A Study On The Algorithms Of BDS Single Epoch Difference Positioning

December 27,2012,China Beidou second-generation satellite navigation system(BDS)officially provide positioning navigation timing(PNT)and short message communication services for the Asia-Pacific region users and is expected will achieve global networking and provide global PNT service by 2020 BDS.At present,China's Beidou satellite navigation system has officially provided regional services.researching Beidou real-time precision positioning theory and algorithm is of great significance for the BDS real-time high-precision positioning service.In this paper,the theory and algorithm of BDS single epoch differential positioning are studied deeply,and ill-posed problem of the Normal equation and partial ambiguity fixation of short baseline single epoch differential positioning is studied emphatically.Firstly,we use the regularization method to improve the ill-posed problem of the equation,and then use the LAMBDA method to search the ambiguity to obtain a reliable fixed solution.Secondly,for the partial ambiguity variance is large and it is difficult to fix correctly.partial ambiguity resolution strategies are used to control the influence of non-optimal ambiguity.Thirdly,we use the regularization method and the partial ambiguity resolution strategy to make the positioning accuracy of Beidou system better than 2cm in plane and elevation.Finally,this paper makes a preliminary evaluation on the Beidou single epoch differential positioning performance and prepared a set of differential positioning software combined with the regularization method and the partial ambiguity resolution strategy.And a certain landslide real-time monitoring software calculating results are compared to validate the correctness of the software.Based on this,this paper carried out the relevant research,the main research contents and achievements are as follows:1,Introduced the the basic theory of BDS single epoch differential positioning.The common stochastic model and common function model of BDS single epoch differential positioning are expounded.The error source of BDS single epoch differential location and its processing strategy are analyzed.And parameter estimation of two commonly used methods are briefly introduced.2,Reserching the ill-posed problem of BDS single epoch differential positioning.Frist of all,the problem of ill-posed problem of double-difference Normal equation is analyzed,and the reason and the method of diagnosis are given.Then,there are two methods for solving the ill-posed problem by the biased estimator and the direct solution of the ill-conditioned equation.In the end,the Tikhonov regularization method is used to improve the serious ill-posed problem of BDS single epoch double difference equation in fast positioning.Reasonable selection of the regularization parameter and regularization matrix improve the precision of ambiguity float solution and weaken the covariance correlation.and then use the LAMBDA method to search the ambiguity to obtain a reliable fixed solution.3,It is difficult to correctly fix the ambiguity with the poor accuracy of partial ambiguity parameter,and the ambiguity with poor accuracy will affect the fixation of the whole ambiguity.Therefore,using the partial ambiguity resolution method,this method can effectively suppress the interference of the non-optimal ambiguity,and improve the correctness of the ambiguity resolution.Finally,this paper makes a preliminary evaluation on the Beidou single epoch differential positioning performance and prepared a set of differential positioning software combined with the regularization method and the partial ambiguity resolution strategy.And a certain landslide real-time monitoring software calculating results are compared to validate the correctness of the software.For the BDS single epoch differential positioning,It provide a reference in deformation monitoring,quasi dynamic positioning and attitude determine.