Research On BDS/GPS Real-time Precise Point Positioning Method

Precise point positioning has the advantages of simple station setting and wide coverage.It has broad application prospects in geodetic survey,low-orbit satellite orbit determination,automatic driving,artificial intelligence,etc.In order to accelerate the real-time application of PPP in various fields,it is necessary to study real-time precise point positioning(RT-PPP)technology.At present,the main problems in RT-PPP include the difficulty in obtaining real-time satellite orbit and clock and the slow convergence.The real-time satellite orbit and clock can be obtained through the real-time data stream broadcasted by IGS and its analysis center.The convergence speed is slow can use ambiguity resolution technology and multi-system combination positioning to solve.Therefore,this paper first briefly describes the basic principle of RT-PPP,and then the real-time acquisition and application of BDS/GPS satellite orbit and clock are introduced in detail.The RT-PPP ambiguity resolution method are discussed,and the RT-PPP ambiguity based on phase biases is fixed.Finally,the BDS/GPS combined RT-PPP with fixed ambiguity is realized by receiving the real-time data stream broadcasted by CNES,and the positioning performance is analyzed.Therefore,the main research contents are as follows:1.The real-time acquisition method of state space representation(SSR)information and the basic principle of high-precision satellite orbit and clock recovery are studied.The data of IGSO,MEO satellite of BDS and GPS satellite in real-time data stream are relatively complete,which can meet the real-time positioning needs of users.The average accuracy of GPS satellite orbit in real-time products is 4.37 cm,and the clock error is better than 0.12 ns,which is significantly better than BDS satellite.The real-time satellite orbit and clock can be used for GPS real-time precise point positioning,which can reach the positioning level of E,N and U directions converge to 10 cm in 23 min.The 3D positioning accuracy of daily solution is better than 3cm,which shows that the real-time satellite orbit and clock obtained through SSR information can meet the needs of RT-PPP.2.The non-integer characteristics of RT-PPP ambiguity are analyzed,and the RT-PPP ambiguity resolution method and verification strategy are deduced.A partial ambiguity resolution method based on LAMBDA algorithm is proposed.The origin of real-time phase biases product and the specific process of fixing the RT-PPP ambiguity based on phase biases are studied.And the fixed solution of RT-PPP ambiguity based on phase biases is programmed.3.With the support of real-time phase biases products,GPS real-time precise point positioning with fixed ambiguity is realized.The results show that the GPS RT-PPP based on phase biases can achieve the first fixed ambiguity within 30 min.When the ambiguity is fixed,the horizontal position error can be reduced from 6cm to 2cm and the 3D position error can be reduced from 10 cm to 5 cm.The positioning accuracy of the observation period within 1h,2h,and 3h does not change much and shows a trend of increasing gradually.The real-time precise point positioning based on phase biases can realize the first fixation of the ambiguity in a short time and maintain the cm-level positioning result.4.The observation model and stochastic model of BDS/GPS combined RT-PPP are studied,and the BDS/GPS combined RT-PPP floating point solution and fixed solution are realized.For the RT-PPP floating point solution,the BDS/GPS combined positioning can reach the positioning level of E,N and U directions that converge to 10 cm in 21 min,the 3D position error of the daily solution is better than 3cm.Compared with the single GPS system,the convergence time and positioning accuracy are partially improved,and the overall performance is equivalent.For the RT-PPP fixed solution,the BDS/GPS combined positioning can achieve the first fixed ambiguity within an average of 28 min,the horizontal position error is better than 2cm and the 3D position error is better than 5cm when the ambiguity is fixed,which have different degrees of improvement than single GPS systems.At the same time,the 3D position error of BDS/GPS combined positioning in 3h observation is 4~5cm,which is equivalent to the short-term observation positioning accuracy of single GPS system RT-PPP.In summary,this paper explores a real-time precise point positioning method that is simple to implement and operability.In the case of BDS/GPS combined positioning,it can achieve fast cm-level positioning within an average of 28 minutes.Compared with traditional PPP begins convergence within half an hour,it has the advantages that the required time is equivalent,but the positioning accuracy is significantly improved.And the real-time positioning in the true sense is realized,which is convenient for popularization.