Research On Network RTK Technology Based On Non-difference Correction Model

Network Real-Time Kinematic(NRTK)technology has been widely used in the field of high-precision positioning.In network RTK technology,the positioning performance of the user depends on the error correction model generated by the reference station network.Currently,the error correction model mostly uses a comprehensive error interpolation algorithm.The algorithm uses a single interpolation model to calculate the error correction model.It does not consider the difference of ionospheric delay and tropospheric delay,which is not conducive to solving the ambiguity.Therefore,how to construct the error correction model of the reference station network according to the error characteristics is the key to improving the positioning accuracy of user.This paper focuses on the research of network RTK technology based on the non-difference correction model.To ensure the technical integrity,the research is carried out from the three dimensions of the ambiguity resolution method between reference stations,the design of the non-difference correction model and the rover ambiguity resolution method.The aim is to improve the positioning accuracy of the user to meet the high-precision requirements for position information of precision navigation operations,and to provide new ideas for the future design of error correction models for reference station networks.The main research contents of this paper are as follows:Aiming at the problem of low wave noise caused by the combination of multi-frequency observations and the low success rate of ambiguity fixation,the ambiguity resolution method between reference stations based on the non-combined observation model is studied,and the wave noise was effectively improved by constructing a non-combined model.At the same time,it combines the Kalman filter algorithm to complete the ambiguity resolution.Through two sets of baseline data experiments,the results show that the ambiguity resolution method between reference stations based on the non-combined observation model can effectively fix the ambiguity and lay a good foundation for the correct construction of the regional non-difference correction model.In order to avoid the problem of the correlation between the satellite and the reference station caused by the double-difference error correction model and affect the ambiguity resolution of the rover,the non-difference correction model is studied.By constructing an error correction model based on non-difference observations,the correlation between the satellite and the reference station can be avoided.On the rover side,the reference satellite can be arbitrarily selected,even if the reference satellite changes,it will not cause the rover ambiguity to re-converge.On this basis,the non-difference correction model only requires one-way communication between the data center and the user,which reduces the communication burden and reduces the risk of user location leakage.The experimental results show that the horizontal positioning accuracy of the rover is better than 4cm,and continuous centimeter-level positioning can be achieved.The non-difference correction model can effectively correct the observation error of the rover.Aiming at the problem that the error correction model ignores the different changes of the ionospheric and tropospheric delay errors and affects the positioning accuracy,a interpolation algorithm that takes into account the different characteristics of each error is proposed.This algorithm uses Linear Interpolation Method(LIM)for the wet component of the tropospheric delay,the ionospheric delay adopts the Low-Order Surface Model(LSM),and the atmosphere-independent error is modeled by the inverse distance weighting method,making the non-difference correction model more accurate reflect the characteristics of atmospheric changes,improve model accuracy,and improve user-side ambiguity resolution and positioning performance.The experimental results show that compared to the comprehensive interpolation method that ignores the different rules of each error,the non-difference correction model of the interpolation method is adopted,the average positioning accuracy of the mobile station in the horizontal direction can be increased by more than 12%,and the standard deviation of the fixed rate of the mobile station ambiguity can be improved by more than 40%.