blind zone of cycle-slip detection as the MW method,so,we integrate the STPIR algorithm into the detection method above.In the experimental stage,we validate the proposed method for the cycle slip detection on two types of sampling interval data(e.g.,one second and 30 seconds)containing the simulated cycle-slip.The results show that the detection error of the reconstruction Doppler integral with a wide lane method is smaller than that of the MW method.3.This paper studies and summarizes the transformation of different coordinate systems and time systems of GNSS,and introduces the post precise ephemeris and real-time precise ephemeris of GNSS.When dealing with SP3 precise ephemeris with Lagrange interpolation method,the following conclusions are obtained by case analysis: if only SP3 ephemeris of the same day is used,the interpolation error of the beginning part and the end part of the ephemeris is large.It is recommended to add the SP3 ephemeris of the day before and the day after.In addition,the method of modifying broadcast ephemeris with SSR is studied.The real-time ephemeris obtained by this method is used for PPP.We compare and analyze the positioning results of single-GNSS and multi-GNSS.4.In this paper,the key technologies of multi-GNSS PPP are studied.These technologies are used in the development of multi-GNSS PPP software on the app designer platform of MATLAB,and PPP of ionosphere-free combination is realized.We use IGS(International GNSS Service)data to verify the availability of this software,and that multiGNSS PPP can not only improve the convergence speed,but also improve the positioning accuracy.