Research On RTD Technology Of Beidou Ground-based Augmentation System

The Beidou Navigation Satellite System(BDS)has been providing services to most parts of Asia Pacific since December 27,2012.Industry is developing rapidly,especially Ground Based Augmentation System which provides users with a high-precision real-time location services.Because of the high cost of high-precision location services,it is only widely used in the field of industry.For the public user,low-cost receiver and real-time decimeter positioning accuracy meet its needs.At present,the domestic and foreign research on network RTD(Real Time Differential)technology is less.This article is based on the Ground Based Augmentation System which is for real-time decimeter positioning accuracy,positioning accuracy around the centimeter-level industry and the public users.Under the premise of reducing the cost of user equipment,the network RTD positioning technology has been studied.The client device sends the user location information to the Ground Based Augmentation System.The data center of the system calculates the pseudo-range observation information of the virtual reference station at the user’s location and sends it to the user.The user uses the pseudo-range information of the virtual reference station to combine the information to locate the solution.In the paper,the main RTD positioning error,the generation of atmospheric correction number and network RTD positioning performance were studied.Research work and research results are as follows:1.The paper systematically introduces the single base station mode and multi-base station mode positioning process in network RTD,which lays the theoretical foundation for the whole text.2.The effect of ionospheric delay on RTD was analyzed by grid-based ionospheric model based on different length baseline.The influence of tropospheric delay on RTD was analyzed by stochastic model and NMF projection function.Experiments show that the two atmospheric delays have a little effect on single base station RTD positioning accuracy.3.The influence of multipath effect on RTD was analyzed by using mathematical model for different lengths of baseline.Experiments show that only the multi-path effect of the base station can be modified,the RTD accuracy can be increased by about 10%.While the multi-path effect of the base station and the rover are modified,the RTD accuracy can be improved by about 30%.4.LCM,LIM,DIM and LSM interpolation models are studied for the generation of atmospheric correction of network RTD.Experiments show that DIM is less affected by the position change of the mobile station,LSM is affected by the change of the position of the mobile station,and the positioning of the mobile station in the network will be better than that out of the network.5.The algorithm of double difference atmospheric correction between base stations is studied.The difference between the base stations of the Beidou GEO,IGSO,MEO satellites and GPS satellites is analyzed and the difference between the base station and the virtual station is interpolated.The experimental results show that the delay of the double differential troposphere is slower than that of the ionosphere.With the increase of baseline length,the amount of atmospheric delay increases,the difference becomes larger,but does not show a linear change.6.The network RTD data processing flow is introduced.The static and dynamic experiments of single base station mode and multi-base station mode are tested.The results show that the plane and elevation of the two modes are in the decimeter level to meet the corresponding user requirements,when the distance from the user to the base station is close.