Research And Software Implementation Of BDS/GPS Double Difference Combined Ambiguity Fixed Algorithm

With the improving of GNSS navigation satellite system,the navigation and positioning services have been developed from the GPS technology to multi-satellite system integration technology.The data processing of muti-satellite system has become possible.The GNSS data processing methods can be divided into zero-difference combination model and double-difference combination model,according to data processing modes.The positioning precision of zero-difference combination model will be affected by the precision of satellite orbit and the correction of various models,while the double-difference combination model can obtain better results by eliminating various error source to some extent.With the construction of BDS system,the establishment of national or global reference framework based on GPS/BDS double-difference combination technology has become a hot topic.When the coordinate reference frame has been realized,the ambiguity resolution is important.In this paper,we have deeply studied double-difference relaxation model based on the normal equation level and the double-difference rigorous model based on the observation level.Combined Sigma-dependent with QIF ambiguity resolution algorithm,the GPS/BDS double-difference combination relaxation,rigorous model ambiguity resolution has been proposed.In order to certify ambiguity resolution rate and resolution successful rate of algorithm,the development software is used to carry out the short?long baseline ambiguity resolution and network adjustment experiment.The main research content and work of this paper as follows:(1)The double-difference observation equation and error equation of L5/LC,MW/LC is derived and double-difference stochastic model is constructed by difference operator.The method of elimination of double difference relaxation combination normal equation rank defect based on the elimination reference ambiguity is described.The method of elimination of double difference rigorous combination normal equation rank defect based on the absolute constraint with small weight is proposed.(2)Combined the double difference relaxation and rigorous combination model with Sigma-dependent and QIF algorithm,we put forward the principle of ambiguity resolution algorithm and the idea of datum transfer.The relationship between ambiguity resolution and datum transfer,the relationship between resolved ambiguity RMS and iterations number are explored based on the different baseline length.(3)A unified method of parameter initial value based on the idea of parameter transformation is derived.lt is proved that the independence of each observation equation is the equivalent condition of sequential adjustment and classical least square adjustment.lt is derived that the implementation form of the minimum constraint datum based on the no-net translation condition in the normal equation.(4)In order to test the resolution rate and resolution successful rate of ambiguity,and take account of the uncorrected error of BDS,The experiment of short,long baseline ambiguity resolution and equivalent weight of GPS/BDS and reduced weight of BDS is carred out by developed software.The results show that the resolution rate of ambiguity of more than 80%based on the Sigma-dependent and QIF algorithm of double difference relaxation-rigorous combination models.When the network-adjustment of before and after of BDS reduced weight using 21 day data,except for some station,The N,E,U coordinate component from most of station are within±5.0 mm.It is proved that the proposed algorithms have excellent ambiguity resolution effect.