Technology Research Of The PPP-RTK Base On The Local Reference Stations

Base on the precise ephemeris and precise satellite clock,the high precision positioning can be realized with a single receiver,and the requirements on the accuracy and timeliness becoming higher and higher.Due to the uncalibrated phase delays(UPD)in Zero-difference phase observations,the float ambiguity estimates of PPP can not be fixed to integer resolution.The PPP-RTK technology can separate the UPD part from float ambiguity,to fixed ambiguity,providing rapid convergence to a reliable centimeter-level positioning accuracy.Domestic and foreign scholars in this area have very fruitful achievements.However the PPP-RTK application with BDS is still lack of.This paper has studied the PPP-RTK technology development,deducing its theory model.This paper briefly introduces the common models of PPP,deducing two kinds of typical technologies based on between-satellite-difference(BSD),analyzing the factors of quality control,compiling the PPP-RTK positioning software,and analyzing the accuracy of the positioning model with the regional CORS station data.In this paper,the main work and conclusions are as follows:(1)Combining of PPP theory equation and basing on the idea of the PPP-RTK positioning principle,this paper summed that the reason of float ambiguity resolution is due to the ambiguity which includes of UPDs.If the fractional part of the UPD parameters can be separated,ambiguity will be fixed to an integer.According to this thought,the generality PPP-RTK positioning equation was deduced.(2)A new method is proposed for choosing the reference satellite basing the middle-of-time and relative-higher elevation angle of satellite.This method improves the efficiency of software and ensures the quality of reference satellite.It is suitable for the regional stations.(3)Applying the UPD model,this paper realizing the correction parameter calculating on the server.Get the CORS(31 stations)observation data and solution the wide lane and narrow lane FCB with the PPP-RTK software.The result show that the RMS of BDS’s FCB is little higher than GPS except MEO satellite,which is four to five times higher.For the narrow lane FCB,the GPS satellites threshold value is smaller than 0.4 cycle,but the BDS satellites is between 0.4-0.85.There still good news for BDS satellite is that they have more than 4 hours to observe and calculate.(4)Realizing ambiguity resolution of PPP on the client.Using the sever side data(wide lane FCB and narrow lane FCB),do the PPP calculate.The experimental results show that: PPP ambiguity-fixed solution improves the efficiency of convergence,and has higher accuracy than the float solution of static single hour.For GPS satellites,the accuracy of site can reach 31.5% improvements in contrast to their ambiguity-float counterparts,for BDS can reach 29.1%.For the kinematic tests,the GPS satellites improve 27.8%,and the BDS improve 21.3%.(5)Based on Visual Studio 2013 C#,the PPP-RTK software is development.It contains server-side and client-side.Also,the functions of sorting and drawing the calculated data are included.