The Research And Implementation Of RTK Location Based On Doppler Frequency Shift Reconstruction Method

Real Time Kinematic(RTK)difference technology is a measurement technology that provides the centimeter-level positioning accuracy in real time.RTK difference technology has the advantages of fast velocity measurement,high accuracy,and no accumulation of the measurement errors.These advantages play an important role in many fields,such as road surveying,railway surveying,marine surveying,land resource survey,etc.RTK positioning also has many limitations: 1.It requires a good DOP value;2.It needs to observe more than five navigation satellites;3.No surrounding terrain to block the signal;4.Small error in multi-path effect.Therefore,in order to solve the problems of the low integer ambiguity fixed rate in the high DOP value environment and the terrain influence on the observation of carrier phase,this thesis proposes a new RTK positioning algorithm based on the Doppler frequency shift reconstruction method to improve the integer ambiguity fixed rate and the positioning accuracy.The main research contents are as follows:1.This thesis analyzes the principle of Real Time Kinematic difference positioning technology,study the feasible technical solutions and apply the Doppler frequency shift reconstruction method to RTK positioning,conducts the accuracy comparison experiments on the different positioning methods,and verifies the improvement effect of the positioning accuracy of the different positioning methods.2.In view of the need of stable velocity measurement in the Doppler frequency shift reconstruction method,this thesis proposes an improved scheme of dual-antenna baseline solution algorithm combined with Kalman filter algorithm to achieve stable velocity measurement of the receiver dynamic baseline.The comparison experiment with the Doppler difference velocity measurement algorithm proves the stability of the velocity measurement,and the variation of the velocity measurement is about 1m/s.3.In view of the noise of the Doppler frequency shift reconstruction method,which affects the application of the Doppler frequency shift reconstruction method in RTK positioning,this thesis proposes a quadratic reconstruction improvement scheme and improves the mutual difference median weighted algorithm.A mutual difference weighted algorithm based on the altitude angle selection is proposed by this thesis.Compared with the original mutual difference median weighted algorithm,the static positioning accuracy of the mutual difference weighted algorithm based on the altitude angle selection is further improved to a level better than 1cm.4.Aiming at the problem that the carrier phase is out of lock and the ambiguity cannot be continuously fixed in a complex environment,this thesis establishes the carrier phase reconstruction model and combines the carrier phase reconstruction model with the mutual difference weighted method based on the altitude angle selection to realize RTK static positioning reconstruction algorithm.The algorithm,in a high DOP value environment,improves the integer ambiguity fixed rate and accuracy of RTK static positioning,and the accuracy of static positioning experiment is within 2 cm and the fixed rate is 100%.The carrier phase reconstruction model is combined with the extended Kalman filter algorithm to realize the RTK dynamic positioning reconstruction algorithm,which improves the ambiguity fixed rate and accuracy of RTK dynamic positioning in the actual environment.The accuracy of the dynamic positioning experiment is within 10 cm,and the fixed rate is 100%.