| As the BDS-3 satellite navigation system completes global networking and officially opens,my country has become the third country in the world to independently own a global satellite navigation system,and it has also brought further improvements in positioning accuracy and reliability.At present,BDS-3 satellites can broadcast observation signals of up to five frequency points.The study of BDS-3 multi-frequency combination is of great significance for achieving fast fixation of ambiguity and improving positioning accuracy;research on satellite navigation and positioning technology in engineering practice based on BDS The application in,helps to serve the strategy of “Transportation Power”.In view of this,the main research work and conclusions of this article are as follows:(1)The basic theory of GNSS positioning was discussed.The undifferenced,single difference,and double difference observation equation and its linearization formula are elaborated;the source of GNSS positioning error and its correction method are analyzed;the data pretreatment and quality control method is given;the GNSS parameter estimation is expounded.Minimum multiplier and Kalman filtering algorithm,and three common random models.(2)The basic positioning performance of the BDS multi-frequency combination is analyzed.The standards of linear combinations of multi-frequency observations are given,and the common combinations of BDS-2 triple-frequency and BDS-3 quad-frequency are listed.The observed value residual estimation model based on station interlenection is expounded,and the high degree of angular random model is constructed according to the observation residual residual,and the experiment shows that the fiaspage and carrier phase observation value of BDS-3 are less than BDS-2.Final comparison analysis of the accuracy of BDS-2 and BDS-3single-frequency SPP and dual-frequency ionosphere-free combination SPP,the overall BDS-3positioning accuracy is superior to BDS-2;BDS-2 single-frequency SPP accuracy B1 I maximum B3 I worst The BDS-3 single-frequency SPP accuracy B1 I is the worst;the BDS-2dual-frequency ionosphere-free combination SPP accuracy B1 I + B2 I is the highest,BDS-3dual-frequency ionosphere-free combination SPP accuracy B1 I + B3 I is the highest;through comparison SPP model positioning accuracy,when the residual ionization layer is affected,the single-frequency SPP accuracy is high,and the opposite of the dual-frequency ionosphere-free layer is high,and the overall plane accuracy is 1m,and the elevation accuracy is 2m.(3)The ambiguity solution based on BDS multi-frequency is studied.First,the geometric free and geometric correlation models used in the multi frequency ambiguity resolution of BDS are described.On the basis of the above model,the advantage of the BDS-3 quad-frequency extra-wide lane ambiguity resolution is fully utilized for short baseline,and the multi-system fusion vectors based on BDS-3 four-frequency constraints are proposed.By experimental analysis of two short baselines,the method can realize the fixed ambiguity of the monochrome,the positioning accuracy is in millimeter,and the ambiguity resolution efficiency is obviously better than the traditional dual-frequency combination;for the medium-long baseline,the combination with minimal ionospheric delay and integer characteristics in BDS-3 quadfrequency will be fully utilized,while the influence of tropospheric delay will be considered,a medium and long baseline solution model based on ionosphere-reduced combination is established.The experimental results of three baselines show that compared with the traditional dual-frequency ionosphere-free model,the ambiguity fixed speed of the model is improved by more than 10%,and the positioning accuracy in N,E and U directions is improved by 7.7%,7.9% and 8.2% respectively compared with the optimal dual frequency ionosphere-free combination(B1C + B2a).(4)Application of BDS multi-frequency positioning technology in intelligent compaction of subgrade and pavement.The application scheme and software development design of BDS intelligent compaction system are discussed,and the key algorithms in the software are designed and tested in detail.The results show that the mean square error of subgrade elevation and layer thickness test points is less than 2cm,and the mean square error of pavement elevation test points is less than 1cm.It can completely replace the traditional fourth-order leveling to measure subgrade and pavement elevation and layer thickness,and meet the needs of intelligent compaction monitoring;At the same time,the preliminary experimental verification of the compaction prediction algorithm is carried out.After training,the prediction error can be controlled within 1%. |
