The Key Technology Research Of High-precision GNSS Base Line Processing

With the rapid development of GNSS technology,there have been some precision positioning technology: static relative positioning,short of RTK,network RTK,precise point positioning,real-time wide-area difference,etc.Static relative positioning has high accuracy,for a few tens of kilometers or hundreds of kilometers of baselines don't need precise ephemeris which can gain satisfactory relative positioning results.because of the influence of ionosphere,RTK precision is not high.It is suitable for real-time lofting and measurement,not suitable for high precision control measurement.Network RTK has a high precision,but it is affected by the communicate lines,not suitable for mountainous and remote areas.Precise point positioning(PPP)can obtain the cm-level accuracy,but the lack of precise ephemeris and the lag of software in this method cannot be widely applied in the engineering.Real-time wide-area difference depends on wide –area difference signal,the XiHe system in our country and some wide-area difference system in abroad all provide services,which can get real-time access to the decimeter level of absolute positioning results.But with the influence of the equipment,the fuzzy degree of convergence problem,in addition to the ocean and no man's land measurement,no more applications in engineering.For long-distance control survey,static relative positioning is still the mainstream in the engineering application of precision positioning model.In the static relative positioning software,due to the particularity of oil exploration control survey,no one is suitable for engineering application with high precision GNSS processing software.In view of this,this article has carried on the following several aspects of research,including static relative positioning algorithm,high-precision GNSS baseline processing strategy,software design and implementation,and so on.The system has studied the precise point positioning equation.In the perspective of program implementation,deduce the single and double difference equation,point out the ignore steps in some textbooks,which help readers to understand the principle of carrier relative positioning.At the same time,studied the difference between the BDS / GLONASS and GPS baseline processing,including coordinate system,time system,satellite position calculation,etc.Also,deduce the frequency division multiple access double difference equation.This system has studied the influence of various errors of baseline processing.the thesis discusses the influence of various error on the baseline.It hasn't listed the formula which is available in the literature,only discussed the error of the size and processing strategy,expounds the processing method of cycle slip,compared the availability of various kinds of methods.In terms of weakening the ionosphere,expounds the LC combination and the IF combination,and compared to the combination of the two kinds of combination of noise,deduced the formula of IF combination of fixed solution.In the aspect of improving precision of baseline processing,this paper proposes using the fixed weight and angle estimation method.Original reference satellite selection method can choose the highest satellite altitude angle in each epoch of satellites as a reference,and do not increase the number of double difference ambiguity,improve the success rate for calculating the baseline.In the process of software implementation of the baseline processing,using the c + + to write the baseline processing core code,c # software method for software interface.This article chose the processing class---open source c + + matrix,which can be efficient and convenient treatment of various large matrices.In computer memory and improve the efficiency of resource use,using the original sparse matrix storage method and the data of synchronous fast search method,using SQLite transaction way to improve the data writing speed.The author gives an overall design to baseline processing module,design the database structure,software function and interface.This paper deals with a lot of actual project data,chooses some representative data,shows the ability of processing of the zero-base software processing line,short baseline,mid-long baseline and super-long baseline,compares the results of the GPS baseline and the BDS baseline,the results of super-long baseline and GAMIT,and other,shows the comparative baseline results between GBC and an another famous software in the world.